fire-induced progressive collapse

Fire-Induced Progressive ‘Damage’ or ‘Collapse’ ? More …

2012-05-02:  Last week, I attended joint meetings of CIB W14: ‘Fire Safety’ … and ISO Technical Committee 92: ‘Fire Safety’, Sub-Committee 3: ‘Fire Threat to People and the Environment’ & Sub-Committee 4: ‘Fire Safety Engineering’ … in Thessaloniki (Salonika), Greece.

The relationship between these two independent groups is symbiotic … ISO TC 92 develops International Fire Standards, while CIB W14 is the pre-normalization forum for discussion and action on a comprehensive approach to Fire Research and Innovation.

I should add, here, that CIB W14’s Aims & Objectives were substantially updated at our meeting in Thessaloniki … and I presented the CIB Research WG IV Reflection Document: ‘Structural Reliability & Fire-Induced Progressive Damage’ for discussion … which was lively, but far too short !

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While I was away, however, the following question was posed by Mr. Panagiotis Kotsovinos, on the Society of Fire Protection Engineers (SFPE-USA) Page of LinkedIn (http://www.linkedin.com/groups?gid=96627).

” I would like to please explain a bit more why the term ‘Fire-Induced Progressive Damage’ is preferred over ‘Fire-Induced Progressive Collapse’, and what is the confusion that exists widely as you say with the later definition ? “

Firstly, apologies for the late reply.  This was due to my absence from base … I am not continuously ‘plugged-in’ to the virtual environment while travelling.  But, I also wished to respond to this and other queries after some thought.  The issues raised are important.

Very briefly … it was NIST, in its 2005 Report, which introduced the term ‘Fire-Induced Progressive Collapse’ to a wide audience.  No definition, or elaboration, of this structural concept was provided in either the 2005 or 2008 Recommendations.  There is no confusion caused by ‘Fire-Induced’.

The reason I have been so quick to focus in on the distinction between ‘Damage’ and ‘Collapse’ is because we went through this whole debate, in Ireland … starting at the end of the 1980’s and continuing on through to the middle of 1990’s.  Because … in January 1987 … a Multi-Storey Apartment Block, called Raglan House, collapsed as a result of a gas explosion.  Two people were killed.  An examination of records at the time will reveal the same general confusion about technical terminology.  And … following the collapse, the Structural Engineering Profession was in disarray.

After a considerable amount of time witnessing, at close hand, these events … I formed the strong opinion that the proper connection of vertical and horizontal structural elements in a building was, and continues to be, a fundamental principle of all good structural engineering design … no matter what the height of the building.

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Colour photograph showing World Trade Center Building No. 7 in ruins, after 9-11 in New York City ... when Fire-Induced Progressive Damage led to Disproportionate Damage, and finally to total building failure ... a Collapse Level Event (CLE). Click to enlarge.

Colour photograph showing World Trade Center Building No. 7 in ruins, after 9-11 in New York City ... when Fire-Induced Progressive Damage led to Disproportionate Damage, and finally to total building failure ... a Collapse Level Event (CLE). Click to enlarge.

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Tackling the current confusion over technical terminology …

In 1987, Raglan House collapsed in Dublin.  In 2001, World Trade Center Building 7 collapsed in New York City.

In English … the word Collapse can have the following meanings, which are very broadly similar …

  • To fall down or cave in suddenly: the whole building collapsed ;
  • To fail completely ;
  • To break down or fall down from lack of strength ;
  • To fold (furniture, etc.) compactly or (of furniture, etc.) to be designed to fold compactly ;
  • The act or instance of suddenly falling down, caving in, or crumbling ;
  • A sudden failure or breakdown.

[from Latin, from collabi to fall in ruins, from labi to fall]

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Black and white image reproducing Figure 1-1 in NIST Report: 'Best Practices for Reducing the Potential for Progressive Collapse in Buildings' (NISTIR 7396, February 2007) ... showing a bird's eye view of the Disproportionate Damage at Ronan Point, in England, which was caused by a gas explosion in 1968. Click to enlarge.

Black and white image reproducing Figure 1-1 in NIST Report: 'Best Practices for Reducing the Potential for Progressive Collapse in Buildings' (NISTIR 7396, February 2007) ... showing a bird's eye view of the Disproportionate Damage at Ronan Point, in England, which was caused by a gas explosion in 1968. Click to enlarge.

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Please examine the photograph above.  Ronan Point (later demolished) was a 22 Storey Residential Tower Block in London, England.  In May 1968, this building suffered Disproportionate Damage as a result of a gas explosion.  As is clear from the photograph … it did not Collapse.

Disproportionate Damage

The failure of a building’s structural system:  (i) remote from the scene of an isolated overloading action;  and (ii) to an extent which is not in reasonable proportion to that action.

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Let me now return to the CIB Research WG IV Reflection Document: ‘Structural Reliability & Fire-Induced Progressive Damage’ … where I began by stating …

Fire-Induced Progressive Damage in Buildings is distinguished from Disproportionate Damage – a related but different structural concept – by the mode of damage initiation, not the final condition of building failure.  Until this phenomenon is properly understood, and unless it is impeded, or resisted, by building design … Fire-Induced Progressive Damage will result in Disproportionate Damage … and may lead to a Collapse Level Event (CLE), which is entirely unacceptable to the general population of any community or society.

… and, later in the document, provided this definition …

Fire-Induced Progressive Damage

The sequential growth and intensification of structural deformation and displacement, beyond fire engineering design parameters, and the eventual failure of elements of construction in a building – during a fire and the ‘cooling phase’ afterwards – which, if unchecked, will result in disproportionate damage, and may lead to total building collapse.

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Quickly Concluding …

‘Progressive Collapse’ is not the same as ‘Disproportionate Collapse’ … and while total building collapse may be the condition of final building failure, this will certainly not always be the case.  Therefore … ‘Damage’ is the more correct word to use than ‘Collapse’.

To go even further … it should not be necessary to have to use the word ‘total’ in the first sentence above.

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Reminder … Please Read the Reflection Document …

The purpose of the Reflection Document issued by CIB W14 Research Working Group IV is to examine the ‘hot form’ structural concept of Fire-Induced Progressive Damage, and to propose a critical update to fire engineering design practice.  It is also intended to encourage a wider discussion about some of fire engineering’s fundamental tenets, and the future direction of our profession in a rapidly evolving trans-disciplinary approach to the design, construction and operation of a Safe and Sustainable Built Environment.

Let me repeat again … and as I emphasized in Greece … ALL comments on the Reflection Document are most welcome !

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‘Fire-Induced Progressive Damage’ – New CIB W14 Document

2012-04-16:  Following the 9-11 World Trade Center Extreme Fire Event, in New York City …

The National Institute of Standards & Technology (NIST), in the USA, recommended that Fire-Induced Progressive Collapse be particularly considered in the case of …

  • High-Rise Buildings ;
  • Iconic Buildings ;
  • Buildings Having a Critical Function ;
  • Buildings of Innovative Design.

However, as recently discussed … in order to avoid the wide confusion which the term ‘Fire-Induced Progressive Collapse’ is continuing to cause at international level … the preferred term should now be Fire-Induced Progressive Damage.

AND … CIB Working Commission 14: ‘Fire Safety’ – Research Working Group IV: ‘Structural Reliability & Fire-Induced Progressive Damage’ … would strongly caution that Fire-Induced Progressive Damage and Disproportionate Damage are fundamental concepts to be applied in the design of all building types.

[ A height threshold of 5 Storeys for the consideration of Disproportionate Damage, in the Building Codes/Regulations of many jurisdictions, including Ireland, is entirely arbitrary.]

So … what is Fire-Induced Progressive Damage ?   And what is the relationship between this structural concept … and Disproportionate Damage ?

Leaving aside all of the crazy conspiracy theories about the collapse of World Trade Center Building No. 7 … is it possible for Conventional Fire Engineering to directly confront what actually happened ?   Unfortunately … the reaction still, even today, is to bury the head, ostrich-like, in the sand … and ignore WTC 7 and the 2008 NIST WTC Recommendations (Final Report NCSTAR 1A) !

Colour photograph showing World Trade Center Building No. 7 in ruins, after 9-11 in New York City ... when Fire-Induced Progressive Damage led to Disproportionate Damage, and finally to total building failure ... a Collapse Level Event (CLE) which is entirely unacceptable to the general population of any community or society. Click to enlarge.

Colour photograph showing World Trade Center Building No. 7 in ruins, after 9-11 in New York City ... when Fire-Induced Progressive Damage led to Disproportionate Damage, and finally to total building failure ... a Collapse Level Event (CLE) which is entirely unacceptable to the general population of any community or society. Click to enlarge.

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Yesterday, on an adjoining page here … I uploaded a New CIB W14 International Reflection Document on ‘Structural Reliability & Fire-Induced Progressive Damage’, with 2 Appendices.  Scroll down to the section headed ‘April 2012’.

This is a Reflection Document issued by CIB W14 Research Working Group IV: ‘Structural Reliability & Fire-Induced Progressive Damage’;  its purpose is to examine the ‘hot form’ structural concept of Fire-Induced Progressive Damage, and to propose a critical update to fire engineering design practice.  It is also intended to encourage a wider discussion about some of fire engineering’s fundamental tenets, and the future direction of our profession in a rapidly evolving trans-disciplinary approach to the design, construction and operation of a Safe and Sustainable Built Environment.

The Document is written in a simple, generic language which is accessible to design disciplines outside the International Fire Science and Engineering Community.  The next phase of this CIB W14 Innovation & Research Project will certainly require the use of a more technical language, complex calculations, computer modelling, etc … and much closer liaison with CIB W14’s other Research Working Groups on Connections, Design Fires & Design Fire Scenarios, and Performance Criteria.

I wish to sincerely thank those individuals and organizations who have contributed to the work of our Research Working Group IV.

Finally, the myth surrounding NIST’s 9-11 WTC Recommendations, i.e. that they are only applicable in the case of Very Tall Buildings during rarely occurring extreme events … must be completely demolished, and obliterated from the face of the earth !

Climate Change Adaptation is already demanding a much higher level of building resilience.

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Your Comments on this CIB W14 Reflection Document should be e-mailed to: fireox@sustainable-design.ie

C.J. Walsh, FireOx International – Ireland, Italy & Turkey.

Chair – CIB W14 Research WG IV.

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Update 2012-04-20 …

In response to a discourteous and unprofessional comment about the above CIB W14 WG IV Reflection Document, posted by Mr. Morgan Hurley (Technical Director at the Society of Fire Protection Engineers in the USA) on the LinkedIn SFPE Group WebPage … I wrote, as follows, this morning …

Good Man Morgan !

Relax … there is no need to become defensive quite yet.  WG IV’s Reflection Document is simply intended to raise issues … ask questions … and solicit comments from within and, more importantly, from outside the International Fire Science and Engineering Community.

Perhaps of more direct relevance to the SFPE Membership, in the USA, might be the following …

NIST Report: ‘Best Practices for Reducing the Potential for Progressive Collapse in Buildings’ (NISTIR 7396 – February 2007) … is a good document on ‘disproportionate damage’, but it has nothing to say about ‘fire-induced progressive damage’.  These two structural concepts are related, but they are not the same.

When discussing Multi-Storey Steel Frame Buildings, on pages 18 and 19, of NIST Report: ‘Best Practice Guidelines for Structural Fire Resistance Design of Concrete and Steel Buildings’ (NISTIR 7563 – February 2009) … what happened to WTC Building 7 on 9-11, and the 2008 NIST WTC Recommendations (NIST NCSTAR 1A), are conveniently and completely ignored.  Instead, there is a launch straight into the BRE Fire Tests at Cardington, and computer calculations, in order to justify a very flawed design approach.  How crazy is that ?

Hope to see you there next week … we missed you at the last CIB W14 Meeting in Paris !

C.J.

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‘Fire-Induced Progressive Collapse’ – A Term Born To Confuse ?

2012-03-26:  Let me lay out the problem this way … recently, after further developing and refining the definition of the term …

‘ The sequential growth and intensification of structural deformation and displacement, beyond fire engineering design parameters, and the eventual failure of elements of construction in a building – during a fire and the ‘cooling phase’ afterwards – which, if unchecked, will result in disproportionate damage, and may lead to total building collapse ‘

… our attention, in CIB W14’s Research Working Group IV, automatically turned towards the term itself.  It didn’t sound right … it didn’t look right … and a lot of people in North America are still completely confused.

Was there anything we could do to clarify the situation ?

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BACKGROUND

The long delay in incorporating the Recommendations of the following 2 Reports …

  • NIST (National Institute of Standards and Technology).  September 2005.  Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Final Report on the Collapse of the World Trade Center Towers.  NIST NCSTAR 1.  Gaithersburg, MD, USA.

and

  • NIST (National Institute of Standards and Technology).  August 2008.  Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Final Report on the Collapse of World Trade Center Building 7.  NIST NCSTAR 1A.  Gaithersburg, MD, USA.

… into building and fire codes/regulations, standards and administrative provisions at international, regional and national levels … can partly be explained by institutional inertia and the stubborn resistance of vested interests in the construction sector.  To be fair, however, although both NIST Reports made extensive reference to the term ‘Fire-Induced Progressive Collapse’ … the structural concept was not defined, or elaborated, in either document.  This was not really a task for NIST.

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WHO IS CONFUSED ?

Since the publication of the 2005 NIST Report above, there has been much confusion about the term ‘Fire-Induced Progressive Collapse’.

Refer, for example, to the Introduction – Paragraph 1.1 on Page 1 – from NIST Document: ‘Best Practices for Reducing the Potential for Progressive Collapse in Buildings’ (NISTIR 7396 – February 2007) … where a lot of people, who should know better, really screwed up … and got it so wrong …

” The term ‘progressive collapse’ has been used to describe the spread of an initial local failure in a manner analogous to a chain reaction that leads to partial or total collapse of a building.  The underlying characteristic of progressive collapse is that the final state of failure is disproportionately greater than the failure that initiated the collapse.  ASCE Standard 7-05 defines progressive collapse as ‘the spread of an initial local failure from element to element resulting, eventually, in the collapse of an entire structure or a disproportionately large part of it’ (ASCE 2005).  The disproportionality refers to the situation in which failure of one member causes a major collapse, with a magnitude disproportionate to the initial event. Thus, ‘progressive collapse’ is an incremental type of failure wherein the total damage is out of proportion to the initial cause.  In some countries, the term ‘disproportionate collapse’ is used to describe this type of failure.

Based on the above description, it is proposed that the professional community adopt the following definition, which is based largely on ASCE 7-05:

progressive collapse – the spread of local damage, from an initiating event, from element to element resulting, eventually, in the collapse of an entire structure or a disproportionately large part of it; also known as disproportionate collapse.

The concept of progressive collapse can be illustrated by the famous 1968 collapse of the Ronan Point apartment building (Fig. 1-1). “

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Colour photograph showing World Trade Center Building No. 7 in ruins after 9-11 in New York City ... when Fire-Induced Progressive Damage led to Disproportionate Damage, and finally to total building failure ... a Collapse Level Event (CLE). Click to enlarge.

Colour photograph showing World Trade Center Building No. 7 in ruins after 9-11 in New York City ... when Fire-Induced Progressive Damage led to Disproportionate Damage, and finally to total building failure ... a Collapse Level Event (CLE). Click to enlarge.

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WE NOW KNOW

Fire-Induced Progressive Damage in Buildings is distinguished from Disproportionate Damage – a related but different structural concept – by the mode of damage initiation, not the final condition of building failure.  Until this phenomenon is properly understood, and unless it is impeded, or resisted, by building design … Fire-Induced Progressive Damage will result in Disproportionate Damage … and may lead to a Collapse Level Event (CLE), which is entirely unacceptable to the general population of any community or society.

So … if unchecked, Fire-Induced Progressive Damage will lead to Disproportionate Damage.

BUT … while it may happen … which it did, when WTC Building 7 failed completely at approximately 17.21 hrs (local time) on the afternoon of 11 September 2001 in New York City … it is not necessarily always the case that Fire-Induced Progressive Damage and Disproportionate Damage will lead to Total Collapse.

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OUR SOLUTION

In order to avoid the wide confusion which the term ‘Fire-Induced Progressive Collapse’ is continuing to cause at international level … the preferred term is now Fire-Induced Progressive Damage.

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2012 Review of Part B & TGD B – Irish Building Regulations

2012-03-02:  Please bear with me while I update you at the start of this post … rather than at the end, which would be more usual here … and logical.

[ In Ireland … a related problem, which continues to fester and cause a great nuisance in an everyday work environment … concerns the lack of proper, i.e. formal, recognition of electronic communications, and information in an electronic format, by public and private organizations … in spite of the following very clear legal text …

2000 Electronic Commerce Act (No. 27 of 2000)

Section 9 – Electronic Form not to Affect Legal Validity or Enforceability

Information (including information incorporated by reference) shall not be denied legal effect, validity or enforceability solely on the grounds that it is wholly or partly in electronic form, whether as an electronic communication or otherwise. ]

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Yesterday afternoon (1 March 2012), we received the following e-mail communication from the Department of Environment, Community & Local Government (DECLG)

Folks,

Could you please send me your submissions in either Microsoft Word or Excel as it it easier to copy and paste into the format that is required , it is proving rather difficult to copy from a PDF document.

Thank You

Claire Darragh, Architecture / Building Standards, DECLG.

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I immediately replied …

Dear Claire,

Further to your informal e-mail message, which we received just a short while ago …

Please note that this is not an acknowledgement that the FireOx International Submission was received by the Department … and we certainly do not wish that you copy and paste anything relating to its contents anywhere else.

IF this is a Proper Public Consultation Process … you must adapt internal DECLG systems to suit the Submissions !   We will be communicating with the Minister’s Office concerning this issue.

Once again, I would ask you to properly acknowledge receipt of our Submission, dated 2012-02-14.

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In connection with the original FireOx International Submission … I would also like to take this opportunity to advise you that:

  • Due to an error in ISO (International Standards Organization) … the publication of ISO 21542: ‘Building Construction – Accessibility and Usability of the Built Environment’, on 12 December 2011, was not notified to people directly involved in its development and drafting, or to the participating national standards organizations ; 

and

  • In order to avoid the wide confusion which the term ‘Fire-Induced Progressive Collapse’ is continuing to cause at international level … the preferred term is now Fire-Induced Progressive Damage.

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I have amended our Submission accordingly.

Kind regards.

C. J. Walsh, FireOx International – Ireland, Italy & Turkey.

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2012-02-18:  The following is the text of  FireOx International’s Submission, dated 14 February 2012, to the Department of the Environment, Community & Local Government (DECLG) in Dublin … concerning the current review of the Irish Building Regulations Part B & TGD B … including, for good measure, some initial and very pertinent comments on the Irish Building Control Regulations.

None of these comments will come as any surprise to regular visitors here.

It should also be noted that the same comments are just as relevant in the case of the British (England & Wales) Building Regulations, Part B and Approved Document (AD) B !

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Ms. Claire Darragh, Architecture & Building Standards Section, DECLG.

Dear Claire,

Thank you for this opportunity to advise the Department on some urgent and necessary improvements to Part B: ‘Fire Safety’ of the 2nd Schedule to the Building Regulations in Ireland … and its supporting Technical Guidance Document (TGD) B.

1.  Some Initial Comments

  • The continuing debacle of the Priory Hall Apartment Complex, in Donaghmede Dublin 13, is just the tip of a very large iceberg in Ireland.  Yet, when we now hear that there will be a ‘risk-based’ approach to Septic Tank Inspections, instead of an approach which involves inspecting all septic tanks … independently, competently and thoroughly … it is clear that the Minister, and senior officials in his Department, have failed to learn any lessons from ‘Priory Hall’.

What was happening on Irish construction sites during the Celtic Tiger boom years … has been happening for twenty years all over the country … more precisely, since the introduction of legal national building regulations in 1991, with NO effective building control … and, before that again, in those parts of the country outside of the major urban areas having legal building bye-laws AND effective building control, i.e. mandatory inspections by competent local authority personnel at the foundation level and drainage level of ALL projects … and, depending on the type of project, occasional or frequent inspections above ground level.

Over the years, local authority officials who carried out building bye-law inspections accumulated a considerable wealth of knowledge and understanding about local construction conditions and practices.  This valuable resource, widely used by the construction industry at the time, has now been diluted and discarded.

PLEASE LEARN THE LESSONS FROM ‘PRIORY HALL’ !!

In connection with ALL Applications for Fire Safety Certificates (Part B) and Disability Access Certificates (Part M) … competent and thorough inspections must, from now on, be carried out by local authority personnel to confirm proper implementation of Part B & M, respectively, of the 2nd Schedule to the Building Regulations.

Furthermore … while on site, local authority personnel must not be discouraged, or restricted, from dealing with any other Parts of the 2nd Schedule to the Building Regulations.  Under the present dysfunctional system, important horizontal linkages between different Parts of the 2nd Schedule are being widely disregarded and ignored, e.g. between Parts B & D, between Parts B & M, and between Parts B & A … or between Parts M & D, etc., etc !

  • European Union (EU) Council Directive 89/106/EEC has been repealed … and, instead, we now have EU Regulation No 305/2011 of the European Parliament and of the Council, of 9 March 2011, laying down Harmonised Conditions for the Marketing of Construction Products.

Unlike the earlier EU Directive … this Regulation, applicable in all EU Member States, is binding in its entirety.

And although Annex I of EU Regulation 305/2011 will enter into force from 1 July 2013 … the Department should now prepare for, and slowly begin the process of, incorporating all of the Annex I Basic Requirements for Construction Works into the 2nd Schedule of the Irish Building Regulations.

SEE BELOW …

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2.  Firefighter Safety

Fully consistent with Basic Requirement for Construction Works 2(e), in Annex I of EU Regulation No. 305/2011 … Revise Part B Requirement 5 to read as follows …

B5  Firefighter Safety, and Access and Facilities for the Fire Service

A building shall be so designed and constructed that the safety of firefighters is adequately considered and, in the event of an outbreak of fire, that there is adequate provision for access for fire appliances and such other facilities as may be required to assist the fire service in the protection of life and property.

Two examples of issues which should be highlighted in a relevant revision/addition to TGD B’s Guidance Text:

  • The incorporation, in building designs, of alternative safe means of approach towards the scene of a fire by firefighters ;
  • The provision of wider staircases in buildings in order to facilitate the recovery of an injured/impaired firefighter during the course of firefighting operations.

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3.  Protection of Vulnerable Building Users from Fire

The European Union ratified the United Nations Convention on the Rights of Persons with Disabilities (CRPD) on 23 December 2010.  Ireland has not yet ratified the Convention.

However … fully consistent with Ireland’s legal obligation, under Article 4.3 of the Treaty on European Union (TEU), to co-operate fully with EU Institutions in their implementation of this UN Convention … Revise Part B Requirement 1 to read as follows …

B1  Means of Evacuation in the Event of an Outbreak of Fire

A building shall be so designed and constructed that the protection of vulnerable building users is adequately considered and, in the event of an outbreak of fire, that there are adequate and accessible means of evacuation from the building to a place of safety remote from the building, capable of being safely and effectively used.

[ Use of the word ‘escape’, in the context of emergencies, should be strongly discouraged at all times. ]

Concerning TGD B’s Guidance Text … reference to ISO 21542: ‘Building Construction – Accessibility and Usability of the Built Environment’ will be more than sufficient.

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Specifically relating to Adequate Protection of Vulnerable Building Users from Fire

NOTE WELL THAT BS 9999 (AND BS 5588:PART EIGHT)  IS (ARE)  ENTIRELY UNFIT FOR PURPOSE !!

Please carefully examine the attached PDF File – My Note for the National Standards Authority of Ireland:  ‘BS 9999:2008 & BS 8300:2009 – Impacts on Accessibility Design in Ireland & Implications for ISO Accessibility & Fire Safety Standards’ , dated June 2009.

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4.  TGD B’s Appendix A – Performance of Materials and Structures

2 Important Notes should be added to Paragraph A21 – Structural Fire Design

  • In complying with Part B, reference should also be made to Part A of the 2nd Schedule of the Building Regulations, particularly Requirement A3 – Disproportionate Collapse ;

and

  • In order to show that a Fire Protection Material/Product/System for Structural Elements properly complies with Part D … it is also necessary, besides showing that it has been adequately fire tested, to show that the material/product/system is durable over a specified, reasonably long life cycle … and that it can adequately resist mechanical damage during construction of the building and, in the event of an outbreak of fire, during the course of that fire incident.

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Specifically relating to Steel Structural Performance in Fire

You should be aware that Table A1 and Table A2 are only appropriate for use by designers in the case of single, isolated steel structural elements.

In steel structural frame systems, no consideration is given in the Tables to adequate fire protection of connections … or limiting the thermal expansion (and other types of distortion) in fire of steel structural elements … in order to reduce the adverse effects of one steel element’s behaviour on the rest of the frame and/or adjoining non-loadbearing fire resisting elements of construction.

In the case of steel structural frame systems, therefore, the minimum fire protection to be afforded to ALL steel structural elements, including connections, should be 2 Hours.  Connections should also be designed and constructed to be sufficiently robust during the course of a fire incident.  This one small revision will contribute greatly towards preventing Fire-Induced Progressive Damage in buildings … a related, but different, structural concept to Disproportionate Damage …

Disproportionate Damage

The failure of a building’s structural system  (i) remote from the scene of an isolated overloading action;  and (ii) to an extent which is not in reasonable proportion to that action.

Fire-Induced Progressive Damage

The sequential growth and intensification of structural distortion and displacement, beyond fire engineering design parameters, and the eventual failure of elements of construction in a building – during a fire and the ‘cooling phase’ afterwards – which, if unchecked, will result in disproportionate damage, and may lead to total building collapse.

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With regard to the above … please carefully examine these 2 Series of Posts on FireOx International’s Technical Blog ( www.cjwalsh.ie ), beginning on the dates indicated …

  • 2011-10-25:  NIST’s (2005) Recommendations on the 9-11 WTC Building Collapses … GROUP 1. Increased Structural Integrity – Recommendations 1, 2 & 3 (out of 30) ;

and

  • 2012-01-18:  Progressive Collapse of WTC 7 – 2008 NIST Recommendations – Part 1 of 2 … GROUP 1. Increased Structural Integrity – Recommendation A … and GROUP 2. Enhanced Fire Endurance of Structures – Recommendations B, C, D & E (out of 13).

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5.  TGD B’s Appendix F – Reference Standards

Add this Important New Standard …

  • ISO 21542 : 2011     Building Construction – Accessibility and Usability of the Built Environment

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6.  TGD B’s Appendix G – Reference Publications

Add these Two Important Publications …

  • NIST (National Institute of Standards and Technology).  September 2005.  Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Final Report on the Collapse of the World Trade Center Towers.  NIST NCSTAR 1.  Gaithersburg, MD, USA.

and

  • NIST (National Institute of Standards and Technology).  August 2008.  Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Final Report on the Collapse of World Trade Center Building 7.  NIST NCSTAR 1A.  Gaithersburg, MD, USA.

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Should you wish to receive further information on any of my comments … please consult FireOx International’s Technical Blog at  www.cjwalsh.ie … or contact me directly.

Please acknowledge receipt of this e-mail communication.

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Kind regards.

C. J. Walsh, FireOx International – Ireland, Italy & Turkey.

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Progressive Collapse of WTC 7 – 2008 NIST Recommendations – Part 2 of 2

1st Series of Posts on the 2005 NIST WTC 1 & 2 Collapse Recommendations … which began towards the end of 2011 …

2011-10-25:  NIST’s Recommendations on the 9-11 WTC Building Collapses … GROUP 1. Increased Structural Integrity – Recommendations 1, 2 & 3 (out of 30)

Previous Post in this New Series …

2012-01-18:  Progressive Collapse of WTC 7 – 2008 NIST Recommendations – Part 1 of 2 … GROUP 1. Increased Structural Integrity – Recommendation A … and GROUP 2. Enhanced Fire Endurance of Structures – Recommendations B, C, D & E (out of 13)

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2012-01-22:  SOME PRELIMINARY COMMENTS …

  1.     Keeping my ear closely to the ground … I hear you wondering: “So … how did the fires actually start in World Trade Center Building 7 ?”

Extracts from the Executive Summary (pages xxxi – xxxv) – 2008 NIST NCSTAR 1A …

[ Refer back to the WTC 1 & 2 Collapse Damage Plan in the previous post.]

The fires in WTC Building 7 were ignited as a result of the impact of debris from the collapse of WTC Tower 1, which was approximately 110 metres to the south.  The debris also caused some structural damage to the south-west perimeter of WTC 7.  The fires were ignited on at least 10 floors;  however, only the fires on Floors 7 to 9 and 11 to 13 grew and lasted until the time of building collapse.  These uncontrolled fires had characteristics similar to those that have occurred previously in tall buildings.  Their growth and spread were consistent with ordinary building content fires.  Had a water supply for the automatic sprinkler system been available and had the sprinkler system operated as designed, it is likely that the fires in WTC 7 would have been controlled, and the collapse prevented.  However, the collapse of WTC 7 highlights the importance of designing fire resisting structures for situations where sprinklers are not present, do not function (e.g. due to disconnected or impaired water supply), or are overwhelmed.

and …

There were no serious injuries or fatalities, because the estimated 4,000 occupants of WTC 7 reacted to the airplane impacts on the two WTC Towers and began evacuating before there was significant damage to WTC 7.  The occupants were able to use both the elevators and the stairs, which were as yet not damaged, obstructed, or smoke-filled.  Evacuation of the building took just over an hour.  The potential for injuries to people leaving the building was mitigated by building management personnel holding the occupants in the lobby until they identified an exit path that was safe from the debris falling from WTC Tower 1.  The decisions not to continue evaluating the building and not to fight the fires were made hours before the building collapsed, so no emergency responders were in or near the building when the collapse occurred.

and …

The design of WTC 7 was generally consistent with the New York City Building Code of 1968 (NYCBC), with which, by policy, it was to comply.  The installed thickness of the thermal insulation on the floor beams was below that required for unsprinklered or sprinklered buildings, but it is unlikely that the collapse of WTC 7 could have been prevented even if the thickness had been consistent with building code requirements.  The stairwells were narrower than those required by the NYCBC, but, combined with the elevators, were adequate for a timely evacuation on 11 September 2001, since the number of building occupants was only about half that expected during normal business hours.

The collapse of WTC 7 could not have been prevented without controlling the fires before most of the combustible building contents were consumed.  There were two sources of water (gravity-fed overhead tanks and the city water main) for the standpipe and automatic sprinkler systems serving Floor 21 and above, and some of the early fires on those upper floors might have actually been controlled in this manner.  However, consistent with the NYCBC, both the primary and back-up source of water for the sprinkler system in the lower 20 floors of WTC 7 was the city water main.  Since the collapses of the WTC Towers had damaged the water main, there was no water available (such as the gravity-fed overhead tanks that supplied water to Floor 21 and above) to control those fires that eventually led to the building collapse.

Link to read and/or download a copy of the 2008 NIST NCSTAR 1A Report … www.fireox-international.eu/fire/structdesfire.htm 

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  2.     On a separate subject and quite by chance … a few days ago, I was invited to review a technical paper for a reputable international fire engineering journal (which shall remain nameless).  The paper was discussing a certain aspect of steel column critical temperatures.  After three days, I replied to the journal’s editor as follows …

2012-01-18.

Most regrettably, I must decline your invitation to review Paper XYZ.

The ‘critical temperature’ approach to the fire engineering design of steel-framed structures is deeply flawed … and obsolete.

C. J. Walsh, FireOx International – Ireland, Italy & Turkey.

The ‘critical temperature’ approach is antiquated … and this nonsense has got to stop !   NOW … would be the best time !!

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  3.     In the last post, I wrote …

Structural Fire Engineering is concerned with those aspects of fire engineering which relate to structural design for fire, and the complex architectural interaction between a building’s structure and fabric, i.e. non-structure, under conditions of fire and its immediate aftermath.

Indeed !   But, more needs to be added …

I hope it is becoming clearer now that Structural Fire Engineering is not just ambient structural engineering with a few extra ‘bells and whistles’ grafted on … in token consideration of what could happen in fire conditions, i.e. at high temperatures.

[ If, in some jurisdictions, there are no legal requirements to add even those ‘bells and whistles’ … then, typically, even they will be omitted ! ]

This brings me right back to the typical education of Civil/Structural Engineers;  because:  (i) they exit the educational system with little understanding of anything beyond ‘structure’ … in other words, a ‘real’ building, which also comprises ‘fabric’, i.e. non-structure, is a mystery to them;  and (ii) they have difficulty reading architectural drawings … which is why a walk-through inspection of a building, as it is nearing completion, is much preferred over a detailed discussion about drawings at the most appropriate stage, which is well before construction commences … when faults can be readily identified and easily rectified !

In ambient conditions … the architectural interaction between a building’s structure and fabric is difficult, not being entirely static.  Before the surface finishes have been applied, it is immediately obvious when this interaction has been properly ‘designed’, and looks neat and tidy … or, on the vast majority of construction sites, when this interaction is a ‘traffic accident’, and the results are desperately ugly … and you know that they can’t apply the surface finishes quickly enough in order to hide everything from view !

In fire conditions … this architectural interaction between building fabric and structure is complex, certainly very dynamic … and fluid !

It would be more appropriate to think of Structural Fire Engineering as ‘Design in the Hot Form’ … which is a completely different mindset.

It is essential, therefore, that Fire Engineers understand ‘real’ buildings … most importantly, the ‘design’ of real buildings … and, that they know which end is ‘up’ on a real construction site !!   See NIST WTC 7 Recommendation L below.

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  4.     Since the collapse of WTC Building 7 on 11 September 2001, it has been generally assumed that Fire-Induced Progressive Collapse is a large-scale, macro-phenomenon only.  But, believe it or not, this phenomenon has also been observed at micro-level in small building types.

In fact … Progressive Collapse was already receiving sporadic attention, in Ireland, as far back as the 1980’s …

  • As organizer of the 1987 Dublin International Fire Conference: ‘Fire, Access & Safety in Residential Buildings’, I requested that the following Paper be presented … ‘Design against Progressive Collapse in Fire’ … by Dr. Willie Crowe, who was Head of Construction Technology, in the old Institute for Industrial Research & Standards (IIRS) in Ireland.  He later became Manager of the Irish Agrément Board (IAB).  Those were the days … and Willie really knew his stuff !

Mr. Noel C. Manning, of FireBar in Ireland (www.firebar.ie),  and I both contributed to the development of his Paper.

And now is as good a time as any to give full credit to Noel Manning for his innovative approach to Structural Fire Engineering back in the early 1980’s.  He’s a ‘hard man’ … a term that we use for some special people in Ireland !

Link to the Dublin International Fire Conferences, and a copy of this Paper … www.fireox-international.eu/fire/dublinfire.htm 

  • For approximately 12 years from the mid-1980’s, I was a Member of the National Masonry Panel – the National Standards Authority of Ireland (NSAI) Masonry Standards Advisory Committee.  A small, but substantial, text on Fire-Induced Progressive Collapse in Buildings was included, by me, in the following standard … Irish Standard 325: Code of Practice for Use in Masonry – Part 2: Masonry Construction (1995).  Appendix A – Determination of Movement in Masonry.  A.3 – Thermal Movement.  Once again … those were the days … when I was the only architect in a sea of engineers !!   Not a pretty experience.

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  5.     What next ?   A final draft of the International CIB W14 Research WG IV Reflection Document on Fire-Induced Progressive Collapse will be completed in time for circulation to all CIB W14 members before the end of March 2012 … well in time for the next CIB W14 Meetings in Greece, near the end of April 2012.

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2008 NIST WTC 7 RECOMMENDATIONS  (Final Report NCSTAR 1A)

5.1.3     GROUP 3.  New Methods for Fire Resisting Design of Structures

The procedures and practices used in the fire resisting design of structures should be enhanced by requiring an objective that uncontrolled fires result in burnout without partial or global (total) collapse.  Performance-based methods are an alternative to prescriptive design methods.  This effort should include the development and evaluation of new fire resisting coating materials and technologies, and evaluation of the fire performance of conventional and high-performance structural materials.

NIST WTC 7 Recommendation F  (NCSTAR 1  Recommendation 8).

NIST recommends that the fire resistance of structures be enhanced by requiring a performance objective that uncontrolled building fires result in burnout without partial or global (total) collapse.  Such a provision should recognize that sprinklers could be compromised, non-operational, or non-existent.  Current methods for determining the fire resistance of structural assemblies do not explicitly specify a performance objective.  The rating resulting from current test methods indicates that the assembly (component or sub-system) continued to support its superimposed load (simulating a maximum load condition) during the test exposure without collapse.  Model Building Codes:  This Recommendation should be included in the national model building codes as an objective, and adopted as an integral pert of the fire resistance design for structures.  The issue of non-operational sprinklers could be addressed using the existing concept of Design Scenario 8 of NFPA 5000, where such compromise is assumed and the result is required to be acceptable to the Authority Having Jurisdiction (AHJ).  Affected Standards:  ASCE-7, AISC Specifications, ACI 318, and ASCE/SFPE 29.

Relevance to WTC 7:  Large, uncontrolled fires led to failure of a critical column and consequently the complete collapse of WTC 7.  In the region of the collapse initiation (i.e. on the east side of Floor 13), the fire had consumed virtually all of the combustible building contents, yet collapse was not prevented.

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NIST WTC 7 Recommendation G  (NCSTAR 1  Recommendation 9).

NIST recommends the development of:  (1) performance-based standards and code provisions, as an alternative to current prescriptive design methods, to enable the design and retrofit of structures to resist real building fire conditions, including their ability to achieve the performance objective of burnout without structural or local fire collapse;  and (2) the tools, guidelines, and test methods necessary to evaluate the fire performance of the structure as a whole system.  Standards development organizations, including the American Institute of Steel Construction, have already begun developing performance-based provisions to consider the effects of fire in structural design.

a.     Standard methodology, supported by performance criteria, analytical design tools, and practical design guidance;  related building standards and codes for fire resistance design and retrofit of structures, working through the consensus process for nationwide adoption;  comprehensive design rules and guidelines;  methodology for evaluating thermo-structural performance of structures;  and computational models and analysis procedures for use in routine design practice.

b.     Standard methodology for specifying multi-compartment, multi-floor fire scenarios for use in the design and analysis of structures to resist fires, accounting for building-specific conditions such as geometry, compartmentation, fuel load (e.g. building contents and any flammable fuels such as oil and gas), fire spread, and ventilation;  and methodology for rating the fire resistance of structural systems and barriers under realistic design-basis fire scenarios.

c.     Publicly available computational software to predict the effects of fires in buildings – developed, validated, and maintained through a national effort – for use in the design of fire protection systems and the analysis of building response to fires.  Improvements should include the fire behaviour and contribution of real combustibles;  the performance of openings, including door openings and window breakage, that controls the amount of oxygen available to support the growth and spread of fires and whether the fire is fuel-controlled or ventilation-controlled;  the floor-to-floor flame spread;  the temperature rise in both insulated and un-insulated structural members and fire barriers;  and the structural response of components, sub-systems, and the total building system due to the fire.

d.     Temperature-dependent thermal and mechanical property data for conventional and innovative construction materials.

e.     New test methods, together with associated conformance assessment criteria, to support the performance-based methods for fire resistance design and retrofit of structures.  The performance objective of burnout without collapse will require the development of standard fire exposures that differ from those currently used.

There is a critical gap in knowledge about how structures perform in real fires, particularly concerning: the effects of fire on the entire structural system (including thermal expansion effects at lower temperatures);  interaction between the sub-systems, elements, and connections;  and scaling of fire test results to full-scale structures (especially for structures with long-span floor systems).

Relevance to WTC 7:  A performance-based assessment of the effects of fire on WTC 7, had it considered all of the relevant thermal effects (e.g. thermal expansion effects that occur at lower temperatures), would have identified the vulnerability of the building to fire-induced progressive collapse and allowed alternative designs for the structural system.

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5.1.4     GROUP 4.  Improved Active Fire Protection

Active fire protection systems (i.e. sprinklers, standpipes/hoses, fire alarms, and smoke management systems) should be enhanced through improvements to the design, performance, reliability, and redundancy of such systems.

NIST WTC 7 Recommendation H  (NCSTAR 1  Recommendation 12).

NIST recommends that the performance, and possibly the redundancy and reliability of active fire protection systems (sprinklers, standpipes/hoses, fire alarms, and smoke management systems), in buildings be enhanced to accommodate the greater risks associated with increasing building height and population, increased use of open spaces, high-risk building activities, fire department response limits, transient fuel loads, and higher threat profile.

Reliability is affected by (a) redundancy, such that when one water supply is out of service (usually for maintenance), the other interconnected water supply can continue to protect the building and its occupants;  (b) automatic operation of water supply systems (not only for starting fire pumps but also for testing and tank replenishment, with appropriate remote alarms to the fire department and local alarms for notifying emergency personnel);  and (c) the use of suitable equipment and techniques to regulate unusual pressure considerations.

Relevance to WTC 7:  No water was available for the automatic suppression systems on the lower 20 storeys of WTC 7, once water from street-level mains was disrupted.  This lack of reliability in the source of the primary and secondary water supplies allowed the growth and spread of fires that ultimately resulted in collapse of the building.

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5.1.5     GROUP 6.  Improved Emergency Response

Technologies and procedures for emergency response should be improved to enable better access to buildings, response operations, emergency communications, and command and control in large-scale emergencies.

NIST WTC 7 Recommendation I  (NCSTAR 1  Recommendation 24).

NIST recommends the establishment and implementation of codes and protocols for ensuring effective and uninterrupted operation of the command and control system for large-scale building emergencies.

a.     State, local, and federal jurisdictions should implement the National Incident Management System (NIMS).  The jurisdictions should work with the Department of Homeland Security to review, test, evaluate, and implement an effective unified command and control system.  NIMS addresses interagency co-ordination and establishes a response matrix – assigning lead agency responsibilities for different types of emergencies, and functions.  At a minimum, each supporting agency should assign an individual to provide co-ordination with the lead agency at each incident command post.

b.     State, local, and federal emergency operations centres (EOC’s) should be located, designed, built, and operated with security and operational integrity as a key consideration.

c.     Command posts should be established outside the potential collapse footprint of any building which shows evidence of large multi-floor fires or has serious structural damage.  A continuous assessment of building stability and safety should be made in such emergencies to guide ongoing operations and enhance emergency responder safety.  The information necessary to make these assessments should be made available to those assigned responsibility (see related Recommendations 15 and 23 in NIST NCSTAR 1).

d.     An effective command system should be established and operating before a large number of emergency responders and apparatus are dispatched and deployed.  Through training and drills, emergency responders and ambulances should be required to await dispatch requests from the incident command system and not to self-dispatch in large-scale emergencies.

e.     Actions should be taken via training and drills to ensure a co-ordinated and effective emergency response at all levels of the incident command chain by requiring all emergency responders that are given an assignment to immediately adopt and execute the assignment objectives.

f.     Command post information and incident operations data should be managed and broadcast to command and control centres at remote locations so that information is secure and accessible by all personnel needing the information.  Methods should be developed and implemented so that any information that is available at an interior information centre is transmitted to an emergency responder vehicle or command post outside the building.

Relevance to WTC 7:  (1) The New York City Office of Emergency Management (OEM) was located in WTC 7 and was evacuated before key fire ground decisions had to be made.  The location of OEM in WTC 7, which collapsed due to ordinary building fires, contributed to the loss of robust interagency command and control on 11 September 2001.  (2) Due to the collapse of the WTC Towers and the loss of responders and fire control resources, there was an evolving site leadership during the morning and afternoon.  Key decisions (e.g. not to fight the fires in WTC 7 and to turn off power to the Con Edison substation) were reasonable and would not have changed the outcome on 11 September 2001, but were not made promptly.  Under different circumstances (e.g. if WTC 7 had collapsed sooner and firefighters were still evaluating the building condition), the outcome could have been very different.

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5.1.6     GROUP 7.  Improved Procedures and Practices

The procedures and practices used in the design, construction, maintenance, and operation of buildings should be improved to include encouraging code compliance by non-governmental and quasi-governmental entities, adoption and application of evacuation and sprinkler requirements in codes for existing buildings, and retention and availability of building documents over the life of a building.

NIST WTC 7 Recommendation J  (NCSTAR 1  Recommendation 27).

NIST recommends that building codes incorporate a provision that requires building owners to retain documents, including supporting calculations and test data, related to building design, construction, maintenance, and modifications over the entire life of the building.*  Means should be developed for off-site storage and maintenance of the documents.  In addition, NIST recommends that relevant information be made available in suitably designed hard copy or electronic formats for use by emergency responders.  Such information should be easily accessible by responders during emergencies.

[ * F-12  The availability of inexpensive electronic storage media and tools for creating large searchable databases makes this feasible.]

Relevance to WTC 7:  The efforts required in locating and acquiring drawings, specifications, tenant layouts, and material certifications, and especially shop fabrication drawings, significantly lengthened the investigation into the collapse of WTC 7.

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NIST WTC 7 Recommendation K  (NCSTAR 1  Recommendation 28).

NIST recommends that the role of the ‘Design Professional in Responsible Charge’* be clarified to ensure that:  (1) all appropriate design professionals (including, e.g. the fire protection engineer) are part of the design team providing the highest standard of care when designing buildings employing innovative or unusual fire safety systems;  and (2) all appropriate design professionals (including, e.g. the structural engineer and the fire protection engineer) are part of the design team providing the highest standard of care when designing the structure to resist fires, in buildings that employ innovative or unusual structural and fire safety systems.

[ * F-13  In projects involving a design team, the ‘Design Professional in Responsible Charge’ – usually the lead architect – ensures that the team members use consistent design data and assumptions, co-ordinates overlapping specifications, and serves as the liaison between the enforcement and reviewing officials and the owner.  This term is defined in the International Building Code (IBC) and in the International Code Council’s Performance Code for Buildings and Facilities (where it is the Principal Design Professional).]

Relevance to WTC 7:  Following typical practice, none of the design professionals in charge of the WTC 7 Project (i.e. architect – structural engineer – fire protection engineer) was assigned the responsibility to explicitly evaluate the fire performance of the structural system.  Holistic consideration of thermal and structural factors during the design or review stage could have identified the potential for the failure and might have prevented the collapse of the building.

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5.1.7     GROUP 8.  Education and Training

The professional skills of building and fire safety professionals should be upgraded through a national education and training effort for fire protection engineers, structural engineers, and architects.  The skills of building regulatory and fire service personnel should also be upgraded to provide sufficient understanding and the necessary skills to conduct the review, inspection, and approval tasks for which they are responsible.

NIST WTC 7 Recommendation L  (NCSTAR 1  Recommendation 29).

NIST recommends that continuing education curricula be developed, and programmes be implemented for:  (1) training fire protection engineers and architects in structural engineering principles and design;  and (2) training structural engineers, architects, fire protection engineers, and code enforcement officials in modern fire protection principles and technologies, including the fire resisting design of structures;  and (3) training building regulatory and fire service personnel to upgrade their understanding and skills to conduct the review, inspection, and approval tasks for which they are responsible.  The outcome would further the integration of the disciplines in effective fire-safe design of buildings.

Relevance to WTC 7:  Discerning the fire-structure interactions that led to the collapse of WTC 7 required research professionals with expertise in both disciplines.  Assuring the safety of future buildings will require that participants in the design and review processes possess a combined knowledge of fire science, materials science, heat transfer, and structural engineering, and design.

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NIST WTC 7 Recommendation M  (NCSTAR 1  Recommendation 30).

NIST recommends that academic, professional short-course, and web-based training materials in the use of computational fire dynamics and thermo-structural analysis tools be developed and delivered to strengthen the base of available technical capabilities and human resources.

Relevance to WTC 7:  NIST stretched the state-of-the-art in the computational tools needed to reconstruct a fire-induced progressive collapse.  This enabled identification of the critical processes that led to that collapse.  Making these expanded tools and derivative, validated, and simplified modelling approaches usable by practitioners could prevent future disasters.

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END

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Progressive Collapse of WTC 7 – 2008 NIST Recommendations – Part 1 of 2

See the 1st Series of Posts on the 2005 NIST WTC 1 & 2 Collapse Recommendations … which began, here, towards the end of 2011 …

2011-10-25:  NIST’s Recommendations on the 9-11 WTC Building Collapses … GROUP 1. Increased Structural Integrity – Recommendations 1, 2 & 3 (out of 30)

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Colour plan showing the World Trade Center Complex in New York City, and its surrounding neighbourhood in Manhattan. By means of yellow shading and annotation in red text, the extent of direct damage caused by the collapse of the 2 WTC Towers on 11 September 2001 is shown. Not shown is the much greater extent of indirect damage caused, e.g. dust and debris from the collapses clogged up and destroyed air conditioning systems and ductwork in buildings. Everywhere south of Canal Street was a disaster zone. Also not shown is the damage caused by WTC 7, at the north-eastern tip of the Complex, which collapsed late on the afternoon of 9-11. Click to enlarge.

Colour plan showing the World Trade Center Complex in New York City, and its surrounding neighbourhood in Manhattan. By means of yellow shading and annotation in red text, the extent of direct damage caused by the collapse of the 2 WTC Towers on 11 September 2001 is shown. Not shown is the much greater extent of indirect damage caused, e.g. dust and debris from the collapses clogged up and destroyed air conditioning systems and ductwork in buildings. Everywhere south of Canal Street was a disaster zone. Also not shown is the damage caused by WTC 7, at the north-eastern tip of the Complex, which collapsed late on the afternoon of 9-11. Click to enlarge.

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2012-01-18:  SOME PRELIMINARY COMMENTS …

  1.     World Trade Center Building 7 was a 47 Storey Office Building located at the north -eastern tip of the WTC Complex in Lower Manhattan, New York City.  It had been built on top of an existing Consolidated Edison of New York electric power substation, on land owned by the Port Authority of New York and New Jersey.

On Tuesday, 11 September 2001 … WTC Building 7 was on fire for almost seven hours … from the time of the collapse of WTC Tower 1 – North Tower, just before 10.30 hrs (local time), until 17.21 hrs … when WTC 7 failed completely, collapsing progressively as a result of ‘real’ fires – as distinct from ‘standard test’ fires – on many floors. 

There were only two certainties on that fateful day (9-11) … the Fire-Induced Progressive Collapse of WTC Building 7 could no longer be ignored by the International Fire Science and Engineering Community … and the ‘reality’, which Modern Fire Engineering must now confront, was significantly altered.  Secondly, it is NEVER acceptable to a general population for buildings to collapse !

Later in 2008, the Mumbai ‘Hive’ Attacks would add a sinister new ingredient to the standard threat profile for buildings, their occupants, and emergency services.

However, long before 9-11 and Mumbai, the growing complexity of modern communities and their rapidly evolving architectural forms had left the Fire Engineer far behind, unable to respond to the new fire safety challenges posed.

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  2.     The second of the NIST Publications being referenced in this New Series of Posts is as follows …

NIST (National Institute of Standards and Technology).  August 2008.  Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Final Report on the Collapse of World Trade Center Building 7.  NIST NCSTAR 1A.  Gaithersburg, MD, USA.

This 2008 NIST Report contains, in Chapter 5, a list of 13 Recommendations for Action (A-M), grouped together under the same 8 Subject Headings used in the 2005 NIST Report (NCSTAR 1) …

     i)       Increased structural integrity … Recommendation A ;

     ii)      Enhanced fire endurance of structures … Recommendations B, C, D & E ;

     iii)     New methods for fire resisting design of structures … Recommendations F & G ;

     iv)     Improved active fire protection … Recommendation H ;

     v)      Improved building evacuation … Long before its collapse, all occupants/users had evacuated WTC 7 … No Recommendation ;

     vi)     Improved emergency response … Recommendation I ;

     vii)    Improved procedures and practices … Recommendations J & K ;   and

     viii)   Education and training … Recommendations L & M.

NIST has clearly stated that “the urgency of these Recommendations is substantially reinforced by their pertinence to the collapse of a tall building that was based on a structural system design that is in widespread use”.

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  3.     The Colour Coding of Texts which I am using in this new series of posts … where NIST has presented new texts relating to WTC Building 7, these are shown in blue … where NIST has chosen to reinforce earlier texts from the 2005 Report on the WTC Towers 1 & 2 Collapses, these are shown in black.  The important new paragraphs describing the critical relevance of WTC Building 7 are shown in red.

Please pay particular attention to these Red Paragraphs.  Having carefully digested their contents … then if, by any chance, you happen to encounter somebody who still insists that the NIST 9-11 WTC Recommendations have no relevance to the design, construction, management and operation of ALL Buildings … that person is either living in Alice’s Wonderland … or he/she has never bothered to read the NIST Recommendations in the first place !!

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  4.     While it is still essential to distinguish clearly between the two closely related structural concepts below … I would like to take this opportunity to bring to your attention a necessary and important modification … more, a refinement … to the definition of Fire-Induced Progressive Collapse

Disproportionate Damage

The failure of a building’s structural system  (i) remote from the scene of an isolated overloading action;  and (ii) to an extent which is not in reasonable proportion to that action.

Fire-Induced Progressive Collapse

The sequential growth and intensification of structural distortion and displacement, beyond fire engineering design parameters, and the eventual failure of elements of construction in a building – during a fire and the ‘cooling phase’ afterwards – which, if unchecked, will result in disproportionate damage, and may lead to total building collapse.

This modification/refinement recognizes the following … that Fire-Induced Progressive Collapse may commence long before any breach occurs in a Fire Compartment Boundary … that, as a result of rampant commercial pressures in our societies, the tendency is for Compartment Volumes to become far too large to be any longer effective … and in the case of a Sustainable Building, for example, where natural patterns of air movement in buildings are used for either heating or cooling purposes, there may be no Compartments at all !

Restricting the application of one or both of these structural concepts, in law, to Multi-Storey Buildings, i.e. in many jurisdictions, those buildings having 5 or more storeys … is a purely arbitrary cut-off point.

CIB W14’s Research Working Group IV: ‘Structural Reliability & Fire-Induced Progressive Collapse’ would argue, rationally, that both of these concepts are fundamental to all structural fire engineering design.

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  5.     Structural Fire Engineering is concerned with those aspects of fire engineering which relate to structural design for fire, and the complex architectural interaction between a building’s structure and fabric, i.e. non-structure, under conditions of fire and its immediate aftermath.

As Chair of CIB W14’s Research Working Group IV … I will shortly be making a Workshop Presentation in Europe, the aim of which will be to set the scene for the launch of an International CIB W14 Research WG IV Reflection Document;  the specific objective of the Presentation, however, will be to accurately describe the phenomenon that is Fire-Induced Progressive Collapse … and to outline a necessary new design approach which will fulfil future requirements, legal and otherwise, concerning adequate resistance to this phenomenon.

It will be shown that the new design approach is fully compatible with the Recommendations contained in the 2005 and 2008 NIST Reports on the 9-11 World Trade Center Buildings 1, 2 & 7 Collapses – NCSTAR 1 & NCSTAR 1A.

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2008 NIST WTC 7 RECOMMENDATIONS  (Final Report NCSTAR 1A)

5.1  GENERAL

In its final report on the collapse of the World Trade Center Towers (NIST NCSTAR 1), NIST made 30 Recommendations for improving the safety of buildings, occupants, and emergency responders.  These encompass increased structural integrity, enhanced fire endurance of structures, new methods for fire resisting design of structures, improved active fire protection, improved building evacuation, improved emergency response, improved procedures and practices, and education and training.

WTC 7 was unlike the WTC Towers in many respects.  It was a more typical tall building in the design of its structural system.  It was not struck by an airplane.  The fires in WTC 7 were quite different from those in the Towers.  Since WTC 7 was not doused with thousands of litres of jet fuel, large areas of any floor were not ignited simultaneously.  Instead, the fires in WTC 7 were similar to those that have occurred previously in several tall buildings where the sprinklers did not function or were not present.  These other buildings did not succumb to their fires and collapse, because they were of structural designs that differed from that of WTC 7.

The Investigation Team has compiled a list of key factors that enabled ordinary fires to result in an extraordinary outcome.  In so doing, the Team recognized that there were additional aspects to be included in the content of some of the earlier 30 Recommendations.

Based on the findings of this Investigation, NIST has identified 1 New Recommendation and has reiterated 12 Recommendations from the Investigation of the WTC Towers.

The urgency of the Prior Recommendations is substantially reinforced by their pertinence to the collapse of a tall building that is based on a structural system design that is in widespread use.  A few of the Prior Recommendations have been modified to reflect the findings of this Investigation.

The partial or total collapse of a building due to fires is an infrequent event.  This is particularly true for buildings with a reliably operating active fire protection system, such as an automatic fire sprinkler system.  A properly designed and operating automatic sprinkler system will contain fires while they are small and, in most instances, prevent them from growing and spreading to threaten structural integrity.

The intent of current practice, based on prescriptive standards and codes, is to achieve life safety, not collapse prevention.  However, the key premise of NIST’s Recommendations is that buildings should not collapse in infrequent (worst-case) fires that may occur when active fire protection systems are rendered ineffective, e.g. when sprinklers do not exist, are not functional, or are overwhelmed by the fire.

Fire scenarios for structural design based on single compartment or single floor fires are not appropriate representations of infrequent fire events.  Such events have occurred in several tall buildings resulting in unexpected substantial losses.  Instead, historical data suggests that infrequent fires which should be considered in structural design have characteristics that include:  ordinary combustibles and combustible load levels, local fire origin on any given floor, no widespread use of accelerants, consecutive fire spread from combustible to combustible, fire-induced window breakage providing ventilation for continued fire spread and accelerated fire growth, concurrent fires on multiple floors, and active fire protection systems rendered ineffective.  The fires in WTC 7 had all of these characteristics.

NIST believes the Recommendations are realistic, appropriate, and achievable within a reasonable period of time.  NIST strongly urges that immediate and serious consideration be given to these Recommendations by the building and fire safety communities in order to achieve appropriate improvements in the way buildings are designed, constructed, maintained, and used – with the goal of making buildings safer in future emergencies.

A complete listing of all 13 Recommendations (Recommendations A through L) based on this Investigation follows.  Under a few of the Recommendations, the pertinent lesson from the reconstruction of the WTC 7 Collapse is reflected in the form of a modification.   For the 12 Reiterated Recommendations, the pertinent codes, standards, and organizations were listed in Table 9-1, and Tables 9-2a through 9-2c of NIST NCSTAR 1 and are not repeated here.  For the 1 New Recommendation, B, this information is provided in the text.

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5.1.1     GROUP 1.  Increased Structural Integrity

The standards for estimating the load effects of potential hazards (e.g. progressive collapse, wind) and the design of structural systems to mitigate the effects of those hazards should be improved to enhance structural integrity.

NIST WTC 7 Recommendation A  (NCSTAR 1  Recommendation 1).

NIST recommends that:  (1) progressive collapse be prevented in buildings through the development and nationwide adoption of consensus standards and code provisions, along with the tools and guidelines needed for their use in practice;  and (2) a standard methodology be developed – supported by analytical design tools and practical design guidance – to reliably predict the potential for complex failures in structural systems subjected to multiple hazards.

Relevance to WTC 7:  Had WTC 7 been expressly designed for prevention of fire-induced progressive collapse, it would have been sufficiently robust to withstand local failure due to the fires without suffering total collapse.

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5.1.2     GROUP 2.  Enhanced Fire Endurance of Structures

The procedures and practices used to ensure the fire endurance of structures should be enhanced by improving the technical basis for construction classifications and fire resistance ratings, improving the technical basis for standard fire resistance testing methods, use of the ‘structural frame’ approach to fire resistance ratings, and developing in-service performance requirements and conformance criteria for sprayed fire resisting materials.

NIST WTC 7 Recommendation B  (New)

NIST recommends that buildings be explicitly evaluated to ensure the adequate performance of the structural system under worst-case design fires with any active fire protection system rendered ineffective.  Of particular concern are the effects of thermal expansion in buildings with one or more of the following features:  (1) long-span floor systems* which experience significant thermal expansion and sagging effects;  (2) connection designs (especially shear connections) that cannot accommodate thermal effects;  (3) floor framing that induces asymmetric thermally-induced (i.e. net lateral) forces on girders;  (4) shear studs that could fail due to differential thermal expansion in composite floor systems;  and (5) lack of shear studs on girders.  Careful consideration should also be given to the possibility of other design features that may adversely affect the performance of the structural system under fire conditions.

[ * F-6   Typical floor span lengths in tall office buildings are in the range of 12-15 metres;  this range is considered to represent long-span systems.  Thermal effects (e.g. thermal expansion) that may be significant in long-span buildings may also be present in buildings with shorter span lengths, depending on the design of the structural system.]

Building owners, operators, and designers are strongly urged to act upon this Recommendation.  Engineers should be able to design cost-effective fixes to address any areas of concern that are identified by these evaluations.  Several existing, emerging, or even anticipated capabilities could have helped prevent the collapse of WTC 7.  The degree to which these capabilities improve performance remains to be evaluated.  Possible options for developing cost-effective fixes include:

  • More robust connections and framing systems to better resist the effects of thermal expansion on the structural system ;
  • Structural systems expressly designed to prevent progressive collapse.  The current model building codes do not require that buildings be designed to resist progressive collapse ;
  • Better thermal insulation (i.e. reduced conductivity and/or increased thickness) to limit heating of structural steel and to minimize both thermal expansion and weakening effects.  Currently, insulation is used to protect steel strength, but it could also be used to maintain a lower temperature in the steel framing to limit thermal expansion ;
  • Improved compartmentation in tenant areas to limit spread of fires ;
  • Thermally resisting window assemblies which limit breakage, reduce air supply, and retard fire growth.

Industry should partner with the research community to fill critical gaps in knowledge about how structures perform in real fires, particularly considering:  the effects of fire on the entire structural system; the interactions between sub-systems, elements, and connections; and scaling of fire test results to full-scale structures, especially for structures with long-span floor systems.

Affected Standards:  ASCE 7, ASCE/SFPE 29, AISC Specifications, and ACI 318.  Development of performance objectives, design criteria, evaluation methods, design guidance, and computational tools should begin promptly, leading to new standards.

Model Building Codes:  The new standard should be adopted in model building codes (IBC, NFPA 5000) by mandatory reference to, or incorporation of, the latest edition of the standard.

Relevance to WTC 7:  The effects of restraint of free thermal expansion on the steel framing systems, especially for the long spans on the east side of WTC 7, were not considered in the structural design and led to the initiation of the building collapse.

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NIST WTC 7 Recommendation C  (NCSTAR 1  Recommendation 4).

NIST recommends evaluating, and where needed improving, the technical basis for determining appropriate construction classifications and fire rating requirements (especially for tall buildings) – and making related code changes now, as much as possible – by explicitly considering factors including:*

[ * F-7  The construction classification and fire rating requirements should be risk-consistent with respect to the design-basis hazards and the consequences of those hazards.  The fire rating requirements, which were originally developed based on experience with buildings less than 20 storeys in height, have generally decreased over the past 80 years since historical fire data for buildings suggest considerable conservatism in those requirements.  For tall buildings, the likely consequences of a given threat to an occupant on the upper floors are more severe than the consequences to an occupant on the first floor or the lower floors.  For example, with non-functioning elevators, both of the time requirements are much greater for full building evacuation from upper floors and emergency responder access to those floors.  The current height and areas tables in building codes do not provide the technical basis for the progressively increasing risk to an occupant on the upper floors of tall buildings that are much greater than 20 storeys in height.]

  • timely access by emergency responders and full evacuation of occupants, or the time required for burnout without partial collapse ;
  • the extent to which redundancy in active fire protection systems (sprinklers and standpipe, fire alarm, and smoke management) should be credited for occupant life safety ;*

[ * F-8  Occupant life safety, prevention of fire spread, and structural integrity are considered separate safety objectives.]

  • the need for redundancy in fire protection systems that are critical to structural integrity ;*

[ * F-9  The passive fire protection system (including the application of fire protection insulation, compartmentation, and fire stopping) and the active sprinkler system each provide redundancy for maintaining structural integrity in a building fire, should one of the systems fail to perform its intended function.]

  • the ability of the structure and local floor systems to withstand a maximum credible fire scenario* without collapse, recognizing that sprinklers could be compromised, not operational, or non-existent ;

[ * F-10  A maximum credible fire scenario includes conditions that are severe, but reasonable to anticipate, conditions related to building construction, occupancy, fire loads, ignition sources, compartment geometry, fire control methods, etc., as well as adverse, but reasonable to anticipate operating conditions.]

  • compartmentation requirements (e.g. 1,200 sq.m*) to protect the structure, including fire rated doorsets and automatic enclosures, and limiting air supply (e.g. thermally resisting window assemblies) to retard fire spread in buildings with large, open floor plans ;

[ * F-11  Or a more appropriate limit, which represents a reasonable area for active fire fighting operations.]

  • the effect of spaces containing unusually large fuel concentrations for the expected occupancy of the building ;   and
  • the extent to which fire control systems, including suppression by automatic or manual means, should be credited as part of the prevention of fire spread.

Relevance to WTC 7:  The floor systems in WTC 7 failed at lower temperatures because thermal effects within the structural system, especially thermal expansion, were not considered in setting the fire rating requirements in the construction classification, which are determined using the ASTM E 119 or equivalent testing standard.

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NIST WTC 7 Recommendation D  (NCSTAR 1  Recommendation 5).

NIST recommends that the technical basis for the century-old standard for fire resistance testing of components, assemblies and systems be improved through a national effort.  Necessary guidance also should be developed for extrapolating the results of tested assemblies to prototypical building systems.  A key step in fulfilling this Recommendation is to establish a capability for studying and testing components, assemblies, and systems under realistic fire and load conditions.

Of particular concern is that the Standard Fire Resistance Test does not adequately capture important thermally-induced interactions between structural sub-systems, elements, and connections that are critical to structural integrity.  System-level interactions, especially due to thermal expansion, are not considered in the standard test method since columns, girders, and floor sub-assemblies are tested separately.  Also, the performance of connections under both gravity and thermal effects is not considered.  The United States currently does not have the capability for studying and testing these important fire-induced phenomena critical to structural safety.

Relevance to WTC 7:  The floor systems failed in WTC 7 at shorter fire exposure times than the specified fire rating (two hours) and at lower temperatures because thermal effects within the structural system, especially thermal expansion, were not considered in setting the endpoint criteria when using the ASTM E 110 or equivalent testing standard.  The structural breakdowns that led to the initiating event, and the eventual collapse of WTC 7, occurred at temperatures that were hundreds of degrees below the criteria that determine structural fire resistance ratings.

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NIST WTC 7 Recommendation E  (NCSTAR 1  Recommendation 7).

NIST recommends the adoption and use of the ‘structural frame’ approach to fire resistance ratings.  This approach requires all members that comprise the primary structural frame (such as columns, girders, beams, trusses, and spandrels) be fire protected to the higher fire resistance rating required for the columns.  The definition of the primary structural frame should be expanded to include bracing members that are essential to the vertical stability of the primary structural frame under gravity loading (e.g. girders, diagonal bracing, composite floor systems that provide lateral bracing to the girders) whether or not the bracing members carry gravity loads.  Some of these bracing members may not have direct connections to the columns, but provide stability to those members directly connected to the columns.  This Recommendation modifies the definition of the primary structural frame adopted in the 2007 supplement to the International Building Code (IBC).  The IBC considers members of floor or roof construction that are not connected to the columns not to be part of the primary structural frame.  This Recommendation ensures consistency in the fire protection provided to all of the structural elements that contribute to overall structural stability.  State and local jurisdictions should adopt and enforce this requirement.

Relevance to WTC 7:  Thermally-induced breakdown of the floor system in WTC 7 was a determining step in causing failure initiation and progressive collapse.  Therefore, the floor system should be considered as an integral part of the primary structural frame.

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NIST WTC Recommendations 25-28 > Improved Practices

Previous Posts in This Series …

2011-10-25:  NIST’s Recommendations on the 9-11 WTC Building Collapses … GROUP 1. Increased Structural Integrity – Recommendations 1, 2 & 3 (out of 30)

2011-11-18:  NIST WTC Recommendations 4-7 > Structural Fire EnduranceGROUP 2.  Enhanced Fire Endurance of Structures – Recommendations 4, 5, 6 & 7

2011-11-24:  NIST WTC Recommendations 8-11 > New Design of StructuresGROUP 3.  New Methods for Fire Resisting Design of Structures – Recommendations 8, 9, 10 & 11

2011-11-25:  NIST WTC Recommendations 12-15 > Improved Active ProtectionGROUP 4.  Improved Active Fire Protection – Recommendations 12, 13, 14 & 15

2011-11-30:  NIST Recommendations 16-20 > Improved People EvacuationGROUP 5.  Improved Building Evacuation – Recommendations 16, 17, 18, 19 & 20

2011-12-04:  NIST WTC Recommendations 21-24 > Improved FirefightingGROUP 6.  Improved Emergency Response – Recommendations 21, 22, 23 & 24

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2011-12-07:  SOME PRELIMINARY COMMENTS …

  1.     Concerning Recommendation 25 below … yes, this Recommendation applies to the types of organizations identified in the text, but it should also be understood as applying to ALL Organizations … public or private, governmental or non-governmental or quasi-governmental, whatever, etc … ‘supported’ (see the text further down in Recommendation 25) with rigorous enforcement, in all cases, by publically appointed building control officials and/or by private, independent, competent technical control professionals.

Once more … and again and again (!) … confirmed by the sort of debacle seen at the Priory Hall Apartment Complex, in Dublin … Self-Certification / Self-Approval, i.e. ‘lite’ regulation, does not work.  For National Authorities Having Jurisdiction (AHJ’s), however, it is a cheap solution to a difficult, resource-devouring issue, i.e. protecting society and the consumer … in that order.

  2.     Concerning the Footnote to Recommendation 26 below … the choice should never be between either Fire Compartmentation or Sprinklers … or the other way around, whichever you prefer.  Neither is 100% reliable !

Fire Compartmentation

The division of a building into fire-tight compartments, by fire and smoke resisting elements of construction, in order …

  • to contain an outbreak of fire, and to facilitate effective firefighting ;
  • to prevent damage, within the building, to other adjoining compartments and/or spaces ;
  • to protect a compartment interior from external fire attack, e.g. fire spread across the building’s facade or from an adjacent building ;
  • to minimize adverse, or harmful, environmental impacts outside the building.

As developed as that definition is above, Fire Compartmentation should be regarded as just one Fire Safety Strategy / Fire Engineering Strategy … not the only strategy, and certainly not the main strategy.

Here are two reasons why not …

a)   The connection between compartment size and the ability to effectively fight a fire within a space of limited volume has been lost … so more and more, commercial pressure is being exerted on national authorities to expand the acceptable compartment sizes in buildings … which significantly increases the fire hazard ;

[ Remembering the difference between the limited Fire Safety Objectives of Building Codes/Regulations and the much broader Project-Specific Fire Engineering Objectives of Ethical Fire Engineering required to protect society and the full interests of our clients … it is easy to understand why national authorities feel that they can respond positively to such commercial pressures.]

b)   In a Sustainable Building … it is a very common design strategy to take advantage of the natural patterns of air movement in a building, for either cooling or heating purposes, depending on local climate conditions.  So there is simply no compartmentation, as understood in conventional fire engineering terms … and this throws up a fundamental conflict between the two.  To be discussed in another post !

  3.     Concerning the 2nd Footnote to Recommendation 28 below … in the very same New York City … at 09.40 hrs on a Saturday morning, 28 July 1945 … lost in fog, a B-25 Bomber slammed head-on into the 79th Floor of the Empire State Building … and caused enormous damage.  That building is still standing today … and surprise, surprise … there was aviation fuel in the B-25 !

In a similar vein … Fire-Induced Progressive Collapse was not observed for the first time, in New York, on 11 September 2001 !

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2005 NIST WTC RECOMMENDATIONS

GROUP 7.  Improved Procedures and Practices

The procedures and practices used in the design, construction, maintenance, and operation of buildings should be improved to include encouraging code compliance by non-governmental and quasi-governmental entities, adoption and application of egress and sprinkler requirements in codes for existing buildings, and retention and availability of building documents over the life of a building.

NIST WTC Recommendation 25.

Non-governmental and quasi-governmental entities that own or lease buildings and are not subject to building and fire safety code requirements of any governmental jurisdiction are nevertheless concerned about the safety of building occupants and responding emergency personnel.  NIST recommends that such entities be encouraged to provide a level of safety that equals or exceeds the level of safety that would be provided by strict compliance with the code requirements of an appropriate governmental jurisdiction.  NIST further recommends that as-designed and as-built safety be certified by a qualified third party, independent of the building owner(s).  The process should not use self-approval for code enforcement in areas including interpretation of code provisions, design approval, product acceptance, certification of the final construction, and post-occupancy inspections over the life of the buildings.*

[ * F-46  The long-standing stated policy of the Port Authority of New York & New Jersey (PANYNJ) was to meet and, where appropriate, exceed the requirements of local building and fire codes, and it entered into agreements with the New York City Department of Buildings and the Fire Department of the City of New York in accordance with that policy.  Although the PANYNJ sought review and concurrence from New York City in the areas listed in the Recommendation, the PANYNJ was not required to yield, and appears not to have yielded, approval authority to New York City.  The PANYNJ was created as an interstate entity, a ‘body corporate and politic’, under its charter, pursuant to Article 1, Section 10 of the United States Constitution permitting compacts between states.  Further, there are many other similar non-governmental and quasi-governmental entities in the U.S.  A comprehensive review of documents conducted as part of this Investigation suggests that the WTC towers generally were designed and maintained consistent with the requirements of the 1968 New York City Building Code.  Areas of concern included fireproofing of the WTC floor system, height of tenant separation walls, and egress requirements for the assembly use spaces of ‘Windows of the World’ in WTC Tower 1 and the ‘Top of the World’ Observation Deck in WTC Tower 2.  These areas of concern did not play a significant role in determining the outcomes related to the events on 11th September 2001.]

NIST WTC Recommendation 26.

NIST recommends that state and local jurisdictions adopt and aggressively enforce available provisions in building codes to ensure that egress and sprinkler requirements are met by existing buildings.*  Further, occupancy requirements should be modified where needed (such as when there are assembly use spaces within an office building) to meet the requirements in model building codes.  Provisions related to egress and sprinkler requirements in existing buildings are available in such codes as the International Existing Building Code (IEBC), International Fire Code, NFPA 1, NFPA 101, and ASME A 17.3.  For example, the IEBC defines three levels of building alteration (removal and replacement or covering of existing materials and equipment, reconfiguration of space or system or installation of new equipment, and extending the work area in excess of 50% of the aggregate area of the building).  At the lowest level, there are no upgrade implications for sprinklers and the egress system.  At the next level, sprinklers are required in work areas serving greater than 30 people if certain other conditions related to building height and use such as shared exits also are met.  There are numerous requirements for means of egress, including number of exits, specification of doorsets, dead-end corridors and travel distances, lighting, signage, and handrails.  At the highest level, the sprinkler and egress requirements are identical to the second level without the minimum 30-person restriction and the other conditions related to building height and use.  The Life Safety Code (NFPA 101) applies retroactively to all buildings, independent of whether any work is currently being done on the building, and ASME A 17.3 applies retroactively to all elevators as a minimum set of requirements.

[ * F-47  The WTC towers were unsprinklered when built.  It took nearly 28 years after passage of New York City Local Law 5 in 1973, which required either compartmentation or sprinklering, for the buildings to be fully sprinklered (the Port Authority chose not to use the compartmentation option in Local Law 5).  This was about 13 years more than the 15-year period for full compliance with Local Law 5 that was set by Local Law 84 of 1979.]

NIST WTC Recommendation 27.

NIST recommends that building codes incorporate a provision that requires building owners to retain documents, including supporting calculations and test data, related to building design, construction, maintenance, and modifications over the entire life of the building.*  Means should be developed for off-site storage and maintenance of the documents.  In addition, NIST recommends that relevant information be made available in suitably designed hard copy or electronic formats for use by emergency responders.  Such information should be easily accessible by responders during emergencies.  Model Building Codes:  Model building codes should incorporate this Recommendation.  State and local jurisdictions should adopt and enforce these requirements.

[ * F-48  The availability of inexpensive electronic storage media and tools for creating large searchable databases makes this feasible.]

NIST WTC Recommendation 28.

NIST recommends that the role of the ‘Design Professional in Responsible Charge’* be clarified to ensure that:  (1) all appropriate design professionals (including, e.g. the fire protection engineer) are part of the design team providing the highest standard of care when designing buildings employing innovative or unusual fire safety systems;**  and (2) all appropriate design professionals (including, e.g. the structural engineer and the fire protection engineer) are part of the design team providing the highest standard of care when designing the structure to resist fires, in buildings that employ innovative or unusual structural and fire safety systems.  Affected Standards:  AIA Practice Guidelines.  Model Building Codes:  The International Building Code (IBC), which already defines ‘Design Professional in Responsible Charge’, should be clarified to address this Recommendation.  NFPA 5000 should incorporate the ‘Design Professional in Responsible Charge’ concept, and address this Recommendation.

[ * F-49  In projects involving a design team, the ‘Design Professional in Responsible Charge’ – usually the lead architect – ensures that the team members use consistent design data and assumptions, co-ordinates overlapping specifications, and serves as the liaison between the enforcement and reviewing officials and the owner.  This term is defined in the International Building Code (IBC) and in the International Code Council’s Performance Code for Buildings and Facilities (where it is the Principal Design Professional).]

[ ** F-50  If the fire safety concepts in tall buildings had been sufficiently mature in the 1960’s, it is possible that the risks associated with jet-fuel ignited multi-floor fires might have been recognized and taken into account when the impact of a Boeing 707 aircraft was considered by the structural engineer during the design of the WTC towers.]

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NIST Recommendations 16-20 > Improved People Evacuation

Previous Posts in This Series …

2011-10-25:  NIST’s Recommendations on the 9-11 WTC Building CollapsesGROUP 1. Increased Structural Integrity – Recommendations 1, 2 & 3 (out of 30)

2011-11-18:  NIST WTC Recommendations 4-7 > Structural Fire EnduranceGROUP 2.  Enhanced Fire Endurance of Structures – Recommendations 4, 5, 6 & 7

2011-11-24:  NIST WTC Recommendations 8-11 > New Design of StructuresGROUP 3.  New Methods for Fire Resisting Design of Structures – Recommendations 8, 9, 10 & 11

2011-11-25:  NIST WTC Recommendations 12-15 > Improved Active ProtectionGROUP 4.  Improved Active Fire Protection – Recommendations 12, 13, 14 & 15

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2011-11-30:  SOME PRELIMINARY COMMENTS …

  1.     In the First Post of this Series, I wrote …

” As such a high level of performance is expected … indeed demanded … of a Sustainable BuildingSustainable Fire Engineering must be ‘reliability-based’ … in other words, it must have a rational, empirical and scientifically robust basis … “

Sustainable Fire Engineering must also be ‘person-centred’ … i.e. a design process (in whatever architectural or engineering discipline) which places ‘real’ people at the centre of creative endeavours and gives due consideration to their responsible needs, and their health, safety, welfare and security in the Human Environment.

In order to prolong, and if at all possible, significantly extend the Life Cycle of a Sustainable Building beyond 100 years … Fire Engineers must begin to feel at ease … and be comfortable … with the following mainstream Sustainable Design Concepts

Flexibility:  The extent to which a building interior is designed, when new, to be capable of being easily modified at any later stage during the life cycle of that building – with minimal cost and user inconvenience – because of a person’s changing living or working needs.

Adaptability:  The extent to which a building, or a building component, is designed when new, or capable of being easily modified at any later stage, to meet the changing life and living needs of the broad range of potential users, who may or may not have activity limitations, or may develop a health condition during the life cycle of that building or component.

Accessibility of a Building:  Ease of independent approach, entry, egress (during normal ambient conditions), evacuation (in the event of an emergency) and/or use of a building and its services and facilities, by all of the building’s potential users with an assurance of individual health, safety and welfare during the course of those activities.

  2.     Group 5 of the 2005 NIST WTC Recommendations is, by far, the most important … introducing some innovative concepts of ‘real’ evacuation … with nothing too startling.  Contrary to the impression given by NIST … these Recommendations are equally valid for complex building types and, in reality, for all but the most simple of low-rise buildings.  It is interesting to note, however, that when discussing fire behaviour or structural performance in fire, for example … the NIST texts are confident and direct.  Here, when dealing with ‘people’ issues … not so confident, prone to some rambling … and lacking clarity.

Shortly after the 2005 NIST Report (NCSTAR 1) was published, I stated the following on the SDI Corporate WebSite … at this FireOx International Pagehttp://www.sustainable-design.ie/fire/structdesfire.htm

” In its treatment of ‘disability’ and ‘people with activity limitations’, the Report does not go far enough, and is seriously flawed.”

Let me explain why …

As you go scan down through NIST’s Recommendations 16-20, you will encounter 1 reference to ‘mobility impaired occupants’ and  2 references to the impersonal ‘mobility impaired’.  IF (and that is still a very big ‘if’, because there is still so much rabid resistance to this topic !) … a New Post-9/11 Evacuation Model, or Construct, Dealing with ‘Disability’ is being developed … all of the major impairment groupings (i.e. visual impairment, hearing impairment, physical function impairment, mental/cognitive impairment, and psychological impairment) must be added to the mix from the beginning.  In other words, our proper focus of attention must be ‘people with activity limitations’ … not just people with disabilities, but also frail older people (not all older people !), children under the age of 5 years, women in the later stages of pregnancy, people with a health condition, etc.

And … because of the social stigma still firmly attaching to ‘disability’ … many building occupants/users will not self-identify … not even if their lives depend on it !

Concentrating on one group only, i.e. people with mobility impairments, is simplistic and entirely inadequate … and we will all end up, in a few years time, having to graft on a consideration of the other impairment groups.

This is exactly what has already gone wrong with the development of Accessibility Design Guidance during the last 30 years … where ‘people with visual or hearing impairments’ received merely token attention … and ‘people with cognitive or psychological impairments’ received no attention at all !   And … we are now grappling with the challenge of having to graft on additional texts to try to re-balance International Design Guidance on Accessibility of the Built Environment.  Been there – done that – I have all of the t-shirts !!

People with Activity Limitations (English) / Personnes à Performances Réduites (French):  Those people, of all ages, who are unable to perform, independently and without aid, basic human activities or tasks – because of a health condition or physical/mental/cognitive/psychological impairment of a permanent or temporary nature.

The above Terms (in English and French) include …

  • wheelchair users ;
  • people who experience difficulty in walking, with or without a facilitation aid, e.g. stick, crutch, calliper or walking frame ;
  • frail, older people ;
  • the very young (people under the age of 5 years) ;
  • people who suffer from arthritis, asthma, or a heart condition ;
  • the visually and/or hearing impaired ;
  • people who have a cognitive impairment disorder, including dementia, amnesia, brain injury, or delirium ;
  • women in the later stages of pregnancy ;
  • people impaired following the use of alcohol, other ‘social’ drugs e.g. cocaine and heroin, and some medicines ;
  • people who suffer any partial or complete loss of language related abilities, i.e. aphasia ;
  • people impaired following exposure to environmental pollution and/or other irresponsible human activities, e.g. war and terrorism ;

and …

  • people who experience a panic attack in a fire situation or other emergency ;
  • people, including firefighters, who suffer incapacitation as a result of exposure, during a fire, to poisonous or toxic substances, and/or elevated  temperatures.

  3.     So … what provision should be made for ‘people with activity limitations’ in typical Fire Engineering Design Projects ?

Equivalent to the concept of Maximum Credible Fire Scenario, which has already been discussed in this Series … at FireOx International, some years ago, we developed the concept of …

Maximum Credible User Scenario

Representing building user conditions which are also severe but reasonable to anticipate …

a)   10% of People Using the Building (occupants, visitors and other users) have an Impairment (visual or hearing, physical function, mental or cognitive, psychological, with some impairments not being identifiable) ;

[ This performance indicator appears in ISO FDIS 21542: ‘Building Construction – Accessibility & Usability of the Built Environment’, which will soon be published.]

b)   The Number of People Using a Building increases, on occasions which cannot be specified, to 120% of designed/calculated maximum building capacity.

[ Generally … the fire safety related texts contained in ISO 21542 are based on the 2005 & 2008 NIST WTC Recommendations.]

  4.     With regard to Recommendation 17 below, and NIST’s reference to the widths of evacuation staircases and door openings, etc … fire codes and regulations, fire authorities having jurisdiction (AHJ’s), and even the fire services themselves … still have a crazy mixed-up approach to defining the width of these building features … an approach which I am not even going to attempt to repeat !   Forget it !!

Without Exception … all understandings of Evacuation Route Width, Evacuation Staircase Width and Evacuation Door Opening Width … must be harmonized with the following definitions of Unobstructed Width

Unobstructed Width – General

Free, unobstructed space – clear of all obstacles below a height of 2.1 metres above finished floor level – necessary for passage along a circulation route, or other route component, e.g. a staircase.

[ For example … the Unobstructed Width of a Staircase is the clear dimension from the edge of one handrail to the edge of the opposite handrail … and there is always a continuous handrail on each side of an evacuation staircase ! ]

Unobstructed Width – Door Opening

Free, unobstructed space – clear of all obstacles below a height of 2.0 metres above finished floor level – necessary for passage through a door opening, measured when the door leaf is opened to an angle of 90°, or when a sliding or folding door leaf is opened to its fullest extent.

[ For example … the Unobstructed Width of a Door Opening is the dimension from the edge of the door leaf (when open at an angle of 90°) to the nearest edge of the door frame.]

This FireOx International Page on the SDI Corporate WebSite provides more guidance … http://www.sustainable-design.ie/fire/appendixd.htm

  5.     With regard to Recommendation 20 below, and NIST’s reference to allowing “all occupants an equal opportunity for evacuation” … this is not just a ‘nice idea’, or an ‘idealistic notion’ … this is now a Human and Social Right which is backed up and supported by International Law !   And … it is no longer acceptable for the Fire Science and Engineering Community to continue its stubborn resistance in the face of this fact !!

For the benefit of my fire engineering colleagues … I will, once again here, reproduce the most relevant extracts from the United Nations Convention on the Rights of Persons with Disabilities …

UN CRPD  Preamble Paragraph (g)

Emphasizing the importance of mainstreaming disability issues as an integral part of relevant strategies of sustainable development, …

UN CRPD  Article 9 – Accessibility

1.  To enable persons with disabilities to live independently and participate fully in all aspects of life, States Parties shall take appropriate measures to ensure to persons with disabilities access, on an equal basis with others, to the physical environment, to transportation, to information and communications, including information and communications technologies and systems, and to other facilities and services open or provided to the public, both in urban and in rural areas.  These measures, which shall include the identification and elimination of obstacles and barriers to accessibility, shall apply to, inter alia:

(a)  Buildings, roads, transportation and other indoor and outdoor facilities, including schools, housing, medical facilities and workplaces ;

(b)  Information, communications and other services, including electronic services and emergency services.

2.  States Parties shall also take appropriate measures:

(a)  To develop, promulgate and monitor the implementation of minimum standards and guidelines for the accessibility of facilities and services open or provided to the public ;

(b)  To ensure that private entities that offer facilities and services which are open or provided to the public take into account all aspects of accessibility for persons with disabilities ;

(c)  To provide training for stakeholders on accessibility issues facing persons with disabilities ;

(d)  To provide in buildings and other facilities open to the public signage in Braille and in easy to read and understand forms ;

(e)  To provide forms of live assistance and intermediaries, including guides, readers and professional sign language interpreters, to facilitate accessibility to buildings and other facilities open to the public ;

(f)  To promote other appropriate forms of assistance and support to persons with disabilities to ensure their access to information ;

(g)  To promote access for persons with disabilities to new information and communications technologies and systems, including the Internet ;

(h)  To promote the design, development, production and distribution of accessible information and communications technologies and systems at an early stage, so that these technologies and systems become accessible at minimum cost.

UN CRPD  Article 11 – Situations of Risk & Humanitarian Emergencies

States Parties shall take, in accordance with their obligations under international law, including international humanitarian law and international human rights law, all necessary measures to ensure the protection and safety of persons with disabilities in situations of risk, including situations of armed conflict, humanitarian emergencies and the occurrence of natural disasters.

[ Note:  An outbreak of fire in a building is a situation of serious risk for all vulnerable building occupants/users.]

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At the time of writing, 153 Countries had signed the UN CRPD … while 106 Countries have ratified the Convention and are, therefore, the ‘State Parties’ referred to above.

These are just a few of the State Parties to the UN CRPD …

  • Argentina  (ratified the UN CRPD, 2008-09-02)
  • Australia  (ratified the UN CRPD, 2008-07-17)
  • Brazil  (ratified the UN CRPD, 2008-08-01)
  • Canada  (ratified the UN CRPD, 2010-03-11)
  • China  (ratified the UN CRPD, 2008-08-01)
  • Cuba  (ratified the UN CRPD, 2007-09-06)
  • European Union  (ratified the UN CRPD, 2010-12-23)
  • India  (ratified the UN CRPD, 2007-10-01)
  • Malaysia  (ratified the UN CRPD, 2010-07-19)
  • Mexico  (ratified the UN CRPD, 2007-12-17)
  • Philippines  (ratified the UN CRPD, 2008-04-15)
  • South Africa  (ratified the UN CRPD, 2007-11-30)
  • Turkey  (ratified the UN CRPD, 2009-09-28)
  • United Arab Emirates  (ratified the UN CRPD, 2010-03-19)

I wonder how implementation is proceeding in these countries !?!

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2005 NIST WTC RECOMMENDATIONS

GROUP 5.  Improved Building Evacuation

Building evacuation should be improved to include system designs that facilitate safe and rapid egress, methods for ensuring clear and timely emergency communications to occupants, better occupant preparedness regarding their roles and duties for evacuation during emergencies, and incorporation of appropriate egress technologies.*

[ * F-36  This effort should include standards and guidelines for the development and evaluation of emergency evacuation plans, including best practices for both partial and full evacuation, and the development of contingency plans that account for expected conditions that may require adaptation, including the compromise of all or part of an egress path before or during evacuation, or conditions such as widespread power failure, earthquake, or security threat that restrict egress from the building.  Evacuation planning should include the process from initial notification of the need to evacuate up to the point when occupants arrive at a place where their safety is ensured.  These standards and guidelines should be suitable for assessing the adequacy of evacuation plans submitted for approval, and should require occupant training through the conduct of regular drills.]

NIST WTC Recommendation 16.

NIST recommends that public agencies, non-profit organizations concerned with building and fire safety, and building owners and managers develop and carry out public education and training campaigns, jointly and on a nationwide scale, to improve building occupants’ preparedness for evacuation in case of building emergencies.  This effort should include better training and self-preparation of occupants, an effectively implemented system of floor wardens and building safety personnel, and needed improvements to standards.  Occupant preparedness should include:

a.     Improved training and drills for building occupants to ensure that they know evacuation procedures for a variety of emergency scenarios (e.g. including evacuation and shelter in place), are familiar with the egress route, and are sufficiently aware of what is necessary if evacuation is required with minimal notice (e.g. footwear consistent with the distance to be travelled, a flashlight/glow stick for pathway illumination, and dust masks).

b.     Building owners and managers should educate tenants on the life safety systems present in their building(s), provide training materials explaining egress routes and stairwell and elevator information, and develop educational programmes explaining the most appropriate responses in emergency situations.  It is further recommended that the owners and managers of office buildings implement the necessary systems for collecting and storing the training history of each building occupant.

c.     Improved training and drills that routinely inform building occupants that roof rescue is not (or is) presently feasible as a standard evacuation option, that they should evacuate down the stairs in any full-building evacuation unless explicitly instructed otherwise by on-site incident commanders, and that elevators can be used if they are still in service and haven’t been recalled or stopped.

d.     Improved codes, laws, and regulations that do not restrict or impede building occupants during evacuation drills from familiarizing themselves with the detailed layout of alternative egress routes for a full building evacuation.*

[ * F-37  New York City Local Law 5 prohibits requiring occupants to practice stairwell evacuation during drills.]

Affected Standard:  ICC/ANSI A117-1.  Model Building and Fire Codes:  The standard should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard.  Affected Organizations:  NFPA, NIBS, NCSBCS, BOMA, and CTBUH.

NIST WTC Recommendation 17.

NIST recommends that tall buildings be designed to accommodate timely full building evacuation of occupants when required in building-specific or large-scale emergencies such as widespread power outages, major earthquakes, tornadoes, hurricanes without sufficient advance warning, fires, explosions, and terrorist attack.  Building size, population, function, and iconic status should be taken into account in designing the egress system.  Stairwell capacity and stair discharge door opening width* should be adequate to accommodate contraflow due to emergency access by responders.

[ * F-38  Egress capacity should be based on an all-hazards approach that considers the number and width of stairs (and door openings) as well as the possible use of scissor stairs credited as a single stair.]

a.     Improved egress analysis models, design methodology, and supporting data should be developed to achieve a target evacuation performance (e.g. time for full building evacuation*) for the design building population by considering the building and egress system designs, and human factors such as occupant size, mobility status, stairwell tenability conditions, visibility, and congestion.

[ * F-39  Use of egress models is required to estimate the egress capacity for a range of different evacuation strategies, including full building evacuation.  NIST found that the average surviving occupant in the WTC towers descended stairwells at about half the slowest speed previously measured for non-emergency evacuations.]

b.     To the degree possible, mobility impaired occupants should be provided a means for self-evacuation in the event of a building emergency.  Current strategies (and law) generally require the mobility impaired to shelter in place.  New procedures, which provide redundancy in the event that the floor warden system or co-worker assistance (i.e. a buddy system) fails, should consider full building evacuation, and may include use of fire-protected and structurally hardened elevators,* motorized evacuation technology (e.g. a battery-operated evacuation chair), and/or dedicated communication technologies for the mobility impaired.

[ * F-40  Elevators should be explicitly designed to provide protection against large, but conventional, building fires.  Fire-protected elevators also should be structurally hardened to withstand the range of foreseeable building-specific or large-scale emergencies.  While progress has been made in developing the requirements and technologies for fire-protected elevators, similar criteria and designs for structurally hardened elevators remain to be developed.]

c.     If protected/hardened elevators are provided for emergency responders but become unusable during an emergency, due to a malfunction or a conventional threat whose magnitude exceeds the magnitude considered in design, sufficient stairwell capacity should be provided to ensure timely emergency responder access to buildings that are undergoing full evacuation.  Such capacity could be provided either via dedicated stairways for fire service use or by building sufficient stairway capacity (i.e. number and width of stairways and/or use of scissor stairs credited as a single stair) to accommodate the evacuation of building occupants while allowing access to emergency responders with minimal hindrance from occupant contraflow.

d.     The egress allowance in assembly use spaces should be limited in state and local laws and regulations to no more than a doubling of the stairway capacity for the provision of a horizontal exit on a floor, as is the case now in the national model codes.*  The use of a horizontal exit creates an area of refuge with a 2 hour fire rated separation, at least one stair on each side, and sufficient space for the expected occupant load.

[ * F-41  The New York City Building Code permits a doubling of allowed stair capacity when one area of refuge is provided on a floor, and a tripling of stair capacity for two or more areas of refuge on a floor.  In the world after 11 September 2001, it is difficult to predict: (1) if, and for how long, occupants will be willing to wait in a refuge area before entering an egress stairway; and (2) what the impact would be of such a large group of people moving down the stairs on the orderly evacuation of lower floors.]

Affected Standards:  NFPA 101, ASME A 17.  Model Building and Fire Codes:  The standards should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard.

NIST WTC Recommendation 18.

NIST recommends that egress systems be designed:  (1) to maximize remoteness of egress components (i.e. stairs, elevators, exits) without negatively impacting on average travel distances;  (2) to maintain their functional integrity and survivability under foreseeable building-specific or large-scale emergencies;  and (3) with consistent layouts, standard signage, and guidance so that systems become intuitive and obvious to building occupants during evacuations.

a.     Within a safety-based design hierarchy that should be developed, highest priority should be assigned to maintain the functional integrity, survivability, and remoteness of egress components and active fire protection systems (sprinklers, standpipes, associated water supply, fire alarms, and smoke management systems).  The design hierarchy should consider the many systems (e.g. stairs, elevators, active fire protection, mechanical, electrical, plumbing, and structural) and system components, as well as functional integrity, tenant access, emergency responder access, building configuration, security, and structural design.

b.     The design, functional integrity, and survivability of the egress and other life safety systems (e.g. stairwell and elevator shafts, and active fire protection systems) should be enhanced by considering accidental structural loads such as those induced by overpressures (e.g. gas explosions), impacts, or major hurricanes and earthquakes, in addition to fire separation requirements.  In selected buildings, structural loads due to other risks such as those due to terrorism may need to be considered.  While NIST does not believe that buildings should be designed for aircraft impact, as the last line of defence for life safety, the stairwells and elevator shafts individually, or the core if these egress components are contained within the core, should have adequate structural integrity to withstand accidental structural loads and anticipated risks.

c.     Stairwell remoteness requirements should be met by a physical separation of the stairwells that provide a barrier to both fire and accidental structural loads.  Maximizing stairwell remoteness, without negatively impacting on average travel distances, would allow a stairwell to maintain its structural integrity independent of any other stairwell that is subject to accidental loads, even if the stairwells are located within the same structural barrier such as the core.  The current ‘walking path’ measurement allows stairwells to be physically next to each other, separated only by a fire barrier.  Reducing the clustering of stairways that also contain standpipe water systems provides the fire service with increased options for formulating firefighting strategies.  This should not preclude the use of scissor stairs* as a means of increasing stair capacity – provided the scissor stair is only credited as a single stair.

[ * F-42  Two separate stairways within the same enclosure and separated by a fire rated partition.]

d.     Egress systems should have consistent layouts with standard signage and guidance so that the systems become intuitive and obvious to all building occupants, including visitors, during evacuations.  Particular consideration should be given to unexpected deviations in the stairwells (e.g. floors with transfer hallways).

Affected Standard:  NFPA 101.  Model Building and Fire Codes:  The standard should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard.

NIST WTC Recommendation 19.

NIST recommends that building owners, managers, and emergency responders develop a joint plan and take steps to ensure that accurate emergency information is communicated in a timely manner to enhance the situational awareness of building occupants and emergency responders affected by an event.  This should be accomplished through better co-ordination of information among different emergency responder groups, efficient sharing of that information among building occupants and emergency responders, more robust design of emergency public address systems, improved emergency responder communication systems, and use of the Emergency Broadcast System (now known as the Integrated Public Alert and Warning System) and Community Emergency Alert Networks.

a.     Situational awareness of building occupants and emergency responders in the form of information and event knowledge should be improved through better co-ordination of such information among emergency responder groups (9-1-1 dispatch, fire department or police department dispatch, emergency management dispatch, site security, and appropriate federal agencies), efficient sharing and communication of information between building occupants and emergency responders, and improved emergency responder communication systems (i.e. including effective communication within steel and reinforced concrete buildings, capacity commensurate with the scale of operations, and interoperability among different communication systems.

b.     The emergency communications systems in buildings should be designed with sufficient robustness and redundancy to continue providing public address announcements or instructions in foreseeable building-specific or large-scale emergencies, including widespread power outage, major earthquakes, tornadoes, hurricanes, fires, and accidental explosions.  Consideration should be given to placement of building announcement speakers in stairways in addition to other standard locations.

c.     The Integrated Public Alert and Warning System (IPAWS) should be activated and used, especially during large-scale emergencies, as a means to rapidly and widely communicate information to building occupants and emergency responders to enhance their situational awareness and assist with evacuation.

d.     Local jurisdictions (cities and counties or boroughs) should seriously consider establishing a Community Emergency Alert Network (CEAN), within the framework of IPAWS, and make it available to the citizens and emergency responders of their jurisdictions to enhance situational awareness in emergencies.*  The network should deliver important emergency alerts, information and real time updates to all electronic communication systems or devices registered with the CEAN.  These devices may include e-mail accounts, cell/mobile phones, text pagers, satellite phones, and wireless PDA’s.

[ * F-43  Types of emergency communications could include life safety information, severe weather warnings, disaster notifications (including information on terrorist attacks), directions for self-protection, locations of nearest available shelters, precautionary evacuation information, identification of available evacuation routes, and accidents or obstructions associated with roadways and utilities.]

Affected Standard:  NFPA 101, and/or a new standard.  Model Building and Fire Codes:  The standard should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard to the extent it is within the scope of building and fire codes.

NIST WTC Recommendation 20.

NIST recommends that the full range of current and next generation evacuation technologies should be evaluated for future use, including protected/hardened elevators, exterior escape devices, and stairwell descent devices, which may allow all occupants an equal opportunity for evacuation and facilitate emergency response access.  Affected Standards:  NFPA 101, ASME A 17, ASTM E 06, ANSI A117.1.  Model Building and Fire Codes:  The standards should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard.

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NIST WTC Recommendations 12-15 > Improved Active Protection

Previous Posts in This Series …

2011-10-25:  NIST’s Recommendations on the 9-11 WTC Building CollapsesGROUP 1. Increased Structural Integrity – Recommendations 1, 2 & 3 (out of 30)

2011-11-18:  NIST WTC Recommendations 4-7 > Structural Fire EnduranceGROUP 2.  Enhanced Fire Endurance of Structures – Recommendations 4, 5, 6 & 7

2011-11-24:  NIST WTC Recommendations 8-11 > New Design of StructuresGROUP 3.  New Methods for Fire Resisting Design of Structures – Recommendations 8, 9, 10 & 11

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2011-11-25:  SOME PRELIMINARY COMMENTS …

  1.     Reliability has always been an issue with Active Fire Protection Systems … but, it is neither acknowledged, nor fully understood, that … Reliability Is Equally An Issue With Passive Fire Protection Measures !

Furthermore, the following should always be taken into account when considering the Safety Factors to be applied in calculating the level of satisfactory fire safety and protection which is provided in a specific project … one of the design objectives in Ethical Fire Engineering.

For example, if Category C below is indicative of the design and construction quality on a particular building site … just think of the Priory Hall Apartment Development in Dublin (!) … the Safety Factors to be applied in the design should be high … and with regard to actual construction, it should be expected that the Reliability of both Active Fire Protection Systems and Passive Fire Protection Measures will be initially low … with Life Cycle Reliability being entirely non-existent.

Quality of Fire Engineering Design & Related Construction 

Category A

(a)   Design of the works is exercised by an independent, appropriately qualified and experienced architect/engineer/fire engineer, with design competence relating to fire safety and protection in buildings … and, most importantly, that he/she interacts directly with the Project Design Professional in Responsible Charge ;

(b)   Installation/fitting of related construction products/systems is exercised by appropriately qualified and experienced personnel, with construction competence relating to fire safety and protection in buildings ;

(c)   Supervision of the works is exercised by appropriately qualified and experienced personnel from the principal construction organization ;

(d)   Regular inspections, by appropriately qualified and experienced personnel familiar with the design, and independent of the construction organization(s), are carried out to verify that the works are being executed in accordance with the fire engineering design.

Category B

(a)   Design of the works is exercised by an independent, appropriately qualified and experienced architect/engineer/fire engineer ;

(b)   Installation/fitting of fire-related construction products/systems is exercised by appropriately qualified and experienced personnel ;

(c)   Supervision of the works is exercised by appropriately qualified and experienced personnel from the principal construction organization.

Category C

This level of design and construction execution is assumed when the requirements for Category A or Category B are not met.

  2.     With regard to Recommendations 12 & 13 below … in an earlier post in this series, and elsewhere, I have defined Disproportionate Damage … and differentiated that structural concept from the related concept of Fire-Induced Progressive Collapse.

A significant number of countries include a requirement on Resistance to Disproportionate Damage in their national building codes.  Often, it is only necessary to consider this requirement in the case of buildings having 5 Storeys, or more … a completely arbitrary height threshold.  I would consider that adequately tying together the horizontal and vertical structural elements of a building … any building … is a fundamental principle of good structural engineering !!

Putting it simply … for the purpose of showing compliance with this structural requirement … it is necessary to demonstrate that a building will remain structurally stable if a portion of the building’s structure is removed … always remembering that every building comprises both structure and fabric, i.e. non-structure.

In reality this may happen, and quite often does happen, when, for example, a large truck runs into the side of a building, which can happen anywhere … or there is a gas explosion in some part of the building, which happened in Dublin’s Raglan House back in 1987, and many times in other countries … or a plane hits a high-rise building, which happened to Milan’s iconic Pirelli Tower in 2002, and to New York’s Empire State Building way back in 1945 … etc., etc.  Raglan House collapsed … the Pirelli Tower and the Empire State Building did not.

[ The World Trade Center Towers were originally designed to absorb the impact of a large plane and to remain structurally stable afterwards … in ambient conditions.  However, what was not considered in the ambient structural design was ‘fire’, i.e. the fuel tanks were empty and no fire in the building would be initiated as a result of the mechanical damage caused by the plane impact … which, on 11 September 2001, proved to be a ridiculous basis for any structural design !   This is why 9-11 should be regarded, at its core, as being a very serious ‘real’ fire incident.]

What I am leading up to is this … the concept of removing a portion of a building, and it remaining structurally stable afterwards … should now – logically and rationally – also be incorporated into the fire engineering design of Active Fire Protection Systems.  In other words, if a portion of a building is removed, will any particular Active Fire Protection System continue to operate effectively in the rest of the building ?   This has implications for the location and adequate protection of critical system components in a building … and for the necessary redundancy, zoning and back-up alternative routeing which must be designed into the system from the beginning !

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2005 NIST WTC RECOMMENDATIONS

GROUP 4.  Improved Active Fire Protection

Active fire protection systems (i.e. sprinklers, standpipes/hoses, fire alarms, and smoke management systems) should be enhanced through improvements to the design, performance, reliability, and redundancy of such systems.

NIST WTC Recommendation 12.

NIST recommends that the performance and possibly the redundancy of active fire protection systems (sprinklers, standpipes/hoses, fire alarms, and smoke management systems) in buildings be enhanced to accommodate the greater risks associated with increasing building height and population, increased use of open spaces, high-risk building activities, fire department response limits, transient fuel loads, and higher threat profile.  The performance attributes should deal realistically with the system design basis, reliability of automatic/manual operations, redundancy, and reduction of vulnerabilities due to single point failures.  Affected Standards:  NFPA 13, NFPA 14, NFPA 20, NFPA 72, NFPA 90A, NFPA 92A, NFPA 92B, and NFPA 101.  Model Building Codes:  The performance standards should be adopted in model building codes by mandatory reference to, or incorporation of, the latest edition of the standard.

NIST WTC Recommendation 13.

NIST recommends that fire alarm and communications systems in buildings be developed to provide continuous, reliable, and accurate information on the status of life safety conditions at a level of detail sufficient to manage the evacuation process in building fire emergencies;  all communication and control paths in buildings need to be designed and installed to have the same resistance to failure and increased survivability above that specified in present standards.  This should include means to maintain communications with evacuating occupants that can both reassure them and redirect them if conditions change.  Pre-installed fire warden telephone systems can serve a useful purpose and may be installed in buildings and, if so, they should be made available for use by emergency responders.  All communication and control paths in buildings need to be designed and installed to have the same resistance to failure and increased survivability above that specified in present standards.  Affected Standards:  NFPA 1, NFPA 72, and NFPA 101.  Model Building and Fire Codes:  The performance standards should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard.

NIST WTC Recommendation 14.

NIST recommends that control panels at fire/emergency command stations in buildings be adapted to accept and interpret a larger quantity of more reliable information from the active fire protection systems that provide tactical decision aids to fire ground commanders, including water flow rates from pressure and flow measurement devices, and that standards for their performance be developed.  Affected Standards:  NFPA 1, NFPA 72, and NFPA 101.  Model Building and Fire Codes:  The performance standards should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard.

NIST WTC Recommendation 15.

NIST recommends that systems be developed and implemented for:  (1) real time off-site secure transmission of valuable information from fire alarm and other monitored building systems for use by emergency responders, at any location, to enhance situational awareness and response decisions, and maintain safe and efficient operation;*  and (2) preservation of that information either off-site, or in a black box that will survive a fire or other building failure, for purposes of subsequent investigations and analysis.  Standards for the performance of such systems should be developed, and their use should be required.  Affected Standards:  NFPA 1, NFPA 72, and NFPA 101.  Model Building and Fire Codes:  The performance standards should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard.

[ * F-35  The alarm systems in the WTC towers were only capable of determining and displaying: (a) areas that had at some time reached alarm point conditions; and (b) areas that had not.  The quality and reliability of information available to emergency responders at the Fire Command Station was not sufficient to understand the fire conditions.  The only information transmitted outside the buildings was the fact that the buildings had gone into alarm.  Further, the fire alarm system in WTC Building 7, which was transmitted to a monitoring service, was on ‘test mode’ during the morning of 11 September 2001, because routine maintenance was being performed.  Under test mode conditions: (1) the system is typically disabled for the entire building, not just for the area where work is being performed; and (2) alarm signals typically do not show up on an operator console.]

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Sustainable Fire Engineering – IABSE Lecture 1 December 2011

2011-11-14 …

On Thursday evening, 1st December 2011, at 19.00 hrs … in the Dublin Institute of Technology … I will present an IABSE-Ireland Sponsored Lecture on the subject: ‘Sustainable Fire Engineering IS THE FUTURE !’.

This Presentation has been in continuous development across a snaking international path … Dubayy (UAE) in 2008 … Lund (Sweden) and Bengaluru (India) in 2009 … Dilli (India), Zurich (Switzerland) and Dublin (Ireland) in 2010 … Paris (France), the IFE’s International Fire Conference in Cardiff (Wales) and the ASFP-Ireland Fire Seminar in 2011 … and on 1 December next, in Dublin, I will be introducing some tough new realities for fire engineering generally … not just in Ireland …

Colour photograph showing the impact of witnessing the 9-11 WTC Incident in New York. Sustainable Fire Engineering must be 'reliability-based' & 'person-centred'. But ... do building designers, including fire engineers, actually understand that the people who use their buildings are 'individuals' ... each having a different range of abilities ? Photograph by Marty Lederhandler/AP. Click to enlarge.

Colour photograph showing the impact of witnessing the 9-11 WTC Incident in New York. Sustainable Fire Engineering must be 'reliability-based' & 'person-centred'. But ... do building designers, including fire engineers, actually understand that the people who use their buildings are 'individuals' ... each having a different range of abilities ? Photograph by Marty Lederhandler/AP. Click to enlarge.

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IABSE Irish National Group Sponsored Lecture

Dublin Institute of Technology, Bolton Street – Michael O’Donnell Room (259)

Thursday, 1 December 2011 @ 19.00 hrs / 7.00 p.m.

CJ Walsh: Sustainable Fire Engineering IS THE FUTURE !  (Lecture Flyer, PDF File, 259 kb)

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The aim of Sustainable Fire Engineering is to realize a safe and sustainable built environment.

Responding ethically, in built and/or wrought form, to the still evolving concept of sustainable human and social development … a principal objective of Sustainable Fire Engineering is to design for maximum credible fire and user scenarios … in order to maintain a proper and satisfactory level of fire safety and protection over the full life cycle of, for example, a building … and for a Sustainable Building, that life cycle is 100 years minimum.

Sustainable Fire Engineering must, therefore, be ‘reliability-based’ & ‘person-centred’.

This presentation will examine the authentic language and meaning of sustainability … and will then track how this impacts on the professional practice of fire engineering.  Special mention will be made of Fire-Induced Progressive Collapse.

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See you all there !   And I will be looking forward to a lot of challenging feedback on the night !!

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