World Trade Center

Upcoming CIB/NIST Workshop on Structural Reliability in Fire ?!?

2014-05-16:  Anybody with even the slightest interest in the Future Development of Fire Engineering Design, and Structural Fire Engineering in particular, should pay attention to the proceedings of an upcoming CIB/NIST Workshop, which will be held on 21-22 May 2014, at the NIST Campus in Maryland, USA …

CIB/NIST Fire Resistance/Resistant/Resisting/Resistive Structures Workshop

It is essential to read 3 White Papersproduced by three separate teams of experts, contracted by NIST, in advance of the Workshop … to get a ‘real’ flavour of how discussions may, or may not, develop next week.  All three papers are available to download from the NIST WebSite (and the links below).  I suggest that you get your hands on them … ASAP !

1.   Fire Behaviour of Steel Structures (March 2014).  20 Pages, 786 Kb.
2.   State-of-the-Art on Fire Resistance of Concrete Structures: Structure-Fire Model Validation (March 2014).  32 Pages, 1.26 Mb.
3.   Fire Resistance of Timber Structures (March 2014).  20 Pages, 998 Kb.

After reading these 3 NIST White Papers … I was not surprised by the large number of ‘unknowns’, or the enormous gaps in our ‘knowns’ …

Taken in whole and all together, however, the three documents are a public confirmation that today’s general practice of Fire Engineering is more akin to that of mid-19th Century Alchemy.  Blinkered practitioners are isolated from the building design process … because they have no understanding of that process, and have no means of effective communication with the many other design disciplines involved.  And minimal, i.e. ‘cost-effective'(?), compliance with the limited and inadequate fire safety objectives in current building codes/regulations is widely regarded as the one and only target for their efforts … a minor one compared to the fundamental, long-term target of realizing a Safe, Resilient and Sustainable Built Environment for All.  At the same time, frontline fire service personnel are forced to operate on shoestring budgets … and, when a fire emergency inevitably occurs, they are regarded as nothing more than an expendable resource.

!!  Structure … Does Not A Building Make  !!

Some comments on the 3 NIST White Papers …

A.  The Papers contain a number of important technical errors:

  • A similar Introduction in two of the Papers refers only to the 2005 NIST Report (NCSTAR 1) on the 9-11 Collapse of WTC Buildings 1 & 2 in New York City, which contained 30 Recommendations.  However, NIST published a later Report in 2008 (NCSTAR 1A) on the Collapse of WTC Building 7, which contained a further 13 Recommendations … 1 new, and 12 revised/updated from the earlier 2005 Report.
  • There is a reference in one of the Papers to a 1989 European Directive on Construction Products (89/106/EEC), and as later amended.  This Directive was repealed, in 2011, by Article 65 of the new European Union (EU) Regulation No.305/2011 on Construction Products.  Unlike a Directive, a Regulation is addressed directly to the EU Member States, and does not permit any flexibility with regard to national implementation. Annex I of Regulation 305/2011 sets out 7 Basic Requirements for Construction Works:

–  Mechanical resistance and stability ;
–  Safety in case of fire ;
–  Hygiene, health and the environment ;
–  Safety and accessibility in use ;
–  Protection against noise ;
–  Energy economy and heat retention ;
–  Sustainable use of natural resources.

Concerning fire safety in buildings … it is incorrect to state, or even suggest, that only the second Basic Requirement is relevant … a building must satisfy all of the Basic Requirements taken together, i.e. the 7 Basic Requirements are inter-dependent.

B.  Having carefully read the Papers … none of the expert teams appear to have paid any attention to any of the NIST Recommendations, in either the 2005 or the 2008 Reports !   Note well that two separate series of posts on both sets of NIST Recommendations have been carried here on this Technical Blog.

C.  If we have learned anything from the WTC 9-11 Building Collapses, it is that the Fire Engineer must be able to communicate effectively with other mainstream building design disciplines … especially ‘ambient’ structural engineers who speak the language of Structural Reliability, Limit State Design and Serviceability Limit States.  The Fire Engineer must also become an active participant in the creative, trans-disciplinary process of design.  These issues have not been seriously considered in any of the Papers.

D.  All of the Papers lack a common and precise starting point … relevant structural fire engineering concepts are either not defined or badly defined … and the ‘dynamic, complex architectural interaction between a building’s structure and fabric under conditions of fire’ requires immediate and urgent investigation …

Structural Reliability

The ability of a structural system to fulfil its design purpose, for a specified time,
under the actual environmental conditions encountered in a building.

Structural Fire Engineering

Those aspects of fire engineering concerned with structural design for fire …
and the dynamic, complex architectural interaction between a building’s structure and
fabric, i.e. non-structure … under conditions of fire and its immediate aftermath,
including but not confined to the ‘cooling phase’.

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.

[ *fire serviceability limit states ]

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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 and Disproportionate Damage are fundamental concepts in the Fire Engineering Design of All Buildings ! ]

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E.  It is not acknowledged in any of the Papers that the Fire Safety Objectives in Current Building Codes/Regulations are, of necessity, limited in scope … and entirely inadequate in the context of Annex I in EU Regulation 305/2011, and the long-term goal of realizing a Safe, Resilient and Sustainable Built Environment for All.  Refer to the updated Scope, Aims & Objectives of CIB Working Commission 14: ‘Fire Safety’.

F.  Once and for all … use of the term Fire Resistance (and any number of variations thereof, e.g. resistant, resisting, resistive, etc.) in connection with any aspect of structural performance in fire … is ridiculous !   It is roughly comparable to use of the term Fire Proof during the first half of the 20th Century.

G.  Finally, for now … the current unwise focus on Crude Pass/Fail Results from the ‘standard fire’ testing of single loadbearing structural elements must evolve … must be transformed into the more detailed and precise measurement of all aspects of ‘real’ structural system performance over the full duration of a ‘design’ fire (including the cooling phase afterwards) … using a much wider range of performance monitoring equipment, e.g. short wave infra-red thermography.

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It is no longer acceptable for Fire Engineering to exist in an isolated Twilight Zone … completely removed from the everyday realities of Mainstream Building & Construction.

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Sustainable Fire Engineering Design – Targeting & MRV !

2014-04-20:  Traditional/Conventional Fire Engineering Practice is slowly, but inevitably, being transformed … in order to meet the regional and local challenges of rapid urbanization and climate change, the pressing need for a far more efficient and resilient building stock, and a growing social awareness that ‘sustainability’ demands much greater human creativity …

Design Target:  A Safe, Resilient and Sustainable Built Environment for All

Design Key Words:  Reality – Reliability – Redundancy – Resilience

Essential Construction & Occupancy Start-Up Processes:  Careful Monitoring & Reporting – Independent Verification of Performance (MRV)

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Sustainable Fire Engineering Design Solutions:

Are Reliability-Based …
The design process is based on competence, practical experience, and an understanding of ‘real’ building performance and resilience during Extreme Man-Made Events, e.g. 2001 WTC 9-11 Attack & 2008 Mumbai Hive Attacks, and Hybrid Disasters, e.g. 2011 Fukushima Nuclear Incident … rather than theory alone.

Are Person-Centred …
‘Real’ people are placed at the centre of creative design endeavours and proper consideration is given to their responsible needs … their health, safety, welfare and security … in the Human Environment, which includes the social, built, economic and virtual environments.

Are Adapted to Local Context & Heritage *
Geography, orientation, climate (including change, variability and severity swings), social need, culture, traditions, economy, building crafts and materials, etc., etc.
[* refer to the 2013 UNESCO Hangzhou Declaration]

In Sustainable Design … there are NO Universal Solutions !

Design Objectives:

To protect society, the best interests of the client/client organization and building user health and safety, and to maintain functionality under the dynamic, complex conditions of fire … Project-Specific Fire Engineering Design Objectives shall cover the following spectrum of issues …

  • Protection of the Health and Safety of All Building Users … including people with activity limitations (2001 WHO ICF), visitors to the building who will be unfamiliar with its layout, and contractors or product/service suppliers temporarily engaged in work or business transactions on site ;
  • Protection of Property from Loss or Damage … including the building, its contents, and adjoining or adjacent properties ;
  • Safety of Firefighters, Rescue Teams and Other Emergency Response Personnel ;
  • Ease and Reasonable Cost of ‘Effective’ Reconstruction, Refurbishment or Repair Works after a Fire ;
  • Sustainability of the Human Environment – including the fitness for intended use and life cycle costing of fire engineering related products, systems, etc … fixed, installed or otherwise incorporated in the building ;
  • Protection of the Natural Environment from Harm, i.e. adverse impacts.

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More Specifically … with Regard to Resilient Building Performance during a Fire Incident and the ‘Cooling Phase’ after Fire Extinguishment:

1.   The Building shall be designed to comply with the Recommendations in the 2005 & 2008 NIST(USA) Final Reports on the World Trade Center(WTC) 1, 2 & 7 Building Collapses.

In one major respect, the 2005 NIST Report is flawed, i.e. its treatment of ‘disability and building users with activity limitations is entirely inadequate.  The Building shall, therefore, be designed to comply with International Standard ISO 21542: ‘Building Construction – Accessibility & Usability of the Built Environment’, which was published in December 2011.

2.   The Building shall remain Serviceable, not just Structurally Stable(!) … until all buildings users (including those users with activity limitations waiting in ‘areas of rescue assistance’) have been evacuated/rescued to an accessible ‘place of safety’ which is remote from the building, and have been identified … and all firefighters, rescue teams and other emergency response personnel have been removed/rescued from the building and its vicinity.

The Building shall be designed to resist Fire-Induced Progressive Damage and Disproportionate Damage.  These requirements shall apply to all building types, of any height.

Under no reasonably foreseeable circumstances shall the Building be permitted to collapse !

3.   The Building shall be designed to comfortably accommodate and resist a Maximum Credible Fire Scenario and a Maximum Credible User Scenario.

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Concerted International Research is Needed …

To creatively resolve the direct conflict which exists between Sustainable Building Design Strategies and Traditional/Conventional Fire Engineering.

An example … for cooling, heating and/or ventilation purposes in a sustainable building, it is necessary to take advantage of natural patterns of uninterrupted air movement in that building. On the other hand, fire consultants in private practice, and fire prevention officers in authorities having jurisdiction, will demand that building spaces be strictly compartmented in order to limit the spread of fire and smoke … thereby dramatically interfering with those natural patterns of air movement. The result is that the sustainability performance of the building is seriously compromised.

If, however, adequate independent technical control is absent on the site of a sustainable building … it is the fire safety and protection which will be seriously compromised !

To effectively deal with the fire safety problems (fatal, in the case of firefighters) which result from the installation of Innovative Building/Energy/EICT Systems and Products in Sustainable Buildings.

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These are appropriate tasks for a new CIB W14 Research Working Group VI: ‘Sustainable Fire Engineering Design & Construction’ !

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9-11 WTC Attacks in New York – ‘Reflections in a Cold Eye’ !

2013-09-13 …

Two days ago, on the 12th Anniversary of the 9-11 World Trade Center Attacks in New York City … I couldn’t help recalling a period of time 20 years earlier, and the still vivid memories of institutional ‘after-shocks’ following the 1981 Dublin Stardust Discotheque Fire in February of that year.  For a very long time afterwards, the Irish Fire Establishment disappeared from public view and hearing … without any trace !   As a young architect, at the time, just starting out in private practice … it was a critical lesson on the importance of ‘reality’ … and the malignancy of ‘realpolitik’.

As the years rolled by, and more and more information was revealed by troubled ‘insiders’ and uncovered by brave journalists … it was clear to me that the Dublin Fire had spawned two entirely separate and unconnected realities:

  1. The Frontline Tragedy … of the fire victims (those who were killed or injured on the night, and those who survived), their families and (to this day) their mournful pleas for justice and truthful answers, the local communities, the first responders, e.g. firefighters, ambulance personnel, and Garda/police and (to this day) their continuing struggle for adequate resources, the staff of the Dublin hospitals … and a shocked public.
  2. Defensive Institutions … senior policy and decision makers in national and local authorities, or agencies, having jurisdiction and/or responsibility for blatantly inadequate building codes and standards, poorly resourced technical control systems over building design and construction, and a dysfunctional emergency response infrastructure … senior politicians, on both sides of the political spectrum, who ‘fixed’ the format and major outcomes from the post-incident investigation (they ensured that minor outcomes were either implemented in a ham-fisted bureaucratic manner, or were ignored) … the various building design disciplines directly involved and their respective professional organizations … etc., etc.

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These Same Realities have been re-born … and have evolved in scale … out of the savage destruction on that Tuesday, 11 September 2001.

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‘Sustainable Fire Engineering for All’ – SDI’s Professional Service

2012-12-14 & 2012-12-30:  Further to this distressing incident … which exposed a profound lack of awareness, care and competence within the general fire safety industrial sector …

Recent Fatal Fire at a Disabled Workshop in SW Germany

… this is how we would like to help you … whether you are an individual, or an organization … whether you are located in Ireland, Italy or Turkey … some other part of Europe, the Arab Gulf Region, India, Japan, China … or wherever !

And … we can, if requested or necessary, work in collaboration with local partners in those different geographical regions.

– FireOx International is the Fire Engineering Division of Sustainable Design International Ltd. (SDI) –

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Colour photograph showing the 2 World Trade Center Towers, in New York City, immediately after the second plane impact. The mechanical damage arising from such a plane impact had been considered in the Initial Building Design Process; incredibly, any type of Fire Incident had not ! In the case of both towers and within a short period of time, Fire-Induced Progressive Damage resulted in Disproportionate Damage, and eventual Total Building Collapse. The horror and carnage at the World Trade Center Complex, and the extensive collateral damage to everywhere south of Canal Street, caused enormous long-term damage to the economy of Manhattan ... and had a very significant adverse impact on Global Financial Markets. Click to enlarge.

Colour photograph showing the 2 World Trade Center Towers, in New York City, immediately after the second plane impact. The mechanical damage arising from such a plane impact had been considered in the Initial Building Design Process; incredibly, any type of Fire Incident had not ! In the case of both towers and within a short period of time, Fire-Induced Progressive Damage resulted in Disproportionate Damage, and eventual Total Building Collapse. The horror and carnage at the World Trade Center Complex also caused enormous long-term damage to the economy of Manhattan … and had a very significant adverse impact on Global Financial Markets. Click to enlarge.

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Introduction

Fundamentally, the 9-11 World Trade Center Incident in New York (2001) was an Extreme ‘Real’ Fire Event.  It presented the International Fire Engineering Community with a catastrophic failure in conventional practices and procedures related to:

  • Fire Engineering, Structural Engineering, and Architectural Design ;
  • Human Building Management Systems ;
  • Emergency Response by Firefighters, Rescue Teams, and Medical Personnel ;
  • National and Local Organizations Having Authority or Jurisdiction (AHJ’s) ;

… and with the serious problem of entirely inadequate Fire Safety Objectives in the building legislation, model codes and design standards of the most economically advanced countries in the world.

Those people who understand the building design process, and have experience as construction practitioners, have long realised that the lessons from 9-11 must be applied across the full spectrum of building types … not just to tall buildings.  Right up to the present day, unfortunately, many people in the International Fire Engineering Community are either unwilling, or unable, to do this.

Furthermore … Fire Engineering, Architectural Design and Structural Engineering must, of urgent necessity, be seamlessly conjoined … with the aim of removing misunderstandings and the wide gaps in client service delivery between the different disciplines.

In 2002, a series of Long-Term 9-11 Survivor Health Studies commenced in the USA … and in 2005 and 2008, the U.S. National Institute of Standards and Technology (NIST) issued a series of Post 9-11 Critical Recommendations concerning the design, construction, management and operation of buildings.

At FireOx International … we have fully integrated this essential design guidance into our frontline fire engineering and architectural practice … we have developed unique and practical solutions for worldwide application, some of which appear in International Standard ISO 21542: ‘Building Construction – Accessibility & Usability of the Built Environment’, published in December 2011.

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Colour photograph showing an armed assailant during the November 2008 'Hive-Attack' on Mumbai ... an extraordinarily violent, co-ordinated assault on the largest (and wealthiest) city in India, which involved the strategic targeting of built environment Places of Public Resort, Iconic Buildings, High-Rise Buildings, Buildings having a Critical Function, Transport Infrastructure and Service Utilities ... with the aim of causing widespread terror among the general population, including tourists, and disruption to the city’s important economic environment. Click to enlarge.

Colour photograph showing an armed assailant during the November 2008 ‘Hive-Attack’ on Mumbai … an extraordinarily violent, co-ordinated assault on the largest (and wealthiest) city in India, which involved the strategic targeting of built environment Places of Public Resort, Iconic Buildings, High-Rise Buildings, Buildings having a Critical Function, Transport Infrastructure and Service Utilities … with the aim of causing widespread terror among the general population, including tourists, and disruption to the city’s important economic environment. Click to enlarge.

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FireOx International’s Commitment to You

As a necessary response to the New 21st Century Paradigm of Real Extreme Event in a Built Environment which is becoming more and more complex … is subject to climate change and severe weather events … and is vulnerable to malign and malevolent disruption –

WE are committed to … the implementation of a Sustainable Human Environment which is Fire Safe and Secure for All, meaning that an ‘appropriate project-specific fire safety level’ is our fire engineering objective, with ‘human health protection’ targeted as a priority … through the use of innovative, reliability-based and person-centred sustainable design practices and procedures.

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What is an ‘Appropriate Fire Safety Level’ in Your Building or Facility ?

It is rarely, if ever, explained to clients/client organizations that the Minimal Fire Safety Objectives in building legislation are focused solely on protecting the ‘interests’ of society, not those of the individual …  are, quite often, inadequate and/or flawed … and are, always, revised only after the latest tragedy !

To properly protect Your Interests as a client/client organization … we strongly advise that the Appropriate Level of Fire Safety in Your Building or Facility should exceed the minimal level of safety required by building legislation.  We would also caution that, in many jurisdictions (e.g. India), compliance with national building legislation is voluntary.

Which raises the issues of whether or not you will actually get what you pay for, and whether or not the Fire Protection Measures in Your Building or Facility are reliable (in other words, will they perform as intended at the time of a ‘real’ fire, which may occur at any time in a building’s long life cycle) !?!   Competent Technical Control of Design and Construction, independent of the design and construction organization(s), is essential.

You should carefully consider the following spectrum of issues which may be directly relevant to Your Project.  Following a process of consultation with you, we then develop Project-Specific Fire Engineering Design Objectives … bearing in mind that you must also comply with safety at work, anti-discrimination, and environmental legislation, etc … maintain business continuity, etc … be energy efficient, etc … and be socially responsible, etc …

–     Protection of the Health of All Building Users … including People with Activity Limitations (2001 WHO ICF), Visitors to the building or facility who may be unfamiliar with its layout, and Contractors or Product/Service Suppliers temporarily engaged in work or business transactions on site ;

–     Protection of Property from Loss or Damage … including the Building or Facility, its Contents, and Adjoining or Adjacent Properties ;

–     Safety of Firefighters, Rescue Teams and Other Emergency Response Personnel ;

–     Ease and Reasonable Cost of ‘Effective’ Reconstruction, Refurbishment or Repair Works after a Fire ;

–     Sustainability of the Human Environment (social – built – virtual – economic) … including Fitness for Intended Use and Life Cycle Costing of fire engineering related products and systems, etc … fixed, installed or otherwise incorporated in the building or facility ;

–     Protection of the Natural Environment from Harm, i.e. Adverse or Damaging Impacts.

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FireOx International – Our Fire Engineering Services

  • WE  will advise you on Fire Safety Policy, Fire Safety Strategy Development, Fire Safety Implementation … and, whether you are within or from outside the European Union, on CE Marking of Fire Protection Related Construction Products

  • WE  understand the process of Design, particularly the new language of Sustainable Design … and we will produce Creative Fire Engineering Solutions for Your Project

  • WE  are thoroughly familiar with the intricacies of Building Sites … and we will verify and/or validate Design Compliance during construction, and at project completion … and, if requested or necessary, as a completely Independent Technical Controller ; 

  • WE  communicate easily and effectively with other Professional Design Disciplines, including architects and structural engineers … and we will act as fully participating members of Your Project Design & Construction Team … and, if requested or necessary, as the Design Professional in Responsible Charge **

  • WE  practice in accordance with a comprehensive Professional Code of Ethics

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Sustainable Fire Engineering Solutions ?

  1. Are adapted to Local Geography, Climate/Climate Change, Social Need, Culture, Economy … and Severe Events (e.g. earthquakes, flooding) ;
  2. Are ‘Reliability-Based’, i.e. that design process based on practical experience, competence and an examination of real extreme events, e.g. 2001 WTC 9-11 & 2008 Mumbai Attacks, and 2011 Fukushima Nuclear Incident … rather than theory alone ;
  3. Are ‘Person-Centred’, i.e. that design process 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.

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FireOx International’s Contact Information

E-Mail:  cjwalsh@sustainable-design.ie

International Phone:  +353 1 8386078   /   National Phone:  (01) 8386078

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Important Note:  This Post should be read in conjunction with an earlier Post …

Sustainable Design International Ltd. – Our Practice Philosophy

It is there, not here, that we define Sustainable Human & Social Development … and describe how our Practice is responding to this open, intricate, dynamic, and still evolving concept.  The resulting transformation in how frontline services are provided to our Clients/Client Organizations ensures a much more comfortable ‘fit’ to their needs … and a greater level of protection, safety and security for society !

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[ ** 2005 NIST(USA) Final Report on 9-11 World Trade Center 1 & 2 Tower Collapses

– Footnote 49 –

… the Design Professional in Responsible Chargeusually the lead architect – ensures that the (Design) Team Members use consistent design data and assumptions, co-ordinates overlapping specifications, and serves as the liaison with enforcement and review officials, and with the client or client organization. ]

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Recent Fatal Fire at a Disabled Workshop in SW Germany

2012-11-28:  On Monday last, 26 November 2012 … Fire broke out at a Sheltered Workshop for People with Activity Limitations, located in the small municipality of  Titisee-Neustadt, south-western Germany … not too far from the borders of France and Switzerland.  It was approximately 14.00 hrs in the afternoon … in broad daylight.

German news reports put the death toll at 14 People, including 1 Carer … with 10 People injured.

News reports also state that it took 2 Hours for Firefighters to bring this incident under control.  At the time that Photograph 1, below, was taken … smoke had spread throughout a major part of the building.

Viewers should look closely at the top of the external staircase … then, ask yourselves how any person with an activity limitation can be safely rescued, or assisted to evacuate, by means of a ladder (obscured, at the end of the building on the left) … and, finally, notice the positioning of fire hoses on the ground and on the staircase … some of the many issues which have been discussed extensively here before …

Click to enlarge.

Click to enlarge.

Click to enlarge.

Click to enlarge.

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2005 NIST(USA) Final Report on 9-11 World Trade Center 1 & 2 Tower Collapses

–  Recommendation  #17b  –

 To the degree possible, people with activity limitations should be provided with a means for self-evacuation in the event of a building emergency.  Current strategies (and law) generally require these people to shelter-in-place and await assistance.  New procedures, which provide redundancy in the event that the fire warden system or co-worker assistance (e.g. the buddy system) fail, should consider full building evacuation, and may include use of fire-protected and structurally hardened elevators, motorized evacuation technology, and dedicated communication technologies.

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At the heart of the impressive show of fire fighting equipment and technology … and the usual reassuring statements by local officials and other people in authority after the event … there is an equally impressive lie …

Photograph by Patrick Seeger(dpa). Click to enlarge.

Photograph by Patrick Seeger(dpa). Click to enlarge.

Current Building Codes and Regulations, Fire Safety Standards, Building Design Practices, and Building Management Procedures … do not seriously consider the safety of People with Activity Limitations … not properly – not adequately – not even INadequately.  Tokenism is the best offer available in just a few European countries.

Photograph by Patrick Seeger(dpa). Click to enlarge.

Photograph by Patrick Seeger(dpa). Click to enlarge.

According to Spiegel OnLine International …

The rescue was difficult because some people panicked, said Local Fire Chief Alexander Widmaier.  “We are dealing here with people who naturally do not respond rationally”, he said.

IF this is an accurate news report, and bearing in mind that it is also a translation … I SAY …

Let us be generous and kind … Local Fire Chief Alexander Widmaier has NO awareness or understanding of People with Activity Limitations and the daily challenges they face in moving around and using a built environment which is inaccessible and unsafe.

According to AFP OnLine …

Gotthard Benitz, of the Titisee-Neustadt fire service, told AFP earlier that the fire began on the ground floor of the building which also had a basement and an upper floor.

“The victims were all on the same floor where the fire was”, he said adding this was the only area to have sustained fire damage and the stairwell had remained smoke-free meaning those on the other two floors had been able to use it.

He also said firefighters were prepared for dealing with an emergency at the workshop as practice fire alarms were regularly carried out there, with the last one having been last year.

The head of Caritas in Germany, Peter Neher, told ZDF public television that emergency practice drills were done regularly.

IF this is an accurate news report, and bearing in mind that it is also a translation … I SAY …

Gotthard Benitz should also look at the top of the external staircase in Photograph 1 above.  IF there are no circulation hazards, e.g. ice, or obstacles, e.g. fire hoses … able-bodied people can easily go up or down a staircase … people who use wheelchairs or other mobility-aid devices cannot.

In their respective positions of responsibility … Gotthard Benitz and Peter Neher should both understand that all building occupants must be facilitated in acquiring the skill of evacuation to a ‘place of safety’, by way of a safe and accessible route.  An emergency practice drill, although carried out regularly once a year … is ENTIRELY inadequate … and will achieve Very Little.

Skill:  The ability of a person – resulting from training and regular practice – to carry out complex, well-organized patterns of behaviour efficiently and adaptively, in order to achieve some end or goal.

Standard fire evacuation training and practice drill procedures must be adapted to the individual-specific abilities of People with Activity Limitations.

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BUT … the new International Standard ISO 21542 is a very small step in the right direction.  See yesterday’s post.

This situation will only improve to a significant degree, however, when People with Activity Limitations, and their Representative Organizations, begin to act decisively, in unison, and with serious intent …

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Self-Protection from Fire in Buildings – Personal Check List for People with Activity Limitations

1.     Upgrade ‘My’ understanding of Accessibility

Ease of independent approach, entry, egress, evacuation 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.     Be assertive (not aggressive) with regard to ‘My’ own self-protection in emergency situations ;

3.     Concerning ‘My’ safety … demand that Building Management actively engages in Meaningful Consultation – and receives your Informed Consent ;

4.     Become familiar with the Fire Defence Plan for the building, and know ‘My’ part well ;

5.     Practice – practice – practice … become skilled in evacuation to a Place of Safety ;

6.     Become involved, and participate directly in the Building’s Safety Procedures.

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Self-Protection from Fire in Buildings  – Must-Do List for Representative Organizations & Groups

1.     Upgrade ‘Our’ understanding of Accessibility in a Social Context, its Current Vocabulary, and its Complexity … groups of individuals wish to socialize together … this is now, afterall, a recognised human and social right !

Ease of independent approach, entry, egress, evacuation 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, and group Wellbeing, during the course of those activities ;

2.     Be assertive (and aggressive) with regard to the availability of proper Data and Statistics – we must clearly identify ‘Our’ problem with the many restrictions placed on our participation in local communities ;

3.     Produce a working statement of an Individual’s Rights – on 1 Page (!) ;

4.     Issue clear guidelines on Reliable Advocacy ;

5.     Become involved, and participate directly in the improvement of Building Codes and Regulations, Fire Safety Standards, Building Design Practices, and Building Management Procedures ;

6.      Demand resources to Monitor ‘Effective’ Implementation … and Target Relevant and ‘Practical’ Research.

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Conventional Structural Fire Engineering Design – How Flawed ?

2012-05-18:  Déjà-vu …

” In the early hours of the morning of Saturday, 14th February 1981, a disastrous fire swept through a building called the Stardust in the North Dublin suburb of Artane during the course of a St. Valentine’s Night ‘disco’ dance.  Forty eight people were killed and one hundred and twenty eight seriously injured.  The overwhelming majority of the victims were young people. “

‘Introduction’, Report of the Tribunal of Inquiry on the Fire at the Stardust, Artane, Dublin, on the 14th February 1981.  Report dated 30 June 1982.

As a young architect in private practice … I witnessed, at first hand, the Dublin Fire ‘Establishment’ disappear from public view, without trace, after the Stardust Fire Tragedy.  It was almost impossible, for at least a year afterwards, to have a meeting with any Fire Prevention Officer in the Dublin Fire Authority.  This was a very valuable lesson.

Later, following the publication of the Stardust Tribunal Report … were its Recommendations implemented … with urgency … and conscientiously ?   No way.  For example, it was more than ten years after the Stardust Fire before an inadequate system of legal National Building Regulations was introduced in Ireland.  And to this day, the system of AHJ monitoring of construction quality, throughout the country, is weak and ineffective … lacking both competent personnel and resources !

The proof of the pudding is in the eating … and one of the results, also in Dublin, has been last year’s debacle at the Priory Hall Apartment Complex … where all of the residents had to leave their expensive apartments for fire safety (and many other) reasons.  The tip of a very large iceberg.  See my post, dated 18 October 2011 .

And this is where the problems usually begin …

” There has been a tendency among students of architecture and engineering to regard fire safety as simply a question of knowing what is required in terms of compliance with the regulations.  The recommendation of the Tribunal of Enquiry into the Summerland Disaster that those responsible for the design of buildings should treat fire safety as an integral part of the design concept itself, has not yet been reflected in the approach to the subject at university level.  There is still clearly a need for a new approach to the structuring of such courses which will in time bring to an end the attitude of mind, too prevalent at the moment, that compliance with fire safety requirements is something that can be dealt with outside the context of the overall design of the building. “

‘Chapter 9 – Conclusions & Recommendations’, Report of the Tribunal of Inquiry on the Fire at the Stardust, Artane, Dublin, on the 14th February 1981.  Report dated 30 June 1982.

This Recommendation has still not been implemented … and note the reference to the earlier fire at the Summerland Leisure Centre in 1973, on the Isle of Man, when 50 people were killed and 80 seriously injured.

Today … the same attitude of mind, described so well above, stubbornly persists in all sectors, and in all disciplines, of the International Construction Industry … even within ISO Technical Committee 92: ‘Fire Safety’ !

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Which brings me, neatly, to the recent question posed by Mr. Glenn Horton on the Society of Fire Protection Engineers (SFPE-USA) Page of LinkedIn ( http://www.linkedin.com/groups?gid=96627 ).   As usual, the shortest questions can prove to be the most difficult to answer …

” Can you expand on, or point to where anyone has discussed, the ‘very flawed design approach’ please ? “

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ESSENTIAL PRELIMINARIES …

     1.  Foundation Documents

I am assuming that ‘people-who-need-to know’, at international level, are familiar with the Recommendations contained in these 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 ;

… and the contents of the CIB W14 Research WG IV Reflection Document … which, together with its 2 Appendices, can be downloaded from this webpage … http://www.cjwalsh.ie/progressive-collapse-fire/ … under the section headed: ‘April 2012’.

However … I am utterly dismayed by the number of ‘people-who-need-to know’ … who do not know … and have never even bothered to dip into the 2 NIST Reports … or the many long-term Post 9-11 Health Studies on Survivors which have already revealed much priceless ‘real’ information about the short and medium term adverse impacts on human health caused by fire !

CIB W14 Research Working Group IV would again strongly caution that Fire-Induced Progressive Damage and Disproportionate Damage are fundamental concepts to be applied in the structural design of all building types.

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     2.  Technical Terminology

While attending the ISO TC92 Meetings in Thessaloniki, during the last week of April 2012, I noticed not just one reference to ‘fire doors’ in a Draft ISO Fire Standard … but many.  It surprised me, since I thought this issue had been successfully resolved, at ISO level, many years ago.  There is no such thing as a ‘fire door’ … and the careless referencing of such an object, which has no meaning, in building codes and standards has caused countless problems on real construction sites during the last 20-30 years.

Please follow this line of thought …

Fire Resistance:  The inherent capability of a building assembly, or an element of construction, to resist the passage of heat, smoke and flame for a specified time during a fire.

Doorset:  A building component consisting of a fixed part (the door frame), one or more movable parts (the door leaves), and their hardware, the function of which is to allow, or to prevent, access and egress.

[Commentary: A doorset may also include a door saddle / sill / threshold.]

Fire Resisting Doorset / Shutter Assembly:  A doorset / shutter assembly, properly installed or mounted on site, the function of which is to resist the passage of heat, smoke and flame for a specified time during a fire.

… and so we arrive at the correct term … Fire Resisting Doorset … which, as an added bonus, also alerts building designers, construction organizations, and even AHJ inspectors, to the fact that there is more involved here than merely a door leaf.

Now then, I wonder … how, in any sane and rational world, can the term Fire Resistance be used in relation to structural performance during a fire, and the cooling-phase afterwards ?   Yet, this is exactly what I read in the building codes of many different jurisdictions.  Do people understand what is actually going on ?   Or, is the language of Conventional Fire Engineering so illogical and opaque that it is nearly impossible to understand ?

And … if this problem exists within the International Fire Science & Engineering Community … how is it possible to communicate effectively with other design disciplines at any stage during real construction projects.  The artificial environments found in academia are not my immediate concern.

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     3.  Fire Research & Development outside CIB W14 & ISO TC92

In 2012 … there is something very wrong when you have to struggle to persuade a group of people who are developing an ISO Standard on Design Fire Scenarios … that they must consider Environmental Impact as one of the major consequences of a fire to be minimized … along with ‘property losses’ and ‘occupant impact’.  This is no longer an option.

Environmental Impact:  Any effect caused by a given activity on the environment, including human health, safety and welfare, flora, fauna, soil, air, water, and especially representative samples of natural ecosystems, climate, landscape and historical monuments or other physical structures, or the interactions among these factors; it also includes effects on accessibility, cultural heritage or socio-economic conditions resulting from alterations to those factors.

So … how timely, and relevant to practitioners, are ISO Fire Standards ?   Perhaps … obsolete at publication … and not very ??

And … there is lot more to the Built Environment than buildings …

Built Environment:  Anywhere there is, or has been, a man-made or wrought (worked) intervention in the natural environment, e.g. cities, towns, villages, rural settlements, service utilities, transport systems, roads, bridges, tunnels, and cultivated lands, lakes, rivers, coasts, and seas, etc … including the virtual environment.

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We should be very conscious that valuable fire-related research takes place outside, and unrelated to, the established fire engineering groupings of CIB W14 & ISO TC92.  But I am curious as to why this research is not properly acknowledged by, or encouraged and fostered within, the ‘system’ ?

Example A:  Responding to Recommendation 18 in the 2005 NIST WTC Report … a Multi-Disciplinary Design Team published an article in the magazine Bâtiment et Sécurité (October 2005) on The PolyCentric Tower.  I very much enjoy giving practitioners a small flavour of this work, whenever I make presentations at conferences and workshops …

Colour image, from one of my Overhead Presentations ... showing The PolyCentric Tower (2005), developed by a French Multi-Disciplinary Design Team in response to Recommendation 18 in the 2005 NIST WTC Report. Click to enlarge.

Colour image, from one of my Overhead Presentations ... showing The PolyCentric Tower (2005), developed by a French Multi-Disciplinary Design Team in response to Recommendation 18 in the 2005 NIST WTC Report. Click to enlarge.

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Example B:  In spite of a less than helpful submission (to put it mildly) from ISO TC92 Sub-Committee 4 … ISO 21542: ‘Building Construction – Accessibility & Usability of the Built Environment’ was finally published in December 2011 … but it was developed by a Sub-Committee of ISO TC59: ‘Buildings & Civil Engineering Works’

Colour image, from one of my Overhead Presentations ... showing the design of a notional Fire Evacuation Staircase, with an adjoining Area of Rescue Assistance, which responds directly to the 2005 NIST WTC Recommendations. See Figure 62 in ISO 21542:2011. Click to enlarge.

Colour image, from one of my Overhead Presentations ... showing the design of a notional Fire Evacuation Staircase, with an adjoining Area of Rescue Assistance, which responds directly to the 2005 NIST WTC Recommendations. See Figure 62 in ISO 21542:2011. Click to enlarge.

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With the involvement and support of ISO Technical Committee 178: ‘Lifts, Elevators & Moving Walks’ during its long gestation … ISO 21542 is now able to indicate that all lifts/elevators in a building should be capable of being used for evacuation in the event of a fire.  This is already a design feature in a small number of completed Tall Building Projects.  Once more, this is no longer an option.

In addition … if a Fire Evacuation Staircase has a minimum unobstructed width of 1.5 m (from edge of handrail on one side of the staircase to edge of handrail on the opposite side) … this will be sufficient to facilitate the following tasks …

  • Assisted Evacuation by others, or Rescue by Firefighters, for those building users who cannot independently evacuate the building, e.g. people with activity limitations … shown above, on the right, is assistance being given by three people (one at each side, with one behind) to a person occupying a manual wheelchair ;
  • Contraflow Circulation … emergency access by firefighters entering a building and moving towards a fire, while people are still evacuating from the building to a ‘place of safety’ remote from the building … shown above, bottom left, is how not to design an evacuation staircase (!) ;
  • Stretcher Lifting … lifting a mobility-impaired person, who may be conscious or unconscious, on a stretcher ;
  • Firefighter Removal & Contraflow … shown above, top left, is removal of a firefighter from a building by colleagues in the event of injury, impairment, or a fire event induced health condition … while other firefighters may still be moving towards the fire.

Note that in a Fire Evacuation Staircase … all Handrails are continuous … each Stair Riser is a consistent 150 mm high … each Stair Tread/Going is a consistent 300 mm deep … and there are No Projecting Stair Nosings.

Most importantly … in order to assign sufficient building user space in the design of an Area of Rescue Assistance … ISO 21542 also provides the following Key Performance Indicator … just one aspect of a ‘maximum credible user scenario’ …

10% of people using a building (including visitors) have an impairment, which may be visual or hearing, mental, cognitive or psychological, or may be related to physical function, with some impairments not being identifiable.

Is There Any Connection Between Examples A & B ?   There is, and it is a connection which is critical for public safety.  The following Performance Indicator illustrates the point …

Innovative Structural Design – Perimeter Core Location – Design for Fire Evacuation – Evacuation for All

” A Building must not only remain Structurally Stable during a fire event, it must remain Serviceable for a period of time which facilitates:

  • Rescue by Firefighters of people with activity limitations waiting in areas of rescue assistance ;
  • Movement of the firefighters and those people with activity limitations, via safe and accessible routes, to Places of Safety remote from the building ;
  • With an assurance of Health, Safety & Welfare during the course of this process of Assisted Evacuation. “

[Refer also to the Basic Requirements for Construction Works in Annex I of the European Union’s Construction Product Regulation 305/2011 – included as Appendix II of the CIB W14 WG IV Reflection Document.  Are the Basic Requirements being interpreted properly … or even adequately ??]

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ANSWERS TO THE QUESTION …

The Greek Paper is included as Appendix I of CIB W14 WG IV Reflection Document … in order to show that Fire-Induced Progressive Damage is also an issue in buildings with a reinforced concrete frame structure.  It is more straightforward, here, to concentrate on buildings with a steel frame structure.

a)  Use of ‘Fire Resistance'(?) Tables for Structural Elements

We should all be familiar with these sorts of Tables.  The information they contain is generated from this type of standard test configuration in a fire test laboratory …

… and this sort of criterion for ‘loadbearing horizontal elements’ in a fire test standard …

A single isolated loaded steel beam, simply supported, is being tested.  As deflection is the only type of deformation being observed and measured … the critical temperature of the steel, i.e. the point when material strength begins to fail rapidly and the rate of beam deflection increases dramatically … is the sole focus for all stakeholders.

Using these Tables, it is very difficult to escape the conclusion that we are merely interior decorators … applying flimsy thermal insulation products to some steel structural elements (not all !) … according to an old, too narrowly focused, almost static (‘cold form’) recipe, which has little to do with how today’s real buildings react to real fires !

This ‘non-design’ approach is entirely inadequate.

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With regard to the use of these Tables in Ireland’s Building Regulations (Technical Guidance Document B), I recently submitted the comments below to the relevant Irish AHJ.  These same comments could just as easily apply to the use of similar Tables in the Building Regulations for England & Wales (Approved Document B) …

” 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 deformation) in fire of steel structural elements … in order to reduce the adverse effects of one 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 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.

Coming from this background and heritage … it is very difficult to communicate with mainstream, ambient structural engineers who are speaking the language of structural reliability, limit state design and serviceability limit states.

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b)  NIST Report: ‘Best Practice Guidelines for Structural Fire Resistance Design of Concrete and Steel Buildings’ (NISTIR 7563 – February 2009)

At the end of Page 18 in NISTIR 7563 …

2.7.2 Multi-Storey Frame Buildings

In recent years, the fire performance of large-frame structures has been shown in some instances to be better than the fire resistance of the individual structural elements (Moore and Lennon 1997).  These observations have been supported by extensive computer analyses, including Franssen, Schleich, and Cajot (1995) who showed that, when axial restraint from thermal expansion of the members is included in the analysis of a frame building, the behaviour is different from that of the column and beam analyzed separately.

A large series of full-scale fire tests was carried out between 1994 and 1996 in the Cardington Laboratory of the Building Research Establishment in England.  A full-size eight-storey steel building was constructed with composite reinforced concrete slabs on exposed metal decking, supported on steel beams with no applied fire protection other than a suspended ceiling in some tests.  The steel columns were fire-protected.  A number of fire tests were carried out on parts of one floor of the building, resulting in steel beam temperatures up to 1000 °C, leading to deflections up to 600 mm but no collapse and generally no integrity failures (Martin and Moore 1997). “

Those were Experimental Fire Tests at Cardington, not Real Fires … on ‘Engineered’ Test Constructions, not Real Buildings !!   And … incredibly, for a 2009 document … there is no mention at all of World Trade Center Buildings 1, 2 or 7 !?!   Where did they disappear to, I wonder ?   Too hot to handle ???

Computer Model Verification and Validation (V&V) are very problematic issues within the International Fire Science and Engineering Community.  The expected outcome of a Model V&V Process, however, is a quantified level of agreement between experimental data (and, if available, real data) and model prediction … as well as the predictive accuracy of the model.

Now … please meditate carefully on the following …

” NCSTAR 1A (2008)  Recommendation D   [See also NCSTAR 1 (2005)  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. “

The design approach outlined in NISTIR 7563 is not only very flawed … it lacks any validity … because very relevant and important real fire data has been totally ignored.  The Cardington Experimental Fires were not all that they seemed.

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c)  Current ISO TC92 International Case Study Comparison

Structural Fire Engineering Design of an Airport Terminal Building serving the Capital City of a large country (which shall remain nameless) … constructed using Portal Steel Frames …

My first concern is that the Structural Fire Engineering Design has been undertaken in isolation from other aspects of the Building’s Fire Engineering Design.

On Page 3 of the Case Study Report …

4.2 Objectives & Functional Requirements for Fire Safety of Structures

The fire safety objectives of the airport terminal emphasize the safety of life, conservation of property, continuity of operations and protection of the environment. “

Should these not be the Project-Specific Fire Engineering Design Objectives ?   Since when, for example, is ‘continuity of operations’ a concern in building codes ??

On Page 7 of the Case Study Report …

5.3  Identify Objectives, Functional Requirements & Performance Criteria for Fire Safety of Structure

The Fire Safety Objective of the Steel Structure:  There should be no serious damage to the structure or successive collapse in case of fire.

The Functional Requirements are defined as the followings:

(1)  Prevent or limit the structural failure in case of fire so as to prevent the fire from spreading within the compartment or to the adjacent fire compartment or the adjacent buildings (to prevent fire spread) ;

(2)  Prevent or limit the partial structural failure in case of fire so as to protect the life safety of the occupants and firefighters (to protect life safety) ;

(3)  Prevent or limit the structural deformation or collapse so as not to increase the cost or difficulties of the after-fire restoration (to reduce reconstruction cost).

One of the following Performance Requirements shall be met:

(1)  The load-bearing capacity of the structure (Rd) shall not be less than the combined effect (Sm) within the required time, that is Rd ≥ Sm.  (The maximum permitted deflection for the steel beam shall not be larger than L/400, and the maximum stress of the structure under fire conditions shall not be larger than fyT) ;   or

(2)  The fire resistance rating of the steel structure (td) shall not be less than the required fire resistance rating (tm), that is, td ≥ tm ;   or

(3)  Td – the critical internal temperature of the steel structure at its ultimate state shall not be less than Tm (the maximum temperature of the structure within required fire resistance time duration), that is Td ≥ Tm.  (300 ℃) “

Once again … we see an emphasis on critical temperature, beam deflection (only), and material strength.  L/400 is an impressive Fire Serviceability Limit State … a different world from L/20 or L/30 … but what about other important types of steel structural member deformation, e.g. thermal expansion and distortion ??

Furthermore … if there is a major fire in the area under the lower roof (see Section above) … because of structural continuity, any serious impact on the small frame will also have an impact on the large frame.  For Structural Fire Engineering reasons … would it not be wiser to break the structural continuity … and have the small and large portal frames act independently ?

It is proposed that the Portal Frames will NOT be fully fire protected … just the columns, up to a height of 8 metres only.  If ‘conservation of property’ and ‘continuity of operations’ are important fire engineering design objectives in this project … why isn’t all of the steel being fully protected ???   What would be the additional cost, as a percentage of the total project cost ?

What exactly is infallible about current Design Fires and Design Fire Scenarios ???   Not much.  And in the case of this particular building, should a ‘maximum credible fire scenario’ be at least considered ?

And … what is the fire protection material, product or system being used to protect the Portal Frames ?   Will it be applied, fixed or installed correctly ?   What is its durability ?   Will it be able to resist mechanical damage during the construction process … and afterwards, during the fire event ?   What is the reliability of this form of fire protection measure ??

So many questions …

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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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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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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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END

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