'A Gentle Whisper in Your Ear' » Sustainable Fire Engineering

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

CJ Walsh — Sun, 22 Jan 2012 18:20:54 +0000

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)

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

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 !!

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.

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.

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.

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.

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.

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.

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.

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.

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

[ * 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.

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.

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.

END

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

CJ Walsh — Wed, 18 Jan 2012 17:29:05 +0000

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)

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.

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.

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”.

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 !!

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.

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.

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.

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.

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.

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.

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.

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.

END

Post-9/11 & Post-Mumbai Fire Engineering – What Future ?

CJ Walsh — Thu, 15 Dec 2011 14:24:20 +0000

Previous Posts in This Series …

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

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

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

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

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

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

2011-12-07: NIST WTC Recommendations 25-28 > Improved Practices … GROUP 7. Improved Procedures and Practices – Recommendations 25, 26, 27 & 28

2011-12-08: NIST WTC Recommendations 29-30 > Improved Fire Education … GROUP 8. Education and Training – Recommendations 29 & 30 (out of 30)

Colour image showing 'The Cloud' Residential Tower Project, in Seoul (South Korea) ... which will be completed in 2015. Design by MVRDV Architects, The Netherlands. Click to enlarge.

2011-12-15: You know what is coming soon … so Merry Christmas & Happy New Year to One and All !!

1. There were 2 Important Reasons for undertaking this Series of Posts …

(a) The General Public, and particularly Client Organizations, should be facilitated in directly accessing the core content of the 2005 NIST WTC Recommendations. Up to now, many people have found this to be a daunting task. More importantly, I also wanted to clearly show that implementation of the Recommendations is still proceeding far too slowly … and that today, many significant aspects of these Recommendations remain unimplemented. Furthermore, in the case of some recent key national standards, e.g. British Standard BS 9999, which was published in 2008 … the NIST Recommendations were entirely ignored.

As a golden rule … National Building Codes/Regulations and National Standards … cannot, should not, and must not … be applied without informed thought and many questions, on the part of a building designer !

(b) With the benefit of hindsight, and our practical experience in FireOx International … I also wanted to add a necessary 2011 Technical Commentary to the NIST Recommendations … highlighting some of the radical implications, and some of the limitations, of these Recommendations … in the hope of initiating a much-needed and long overdue international discussion on the subject.

Colour photograph showing the Taipei 101 Tower, in Taiwan ... which was completed in 2004. Designed by C.Y. Lee & Partners Architects/Planners, Taiwan. Click to enlarge.

” Architecture is the language of a culture.”

” A living building is the information space where life can be found. Life exists within the space. The information of space is then the information of life. Space is the body of the building. The building is therefore the space, the information, and the life.”

C.Y. Lee & Partners Architects/Planners, Taiwan

[ This is a local dialect of familiar Architectural Language. However, the new multi-aspect language of Sustainable Design is fast evolving. In order to perform as an effective and creative member of a Trans-Disciplinary Design & Construction Team ... can Fire Engineers quickly learn to communicate on these wavelengths ?? Evidence to date suggests not ! ]

2. ‘Climate Change’ & ‘Energy Stability’ – Relentless Driving Forces for Sustainable Design !

Not only is Sustainable Fire Engineering inevitable … it must be ! And not at some distant point in the future … but now … yesterday !! There is such a build-up of pressure on Spatial Planners and Building Designers to respond quickly, creatively, intuitively and appropriately to the relentless driving forces of Climate Change (including climate change mitigation, adaptation, and severe weather resilience) and Energy Stability (including energy efficiency and conservation) … that there is no other option for the International Fire Science and Engineering Community but to adapt. Adapt and evolve … or become irrelevant !!

And one more interesting thought to digest … ‘Green’ is not the answer. ’Green’ looks at only one aspect of Sustainable Human & Social Development … the Environment. This is a blinkered, short-sighted, simplistic and ill-conceived approach to realizing the complex goal of a Safe and Sustainable Built Environment. ‘Green’ is ‘Sustainability’ for innocent children !!

Colour image showing the Shanghai Tower Project, in China ... which will be completed in 2014. Design by Gensler Architects & Planners, USA. Click to enlarge.

(a) Organization for Economic Co-Operation & Development (OECD) – 2012′s Environmental Outlook to 2050

Extract from Pre-Release Climate Change Chapter, November 2011 …

‘ Climate change presents a global systemic risk to society. It threatens the basic elements of life for all people: access to water, food production, health, use of land, and physical and natural capital. Inadequate attention to climate change could have significant social consequences for human wellbeing, hamper economic growth and heighten the risk of abrupt and large-scale changes to our climatic and ecological systems. The significant economic damage could equate to a permanent loss in average per capita world consumption of more than 14% (Stern, 2006). Some poor countries would be likely to suffer particularly severely. This chapter demonstrates how avoiding these economic, social and environmental costs will require effective policies to shift economies onto low-carbon and climate-resilient growth paths.’

(b) U.N. World Meteorological Organization (WMO) Greenhouse Gas Bulletin No.7, November 2011

Executive Summary …

The latest analysis of observations from the WMO Global Atmosphere Watch (GAW) Programme shows that the globally averaged mixing ratios of Carbon Dioxide (CO₂), Methane (CH₄) and Nitrous Oxide (N₂O) reached new highs in 2010, with CO₂ at 389.0 parts per million (ppm), CH₄ at 1808 parts per billion (ppb) and N₂O at 323.2 ppb. These values are greater than those in pre-industrial times (before 1750) by 39%, 158% and 20%, respectively. Atmospheric increases of CO₂ and N₂O from 2009 to 2010 are consistent with recent years, but they are higher than both those observed from 2008 to 2009 and those averaged over the past 10 years. Atmospheric CH₄ continues to increase, consistent with the past three years. The U.S. National Oceanic & Atmospheric Administration (NOAA) Annual Greenhouse Gas Index shows that from 1990 to 2010 radiative forcing by long-lived Greenhouse Gases (GHG’s) increased by 29%, with CO₂ accounting for nearly 80% of this increase. Radiative forcing of N₂O exceeded that of CFC-12, making N₂O the third most important long-lived Greenhouse Gas.

(c) International Energy Agency (IEA) – World Energy Outlook, November 2011

Extract from Executive Summary …

‘ There are few signs that the urgently needed change in direction in global energy trends is underway. Although the recovery in the world economy since 2009 has been uneven, and future economic prospects remain uncertain, global primary energy demand rebounded by a remarkable 5% in 2010, pushing CO₂ emissions to a new high. Subsidies that encourage wasteful consumption of fossil fuels jumped to over $400 billion. The number of people without access to electricity remained unacceptably high at 1.3 Billion, around 20% of the world’s population. Despite the priority in many countries to increase energy efficiency, global energy intensity worsened for the second straight year. Against this unpromising background, events such as those at the Fukushima Daiichi Nuclear Power Plant and the turmoil in parts of the Middle East and North Africa (MENA) have cast doubts on the reliability of energy supply, while concerns about sovereign financial integrity have shifted the focus of government attention away from energy policy and limited their means of policy intervention, boding ill for agreed global climate change objectives.’

Colour image showing the One World Trade Center Project, in New York City (USA) ... which will be completed in 2013. Design by Skidmore Owings & Merrill, Architects/Planners, USA. Click to enlarge.

[ Not just in the case of Tall, Super-Tall and Mega-Tall Buildings ... but the many, many Other Building Types in the Built Environment ... are Building Designers implementing the 2005 & 2008 NIST WTC Recommendations ... without waiting for Building and Fire Codes/Regulations and Standards to be properly revised and updated ?? Evidence to date suggests not ! ]

3. Separate Dilemmas for Client Organizations and Building Designers …

As discussed earlier in this Series … the Fire Safety Objectives of Building and Fire Codes/Regulations are limited to:

The protection of building users/occupants ; and
The protection of property … BUT only insofar as that is relevant to the protection of the users/occupants ;

… because the function of Building and Fire Codes is to protect Society. Well, that is supposed to be true ! Unfortunately, not all Codes/Regulations are adequate or up-to-date … as we have been observing here in these posts.

Just taking the Taipei 101 Tower as an example, I have very recently sent out three genuine, bona fide e-mail messages from our practice …

2011-12-08

Toshiba Elevator & Building Systems Corporation (TELC), Japan.

To Whom It May Concern …

Knowing that your organization was involved in the Taipei 101 Project … we have been examining your WebSite very carefully. However, some important information was missing from there.

For our International Work … we would like to receive technical information on the Use of Elevators for Fire Evacuation in Buildings … which we understand is actually happening in the Taipei Tower, since it was completed in 2004.

The Universal Design approach must also be integrated into any New Elevators.

Can you help us ?

C.J. Walsh

[2012-01-10 ... No reply yet !]

2011-12-12

Mr. Thomas Z. Scarangello P.E. – Chairman & CEO, Thornton Tomasetti Structural Engineers, New York.

Dear Thomas,

Knowing that your organization was involved in the structural design of the Taipei 101 Tower, which was completed in 2004 … and in the on-going design of many other iconic tall, super-tall and mega-tall buildings around the world … we have been examining your Company Brochures and WebSite very carefully. However, some essential information is missing.

As you are certainly aware … implementation of the 2005 & 2008 National Institute of Standards & Technology (NIST) Recommendations on the Collapse of WTC Buildings 1, 2 & 7, in New York, on 11 September 2001 … is still proceeding at a snail’s pace, i.e. very slowly. Today, many significant aspects of NIST’s Recommendations remain unimplemented.

For our International Work … we would like to understand how you have responded directly to the NIST Recommendations … and incorporated the necessary additional modifications into your current structural fire engineering designs.

Many thanks for your kind attention. In anticipation of your prompt and detailed response …

C.J. Walsh

[2012-01-10 ... No reply yet !]

2011-12-14

Mr. C.Y. Lee & Mr. C.P. Wang, Principal Architects – C.Y. Lee & Partners Architects/Planners, Taiwan.

Dear Sirs,

Knowing that your architectural practice designed the Taipei 101 Tower, which was completed in 2004 … and, later, was also involved in the design of other tall and super-tall buildings in Taiwan and China … we have been examining your Company WebSite very carefully. However, some essential information is missing.

As you are probably aware … implementation of the 2005 & 2008 U.S. National Institute of Standards & Technology (NIST) Recommendations on the Collapse of WTC Buildings 1, 2 & 7, in New York City, on 11 September 2001 … is still proceeding at a snail’s pace, i.e. very slowly. Today, many significant aspects of NIST’s Recommendations remain unimplemented.

Many thanks for your kind attention. In anticipation of your prompt and detailed response …

C.J. Walsh

[2012-01-10 ... No reply yet !]

So … how many Clients, or Client Organizations, are aware that to properly protect their interests … even, a significant part of their interests … it is vitally necessary that Project-Specific Fire Engineering Design Objectives be developed which will have a much wider scope ? The answer is … not many !

How many Architects, Structural Engineers, and Fire Engineers fully explain this to their Clients or Client Organizations ?

And how many Clients/Client Organizations either know that they should ask, or have the balls to ask … their Architect, Structural Engineer and Fire Engineer for this explanation … and furthermore, in the case of any High-Rise Building, Iconic Building, or Building having an Important Function or an Innovative Design … ask the same individuals for some solid reassurance that they have responded directly to the 2005 & 2008 NIST WTC Recommendations … and incorporated the necessary additional modifications into your current designs … whatever current Building and Fire Codes/Regulations do or do not say ?? A big dilemma !

A common and very risky dilemma for Building Designers, however, arises in the situation where the Project Developer, i.e. the Client/Client Organization … is the same as the Construction Organization. The Project Design & Construction Team - as a whole - now has very little power or authority if a conflict arises over technical aspects of the design … or over construction costs. An even bigger dilemma !!

Colour image showing the Kingdom Tower Project, in Jeddah (Saudi Arabia) ... which will be completed in 2018. Design by Adrian Smith & Gordon Gill Architecture, USA. Click to enlarge.

4. The Next Series of Posts – 2008 NIST WTC Recommendations

In the new year of 2012 … I will examine the later NIST Recommendations which were a response to the Fire-Induced Progressive Collapse of World Trade Center Building No.7.

Colour image showing the Signature Tower Project, in Jakarta (Indonesia) ... which will be completed in 2016. Design by Smallwood Reynolds Stewart Stewart Architects & Planners, USA. Click to enlarge.

5. Please … Your Comments, Views & Opinions ?!?

The future of Conventional Fire Engineering ended on the morning of Tuesday, 11 September 2001, in New York City … an engineering discipline constrained by a long heritage deeply embedded in, and manacled to, an outdated and inflexible prescriptive approach to Codes/Regulations and Standards … an approach which is irrational, ignores the ‘real’ needs of the ‘real’ people who use and/or occupy ‘real’ buildings … and, quite frankly, no longer makes any scientific sense !!

On the other hand … having confronted the harsh realities of 9/11 and the Mumbai ‘Hive’ Attacks, and digested the 2005 & 2008 NIST WTC Recommendations … Sustainable Fire Engineering … having a robust empirical basis, being ‘person-centred’, and positively promoting creativity … offers the International Fire Science and Engineering Community a confident journey forward into the future … on many diverse routes !

This IS the only appropriate response to the exciting architectural innovations and fire safety challenges of today’s Built Environment.

BUT … what do you think ?

END

NIST WTC Recommendations 29-30 > Improved Fire Education

CJ Walsh — Thu, 08 Dec 2011 21:51:43 +0000

Previous Posts in This Series …

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

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

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

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

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

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

2011-12-07: NIST WTC Recommendations 25-28 > Improved Practices … GROUP 7. Improved Procedures and Practices – Recommendations 25, 26, 27 & 28

2011-12-08: SOME PRELIMINARY COMMENTS …

1. At last, we arrive at the Group 8 Recommendations ! At this stage … my impression is that the NIST Team began to run out of steam, because these two short Recommendations barely scratch the surface with regard to the significant education and training needs of the many different design, construction, management, operation, maintenance and emergency response disciplines engaged with, and confronted by, the Built Environment … every day of every week.

After a careful reading of all 30 NIST WTC Recommendations, I hope that you have satisfied yourself/yourselves that these Recommendations must be applied to ALL Buildings … not just Tall Buildings. At various times … Iconic Buildings, and Buildings having a Critical Function or an Innovative Design have been specifically mentioned. And look back to Recommendation 22a … tunnels and subways also made an appearance ! The proper focus for the International Fire Science and Engineering Community must be on the Built Environment as a whole.

At All Levels in a Typical Construction Project … there are also pressing education and training needs. It is of little use if the Project Design Documentation is 100% … and the people actually installing the passive fire protection measures or the active fire protection systems on site don’t know which end is ‘up’ ! The Project Design Documentation, in whatever format, is merely a means to an end … a fully realized and occupied Building, which is fire-safe.

Preferably … we should be discussing the mandatory Re-education and Re-training of Practitioners in the different Disciplines … [CPD (Continuing Professional/Personal Development) is not at all sufficient !] … accompanied by a very necessary Re-engineering of the Stakeholder Professional and Educational Institutions … and other related Organizations, particularly National Authorities Having Jurisdiction (AHJ’s).

Our Best Hope for Transformation … lies with the current crop of third-level undergraduate students in the different disciplines. And, as we are discovering with the introduction of the Structural EuroCodes in the European Union, it will take perhaps 5-8 years of continuous student output to transform pre-9/11 conventional fire engineering … into a post-9/11 and post-Mumbai fire engineering which is properly ‘reliability-based’ and ‘person-centred’, i.e. Sustainable Fire Engineering !

As for the Future, and Some Conclusions to this Series … coming shortly to a computer monitor screen near you !

2005 NIST WTC RECOMMENDATIONS

GROUP 8. Education and Training

NIST WTC Recommendation 29.

NIST WTC Recommendation 30.

END

NIST WTC Recommendations 25-28 > Improved Practices

CJ Walsh — Wed, 07 Dec 2011 17:47:01 +0000

Previous Posts in This Series …

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

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

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

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

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

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

2011-12-07: SOME PRELIMINARY COMMENTS …

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

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

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

Fire Compartmentation

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

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

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

Here are two reasons why not …

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

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

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

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

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

2005 NIST WTC RECOMMENDATIONS

GROUP 7. Improved Procedures and Practices

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

NIST WTC Recommendation 25.

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

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

NIST WTC Recommendation 26.

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

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

NIST WTC Recommendation 27.

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

NIST WTC Recommendation 28.

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

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

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

END

NIST WTC Recommendations 21-24 > Improved Firefighting

CJ Walsh — Sun, 04 Dec 2011 16:54:42 +0000

Previous Posts in This Series …

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

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

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

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

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

2011-12-04: SOME PRELIMINARY COMMENTS …

1. Such is the pervasively high level of both direct and indirect fire losses, not all of which have yet been identified … that a force of committed firefighters, having sufficient numbers and properly trained and equipped, is a valuable social asset in any community … and one not to be weakened or diluted easily.

2. Lack of discipline among firefighters was an issue during the day of 9-11 (11th September 2011) in New York …

In real life or death situations, however, discipline is essential … but competent and efficient command, control and co-ordination … facilitated by reliable systems of communication (human and electronic) … are critical.

And accurate, real time information about what is happening at a building fire incident of whatever scale … i.e. situation awareness … is a tool which propels forward and encourages the effective functioning of both the firefighter and the user/occupant evacuating the building.

3. A serious gap, internationally … a deep cavern … in the awareness, training and education of firefighters at all levels … is the issue of ‘disability’ and the varying range of abilities in a typical building user/occupant profile.

It is not fully appreciated by firefighters that certain people may die if placed in a standard fireman’s lift position … or, if shouted and screamed at, many people may have no understanding whatever of the firefighter’s intended meaning … or that, in order for everyone to reach a place of safety, it is necessary for firefighters to ensure that safe, accessible routes from the building (i.e. clear of all obstacles, e.g. fire hose lines) are prepared for, thoroughly, in advance of any fire incident … and actually provided should one occur.

Panic attacks during an emergency do exist ! Standard movement times for people evacuating do not exist !! And … firefighters may themselves become impaired during a building fire incident !!!

4. As for building designers … where do I even start ?? Much could, and should, be done in the design and initial construction of a building to assure firefighter safety. But … where does any requirement to consider this issue appear in national building codes/regulations ??

I have already discussed this matter in relation to European Union (EU) Regulation 305/2011 on Construction Products, where such a requirement is contained in Basic Requirement for Construction Works 2: ‘Safety in Case of Fire’ (Annex I).

2005 NIST WTC RECOMMENDATIONS

GROUP 6. Improved Emergency Response

NIST WTC Recommendation 21.

NIST recommends the installation of fire-protected and structurally hardened elevators to improve emergency response activities in tall buildings by providing timely emergency access to responders and allowing evacuation of mobility-impaired building occupants. Such elevators should be installed for exclusive use by emergency responders during emergencies.* In tall buildings, consideration also should be given to installing such elevators for use by all occupants. NIST has found that the physiological impacts on emergency responders of climbing numerous (e.g. 20 or more) storeys makes it difficult to conduct effective and timely firefighting and rescue operations in building emergencies without functioning elevators. The use of elevators for these purposes will require additional operating procedures and protocols, as well as a requirement for release of elevator door restrictors by emergency response personnel.

[ * F-44 The access time for emergency responders, in tall building emergencies where elevators are not functioning and only stairways can be used, averages between 1 minute and 2 minutes per floor, which, for example, corresponds to between 1½ and 2 hours (depending on the amount of gear and equipment carried) to reach the 60th floor of a tall building. Further, the physiological impact on the emergency responders of climbing more than 10 to 12 floors in a tall building makes it difficult for them to immediately begin aggressive firefighting and rescue operations.]

Affected Standards: ASME A 17, ANSI 117.1, NFPA 70, NFPA 101, NFPA 1221, NFPA 1500, NFPA 1561, NFPA 1620, and NFPA 1710. Model Building and Fire Codes: The standards should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard.

NIST WTC Recommendation 22.

NIST recommends the installation, inspection, and testing of emergency communications systems, radio communications, and associated operating protocols to ensure that the systems and protocols: (1) are effective for large-scale emergencies in buildings with challenging radio frequency propagation environments; and (2) can be used to identify, locate, and track emergency responders within indoor building environments and in the field. The federal government should co-ordinate its efforts that address this need within the framework provided by the SAFECOM programme of the Department of Homeland Security.

a. Rigorous procedures, including pre-emergency inspection and testing, should be developed and implemented for ensuring the operation of emergency communications systems and radio communications in tall buildings and other large structures (including tunnels and subways), or at locations where communications are difficult.

b. Performance requirements should be developed for emergency communications systems and radio communications that are used within buildings or in built-up urban environments, including standards for design, testing, certification, maintenance, and inspection of such systems.

c. An interoperable architecture for emergency communication networks – and associated operating protocols – should be developed for unit operations within and across agencies in large-scale emergencies. The overall network architecture should cover local networking at incident sites, dispatching, and area-wide networks, considering: (a) the scale of needed communications in terms of the number of emergency responders using the system in a large-scale emergency and the organizational hierarchy; and (b) challenges associated with radio frequency propagation, especially in buildings; (c) interoperability with existing legacy emergency communications systems (i.e. between conventional two-way systems and newer wireless network systems); and (d) the need to identify, locate, and track emergency responders at an incident site.

Affected Standards: FCC, SAFECOM, NFPA Standards on Electronic Safety Equipment, NFPA 70, NFPA 297, and NFPA 1221. Model Building Codes: The standards should be adopted in model building codes by mandatory reference to, or incorporation of, the latest edition of the standard.

NIST WTC Recommendation 23.

NIST recommends the establishment and implementation of detailed procedures and methods for gathering, processing, and delivering critical information through integration of relevant voice, video, graphical, and written data to enhance the situational awareness of all emergency responders. An information intelligence sector* should be established to co-ordinate the effort for each incident.

[ * F-45 A group of individuals that is knowledgeable, experienced, and specifically trained in gathering, processing, and delivering information critical for emergency response operations, and is ready for activation in large and/or dangerous events.]

Affected Standards: National Incident Management System (NIMS), NRP, SAFECOM, FCC, NFPA Standards on Electronic Safety Equipment, NFPA 1221, NFPA 1500, NFPA 1561, NFPA 1620, and NFPA 1710. Model Building Codes: The standards should be adopted in model building codes by mandatory reference to, or incorporation of, the latest edition of the standard.

NIST WTC Recommendation 24.

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.

END

NIST WTC Recommendations 12-15 > Improved Active Protection

CJ Walsh — Fri, 25 Nov 2011 16:52:35 +0000

Previous Posts in This Series …

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

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

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

2011-11-25: SOME PRELIMINARY COMMENTS …

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

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

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

Quality of Fire Engineering Design & Related Construction

Category A

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

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

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

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

Category B

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

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

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

Category C

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

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

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

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

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

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

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

2005 NIST WTC RECOMMENDATIONS

GROUP 4. Improved Active Fire Protection

NIST WTC Recommendation 12.

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

NIST WTC Recommendation 13.

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

NIST WTC Recommendation 14.

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

NIST WTC Recommendation 15.

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

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

END

NIST WTC Recommendations 4-7 > Structural Fire Endurance

CJ Walsh — Fri, 18 Nov 2011 13:52:06 +0000

First Post in This Series …

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

2011-11-18: SOME PRELIMINARY COMMENTS …

1. Before launching into the next Group of NIST WTC Recommendations, it would be useful to distinguish between the following technical terms … which have been adapted from ISO/TR 10158: ‘Principles and Rationale Underlying Calculation Methods in Relation to Fire Resistance of Structural Elements’ …

Real Fire: A fire which develops in a building and which is influenced by such factors as the type of building and its occupancy; the combustible content (fire load); the ventilation, geometry and thermal properties of the fire compartment, or building space (should no fire compartmentation exist); the fire suppression systems in the building and the actions of the fire services.

Real Fires are complex phenomena. Consequently, in structural fire engineering, idealized versions of ‘real fires’ are employed.

Experimental Fire: A full or reduced scale fire with specified and controlled characteristics.

Design Fire: A fire with specified exposure data intended for use in connection with structural fire engineering calculations.

A Design Fire may either be representative of the thermal exposure described by the standard time-temperature-pressure relationship in an International/European/National Standard, or some non-standard exposure intended to simulate particular fire exposure conditions.

However, in SDI Technical Guidance Note 95/102: ‘Proper Evidence of a Fire Test Result within the European Economic Area (EEA)’, issued on 22 May 1995, I included the following caution …

#1.7 A Fire Test in a Fire Test Laboratory, involving exposure of a test specimen or prototype to ‘test fire’ conditions, gives only a limited indication of: (a) the likely performance of a particular product, material or component when exposed to ‘real fire’ conditions; and (b) the suitability of a product, material or component for a particular end use.

2. In conventional fire engineering, much confusion arises because of a failure to properly distinguish between these two concepts …

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.

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.

[ In structural fire engineering, the concern must be that the structure will fulfil its purpose, both during the fire - and for a minimum period afterwards, during the 'cooling phase'.]

3. Therefore, with regard to Recommendation 6 … it is more correct and precise to refer to ‘Steel Fire Protection Systems’, rather than to ‘steel fire resisting materials’ ! AND … the same questions must be asked about All Lightweight Steel Fire Protection Systems … not just the sprayed systems.

Lightweight Fire Protection Systems are also used to protect concrete in buildings and tunnels.

4. These 2005 NIST Recommendations will later be confirmed, and further reinforced, by the 2008 NIST Recommendations. Bringing Recommendation 7, below, closer to home … it is interesting to note that a very necessary discussion on the technical adequacy of the approach taken to structural performance in fire … in both Technical Guidance Document B (Ireland) and Approved Document B (England & Wales) … has yet not even commenced !

2005 NIST WTC RECOMMENDATIONS

GROUP 2. Enhanced Fire Endurance of Structures

NIST WTC Recommendation 4.

[ * F-23 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. It is not clear how the current height and areas tables in building codes consider 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-24 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-25 The passive fire protection system (including 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-26 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-27 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.

Adoption of this Recommendation will allow building codes to distinguish the risks associated with different building heights, fuel concentrations, and fire protection systems. Research is needed to develop the data and evaluate alternative proposals for construction classifications and fire ratings. Model Building Codes: A comprehensive review of current construction classifications and fire rating requirements and the establishment of a uniform set of revised thresholds with a firm technical basis that considers the factors identified above should be undertaken.*

[ * F-28 The National Fire Protection Association (NFPA) 5000 model code and the International Building Code (IBC) both recognize the risks associated with different building heights and accepted changes in 2001 and 2004, respectively. Both model codes now require that buildings 126 metres and higher have a minimum 4 hour structural fire resistance rating. The previous requirement was 2 hours. The change provides increased fire resistance for the structural system leading to enhanced tenability of the structure and gives firefighters additional protection while fighting a fire. While NIST supports these changes as an interim step, NIST believes that it is essential to complete a comprehensive review that will establish a firm technical basis for construction classifications and fire rating requirements.]

NIST WTC Recommendation 5.

This effort should address the technical issues listed below: *

[ * F-29 The technical issues were identified from the series of four fire resistance tests of the WTC Floor system, and the review and analysis of relevant documents that were conducted as part of this Investigation.]

a. Criteria and test methods for determining:

structural limit states, including failure, and means for measurement ;
effect of scale of test assembly versus prototype application, especially for long-span structures that significantly exceed the size of test furnaces ;
effect of restraining thermal expansion (end-restraint conditions) on test results, especially for long-span structures that have greater flexibility ;
fire resistance of structural connections, especially the fire protection required for a loaded connection to achieve a specified rating ; *

[ * F-30 There is a lack of test data on the fire resistance ratings of loaded connections. The fire resistance of structural connections is not rated in current practice. Also, standards and codes do not provide guidance on fire protection requirements for structural connections when the connected members have different fire resistance ratings.]

effect of the combination of loading and exposure (time-temperature profile) required to adequately represent expected conditions ;
the repeatability and reproducibility of test results (typically, results from a single test are used to determine the rating for a component or assembly) ; and
realistic ratings for structural assemblies made with materials that have improved elevated temperature properties (strength, modulus, creep behaviour).

b. Improved procedures and guidance to analyze and evaluate existing data from fire resistance tests of building components and assemblies for use in qualifying an untested building element.

c. Relationships between prescriptive ratings and performance of the assembly in real fires.

Affected National and International Standards: * ASTM E 119, NFPA 251, UL 263, and ISO 834. Model Building Codes: The standards should be adopted in model building codes by mandatory reference to, or incorporation of, the latest edition of the standard.

[ * F-31 While the NIST Recommendations are focused mainly on U.S. national standards, each U.S. standard has counterpart international standards. In a recent report (ISO/TMB AGS N 46), the International Organization for Standardization (ISO), through its Advisory Group for Security (AGS), has recommended that since many of the ISO standards for the design of buildings date back to the 1980's, they should be reviewed and updated to make use of the studies done by NIST on the World Trade Center disaster, the applicability of new technology for rescue from high buildings, natural disasters, etc. ISO's Technical Advisory Group 8 co-ordinates standards work for buildings.]

NIST WTC Recommendation 6.

NIST recommends the development of criteria, test methods, and standards: (1) for the in-service performance of Sprayed Fire Resisting Materials (SFRM, also commonly referred to as fire protection insulation) used to protect structural components; and (2) to ensure that these materials, as installed, conform to conditions in tests used to establish the fire resistance rating of components, assemblies, and systems.

This should include:

Improved criteria and testing methodologies for the performance and durability of SFRM (e.g. adhesion, cohesion, abrasion, and impact resistance) under in-service exposure conditions (e.g. temperature, humidity, vibration, impact, with/without primer paint on steel*) for use in acceptance and quality control. The current test method to measure the bond strength, for example, does not distinguish the cohesive strength from the tensile and shear adhesive strengths. Nor does it consider the effect of primer paint on the steel surface. Test requirements that explicitly consider the effects of abrasion, vibration, shock, and impact under normal service conditions are limited or do not exist. Also, the effects of elevated temperatures on thermal properties and bond strength are not considered in evaluating the performance and durability of SFRM.

[ * F-32 NIST tests show that the adhesive strength of SFRM on steel coated with primer paint was a third to half of the adhesive strength on steel that had not been coated with primer paint. The SFRM products used in the WTC towers were applied to steel components coated with primer paint.]

Inspection procedures, including measurement techniques and practical conformance criteria, for SFRM in both the building codes and fire codes for use after installation, renovation, or modification of all mechanical and electrical systems and by fire inspectors over the life of the building. Existing standards of practice (AIA MasterSpec and AWCI Standard 12), often required by codes for some buildings need to be broadly applied to both new and existing buildings. These standards may require improvements to address the issues identified in this Recommendation.
Criteria for determining the effective uniform SFRM thickness – thermally equivalent to the variable thickness of the product as it is actually applied – that can be used to ensure that the product in the field conforms to the near uniform thickness conditions in the tests used to establish the fire resistance rating of the component, assembly, or system. Such criteria are needed to ensure that the SFRM, as installed, will provide the intended performance.
Methods for predicting the effectiveness of SFRM insulation as a function of its properties, the application characteristics, and the duration and intensity of the fire.
Methods for predicting service life performance of SFRM under in-service conditions.

Affected Standards: AIA MasterSpec and AWCI Standard 12 for field inspection and conformance criteria; ASTM standards for SFRM performance criteria and test methods. Model Building Codes: The standards should be adopted in model building codes by mandatory reference to, or incorporation of, the latest edition of the standard. (See Recommendation 10 for more on this issue.)

NIST WTC Recommendation 7.

NIST recommends the adoption and use of the ‘structural frame’ approach to fire resistance ratings. This approach requires that structural members – such as girders, beams, trusses, and spandrels having direct connection to the columns, and bracing members designed to carry gravity loads – be fire protected to the same fire resistance rating as columns. This approach is currently required by the International Building Code (IBC), one of the model codes, and is in the process of adoption by NFPA 5000, the other model code. This requirement 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.

[ * F-33 Had this requirement been adopted by the 1968 New York City building code, the WTC floor system, including its connections, would have had the 3 hour rating required for the columns since the floors braced the columns.]

END

NIST’s Recommendations on the 9-11 WTC Building Collapses

CJ Walsh — Tue, 25 Oct 2011 21:56:16 +0000

2011-10-25: Since shortly after my visit to Lower Manhattan in mid-October 2001 … we have maintained an Archive Page on ‘Structural Fire Engineering, World Trade Center Incident (9-11) & Fire Serviceability Limit States‘ … at SDI’s Corporate WebSite. And I have referenced here … many, many times … the Recommendations contained in the 2005 & 2008 Final Reports of the U.S. National Institute of Standards & Technology (NIST) on the 9-11 World Trade Center Building 1, 2 & 7 Collapses.

In this post (and a series of future posts) … I find it most necessary that the 2005 & 2008 NIST Recommendations now be presented for everyone to read. Yes, some of Recommendations apply specifically to Tall and Very Tall Buildings … and Building Designers in India, China, Brazil, Russia & South Africa (BRICS), the Arab Gulf Region, Europe and North America, etc., should be fully aware of their contents.

BUT … I am also strongly convinced … precisely because I am an Architect, a Fire Engineer and a Technical Controller … that most of the NIST Recommendations apply to ALL Buildings … so catastrophic was the failure exposed on that fateful day (11 September 2001) … in all of our common design and construction practices … and our operation, maintenance and emergency response procedures !

PRELIMINARY COMMENTS

1. Extract from Paragraph #9.2, Chapter 9, NIST Final Report on the Collapse of the World Trade Center Towers – Report Reference NIST NCSTAR 1 (2005) …

NIST believes that these Recommendations are both realistic and achievable within a reasonable period of time, and that their implementation would make buildings safer for occupants and emergency responders in future emergencies.
NIST strongly urges that immediate and serious consideration be given to these Recommendations by the building and fire safety communities – especially designers, owners, developers, codes and standards development organizations, regulators, fire safety professionals, and emergency responders.
NIST also strongly urges building owners and public officials to: (i) evaluate the safety implications of these Recommendations for their existing inventory of buildings; and (ii) take the steps necessary to mitigate any unwarranted risks without waiting for changes to occur in codes, standards, and practices.

2. At the time of writing … it is important to point out that although they are related Structural Concepts … and there is still, to this day, a lot of confusion about these concepts in the USA … it is important to clearly distinguish between …

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 distortion, displacement and 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.

3. Recommendation 2, below, would certainly need to be understood and implemented within today’s additional design constraints of Sustainable Climate Change Adaptation and Resilience to Severe Weather Events. Therefore … Design Wind Speeds must be increased, accordingly, for ALL Buildings.

4. As such a high level of performance is expected … indeed demanded … of a Sustainable Building … Sustainable Fire Engineering must be ‘reliability-based’. In other words, it must have a rational, empirical and scientifically robust basis … unlike conventional fire engineering, which is yet aimlessly wandering around in pre-historic caves !

5. Finally … there is no use trying to hide the fact that progress on implementing the NIST Recommendations, within the USA, has been lamentably slow. Outside that jurisdiction, the response has ranged from mild interest, to complete apathy, and even to vehement antipathy. The implications arising from implementation are much too hard to digest … for long established fire safety professionals and researchers who are unswervingly committed to the flawed and out-of-date practices and procedures of conventional fire engineering and, especially, for vested interests !

However … is it either in society’s interest, or in the interests of our clients/client organizations … that, to give you a simple example which is relevant close to home, British Standard 9999 (published on 31 October 2008): ‘Code of Practice for Fire Safety in the Design, Management and Use of Buildings’ takes absolutely no account of any of the NIST Recommendations ? As far as the British Standards Institution is concerned … 9-11 never happened … which I think is an inexcusable and unforgivable technical oversight !

For this reason, the General Public in ALL of our societies and Clients/Client Organizations in ALL countries should also be fully aware of the contents of these Recommendations …

Colour photograph showing the two World Trade Center Towers immediately after the impact of the second plane. At a fundamental level, this was a very serious 'real' fire incident ... which was extensively, and very thoroughly, investigated by the U.S. National Institute of Standards & Technology (NIST) ... and resulted in the important 2005 & 2008 NIST Recommendations. Click to enlarge.

2005 NIST WTC RECOMMENDATIONS

GROUP 1. Increased Structural Integrity

NIST WTC Recommendation 1.

a. Progressive collapse* should be prevented in buildings.

[ * F-19 Progressive collapse (or disproportionate damage) occurs when an initial local failure spreads from structural element to structural element resulting in the collapse of an entire structure or a disproportionately large part of it.]

The primary structural systems should provide alternate paths for carrying loads in case certain components fail (e.g. transfer girders or columns). This is especially important in buildings where structural components (e.g. columns, girders) support unusually large floor areas.*

[ * F-20 While the WTC towers eventually collapsed, they had the capacity to redistribute loads from impact and fire damaged structural components and sub-systems to undamaged components and sub-systems. However, the core columns in the WTC towers lacked sufficient redundant (alternative) paths for carrying gravity loads.]

Progressive collapse is addressed only in a very limited way in practice and by codes and standards. For example, the initiating event in design to prevent progressive collapse may be removal of one or two columns at the bottom of the structure. Initiating events at multiple locations within the structure, or involving other key components and sub-systems, should be analyzed commensurate with the risks considered in the design. The effectiveness of mitigation approaches involving new system and sub-system design concepts should be evaluated with conventional approaches based on indirect design (continuity, strength and ductility of connections), direct design (local hardening), and redundant (alternate) load paths. The capability to prevent progressive collapse due to abnormal loads should include: (i) comprehensive design rules and practice guides; (ii) evaluation criteria, methodology, and tools for assessing the vulnerability of structures to progressive collapse; (iii) performance-based criteria for abnormal loads and load combinations; (iv) analytical tools to predict potential collapse mechanisms; and (v) computer models and analysis procedures for use in routine design practice. The federal government should co-ordinate the existing programmes that address this need: those in the Department of Defence; the General Services Administration; the Defence Threat Reduction Agency; and NIST. Affected Standards: ASCE-7, AISC Specifications, and ACI 318. These standards and other relevant committees should draw on expertise from ASCE/SFPE 29 for issues concerning progressive collapse under fire conditions. Model Building Codes: The consensus standards should be adopted in model building codes (i.e. the International Building Code and NFPA 5000) by mandatory reference to, or incorporation of, the latest edition of the standard. State and local jurisdictions should adopt and enforce the improved model building codes and national standards based on all 30 WTC Recommendations (2005). The codes and standards may vary from the WTC Recommendations, but satisfy their intent.

b. A robust, integrated predictive capability should be developed, validated, and maintained to routinely assess the vulnerability of whole structures to the effects of credible hazards. This capability to evaluate the performance and reserve capacity of structures does not exist and is a significant cause for concern. This capability would also assist in investigations of building failure – as demonstrated by the analyses of the WTC building collapses carried out in this Investigation. The failure analysis capability should include all possible complex failure phenomena that may occur under multiple hazards (e.g. bomb blasts, fires, impacts, gas explosions, earthquakes, and hurricane winds), experimentally validated models, and robust tools for routine analysis to predict such failures and their consequences. This capability should be developed via a co-ordinated effort involving federal, private sector, and academic research organizations in close partnership with practicing engineers.

NIST WTC Recommendation 2.

NIST recommends that nationally accepted performance standards be developed for: (1) conducting wind tunnel testing of prototype structures based on sound technical methods that result in repeatable and reproducible results among testing laboratories; and (2) estimating wind loads and their effects on tall buildings for use in design, based on wind tunnel testing data and directional wind speed data. Wind loads specified in current prescriptive codes may not be appropriate for the design of very tall buildings since they do not account for building-specific aerodynamic effects. Further, a review of wind load estimates for the WTC towers indicated differences by as much as 40 % from wind tunnel studies conducted in 2002 by two independent commercial laboratories. Major sources of differences in estimation methods currently used in practice occur in the selection of design wind speeds and directionality, the nature of hurricane wind profiles, the estimation of ‘component’ wind effects by integrating wind tunnel data with wind speed and direction information, and the estimation of ‘resultant’ wind effects using load combination methods. Wind loads were a major factor in the design of the WTC tower structures and were relevant to evaluating the baseline capacity of the structures to withstand abnormal events such as major fires or impact damage. Yet, there is lack of consensus on how to evaluate and estimate winds and their load effects on buildings.

a. Nationally accepted standards should be developed and implemented for conducting wind tunnel tests, estimating site-specific wind speed and directionality based on available data, and estimating wind loads associated with specific design probabilities from wind tunnel test results and directional wind speed data.

b. Nationally accepted standards should be developed for estimating wind loads in the design of tall buildings. The development of performance standards for estimating wind loads should consider: (1) appropriate load combinations and load factors, including performance criteria for static and dynamic behaviour, based on both ultimate and serviceability limit states; and (2) validation of wind load provisions in prescriptive design standards for tall buildings, given the universally acknowledged use of wind tunnel testing and associated performance criteria. Limitations to the use of prescriptive wind load provisions should be clearly identified in codes and standards.

The standards development work can begin immediately to address many of the above needs. The results of those efforts should be adopted in practice as soon as they become available. The research that will be required to address the remaining needs also should begin immediately and results should be made available for standards development and use in practice. Affected National Standard: ASCE-7. Model Building Codes: The standard should be adopted in model building codes by mandatory reference to, or incorporation of, the latest edition of the standard.

NIST WTC Recommendation 3.

NIST recommends that an appropriate criterion be developed and implemented to enhance the performance of tall buildings by limiting how much they sway under lateral load design conditions (e.g. winds and earthquakes). The stability and safety of tall buildings depend upon, among other factors, the magnitude of building sway or deflection, which tends to increase with building height. Conventional strength-based methods, such as those used in the design of the WTC towers, do not limit deflections. The deflection limit state criterion, which is proposed here is in addition to the stress limit state and serviceability requirement; it should be adopted either to complement the safety provided by conventional strength-based design or independently as an alternate deflection-based approach to the design of tall buildings for life safety. The recommended deflection limit state criterion is independent of the criterion used to ensure occupant comfort, which is met in current practice by limiting accelerations (e.g. in the 15 to 20 milli-g range). Lateral deflections, which already are limited in the design of tall buildings to control damage in earthquake-prone regions, should also be limited in non-seismic areas.*

[ * F-22 Analysis of baseline performance under the original design wind loads indicated that the WTC towers would need to have been between 50 % and 90 % stiffer to achieve a typical drift ratio used in current practice for non-seismic regions, though not required by building codes. Limiting drift would have required increasing exterior column areas in lower stories and/or significant additional damping.]

Affected National standards: ASCE-7, AISC Specifications, and ACI 318. Model Building Codes: The standard should be adopted in model building codes by mandatory reference to, or incorporation of, the latest edition of the standard.

END

‘Priory Hall’, Fire Engineering & Protecting Society’s Interests ??

CJ Walsh — Sun, 23 Oct 2011 15:25:37 +0000

2011-10-23: Further to my post, dated 18 October 2011 …

Has anybody’s interests been protected by what has happened at the ‘Priory Hall’ Apartment Development, in Donaghmede, Dublin 13 ? NO.

Now that the buildings there have been completed … will it be possible to effectively repair the most serious fire protection, sound transmission and energy conservation problems with the buildings ?? NO.

At the heart of these problems lie Fundamental Design and Construction Flaws … because, back in the 1990′s and early 2000′s, indigenous builders of simple two storey semi-detached houses suddenly became ‘developers’ of apartment complexes … and these were very different building animals altogether, requiring a degree of technical competence well beyond their reach. And, of course, during the actual construction process everything had to be finished ‘yesterday’, and as cheaply as possible (a policy of cheap product substitution was the un-stated national norm !). In fact, so many corners were cut on Irish Building Sites, at the time, that we should refer to almost the entire construction output from this era as: The Celtic Tiger Round Towers !

And guess who is going to carry out the Corrective/Repair/Refurbishment Works at ‘Priory Hall’ ? The very same Construction Organization which created the mess in the first place !! Can you believe it ??

Furthermore … once these Corrective/Repair/Refurbishment Works are eventually finished … the performance of the Fire Protection Measures in ‘Priory Hall’ will still be compromised, because you can only do so much, physically, when a building is completed. BUT … it would be possible to achieve a Proper Level of Fire Safety in ‘Priory Hall’ … by installing a Fire Suppression System (sprinklers or mist) throughout the development. That’s what it will take !!

Tremendous fire damage was caused to the local environment in Buncefield ... but SOCIETY can no longer suffer this scale of damage ... and these Criminal Human Acts! Click to enlarge.

WHO IS PROTECTING SOCIETY ?

So extensive is the damage caused by fire … throughout Europe … that not all of the Direct and Indirect Fire Losses have yet been identified.

Pause, to consider this definition …

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.

And this means, of course, that our current Fire Loss Data and Statistics are unreliable.

It is not well known, or widely publicised, that the Fire Safety Objectives of Building Regulations are limited to protecting building occupants. The Objectives are only concerned with protecting property, insofar as it is relevant to the protection of those building occupants.

Can you image the look of astonishment on the face of a Managing Director, after his/her factory has been entirely destroyed by a fire, when told by a fire consultant …

” We complied with Part B of the Building Regulations, and here is your Fire Safety Certificate to prove it” ??

What should be happening instead ?

1. Fire Engineering Design & Practice cannot … and must not … be concerned merely with the ‘cost-effective’ compliance with minimal (which they most certainly are !) Fire Safety Objectives mandated by Building Legislation.

2. To properly protect the interests of Society and Clients/Client Organizations … Fire Engineering Design & Practice must also take into account: Safety at Work Legislation; Rights, Equality & Anti-Discrimination Legislation; Environmental Impact Legislation; Public Procurement Legislation; Product Liability Legislation; etc., etc.

3. There is an evolving realization in Ethical Fire Engineering Design & Practice, however, that there is still a significant gap to be bridged. There is no legislation (effective, or otherwise) yet in place, anywhere, which deals with such issues as …

Resistance to Fire-Induced Progressive Collapse – as very strongly recommended in the 2005 & 2008 U.S. NIST Final Reports on the 9-11 World Trade Center Building 1, 2 & 7 Collapses ;
Protection of Vulnerable Building Users in ‘Situations of Risk’ – as required, for example, by Article 11 of the UN Convention on the Rights of Persons with Disabilities (CRPD) ;
Safety of Firefighters/Rescue Teams – as specified in Basic Requirement for Construction Works No.2, in Annex I of European Union Construction Product Regulation 305/2011 ;
Adaptation to Climate Change and Severe Weather Events – the Developed World Economies appear to have no interest, whatsoever, in these issues ;
Sustainable Human & Social Development !

4. We must clearly distinguish, therefore, between the Fire Safety Objectives of Building Regulations/Codes … and Project-Specific Fire Engineering Design Objectives. This difference must be fully understood by the Fire Engineer himself/herself … and then, in all circumstances, properly explained to the Client/Client Organization.

In designing a Building for conditions of fire, and its aftermath … which may take place at any time during the Life Cycle of that Building … Project-Specific Fire Engineering Design Objectives should cover the following spectrum of concerns … in order to properly protect the interests of Society and our Clients/Client Organizations …

- Protection of the Health & Safety of All Building Users … including People with Activity Limitations (2001 WHO ICF), visitors to the building who may be unfamiliar with its layout, and contractors or product/service suppliers temporarily engaged in work or business transactions on the premises ;

- Protection of Property … including the building, its contents, and adjoining or adjacent properties … from loss or damage ;

- Protection of the Health & Safety of Firefighters, Rescue Teams & Other Emergency First Response Personnel ;

- Facility, Ease & Efficient Cost of Carrying Out 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, components, systems, etc., fixed, installed or incorporated in the building ;

- Protection of the Natural Environment from Harm, i.e. Adverse Impacts.

CRIMINAL RESPONSE TO 1981 DUBLIN STARDUST TRAGEDY !

As I write … a stampede has just commenced by the various Construction-Related Professional Institutes and Organizations … to demand closer independent monitoring of what is happening on Irish Building Sites. Far too little … and definitely, far too late ! Back in the early 1990′s, everybody stood by … and co-operated with the installation of an entirely ineffective and dysfunctional system of National Building Control in Ireland … which, let us not forget, survives intact to this day … while, at the same time, the strong long-established and well-resourced Building Control Sections in Dublin and Cork were being quietly dismantled.

The Minister for the Environment, Community & Local Government, Mr. Phil Hogan T.D. … is also chirping in from his ivory tower !

Crocodile Tears !!

Take a Fire Safety Certificate for a Building, for example …

With or Without Conditions … this document confirms that the Local Building Control/Fire Authority is satisfied that the Design Documentation for that building shows proper compliance with the Legal Requirements of Part B of the Irish Building Regulations.

Focus in on the relevant wording of a Fire Safety Certificate, which is as follows …

‘ … hereby certify that the works or building to which the application relates, will, if constructed in accordance with the plans, calculations, specifications and particulars submitted, comply with the requirements of Part B of the Second Schedule to the Building Regulations 1997 to 2008.’

Fire Safety Related Inspections of Construction Projects are not carried out by Competent Local Authority Personnel, or by Competent Independent Technical Controllers. Therefore … a Fire Safety Certificate cannot give, and is not intended to give, any indication with regard to Fire Safety in the Completed Building. The ‘Fire’ Establishment in Ireland knows full well that this is the situation !

Is this any sort of a reasonable, caring or competent response to the 1981 Stardust Discotheque Fire Tragedy in Dublin ??

END