2016-05-05: A Mickey Mouse Effort would be a polite way of describing the long drawn-out and tortuous process of implementing NIST’s Recommendations in the United States. A better description might be … FUBAR !
15 Years After the 2001 WTC 9-11 Attacks in New York City … absolutely nothing has been done concerning the implementation of a significant number of Recommendations … other Recommendations have been only partially implemented, with many being limited to application in buildings over 128m high (420 feet in ye olde silly imperial units of measure), or else buildings over 22.86m high (75 feet) which have an occupant load exceeding 5,000 people or are essential facilities, e.g. hospitals. And believe it or not, some implementing measures are still being challenged and they may yet be reversed in the years ahead. Forget about discussing the already narrow Fire Safety Objectives in building codes/regulations, or Protecting Society, etc., etc. In essence, it has all come down to that ‘durty’ four letter word: COST !
But read this 2011 Status Report for yourselves. I have kept in touch with the current situation over there.
In 2005 & 2008, the U.S. National Institute of Standards & Technology issued a series of very important [ critical ] Recommendations on badly needed revisions to the Design – Construction – Management – Firefighting Procedures for Very High/Tall Buildings, High-Risk Buildings, Iconic Buildings, and Innovatively Designed Buildings. Many, if not all, of these Recommendations were, and remain, just as valid and just as necessary in the case of other building types … whatever their height.
A lot of effort was expended here, a few years ago, on a detailed examination of the NIST Recommendations. In one respect, the Recommendations have become dated and obsolete. The recent 2016 Brussels and 2015 Paris Hive Attacks have altered how we must categorize and deal with buildings of ‘high-risk’. From the start, however, the disability-related Recommendations only concerned mobility impaired building occupants … a serious flaw.
NIST does not have the legal authority to implement its own Recommendations within the United States. However, implementation by the Model Code (e.g. IBC & NFPA) Organizations has been brutally slow and entirely inadequate.
And … it is very noticeable how so many other countries around the world are continuing to completely ignore NIST’s Recommendations. 9-11 never happened !
2015-01-31: The beginning of this 21st Century is deeply unsettling … history is catching up on us, and old certainties are crumbling before our eyes …
The recent, extremely violent Paris Hive Attacks … which occurred between Wednesday and Friday (7-9 January 2015) … have again shown that co-ordinated attacks on a small number of carefully chosen, low-level targets can be just as effective in causing widespread social and economic disruption in a City as a single attack on a high-level target. Search for our previous detailed discussion, here, on the 2008 Mumbai ‘Hive’ Attacks.
On this tragic occasion, the attacks happened in Europe … not, as before, in far-off India.
Following the 2001 WTC 9-11 Attacks in New York City … the U.S. National Institute of Standards and Technology (NIST), in 2005 and 2008, recommended that these Building Types should be treated as ‘Risk Priorities’ …
• Tall / High-Rise Buildings ;
• Iconic Buildings ;
• Buildings Having a Critical Function ;
• Buildings Having an Innovative Design.
However, a typical medium-rise office building (in Paris) and off-street supermarket do not fall into the above categories … another indication that the NIST Recommendations must soon undergo a thorough international review and updating.
In the real world, the whole urban and sub-urban infrastructure of a City is at risk from Extreme Man-Made Events … one more risk among significant others, i.e. Hybrid Disasters (e.g. 2011 Fukushima Nuclear Incident), Severe Natural Events (e.g. earthquakes, typhoons, tsunamis) and Complex Humanitarian Emergencies (e.g. mass human migrations, regional famines). And with 50% of the world’s population already living in Cities, and substantial urban population growth projected over the coming decades … it is clear that, in the short to medium term, Cities must become much more resilient. Search for our continuing discussion, here, about Sustainable Urban Resilience.
In this context, compliance solely with the minimal and limited fire safety objectives in current national legislation – from whatever source around the world – is so far from being either adequate or acceptable … that it is no longer worth a moment’s consideration.
A Fire Engineering which is ‘fit for purpose’, i.e. is both ethical and professional, in today’s complex and dynamic Human Environment … has an essential and critical part to play in the realization of a Safe, Resilient and Sustainable Built Environment for All !
2013-05-22: Whatever Service Providers claim … every day, we experience mobile/cell phone reception variability, drop-off and failure in buildings … whether we are fully conscious of it or not. It’s inconvenient, but all we have to do is change location, even slightly … and ‘re-dial’. However, if we are travelling on a train or bus, and it enters a tunnel … the problem can be annoying, as the situation is beyond our control !
On the other hand, however … not too far from where I live, there is an art house cinema with underground screens on different levels. In this particular case, mobile/cell phone reception failure can be a positive joy – it will not be necessary to listen to someone else’s loud conversations during the film !
BUT … emergency first responders use radio frequency-based communication systems during the normal course of their work … and in the current built environment, these systems can also be unreliable. Improved climate resilience in our future building stock will make matters worse. So, it makes a lot of sense to take this issue seriously now !
Fire Departments equip their firefighters with a Radio Frequency-Based Personal Alert Safety System (PASS) … also known as an Automatic Distress Signal Unit (ADSU) … which sends out a signal to a fire incident base / control centre / command post when the firefighter is motionless or in distress, with a clear indication of his/her location … or, if necessary, a general warning can be sent from the fire incident base / control centre / command post to all firefighters to evacuate a building immediately … for example, if extensive structural collapse is imminent.
Recently, the National Institute of Science & Technology (USA) issued Technical Note 1792. I have just a few short comments to make before jumping into the document …
1. The Empire State Building and a Subway Station in New York City are both iconic building types … and unusual, in the context of the USA generally … but not so in Europe, with our long tradition for ‘hard/heavy’ construction. Challenging environments for radio frequency-based communication systems are encountered in our basement / underground building types, and low-rise complex building types … never mind high-rise and tall buildings.
2. Outside buildings, adequate external access routes for Firefighting Vehicles are mandated in building codes and standards … and Firefighter Lifts are provided inside buildings, etc., etc., etc. Facilitating reliable radio frequency-based emergency communications should become a normal part of thinking about … and designing for … Safe Firefighter Access. And … before new buildings are occupied, it should become routine to carry out an emergency communications check, as part of a wider collaborative effort between Building Management Teams and Local Fire Services.
3. This NIST Technical Note is further evidence … as if any more evidence were needed … that it is a continuing and difficult process to fully implement the 2005 & 2008 NIST WTC 9-11 Recommendations. To date, the easier low hanging fruit (system and procedural inadequacies !) have been tackled, which may be presented and/or described as substantive changes in building codes and standards … mere window dressing … tokenism, at its worst ! However, as discussed here before many times, some European countries continue to completely ignore these important NIST Recommendations.
March 2013 – NIST Technical Note 1792: ‘Performance Analysis of RF-Based Electronic Safety Equipment in a Subway Station and the Empire State Building’.
Radio Frequency (RF) PASS Tests were performed in a New York Subway Station and the Empire State Building because these types of structures provide challenging RF propagation-channel environments. In the Subway, the RF PASS systems were limited in their ability to communicate beyond the initial entrance level. Without the use of repeaters, most of the systems could communicate only a short distance beyond the bottom of the stairwell that connected the token booth corridor to the street. Two systems used repeaters to extend the coverage area. When a repeater was located at the base of the stairwell leading up to the street, those two systems were able to communicate the RF PASS alarms between the street level and the first passenger platform. However, with only a single repeater, neither of the two repeater systems was able to communicate between the external receive site and the second passenger level. This suggests that for structures with sizable subterranean sections, a repeater system will likely be required to reach an external incident command post. If the structure has multiple subterranean levels of increasing depth, a multiple-hop relay system will likely be necessary to ensure the reliability of the communication channel.
In the path-loss measurements and analysis performed at five frequencies, ranging from 430 MHz to 2405 MHz, there are several important insights. Based on the upper adjacent values in the box-plot statistical representation of the path-loss data from the Empire State Building (see Figure 36), path-loss values of 140 dB to 175 dB are possible for high-rises. For the Subway, the path-loss values exceed 210 dB to 240 dB at the lower two passenger platforms (see Figure 35). The frequency dependence is more pronounced for the Empire State Building results, but less apparent in the Subway data. Thus, while a system may function well at the lower end of the frequency spectrum in the above ground portions of a large building, the subway results demonstrate that subterranean structures can cause path-loss values greater than 200 dB across the 430 to 2400 MHz range.
The testing completed here focused on RF PASS system performance and RF propagation-channel measurements in a high-rise and subway station. While a primary goal of the effort was to look at the correlation between the system performance and path-loss behaviour, a secondary goal was to gather path-loss data in two high-attenuation settings. Thus, parameter values for log-normal distributions that will allow simulation of the measured path-loss conditions are included in this report. The authors hope that the data presented here, along with future sets of data, can be used to develop a complete suite of test methods, not only for RF-based PASS systems, but also for other RF-based electronic safety equipment. The path-loss values obtained here are general and could be used to develop standards for other equipment as the need arises for standards for these systems.
In Ireland …10 UHF Channels have been allocated to the Fire Services for use with hand portable radios …
2012-04-16: Following the 9-11 World Trade Center Extreme Fire Event, in New York City …
The National Institute of Standards & Technology (NIST), in the USA, recommended that Fire-Induced Progressive Collapse be particularly considered in the case of …
High-Rise Buildings ;
Iconic Buildings ;
Buildings Having a Critical Function ;
Buildings of Innovative Design.
However, as recently discussed … in order to avoid the wide confusion which the term ‘Fire-Induced Progressive Collapse’ is continuing to cause at international level … the preferred term should now be Fire-Induced Progressive Damage.
AND … CIB Working Commission 14: ‘Fire Safety’ – Research Working Group IV: ‘Structural Reliability & Fire-Induced Progressive Damage’ … would strongly caution that Fire-Induced Progressive Damage and Disproportionate Damage are fundamental concepts to be applied in the design of all building types.
[ A height threshold of 5 Storeys for the consideration of Disproportionate Damage, in the Building Codes/Regulations of many jurisdictions, including Ireland, is entirely arbitrary.]
So … what is Fire-Induced Progressive Damage ? And what is the relationship between this structural concept … and Disproportionate Damage ?
Leaving aside all of the crazy conspiracy theories about the collapse of World Trade Center Building No. 7 … is it possible for Conventional Fire Engineering to directly confront what actually happened ? Unfortunately … the reaction still, even today, is to bury the head, ostrich-like, in the sand … and ignore WTC 7 and the 2008 NIST WTC Recommendations (Final Report NCSTAR 1A) !
Yesterday, on an adjoining page here … I uploaded a New CIB W14 International Reflection Document on ‘Structural Reliability & Fire-Induced Progressive Damage’, with 2 Appendices. Scroll down to the section headed ‘April 2012’.
This is a Reflection Document issued by CIB W14 Research Working Group IV: ‘Structural Reliability & Fire-Induced Progressive Damage’; its purpose is to examine the ‘hot form’ structural concept of Fire-Induced Progressive Damage, and to propose a critical update to fire engineering design practice. It is also intended to encourage a wider discussion about some of fire engineering’s fundamental tenets, and the future direction of our profession in a rapidly evolving trans-disciplinary approach to the design, construction and operation of a Safe and Sustainable Built Environment.
The Document is written in a simple, generic language which is accessible to design disciplines outside the International Fire Science and Engineering Community. The next phase of this CIB W14 Innovation & Research Project will certainly require the use of a more technical language, complex calculations, computer modelling, etc … and much closer liaison with CIB W14’s other Research Working Groups on Connections, Design Fires & Design Fire Scenarios, and Performance Criteria.
I wish to sincerely thank those individuals and organizations who have contributed to the work of our Research Working Group IV.
Finally, the myth surrounding NIST’s 9-11 WTC Recommendations, i.e. that they are only applicable in the case of Very Tall Buildings during rarely occurring extreme events … must be completely demolished, and obliterated from the face of the earth !
Climate Change Adaptation is already demanding a much higher level of building resilience.
C.J. Walsh, FireOx International – Ireland, Italy & Turkey.
Chair – CIB W14 Research WG IV.
Update 2012-04-20 …
In response to a discourteous and unprofessional comment about the above CIB W14 WG IV Reflection Document, posted by Mr. Morgan Hurley (Technical Director at the Society of Fire Protection Engineers in the USA) on the LinkedIn SFPE Group WebPage … I wrote, as follows, this morning …
Good Man Morgan !
Relax … there is no need to become defensive quite yet. WG IV’s Reflection Document is simply intended to raise issues … ask questions … and solicit comments from within and, more importantly, from outside the International Fire Science and Engineering Community.
Perhaps of more direct relevance to the SFPE Membership, in the USA, might be the following …
NIST Report: ‘Best Practices for Reducing the Potential for Progressive Collapse in Buildings’ (NISTIR 7396 – February 2007) … is a good document on ‘disproportionate damage’, but it has nothing to say about ‘fire-induced progressive damage’. These two structural concepts are related, but they are not the same.
When discussing Multi-Storey Steel Frame Buildings, on pages 18 and 19, of NIST Report: ‘Best Practice Guidelines for Structural Fire Resistance Design of Concrete and Steel Buildings’ (NISTIR 7563 – February 2009) … what happened to WTC Building 7 on 9-11, and the 2008 NIST WTC Recommendations (NIST NCSTAR 1A), are conveniently and completely ignored. Instead, there is a launch straight into the BRE Fire Tests at Cardington, and computer calculations, in order to justify a very flawed design approach. How crazy is that ?
Hope to see you there next week … we missed you at the last CIB W14 Meeting in Paris !
2012-03-26: Let me lay out the problem this way … recently, after further developing and refining the definition of the term …
‘ The sequential growth and intensification of structural deformation and displacement, beyond fire engineering design parameters, and the eventual failure of elements of construction in a building – during a fire and the ‘cooling phase’ afterwards – which, if unchecked, will result in disproportionate damage, and may lead to total building collapse ‘
… our attention, in CIB W14’s Research Working Group IV, automatically turned towards the term itself. It didn’t sound right … it didn’t look right … and a lot of people in North America are still completely confused.
Was there anything we could do to clarify the situation ?
The long delay in incorporating the Recommendations of the following 2 Reports …
NIST (National Institute of Standards and Technology). September 2005. Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Final Report on the Collapse of the World Trade Center Towers. NIST NCSTAR 1. Gaithersburg, MD, USA.
NIST (National Institute of Standards and Technology). August 2008. Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Final Report on the Collapse of World Trade Center Building 7. NIST NCSTAR 1A. Gaithersburg, MD, USA.
… into building and fire codes/regulations, standards and administrative provisions at international, regional and national levels … can partly be explained by institutional inertia and the stubborn resistance of vested interests in the construction sector. To be fair, however, although both NIST Reports made extensive reference to the term ‘Fire-Induced Progressive Collapse’ … the structural concept was not defined, or elaborated, in either document. This was not really a task for NIST.
WHO IS CONFUSED ?
Since the publication of the 2005 NIST Report above, there has been much confusion about the term ‘Fire-Induced Progressive Collapse’.
Refer, for example, to the Introduction – Paragraph 1.1 on Page 1 – from NIST Document: ‘Best Practices for Reducing the Potential for Progressive Collapse in Buildings’ (NISTIR 7396 – February 2007) … where a lot of people, who should know better, really screwed up … and got it so wrong …
” The term ‘progressive collapse’ has been used to describe the spread of an initial local failure in a manner analogous to a chain reaction that leads to partial or total collapse of a building. The underlying characteristic of progressive collapse is that the final state of failure is disproportionately greater than the failure that initiated the collapse. ASCE Standard 7-05 defines progressive collapse as ‘the spread of an initial local failure from element to element resulting, eventually, in the collapse of an entire structure or a disproportionately large part of it’ (ASCE 2005). The disproportionality refers to the situation in which failure of one member causes a major collapse, with a magnitude disproportionate to the initial event. Thus, ‘progressive collapse’ is an incremental type of failure wherein the total damage is out of proportion to the initial cause. In some countries, the term ‘disproportionate collapse’ is used to describe this type of failure.
Based on the above description, it is proposed that the professional community adopt the following definition, which is based largely on ASCE 7-05:
progressive collapse – the spread of local damage, from an initiating event, from element to element resulting, eventually, in the collapse of an entire structure or a disproportionately large part of it; also known as disproportionate collapse.
The concept of progressive collapse can be illustrated by the famous 1968 collapse of the Ronan Point apartment building (Fig. 1-1). “
WE NOW KNOW
Fire-Induced Progressive Damage in Buildings is distinguished from Disproportionate Damage – a related but different structural concept – by the mode of damage initiation, not the final condition of building failure. Until this phenomenon is properly understood, and unless it is impeded, or resisted, by building design … Fire-Induced Progressive Damage will result in Disproportionate Damage … and may lead to a Collapse Level Event (CLE), which is entirely unacceptable to the general population of any community or society.
So … if unchecked, Fire-Induced Progressive Damage will lead to Disproportionate Damage.
BUT … while it may happen … which it did, when WTC Building 7 failed completely at approximately 17.21 hrs (local time) on the afternoon of 11 September 2001 in New York City … it is not necessarily always the case that Fire-Induced Progressive Damage and Disproportionate Damage will lead to Total Collapse.
In order to avoid the wide confusion which the term ‘Fire-Induced Progressive Collapse’ is continuing to cause at international level … the preferred term is now Fire-Induced Progressive Damage.
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 …
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.
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.
2011-12-08:NIST WTC Recommendations 29-30 > Improved Fire Education … GROUP 8. Education and Training – Recommendations 29 & 30 (out of 30)
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.
” 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 ! ]
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 !!
(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.’
[ 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 …
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 ?
[2012-01-10 … No reply yet !]
Mr. Thomas Z. Scarangello P.E. – Chairman & CEO, Thornton Tomasetti Structural Engineers, New York.
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 …
[2012-01-10 … No reply yet !]
Mr. C.Y. Lee & Mr. C.P. Wang, Principal Architects – C.Y. Lee & Partners Architects/Planners, Taiwan.
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.
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 architectural designs.
Many thanks for your kind attention. In anticipation of your prompt and detailed response …
[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 !!
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.
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.
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
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 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. Affected Organizations: AIA, SFPE, ASCE, ASME, AISC, ACI, and state licensing boards. Model Building Codes: Detailed criteria and requirements should be incorporated into the model building codes under the topic ‘Design Professional in Responsible Charge’.
NIST WTC 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.Affected Organizations: AIA, SFPE, ASCE, ASME, AISC, ACI, ICC, and NFPA.
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 !
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.
NIST recommends that building codes incorporate a provision that requires building owners to retain documents, including supporting calculations and test data, related to building design, construction, maintenance, and modifications over the entire life of the building.* Means should be developed for off-site storage and maintenance of the documents. In addition, NIST recommends that relevant information be made available in suitably designed hard copy or electronic formats for use by emergency responders. Such information should be easily accessible by responders during emergencies.Model Building Codes: Model building codes should incorporate this Recommendation. State and local jurisdictions should adopt and enforce these requirements.
[ * F-48 The availability of inexpensive electronic storage media and tools for creating large searchable databases makes this feasible.]
NIST WTC Recommendation 28.
NIST recommends that the role of the ‘Design Professional in Responsible Charge’* be clarified to ensure that: (1) all appropriate design professionals (including, e.g. the fire protection engineer) are part of the design team providing the highest standard of care when designing buildings employing innovative or unusual fire safety systems;** and (2) all appropriate design professionals (including, e.g. the structural engineer and the fire protection engineer) are part of the design team providing the highest standard of care when designing the structure to resist fires, in buildings that employ innovative or unusual structural and fire safety systems.Affected Standards: AIA Practice Guidelines. Model Building Codes: The International Building Code (IBC), which already defines ‘Design Professional in Responsible Charge’, should be clarified to address this Recommendation. NFPA 5000 should incorporate the ‘Design Professional in Responsible Charge’ concept, and address this Recommendation.
[ * F-49 In projects involving a design team, the ‘Design Professional in Responsible Charge’ – usually the lead architect – ensures that the team members use consistent design data and assumptions, co-ordinates overlapping specifications, and serves as the liaison between the enforcement and reviewing officials and the owner. This term is defined in the International Building Code (IBC) and in the International Code Council’s Performance Code for Buildings and Facilities (where it is the Principal Design Professional).]
[ ** F-50 If the fire safety concepts in tall buildings had been sufficiently mature in the 1960’s, it is possible that the risks associated with jet-fuel ignited multi-floor fires might have been recognized and taken into account when the impact of a Boeing 707 aircraft was considered by the structural engineer during the design of the WTC towers.]