the future direction of our profession in a rapidly evolving trans-disciplinary approach

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

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

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

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

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

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

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

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

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

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

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

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Tackling the current confusion over technical terminology …

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

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

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

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

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

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

Disproportionate Damage

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

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

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

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

Fire-Induced Progressive Damage

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

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Quickly Concluding …

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

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

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Reminder … Please Read the Reflection Document …

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Chair – CIB W14 Research WG IV.

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Update 2012-04-20 …

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

Good Man Morgan !

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

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

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

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

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

C.J.

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