Structural Fire Engineering

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

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

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

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

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

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

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

!!  Structure … Does Not A Building Make  !!

Some comments on the 3 NIST White Papers …

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

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

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

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

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

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

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

Structural Reliability

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

Structural Fire Engineering

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

Fire-Induced Progressive Damage

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

[ *fire serviceability limit states ]


Disproportionate Damage

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

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


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

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

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


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




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NIST WTC Recommendations 4-7 > Structural Fire Endurance

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)



  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 !



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 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-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.

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.

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.]




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

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 RegionEurope 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 !



  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 BuildingSustainable 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.

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.



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 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.

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.




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Fixing ‘Priory Hall’ in Dublin – Practical Solutions Needed Now !

2011-10-18:  A large ‘can of worms’ has recently been opened in Ireland …

For the last few days, including today, I have been listening intently to Joe Duffy on the RTE Radio ‘Liveline’ Programme at lunchtime.  Joe is being very cautious because he cannot quite believe his ears … either about the unfolding harrowing events for occupants in ‘Priory Hall’, Donaghmede, Dublin 13 – a Private, Multi-Storey Apartment Development – or the tales and anecdotes about Irish Building Sites during the Celtic Tiger Years.

This will be of no consolation to anybody … but the big surprise, for me, is that there is so much public shock.  ‘Priory Hall’ is the Tip of the Iceberg !   Ireland’s current dysfunctional approach to the development of Our(!) Built Environment … has been designed (for want of a better word) in a chaotic, haphazard and malevolent way … to end up in exactly the sort of mess which we are all now witnessing in North County Dublin.

Just to be clear … what has been happening in the Irish Construction Industry, during the boom years, has been happening for twenty years all over the country … more precisely, since the introduction of Legal National Building Regulations, with NO Effective Building Control, in 1991 … and, before that again, in those parts of this jurisdiction, outside of the major urban areas having Legal Building Bye-Laws, and Effective Building Control, i.e. mandatory inspections by competent local authority personnel at the foundation level and drainage level of all building sites … and, depending on the type of project, occasional or frequent inspections above ground level.

[ 1991:  Statutory Instrument No.304 of 1991 – Building Control Act, 1990 (Commencement Order), 1991;  Statutory Instrument No.305 of 1991 – Building Control Regulations, 1991;  Statutory Instrument No.306 of 1991 – Building Regulations, 1991 ]

And the biggest joke of all … is that the sum of the many resources, both human and material, required to repair sub-standard construction throughout Ireland … will count as a positive contribution towards the economic indicator of GDP (Gross Domestic Product) !   FUBAR


Colour photograph showing 'Priory Hall' ... a private, multi-storey apartment development located in North County Dublin, Ireland. Click to enlarge.

Colour photograph showing 'Priory Hall' ... a private, multi-storey apartment development located in North County Dublin, Ireland. Click to enlarge.



What I have not been hearing from the radio, or reading in the newspapers, is practical solutions.

Lest there be any doubt … this is one of the professional services we provide at Sustainable Design International !

So … how do we fix Priory Hall as the situation now presents itself … in such a way that, as soon as it is practicable, a satisfactory level of long-term safety, protection, convenience and comfort will be provided for the occupants of Priory Hall … and the social wellbeing of the local community, there, can be restored.

Afterwards … we can worry about who’s responsible, and about the reasons for the many ‘system’ failures in Ireland.



The following list of practical suggestions … a simple roadmap … is addressed to the Owners and Occupants of Apartments in Priory Hall.

As they have a large vested interest in the problems of Priory Hall … either directly or indirectly … no assurances or undertakings should be accepted, on face value, from either Dublin City Council (DCC) or the Department of the Environment, Community & Local Government (DECLG) … or their representatives.

     1.  Informed Consent of Apartment Owners and Occupants

Demand that the Informed Consent of the Owner/Occupant of an Apartment is required, in writing, before any necessary Corrective/Repair/Refurbishment Works are carried out …

Informed Consent:  Consent freely obtained – without threats or improper inducements – after appropriate disclosure to a person of relevant, adequate and easily assimilated information in a form and language understood by that person.

     2.  ‘As Constructed’ Drawings & Specification of Entire Development

If they exist … we’re on the way !   But, if they don’t exist … and they may not … demand that an ‘As Constructed’ Survey of the Entire Development be carried out immediately.

Demand to see a copy of the Detailed ‘As Constructed’ Drawings, and Specification, for the Entire Development.

CHECK the adequacy of the Detailed Drawings and Specification !

At this stage, remember … all of the emphasis must now be placed on actual construction … not on paperwork !   The ‘As Constructed’ Survey Drawings and Specification are only a means towards a satisfactory end … that’s all !!

     3.  Failures to Properly Comply with Current Building Regulation Requirements A to M (Second Schedule to Irish Building Regulations)

Demand to see a Detailed Schedule of the many failures to properly comply with current Building Regulation Requirements, i.e. Parts A to M in the Second Schedule to the Building Regulations, as amended.

Do not entertain, even for a moment, any discussion about past legal building regulation requirements, which were in force at the time of initial design or construction !

An important point to note !   The Guidance Texts in, for example, Technical Guidance Document B: ‘Fire Safety’ are merely that … GUIDANCE !   This guidance is not infallible … and in a few respects, is entirely inadequate … for example, when dealing with the structural performance of buildings during conditions of fire, and the ‘cooling phase’ immediately afterwards … and the fire evacuation of people with activity limitations, in which case the guidance actually ensures that fire evacuation is made extremely difficult, if not prevented altogether !

Do not be sucked in to any conversations about what is stated, or not stated, in the Technical Guidance Documents.  This is irrelevant.  The Law mandates proper compliance with the Requirements !

Some people may even attempt to quote from the Building Regulation Approved Documents for England & Wales.  Just tell them to take a long jump off a short pier … suggest Howth Harbour !

Become very, very suspicious whenever there is a use of, or reference to, the term ‘Substantial Compliance’ !!

CHECK the adequacy of this Detailed Schedule !   And … ensure that it is Comprehensive !!

     4.  The Necessary Corrective/Repair/Refurbishment Works

Demand to see Full Detailed Information, in the form of annotated drawings and descriptive texts, etc., etc … on the exact nature, timetable and phasing of all of the Corrective/Repair/Refurbishment Works which are necessary to effectively solve the serious problems in the Development.

Beware of decorative solutions, which look good to a superficial visual inspection in ambient conditions … but don’t actually solve anything !

CHECK the adequacy of this Full Detailed Information !

     5.  Independent Technical Control of Construction Works

Demand only Category A Construction Execution of the necessary Corrective/Repair/Refurbishment Works …

Category A Construction Execution:

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

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

Demand receipt of a clear undertaking, in writing, that this will be the case … before any Corrective/Repair/Refurbishment Works commence.

And remember these words from the 2005 Final Report of the U.S. National Institute of Standards & Technology (NIST) on the 9-11 World Trade Center Tower Collapses …

” NIST urges state and local agencies to rigorously enforce building codes and standards since such enforcement is critical to ensure the expected level of safety.  Unless they are complied with, the best codes and standards cannot protect occupants, emergency responders, or buildings.”

CHECK the adequacy of the Proposed Method of Independent Technical Control during execution of the Corrective/Repair/Refurbishment Works !

     6.  Meeting & Discussion with Other Owners/Occupants

Do not act alone … meet the other Owners/Occupants, and discuss issues with them.  Share and collate all available information together.  Try to identify information gaps.  If you do not understand something … ask !

When, and only when, you are happy … signal your Informed Consent that works should commence.

     7.  Commencement of Corrective/Repair/Refurbishment Works

Visit the Construction Site Office regularly … to show that you are taking a keen interest in what is happening.  Keep your eyes and ears wide open.

Expect that you will not be permitted to just wander around the Site.  Construction Sites are one of the most hazardous ‘workplaces’ in this country !

CHECK the adequacy of the Independent Technical Control actually being undertaken.

Demand to be updated, regularly, and at the very least on the progress of Corrective/Repair/Refurbishment Works at your Apartment … in the Common Areas of your Block … and throughout the full extent of the Approach Routes to your Block Entrances and Exits.



Advisory Note:  Should you, or the Residents’ Committee of your Building or Development, be concerned about any matter discussed in this Post … please contact C.J. Walsh  by e-mail:  or by phone: (01) 8386078 / +353 1 8386078.



END  (for now, but to be continued soon !)

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Fire Performance of Concrete Tunnel Lining(s) – Student Study

My father was a secondary school teacher at Presentation College Bray, in County Wicklow … so I have always had a soft spot for education … especially life-long education.

Education is the key to a far deeper and more enriched experience of life !


Very often these days … we receive Queries from Under-Graduate and Post-Graduate Students at Universities and Institutes of Technology … and not just in Ireland !

This was an interesting one recently …

My name is … and I am a Final Year Student in … , studying B.Eng Hons. Civil Engineering.  For my dissertation, I am completing a study on Concrete Tunnel Linings in Fire.  I was hoping to carry out a case study on the Dublin Port Tunnel for my Project.  Have you any advice on the topic ?   Any help would be appreciated.

My response … bearing in mind that it is the student, himself/herself, who must do the hard work …

A few things come to mind right now …

There is a lot of information out there about the Real Fire Performance of Concrete Tunnel Lining(s).  You have to access as much of that information as practicable … in detail !   Pay very close attention to that information.

Next … please check out this Page on our Corporate WebSite … … in order to approach the subject from the viewpoint of Concrete Spalling being a Fire Serviceability Limit State.

Don’t waste your time looking at fire protection products which are applied to the surface of the concrete … this avoids the substantive (fire engineering) issues involved here.

And … what about the Effective Repair of Fire-Damaged Concrete Tunnel Lining(s) ?

Some Innovative (Fire Engineering) Design Recommendations would be a nice result from your work !

Good luck with the dissertation.


Would anybody else have some suggestions ?




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2009 Camberwell Fire – Today’s Fire Engineering Challenges

In Ireland, it is rarely the case that there is an opportunity to practice Rational, Evidence-Based Fire Engineering … and to apply its Principles in a manner which is both professional and project-specific.  The grim reality of everyday fire consultancy revolves around playing ‘cat and mouse’ with current national building and fire regulations/codes … with ‘cost effectiveness’, i.e. to achieve a defined objective at the lowest cost, or to achieve the greatest benefit at a given cost … being the real, hidden driver behind such dangerous games !   Who wants to hear that the Irish Fire Safety Certification System is little more than a charade … an elaborate, resource consuming paper exercise … made all the more meaningless because Part B: ‘Fire Safety’ (of the Second Schedule to the 1997 Building Regulations, as amended) is isolated from a necessary and vital consideration of the other Parts, particularly Parts A: ‘Structure’; D: ‘Materials & Workmanship’; K: ‘Stairways, Ladders, Ramps & Guards’; and M: ‘Access for People with Disabilities’ ?


Colour photograph showing an external view of Lakanal House, Sceaux Estate, Camberwell, London (GB) ... after the Fatal Fire which occurred at 16.19 hrs, on 3rd July 2009. The fire was caused by a faulty television set, and resulted in the loss of 6 lives, with 15 residents and 1 firefighter left injured. London Fire Brigade was required to assist the evacuation of a further 40 building occupants to safety. Along with the serious loss of life, and the large number of injured people ... over 90 families had to vacate their flats.

Colour photograph showing an external view of Lakanal House, Sceaux Estate, Camberwell, London (GB) ... after the Fatal Fire which occurred at 16.19 hrs, on 3rd July 2009. The fire was caused by a faulty television set, and resulted in the loss of 6 lives, with 15 residents and 1 firefighter left injured. London Fire Brigade was required to assist the evacuation of a further 40 building occupants to safety. Along with the serious loss of life, and the large number of injured people ... over 90 families had to vacate their flats.


Discussing the Principles of Fire Engineering … and elaborating on the significant differences between the limited Fire Safety Objectives of legal regulations/codes … and the much broader range of Fire Engineering Design Objectives intended to fully protect social wellbeing and the interests of clients/client organizations, i.e. to properly protect their asses and their assets, in the event of a fire … is a constant, tortuous, but rewarding, struggle.  Masochism does help !

However, the 2009 Fire in a High-Rise Flat Complex at Camberwell, London (GB) … from just looking at the photograph above and reading available information about the spread of fire internally … raises some challenging fire engineering issues for building designers, property managers and construction organizations.

1.  Reliability of People Strategies in a Fire Emergency ?

In spite of the People Strategies elaborated in current Fire Codes/Regulations/Standards … it is totally and utterly irresponsible to advise people to wait in their own flats/apartments during a fire incident, or to develop fire safety strategies based on this approach … unless the confidence level (of ‘Competent Persons’ in Control … managers, designers and builders … of the flat/apartment complex) with regard to the following aspects of construction is very high

  • reliability of both passive and active fire protection measures ;
  • reliability of fire compartmentation (see below) ;
  • reliability of not just the building’s structural stability, but also its serviceability, during the fire and for a minimum period of time afterwards, i.e. the ‘cooling’ phase.

Competent Person:  A person capable of making sound value judgements in the area of professional  endeavour in which he/she possesses profound knowledge, understanding and practical experience.

Fire Codes/Regulations/Standards, wherever or whatever their origin, are NOT Infallible … and it is unbelievably mind-boggling, and sad, to witness a blind and unquestioning faith in such documents !

Looking beyond the headline figure of 6 Fatalities in the 2009 Camberwell Fire … adequate attention should also be focused on the 16 Injured … comprising building occupants and firefighters … the lengthy disruption of community wellbeing resulting from the fire … 90 Families had to be re-located … and, of course, the tremendous amount of direct and indirect damage to property and the environment.  And, I wonder … how did the more vulnerable occupants … and there may also have been visitors present in the complex at the time … cope in this emergency situation ?

This is why Fire Safety, Protection and Evacuation for All must be a Priority on any ‘Sustainability’ Agenda


2.  Independent Technical Control of AHJ Construction ?

I have said this before, but it is worth repeating here again … Self-Regulation Is No Regulation !   Surely this lesson has been burnt into our souls, following the recent scandals, financial and otherwise, in Ireland ?   National and Local Authorities Having Jurisdiction (AHJ’s) … Government Departments & Agencies, Semi-State Organizations, a myriad of Qwangos, the Office of Public Works and Local Authorities are complacent, careless and stubborn concerning proper compliance with even the minimal performance requirements specified in fire regulations, codes and standards.

The 2005 & 2008 National Institute of Standards & Technology (USA) Reports on the 9-11 WTC Incident in New York presented us with some stark language … and a set of important Recommendations which must be heeded …

‘ 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.

To gain broad public confidence … 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.’

[2005 NIST Final Report on WTC 1 & 2 Collapses – Recommendation No. 25]

Later posts, here, will examine the individual NIST Recommendations in more detail.

However … many individuals and organizations, with vested interests, are still trying to discredit and/or ignore the Recommendations contained in the 2005 & 2008 NIST Reports on the WTC 9-11 Incident.   British Standard BS 9999:2008 is a typical case in point … a document which is slowly seeping into the marrow of the Irish Fire Establishment.  The complete and abject failure to consider any of the NIST Recommendations during the long development of this British Standard, or even to reference the Reports in the Standard’s Bibliography … was an inexcusable and unforgivable technical oversight.  The result was … and remains … a sloppy, crassly inadequate, deeply flawed and discriminatory national fire safety standard.  The British Public deserves far better !

At this stage … reluctantly … I must invite the Chair of British Standards Institution Committee FSH/14, Mr. David B. Smith, to seriously re-consider his position. 

3.  Fire Resistance, Compartmentation & Fire-Induced Progressive Collapse ?

Every person participating in the design, construction, management or operation of a building, no matter how simple or complex, must have a working knowledge and proper understanding of the Fire Engineering Principle of 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 ;

–   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.


BUTButbut … buildings are no longer designed and constructed, today, as they were in the 18th or 19th Centuries …

In a fire situation, Fire-Induced Progressive Collapse may commence before any breach of ‘integrity’ occurs in the boundary of such a Fire Compartment, i.e. the building compartment of fire origin.

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.

… which is related to, but distinguishable from …

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.

Structural Fire Engineering:  Those aspects of fire engineering concerned with 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 aftermath.


ANDAndand … a designer of a Sustainable Building will want to utilize … in order to conserve energy … natural patterns of air movement for heating or cooling.  This means that it will be necessary to have gaps between elements of construction which are continuously open … in direct conflict with the Principle of Fire Engineering just quoted above !

What happens when this sort of conflict … or lack of resolution (!) … occurs in modern, highly energy-efficient construction projects ?   At the final stages of approval/certification … the Fire Prevention Officer will insist on following the outdated prescriptive approach in his/her rulebook.  In other words, he/she will illegally apply the guidance text of Technical Guidance Document B as if it were prescriptive regulation.  Fire Compartmentation will be uncompromisingly slapped onto ‘unresolved’ areas of a completed building design … to achieve the limited Fire Safety Objectives of Building Regulations … and the fire safety related construction will probably be badly executed, anyway, because the un-supervised sub-contractors of sub-contractors of sub-contractors couldn’t care less if it goes one way or the other !   The outcome is … nobody wins !!!

In Sustainable Building Design, therefore, Fire Resistance (a ‘passive’ protection concept) must not only be extended to consider a complementary relationship with ‘active’ fire protection concepts, but be stretched … ‘intelligently’ … to embrace the concept of ‘non-construction’ …

Building Sterile Space (Fire):  An open space of sufficient and appropriate extent which is designed to retain an exceptionally low level of fire hazard and risk, and is ‘intelligently’ fitted with a suitable fire suppression system – in order to resist and control, for a specified time during a fire, the advance of heat, smoke and flame.

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. 



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