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Fire Engineering for a Sustainable Future

THE ROLE OF FIRE ENGINEERING IN ACHIEVING SUSTAINABLE, ENVIRONMENTALLY EFFICIENT,

ETHICAL AND SECURE BUILDING DESIGN

Mahmut Horasan and Russell Kilmartin

Director, Scientific Fire Services (HK) Limited and Scientific Fire Services Pty Limited Australia

ABSTRACT Traditionally the objective of the construction industry has been planning and designing the appropriate buildings in line with varying architectural visions, ensuring that they are not only constructed and fitted out as safe and high quality code complying structures but also maintained and managed as one for their lifespan. In today’s highly demanding commercial environment the objectives do not stop there. The designs are also expected to be ethical; sustainable and environmentally efficient and secure against various threats. Hence, a building design needs to be “holistic” in its approach to fire safety if it is expected to satisfy multiple objectives. This creates a challenge with respect to building codes where multiple prescriptive restrictions are applied from the perspective of fire safety systems; construction type and materials and egress provisions. Fire engineering through a performance based approach provides a means to overcome these restrictions without sacrificing the core code objectives of life safety, fire services safety and fire spread control while at the same time satisfying the objective of achieving sustainable, environmentally efficient, ethical and secure building design. This paper discusses the application of fire engineering to multi-objective holistic building designs and provides examples from real life projects. Keywords: Fire engineering, green buildings, secure buildings, ethical construction materials


1. INTRODUCTION A building being “green” or “sustainable” or “environmentally efficient” is not a gimmick or ideological statement anymore. What started as some novelty approach about two decades ago is now an integrate part of building designs. Buildings are now genuinely expected to be “green” or “sustainable” or “environmentally efficient”. The projects adopting “green” approaches are rewarded through various schemes. The expectations from a new building design do not stop there. In today’s highly security conscious environment some buildings are also required to be prepared against almost extreme security threats. A relatively more recent development for building projects is the requirement that they are “ethical”. The ethicality could relate to various aspects of the project such as sourcing and types of materials used in construction (which is taken into consideration as part of this paper) or the sourcing of labour for the project (which is outside the scope of this paper). All these diverse objectives can be satisfied individually with some effort. However, satisfying a combination of these objectives becomes a significant challenge. They relate to different agendas, codes or regulations. The solutions and designs developed are not expected to only satisfy the relevant criteria but they are also required not to contradict with the core code objectives of a building project with respect to life safety, fire services safety and fire spread control. Fire engineering through a performance based approach provides a means to overcome these challenges and restrictions. A performance based fire engineering approach is a holistic approach to building design. It creates an environment where different aspects of a design may be evaluated from a perspective of overall performance of the building. While the main objective is to satisfy the key objectives of the local building codes, a performance based approach creates an environment for more innovative approaches to design and construction. As long as the fire engineer is able to demonstrate through scientific means that code objectives can be satisfied with the proposed design, achieving green credentials or using ethically sourced unconventional building materials or adopting innovative security schemes becomes a much less challenging task. 2. GREEN BUILDINGS AND FIRE SAFETY ENGINEERING An environmentally sustainable building, designed, constructed and operated to minimise the total environmental impacts is labelled as being “green”. Green buildings are based on designs that aim to increase the efficiency of use of resources such as energy, water, and materials and reduce the impact of the building on human health and the environment during the building's lifecycle. Green buildings are expected to adopt construction practices and materials that are environmentally responsible and resource-efficient from the design phase through to construction and continuing maintenance. According to the U.S. Green Building Council, green buildings reduce the negative impacts of buildings on occupants and the environment in five general categories:

• sustainable site planning; • safeguarding water and water efficiency; • energy efficiency and renewable energy;


• conservation of materials; and • resources and indoor environmental quality.

A number of these categories overlap with some of the main fire safety categories such as fire safety systems and fire rated construction. Designing and developing a green building may be a significant objective. However, all buildings before anything else must satisfy the local fire codes and regulations. Hence, the overriding objective becomes reaching a compromise between the two aspects of the design. Simple examples of this may include:

• providing water based suppression systems while safeguarding water and water efficiency;

• ensuring that the construction is fire rated and using materials with certain fire and smoke spread characteristics while trying to conserve materials; and

• designing a smoke hazard management system which will maintain tenable conditions in the event of a fire while also designing an associated indoor heating/cooling system with green credentials.

The rigid nature of prescriptive building codes makes it an almost impossible challenge to achieve a design which successfully satisfies both the green objectives and the code objectives of the building design. The prescriptive building codes impose strict restrictions to fire rating of constructions; building geometries; smoke hazard management system type and design; suppression system design and installation and building access and egress. This is a global fact and whether it is the Hong Kong Codes of Practice, NFPA or Building Code of Australia, the objective always is to ensure every building is designed and constructed to a standard that is acceptable to the society with respect to life safety and property protection. Recognising the limitations introduced by the rigid “prescriptive” approach, the majority of the developed and developing countries around the world facilitated an alternative “performance based” approach. A performance-based approach is perceived to offer a number of advantages over the prescriptive approach such as:

• a less conservative and more cost-effective design; • greater flexibility; • more appropriate to the use of new technology and materials; and • can be suitably applied to large or unusual buildings.

These characteristics of a performance based approach become highly beneficial and useful in designing green buildings. With a performance based approach a building:

• can be constructed from unconventional and even previously untried material with high “green” credentials;

• can have a more energy and resource efficient architectural design; • can adopt innovative fire safety systems which allows for less use of resources

(water, fuel)


The advantages of a performance based fire safety engineering approach to green building design may be discussed in more detail under a number of main headings:

• Materials used • Architectural design (i.e. building geometry and layout) • Smoke hazard management system design • Suppression systems design

2.1 Materials Used The use of materials in buildings is strictly regulated through fire codes. Clause 6.5 of the Code of Practice for Fire Rated Construction in Hong Kong (1996) states that:

The construction of materials specified in Tables A-F in this code are deemed to satisfy the FRP as listed therein. If other material, products and construction are used, they should be tested in accordance with or against BS476: Parts 20 to 24: 1987 and certified as being capable of resisting the action of fire for the specified periods.

Many building materials with green credentials when tested may not achieve fire resistance capabilities as required by the codes. This would lead to the dilemma where the project team will have to either sacrifice from the green credentials of their building or end up in a situation where they are not able to satisfy the prescriptive requirements of the building codes. By adopting a performance based approach a compromise may be reached. In relation to construction materials the codes establish the minimum levels of:

• Fire rating characteristics • Fire ignition characteristics • Fire spread characteristics; and • Smoke spread characteristics

It would not be unreasonable to expect any material adopted to at least satisfy the minimum ignition, fire spread and smoke spread requirements. However, fire resistance levels can be approached with a less restrictive attitude especially in a performance based fire safety engineering context. The objective of establishing fire rating benchmarks in a building is to ensure that the building structure is capable of maintaining its integrity, stability and insulation characteristics significantly beyond the duration it would take a worst credible case fire to consume the fuel within the enclosure(s) of fire origin. This duration is a function of the fire enclosure geometry, ventilation conditions and the nature and quantity of fuel contained within the fire enclosure. Hence, it is a quantifiable entity. There are various methods (i.e. the Euro-code Method (CEN, 2002), Lie’s method (Lie, 1974, Law’s method (England, 2000) to calculate the likely fire duration which is also known as “fire severity” or “equivalent fire duration”. It is not uncommon to conclude in many instances that the required fire ratings are extensively higher than the expected fire severity based on worst case scenarios. Computational Fluid Dynamics (CFD) models are also highly sophisticated tools that can be adopted in predicting the impact of a fire in a building based on materials used, systems installed and the architectural design. Hong Kong Prescriptive Building Codes, similar to a number of codes from other countries,


do not allow for any dispensations with respect to FRP requirements based on the systems available in a building, such as sprinklers. Various studies demonstrated that the reliability of modern sprinkler systems in developed countries can be above 98% (Moinuddin, 2009). In the context of a particular building design the impact of sprinklers and the corresponding risk may be evaluated through risk analysis, adopting methods such as event trees. Scientifically sound equations, computer modelling tools, risk analysis methods are all among the tools of the trade for fire engineers. Hence, by adopting the most appropriate method and by demonstrating that a certain building material when used as part of a specific design a fire engineer can facilitate the use of materials that would not be allowed under a prescriptive approach. Whether the subject material is recycled timber used internally or BIPVs (Building Integrated Photovoltaics) installed on a building’s façade, its performance can be evaluated under fire conditions using the scientifically validated tools available to fire engineers. Evaluations and assessments conducted by a fire engineer in relation to materials used in a building may be required to address the following key aspects:

• The ignition, fire spread and smoke spread characteristics of the material • The gaseous, liquid and solid products of fire once the material is ignited • The integrity, structural stability and insulation characteristics of the material

The assessment should also take into consideration the impact of proposed fire systems on the materials, such as wall wetting sprinklers or intumescent paints. The objective after all is to establish whether a particular building using “green” construction materials can satisfy the performance requirements of building codes with respect to materials performance and FRPs. 2.2 Architectural Design The “greenness” of a building highly relies on the building layout and the geometry. Design aspects such as efficient space use; provision of natural lighting; presence of atria of varying sizes; utilisation of daily pedestrian traffic paths also as emergency egress paths and presence of open circulation stairs in atria are some typical examples. Many of the design issues will lead to a non-compliance with the local building codes, such as:

i. A building design may be based on floor to floor glazing without any vertical spandrel construction to maximise natural lighting.

ii. A building may include a large atrium which exceeds the compartment size limits of the codes.

iii. The egress paths may consist of open staircases and external balconies in lieu of fire stairs and fire corridors in a building.

These examples may require extensive quantitative fire engineering analysis before they can be approved by the authorities and adopted. Fore example, the fire engineer will need to prove that the alternative proposed to the vertical spandrels will prevent the vertical spread of fire by means of fire spread modelling, preferably using CFD modelling. Or, to demonstrate that the proposed open egress system design will result in successful evacuation prior to onset of untenable conditions and meet the code performance requirements, the fire engineer will need to conduct extensive smoke spread and evacuation modelling. The same approach will also be required to demonstrate the acceptability of large compartment sizes. 2.3 Smoke Hazard Management System Design


The smoke hazard management systems in green buildings usually aim to incorporate the daily use heating/cooling and ventilation aspects of the building into their design and also aim to minimise the use of energy dependent mechanical systems. Where possible, natural venting systems are adopted for smoke venting and/or make up air provision purposes in lieu of mechanical systems. By adopting a fire engineering approach the smoke hazard management systems in a building can be optimised. Some means of achieving this would include the following.

i. A quantitative assessment based on computer modelling may reduce the smoke extraction capacity required by demonstrating life safety can be achieved with rates below what the codes and standards would prescribe.

ii. By using sprinkler systems (which may not be a requirement of the codes for that particular project) or improving the effectiveness and reliability of sprinkler systems, the likely fire sizes can be reduced/minimised, hence lowering the volume of smoke generated.

iii. In buildings with atrium, the space can be used to create a large smoke reservoir. This will allow smoke to be channelled into the reservoir by natural airflow and allow the smoke to be diluted in the process.

Fire engineering allows for the evaluation of a systems design which may be based on one or more of the concepts listed above. Again, the objective is to quantitatively demonstrate that the core code objectives of occupant and fire services life safety and prevention of fire spread to adjacent properties can be achieved. This concept is further discussed and demonstrated as part of the Case Study presented in this paper. 2.4 Suppression Systems Design Green buildings employ water saving systems such as rainwater tanks or grey (reclaimed) water systems. When used to supply sprinkler systems such water resources could lead to problems in relation to back-flow, sediment build-up and microbiologically influenced pipe corrosion (MIC). The approach to these problems in green buildings is not likely to be a scientific evaluation approach but more of a systematic problem elimination approach. Back-flow may be eliminated with system based solution (i.e. back-flow valves). Sediment build up may be prevented by means of filter systems. The MIC issue can be more difficult to address as the use of chemicals is not desirable in green buildings. 2.5 Egress Provisions As discussed above in the “Architectural Design” section the green design can directly or indirectly impact on the egress provisions. This may be mainly due to:

• The open design of the building including open stairs and corridors on the egress paths;

• The materials used in construction and finishes within the egress paths; • The systems adopted to maintain tenability within the egress paths;

The concept of open design is not an issue exclusive to green buildings. In contemporary architecture open and spacious building layouts are commonly adopted. Many assembly buildings and shopping centres include multiple atria in varying sizes. In some instances horizontal fire shutters are omitted from voids and occupants are provided with the option of


travelling through open stairs and/or escalators on their way to evacuation. All of these design options result in significant non-compliances with the prescriptive codes and can only be addressed by a fire engineering approach. Hence, in this context, it may be stated that the issues in relation to open architectural design and the impact on egress provisions in green buildings must be subjected to a high level of scrutiny by suitable qualified engineers. Unless a valid alternative solution is developed the green design must not be approved. The finishing adopted to the surfaces on egress paths must satisfy the requirements of the codes and regulations with respect to:

• Ignitability • Smoke spread • Flame spread

This is an area where compromises would not be appropriate and corresponding risk would be too high. The active and passive systems with green characteristics may impact on the egress provisions. The design objective is to ensure tenable conditions are maintained on egress paths for extended periods of time. It must be demonstrated the systems adopted would ensure tenability for all “credible” fire scenarios with different fire sizes and growth rates. 3. ETHICAL BUILDINGS AND FIRE SAFETY ENGINEERING An ethical building project may simply be described as a project which adopts ethical trade principles. A definition of ethical trade in relation to the construction industry is provided by Mustow (2004) as follows:

Trade in which the relationship between the interested parties is influenced by concern for:

• Protection of the environment and natural resources • Making a positive contribution to people and society, including protecting

the rights and livelihoods of workers and producers • Enhancing local and national economies

This definition of ethical trade for the construction sector is essentially the same as ‘sustainable trade’ in that social, economic and environmental factors are all considered (Figure 1). Ethical procurement aims to ensure that products are purchased from supply chains that have undertaken ethical trade. The global trade in construction materials and products is worth about US$305 billion. The majority of these materials are stone, gravel, sand, clay, iron ore and other quarried products. Construction and the operation of buildings also account for 25% of all virgin wood use (Mustow, 2004). The trade encompasses a diverse range of goods, including:

• Quarry products • Wood products • Finishes, coatings, adhesives etc • Plastic products • Fabricated metal products • Cabling, wiring and lighting • Glass-based products


• Ceramic products • Bricks and other clay-based products • Cement, plaster etc • Stone and other non-metallic mineral products

Figure 1: Issues Addressed by Different Types of Alternative Trade Mustow (2004)

Due to the limitations in the availability of a wide range of construction materials sourced through “ethical trade” the available materials when tested may not achieve fire material and resistance capabilities as required by the codes. This is similar to issue of using “green” materials for sustainable buildings which was discussed previously. Hence, the role of fire engineering would also be similar where the material performance can be evaluated and demonstrated by various scientific tools available to fire engineers. The impact of fire systems may also be taken into consideration when the performance of ethically sourced construction materials is assessed. 4. BUILDING SECURITY AND FIRE SAFETY ENGINEERING The relation between building security and fire engineering can be complex. In most cases the security systems within a building has a significant potential to improve the fire safety. Where as, the impact of fire engineering on security improvements may be more ambiguous. An important aspect of fire engineering is risk management. It may be argued that the performance based fire engineering approach is a means of developing a fire risk management plan for a building comprising active and passive systems and management procedures. This becomes more evident when we examine the main fire risk management tasks, which are:

i. Minimising fire starts and fire development ii. Early detection and warning iii. Early suppression iv. Later suppression v. Effective evacuation vi. Housekeeping

All of the items of risk management could relate to security operations within a building to a certain extent and in many instances security systems adopted in buildings can have a


positive impact on fire safety. Security measures may be either systems based or staff based. In buildings where security staff are employed and used extensively, fire start minimisation, early detection of ignitions, early intervention and early suppression are a common occurrence. Security staff also plays a key role in the evacuation process. A major Casino building in Australia was evaluated to establish the impact of security staff on fire safety. The Casino which was developed with a performance based fire engineering approach adopted a fire risk management system which directly utilised security systems and staff. It is common knowledge that Casinos employ a very large number of security staff who are constantly present in all parts of the facility. The security staff, in the case of the Australian Casino, are required to receive fire training. They are a well trained resource that can immediately intervene when they observe hazardous behaviour and can play an integral role in the removal of ignition sources, hence, minimising fire starts and fire development. In the event of an ignition they are capable of intervening immediately and extinguishing the fire before it is fully developed using extinguishers, fire hose reels or any other method available to them (early suppression). If the fire continues to develop they can communicate with the security/control room and notify them of the situation even before the fire is automatically detected (early detection and warning). Once the evacuation is initiated they play a key role in achieving orderly evacuation and they prove to be highly effective in convincing “stubborn gamblers” who may not be too keen to abandon their highly addictive activity (effective evacuation). Being omnipresent, security staff are also able to identify poor housekeeping activities where fuel loads may be left unattended or exit paths are blocked by various items (housekeeping). The security staff also can assist fire fighters when they arrive by ensuring the evacuation is completed and the fire zone is under control (later suppression). In addition to the role staff play common security devices, such as CCTV cameras, have also proven to be effective as early detection devices in the Casino. While they are not designed to be automatic detection devices, each of the 2500 CCTV cameras provide an opportunity to the security room staff to identify ignitions at very early stages even in the most isolated parts of the Casino. Other examples of the relation between fire risk management and building security are airports and large exhibition buildings. Both of these occupancy types employ large number of security staff and are equipped with multiple security devices such as CCTV cameras. In Hong Kong the fire engineer may be required to be involved in the development of a Fire Safety Management Plan for the subject building. This provides an opportunity for the fire engineer to review the security systems in the building and adopt aspects of it as part of the overall fire risk management plan. On the other hand it should be noted that there are instances where high levels of security may have negative impact on building fire safety. In buildings where access is highly restricted and controlled, egress may also become highly restricted due to presence of security doors and advance security access systems such as key cards or physiological recognition devices. A holistic evaluation through a performance based approach may assist in the elimination of any negative impact the security systems may have. 5. FIRE ENGINEERING TOOLS


The engineering tools which fire engineers often employ in addressing issues related to green and/or ethical and/or secure buildings comprise various correlations, equations and computer models. Like any other engineering approach there are certain conditions for adopting a correlation or equation to a situation. All correlations are based on experimental research studies. Hence, there are always limitations to the applicability of a correlation. For example if a sprinkler activation time equation is based on experiments conducted for ceilings lower than 10 metres the outcome when it is applied to a 15 metres high ceiling could be highly unreliable. The fire engineer must show utmost care in selecting and adopting correlations and equation in their assessment of a building. The use of computer models is also not without serious concerns. As a consequence of significant development in computer hardware fire engineers have easy access to extremely powerful tools such as Computational Fluid Dynamics (CFD) models or three dimensional behavioural egress models. An engineer must understand the capabilities and also the advantages and disadvantages of a modelling tool prior to using it. For example some advantages of CFD models can be listed as follows:

• Several detailed cases can be worked out, enabling speedy design decisions • Complete and detailed answers (can be used to supplement experiment; leads to

improved understanding) • Ability to simulate realistic conditions (large sizes, high temperature, toxic substances,

fast transients) • Ability to simulate ideal conditions (such as two-dimensionality and constant density)

Similarly some disadvantages of CFD models inlcude: • Mathematical model may not correspond to reality. • Sufficient experimental verification is essential. • Sophisticated output presentation may mislead inexperienced assessors. • For difficult problems, numerical solution may experience instability and divergence.

Solution, if possible, may be excessively expensive. While the theory behind such software is highly validated there can be significant problems in relation to the construction of a model and the data adopted. The experienced fire engineer must never accept the output from a computer model without subjecting it to engineering and scientific scrutiny. A partial assessment using hand calculations may prove to be highly effective in validating the outcome. Running trial models based on real life experiments can provide the engineer with valuable knowledge on the appropriateness of the modelling tool in general and the casse being evaluated in particular. Another aspect of computer modelling relates to the selection of input data. For example, the design fire characteristics for fire modelling or occupant characteristics for evacuation modelling will dictate the outcome of the assessment. Hence, for such models the selection of input data must be the consequence of a meticulous engineering process. The input data must always be subject to independent review. 6. HAZARD ANALYSIS Hazard analysis is a vital aspect of a performance based fire safety engineering assessment.


The fire engineer must establish the core hazards in a building with respect to: • Ignition sources and probabilities • Typical fuel load type, distribution and quantities • Aspects of the design which may play a critical role in the ignition and

development of fire or the evacuation process • Occupant characteristics which may play a critical role in the evacuation process

The hazard analysis should dictate the most or (worst) credible fire scenarios, design fires and the corresponding schematic design fires that are to be adopted for the assessment. The parameters that will need to be taken into consideration in that process would include:

• Fire location • The ignition source • Fuel load • Suppression systems • Detection and warning systems • Smoke hazard management systems

The performance based alternative solution is most likely a system based solution and the two systems most influential fire safety systems which are commonly adopted and manipulated are suppression and smoke hazard management systems. Suppression systems design is based on building Hazard classification. Unless the green or ethical or security related aspects of the building places a building in a higher hazard category the sprinkler system design is not likely to vary from a conventional building system design. The design fire in a sprinklered building is a function of the building geometry and the sprinkler system design with respect to its layout, activation temperature and RTI value. The fuel type will dictate the fire growth level and hence will also impact on the sprinkler activation time. However, the fuel load is not a key factor in the quantification of design fires based on the fact that the sprinklers are assumed to control the fire. The fire size will also be influenced by the assumption of which sprinkler head(s) will control the fire, i.e. the last sprinkler on the first ring of sprinklers or the first sprinkler on the second ring of sprinklers. On the other hand the smoke hazard management system design in a performance based project will be a function of the building geometry, design fire location and size and fuel characteristics with respect to burning fuel by-products, including soot yield. As discussed previously in a sprinklered building the fuel load is not expected to have a direct impact on the fire size. However, in an un-sprinklered building or for sensitivity study scenarios where sprinklers are assumed not to operate the fuel content becomes relevant. It will be the responsibility of a fire engineer to develop the most accurate and realistic design fires for scenarios without sprinkler control. The factors the fire engineer may want to take into consideration in developing a design fire then will include (but not be limited to) the following:


• Material type and content of the main fire fuel • Fire characteristics such as the typical fuel load (kg/m2), unit calorific value-heat

of combustion (Mj/kg), burning rate per unit area (kg/m2s), etc. The typical fuel loads and densities for different building classifications are well researched and documented. Hence, there will be no reason for the fire engineer to assume that a green or ethical or secure building would be any different from fully complying buildings of similar classification and use. However, if the green et al aspect of the building is likely to contribute to the fuel loads and/or characteristics this must be taken into consideration. Unless the building has a sophisticated management system (such as a mega mall or an exhibition building or a high end high rise building) controlling the fuel load or placing restrictions on allowable fuel loads will neither be practical nor realistic. Hence, in such buildings it will be preferable to rely on systems instead of management procedures. 7. CASE STUDY The subject building is a five storey office building constructed in Tasmania, Australia. It is the first building to achieve a Five Star Green Building Rating in the State. The Green Building Council of Australia has established a Green Star rating system which can be adopted at design and/or construction phases. Green Star is a comprehensive, national, voluntary environmental rating system that evaluates the environmental design and construction of buildings. In certain aspects the Green Star rating system shows similarities with the HK-BEAM (Hong Kong Building Environmental Assessment Method) (Yik, 1998) . A 5 Star Green Star Certified Rating signifies 'Australian Excellence' in environmentally sustainable design and/or construction. The subject building has a total rise in storeys of five (5) and the predominant construction is concrete columns, beams and floor consisting of hollow concrete planks overlain by a concrete screed. Within the building there is an atrium from ground floor through to the roof of Level 4. Generally this atrium is bounded by fixed glazing over a low timber panel dado wall. The timber used in the wall structure is recycled timber. Also sections of the façade design incorporate timber. Mechanical louvers are incorporated above one wall of the glazing on Levels 1 to 3 (Figures 2 and 3). To achieve a high energy saving rating to meet an accord with the green star energy rating scheme, the building incorporates a mix of mechanical louvers and windows for natural ventilation. As a consequence the bounding wall construction of the atrium wall does not meet the requirements of the Building codes. A rationalised smoke hazard management system that consists of a mechanical smoke extraction fan located at the top of the atrium and a matrix of natural make up air provisions and mechanical operation of louvers has been adopted (Figure 4). The system illustrated in Figure 5 is adopted for both the environmental cooling/heating and fire event smoke extraction purposes. In daily use various open/closed combinations of windows, atrium boundary louvers and roof top natural vent openings are adopted for cooling and heating purposes.


For smoke hazard management purposes a system which utilises the roof top fan in combination with windows and atrium boundary louvers was adopted. The basic system operation can be explained as follows:

On all levels (except for Level 5) in the event of a fire on detector activation: i. Atrium roof smoke extraction fan activates ii. The louvers between the office floor of fire origin and the atrium void open iii. The louvers between the non-fire office floors and the atrium void and the roof

top louvers close iv. All windows (A, B and C) open. Office floor windows provide make-up air, other

windows positively pressurise the non-fire floors.

Level 5 adopts an independent system where in the event of a fire on detector activation the roof vents and windows open to vent the smoke.

Figure 2: Building Appearance and Plan


Figure 3: Building Atrium Walls and Boundary Louvers

Figure 4: Atrium top Smoke Extraction Fan

The atrium top smoke extraction fan

Atrium boundary mechanical louvers (external and internal views)

Recycled timber atrium walls


Figure 5: The Smoke Hazard Management System The two areas where the building has achieved its Green Star rating are:

• The materials adopted. • Ventilation.

While the proposed design resulted in the building becoming eligible to obtain Green Star rating, it also resulted in the building becoming non-compliant with the prescriptive requirements of the local building fire codes in a number of areas including the use of non-listed combustible materials and installation of a hybrid smoke hazard management system not complying with the relevant codes and standards. Hence, it was decided that a fire safety engineering approach would be adopted to demonstrate that the proposed design would satisfy the performance requirements of the code. As part of the fire safety engineering assessment the effectiveness of the proposed system was tested and verified by means of CFD modelling (Figure 6). Multiple fire scenarios involving fires on each floor were modelled.

A

B

C

W

X

Y

Atrium Void

Smoke extract

fan

Natural Venting Louvers

Level 1

Level 2

Level 3

Level 4

Level 5

A, B, C: Windows to outside X, Y, Z: Atrium boundary louvers

Z


Figure 6: The CFD Model Layout The modelling demonstrated that the proposed system would be effective in ensuring that the building occupants would not be exposed untenable conditions in the event of a fire regardless of the fire location. Figure 7 provides examples of output obtained from CFD modelling.

Figure 7: Various CFD Model Output Illustrations

Another aspect of the analysis was to demonstrate that the recycled timber used as atrium boundary wall cover would perform satisfactorily in the context of fire spread and smoke generation in the event of fire. Additional CFD models were constructed and run utilising heat of combustion fire sources and fire spread analysis components to evaluate the performance of the wall cover material.

Office floors

Atrium void


The fire engineering assessment demonstrated that the proposed design would satisfy the performance requirements of the code with respect to:

• ignitions, fire development and spread; and • smoke hazard management

Once the building approval was obtained in relation to fire safety aspects of the design the green star rating rewarded to the building was confirmed. 8. THE HOLISTIC APPROACH The concepts discussed in this paper can be combined in order to develop a systematic approach. The main areas where performance fire engineering approach can be adopted to satisfy additional objectives of sustainability, ethicality and security are:

i. Performance of structural and non-structural materials used (ignition, fire growth, fire spread)

ii. Fire safety systems and their interaction with the other cooling/heating systems and utilities in the building (smoke spread, suppression)

iii. Emergency evacuation (detection and warning, pre-movement and movement) iv. Fire brigade access

The following flowchart was developed to be used as a guide on how to adopt a fire safety engineering approach to buildings with multiple objectives. START Identify project objectives

Fire Safety Green Rating Ethicality Security

Identify non-compliances with the Codes resulting from the project objectives:

A. Fire rated construction B. Fire systems

Detection & warning Suppression Smoke hazard management

C. Means of egress D. Means of access

A1. What materials are proposed to be used in the project in a structural and non-structural context?


A2. What type of analysis will be required to evaluate the performance of the materials?

Testing Fire modelling (CFD analysis) Fire severity analysis ((CFD analysis, fire severity equations) Structural performance analysis (CFD analysis, structural performance equations, finite element analysis)

A3. Do the modelling outcomes satisfy performance requirements in relation to the project objectives?

If YES assessment is finalised If NO

What additional systems (active, passive, management) can be adopted to satisfy performance requirements?

B1. What aspects of the proposed design need to be evaluated?

Smoke hazard management systems Suppression systems

B2. What type of analysis will be required to evaluate the performance of the systems?

Fire and smoke modelling (CFD analysis) Risk analysis (i.e. event trees, fault trees, risk indices)

B3. Do the modelling outcomes satisfy performance requirements in relation to the project objectives?

If YES assessment is finalised If NO

What additional systems (active, passive, management) can be adopted to satisfy performance requirements?

C1. What aspects of the design impacts on the egress provisions from the building?

Extended travel distances or reduced egress widths Open stairs or egress corridors Large compartment sizes Building access security systems Warning systems

C2. What type of analysis will be required to evaluate the performance of the systems?

Evacuation modelling (computer models) Detector activation modelling (CFD models, computer models, hand calculations)


C3. Do the modelling outcomes satisfy performance requirements in relation to the project objectives?

If YES assessment is finalised If NO What additional systems (active, passive, management) can be adopted to satisfy performance requirements?

D1. What aspects of the design impacts on the fire brigade access provisions to the building? D2. What type of analysis will be required to evaluate the performance of the access provisions? D3. Do the analysis outcomes satisfy performance requirements in relation to the project objectives?

If YES assessment is finalised If NO What additional systems (active, passive, management) can be adopted to satisfy performance requirements?

FINISH 9. CONCLUSION The prescriptive codes in all countries set the bench mark for minimum acceptable fire safety standards under the limitations of a prescriptive format. The desire to adopt sustainable, green designs; ethical approaches and high levels of security in buildings usually leads to design issues that deviate from the minimum prescriptive requirements of the codes. The only way to achieve non-conventional building designs without jeopardising the key objectives of the prescriptive codes is to address the compliance issue under the “performance based approach”. The countries, such as Hong Kong, where performance based designs have become common practice; the development of an alternative design is controlled through circulars or performance requirements issued or published by the same departments which control the prescriptive codes. Performance based approaches and fire engineering provides building developers, architects and project managers with an all encompassing tool for designing buildings that are required to be green, ethical and secure without compromising from the life safety aspects of the design. By demonstrating that the design can satisfy the performance requirements of the code(s) the issue of code non-compliance can be addressed. Fire engineering relies on scientific tools, validated models and verified methods in achieving its purpose.


REFERENCES [1] Building Authority Hong Kong, Code of Practice for Fire Rated Construction in Hong

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