Fire Safety Engineering (as defined by Dennis Nolan, Encyclopedia of Fire Protection) is the engineering discipline that applies scientific and technical principles to safeguard life, property, loss of income, and threat to the environment from the effects of fires, explosions, and related hazards. It is associated with the design and layout of equipment, processes, and supporting systems. It is concerned with fire prevention, control, suppression, and extinguishment and provides for consideration of functional, operational, economic, aesthetic, and regulatory requirements.
The goal of Fire Safety Engineering (FSE) has always been to design an optimized strategy that provides the necessary human safety and property protection.
Developing Fire Safety Engineering as a Practice in Nigeria
This article is geared towards creating awareness of FSE concepts used internationally and potential growth for the Safety design practice in Nigeria. Current practice related to fire safety strategies relies primarily on architects or code consultants who either apply prescriptive code clauses or attempt to demonstrate equivalency to the prescriptive solutions. While discipline experts such as the Mechanical and electrical engineers may design different systems and equipment in line with the requirements of the different discipline-specific codes and the structural engineers demonstrate their design has the required fire resistance ratings, the architect is still primarily responsible for overseeing the implementation of these elements in the overall structure.
In order for the role of FSE professionals to be recognized among peers, it is essential that design solutions be published for the community to learn, and critique. Professionals must practice within the public view, under regulating body and peer review, if the field is to advance and provide an opportunity for the safe adaptation of past FSE designs into new projects at the conceptual stage.
Design Strategies
There are three basic design measures that can be employed in a combination of strategies. These categories include Occupant Egress, Smoke Control, and Flame Spread Containment, and Structural Fire Protection. Various strategies have been assembled after the review of numerous case studies from successful fire engineering projects.
Occupant Egress
- A direct way to demonstrate the safety of an occupant egress strategy is to compare the Required Safe Evacuation Time (RSET) for the occupants to exit to a safe area, versus the Available Safe Evacuation Time (ASET) before fire conditions are no longer tenable for human safety. This is typically done through occupant movement, simulations or calculations, and smoke and heat development analyses. This can be used to justify longer travel distances or reduced exit widths for egress routes. Note that it has been observed that the width of the exit (and therefore the queuing time at the exits) usually governs the RSET rather than increased travel distances, where spaces are open and clear.
- There are several different evacuation strategies that can be developed for building management. Phased evacuation is when only the zone in the building with immediate hazard is evacuated first, allowing for reduced demand on the egress routes and increased business continuity in the event of a false alarm. Horizontal evacuation can be used with fire-separated zones, where the egress strategy is to move occupants into another safe compartment within the building. This reduces total evacuation times and again allows for business continuity. Egress elevators are another emerging strategy in which working elevators can be considered means of evacuation, especially for accessibility or tall building applications, but are still under much scrutiny in practical situations as generations of individuals have been trained not to utilize elevators in an emergency.
- It is often justifiable and beneficial to design normal circulation routes as primary means of egress as it has been proven that occupants typically feel inclined to exit the building the way they entered in emergency scenarios, and alternate egress routes or stairwells are often overlooked.
Smoke Control & Flame Spread Containment
- Smoke control is an effective way of increasing ASET through exhaust or pressurization systems. Exhaust systems can be implemented through natural or power ventilation. If designed properly, pressurization systems utilize high-pressure zones within egress routes or fire-fighting shafts to induce airflow out of the zones and therefore inhibit infiltration of smoke into said zones. However, there is concern that the systems do not always perform as intended during design which demonstrates the importance of a holistic approach to FSE, and for designers to understand the limitations of the systems they implement.
- A “cabin” methodology can be used to contain the flame spread and smoke within one area, through the use of suppression systems and fire barriers. These areas are typically high-risk fire zones with large fuel loads and can be compartmentalized through fire-rated walls or fire shutters, or open concepts. In any situation, the cabin should be designed so that smoke and flames can be contained within that zone with a combination of automatic extinguishing systems (sprinkler or gas), strategically placed barriers, and smoke exhaust vents.
- The “island” methodology is another concept developed in which fire spread is contained simply through the distance between combustible materials. This can be employed in large, open-concept areas such as concourses or waiting areas in transportation buildings, where there are very small amounts of combustibles. The heat release from a fire in one island of combustibles, or fuel, is determined considering the type of materials and ventilation. Next, an analysis is done to ensure the heat release is not sufficient to ignite another adjacent combustible island, therefore preventing the spread of the fire from its origin.
- Various detection systems can be designed or specified to ensure a fire engineering strategy is well-executed, and to aid in reducing RSET and increasing the amount of the ASET that occupants are able to use effectively (i.e. movement time may begin earlier). The choice of the detection system is highly important, and the appropriate type of system varies in every building application. The varieties include smoke detectors, heat detectors (either sensing a rate of temperature rise or a given temperature threshold), and infrared flame detectors. “Double interlock” detection systems can also be employed which only activate minor alarms (rather than throughout the entire building) until a second detector or manual pull is triggered, reducing the likelihood of a false alarm. Avoiding false alarms is not only important for business continuity but also to reduce the desensitization of building occupants to emergency alarms and evacuations.
- Automatic sprinkler systems can often aid in the containment of fire within high fuel load compartments but can be ineffective in multi-story atria. Simulations should be run to determine whether or not air and smoke reaching the sprinklers will be hot enough to activate the system. Typical ceiling sprinklers can be used, along with other options including long-distance throw or sidewall sprinklers if required.
Structural Fire Protection
- A structural failure in a fire can be judged by three criteria: loss of load-bearing capacity, infiltration of smoke through cracks or openings, and transfer of sufficient heat to ignite materials on the opposite side of the structural element. The latter two criteria are applicable for load-bearing fire-rated wall assemblies, or non-loadbearing fire separation partitions. Non-load bearing fire separation partitions and other mechanical integrity elements are treated differently than structural members and their performance must be determined through testing. These elements may impact structural performance by altering the size of the compartment if they fail and thus changing the characteristics of the fire.
- A strategy that has been used to optimize the amount of fire protection is partial fire protection (for example, on steel structural elements), which should be validated through finite element analysis (FEA) of critical members in several design fires. When proposing to leave an element unprotected, a full structural analysis must demonstrate that stability is maintained throughout the fire duration. If the analysis demonstrates a collapse (failure) mechanism, redundancy is critical.
At least two separate analyses could be done to prove that:
- The element can be removed from the structure without inducing a progressive collapse of the building, or
- the element can be allowed to thermally expand and the induced loading on the surrounding structure will not cause a progressive collapse of the building. The extent of local failure allowed is an important performance objective to be developed which may have different implications in each unique building system.
Typically, elements that can be proven to remain unprotected are secondary beams and structural elements over several meters high from the floor. Generally, structures only supporting a roof assembly (that is not a publicly accessible roof) may not require protection, but in complex cases, a design fire analysis should be done to determine whether or not fire protection for the roof structure is critical to the whole building fire
safety. Additionally, frame connections are critical elements in the stability of a building and should be given specific attention in thermal and structural analyses. Other common construction materials have seen progress internationally, such as timber with sacrificial charring layers, and concrete with optimizing rebar cover – however, performance-based solutions have not yet been fully developed for these materials.
- Another common strategy of reducing fire protection requirements is on exterior structural members. According to the building code, members at least one meter away from the façade in certain building types do not require protection (clause 3.2.2.3, NRC2015). However, it has been justified to leave unprotected elements that are closer, through the two analysis types discussed previously.
Conclusion
Increasingly, asset and business owners are beginning to look at the resilience of their properties. When extreme events occur, either malicious events or inadvertent ignitions. Buildings must be able to sustain the events to a level that is acceptable by the Authority Having Jurisdiction (AHJ). The buildings must also be able to adapt to these events and quickly recover so that the businesses within them may operate at a necessary level.
A building that can remain operational during an event or shortly thereafter will enable the business within it to be more resilient. The business continuity plans of these businesses may rely on the performance of the building to be effective
In order to implement sound FSE services in Nigeria at a consultancy level, it is important to initiate a culture of continuous improvement and adoption of Recognized and Generally Accepted Good Engineering Practices (RAGAGEP) as a basis for engineering activities. Engineering consultants such as Safety Consultants and Solution Providers have provided fire engineering services on hundreds of projects and this has allowed us to be part of the design team for some of the most innovative and iconic buildings in Nigeria.
Visit here for more information about us. Our past project experience is also value proposition & project experience.
References
Bartlett, R. 2005. Structural Fire Protection Determined Through Fire Protection Engineering Applications At Nova Scotia Community College, Advantage Steel, 23.
Bell, J., Birchall, S., Clixby, D., Drabble, I., Given, E. et al. 2014. Fire Strategy in First Direct Arena, The Arup Journal 1/2014, London, England, p.48.
Bergeron, D., Desseud, R.J., Haysom, J. C. 2004. The Original and development of Canada’s objective-based code concept: Proceedings of the CIB 2004 World Building Congress, Toronto, pp.1-10.
Bisby, L., Gales, J. and Maluk, C. 2013. A contemporary review of large-scale non-standard structural fire testing. Fire Science Reviews, 2(1), pp.1-27.
Block, F., Summers, F., Black, D. and Kho, T. S. 2015. Structural Fire Design and Approval of a 156m Tall High-End Residential Building in Abu Dhabi, CTBUH Research Paper, New York Conference, pp.678-684.
Buchanan, A. 2002. Structural Design for Fire Safety. John Wiley & Sons Ltd, West Sussex, England.
Buchanan, A. and Abu, A. 2017. Structural Design for Fire Safety, Second Edition, Wiley, Christchurch, NZ.
Bundy, M. Hamins, A., Gross, J., Grosshandler, W., Choe, L. 2016. Structural Fire Experimental Capabilities at the NIST National Fire Research Laboratory, Fire Technology, 52, Springer, New York, USA, pp.959-966. doi:10.1007/s10694-015-0544-4
Carfrae, T., Cheng, V., Di, L., Ho, G., Kwong, E. et al. 2011. Fire Engineering in Beijing South Railway Station, The Arup Journal 1/2011, London, England, pp.21-24.
Chen, J., Cheng, V., Chong, K., Dodd, G., Guoet, D. et al. 2014. Fire Safety in Shenzhen Stock Exchange, The Arup Journal 2/2014, London, England, p.77.
Dixon, A., Ferguson, A., Lane, B. and Wardak, R. 2010. Case Studies: Beijing Olympics Water Cube in Human movement and safety: New approaches to facilities design, The ArupBuchanan, A. 2002. Structural Design for Fire Safety. John Wiley & Sons Ltd, West Sussex, England.
Buchanan, A. and Abu, A. 2017. Structural Design for Fire Safety, Second Edition, Wiley, Christchurch, NZ.
Bundy, M. Hamins, A., Gross, J., Grosshandler, W., Choe, L. 2016. Structural Fire Experimental Capabilities at the NIST National Fire Research Laboratory, Fire Technology, 52, Springer, New York, USA, pp.959-966. doi:10.1007/s10694-015-0544-4
Carfrae, T., Cheng, V., Di, L., Ho, G., Kwong, E. et al. 2011. Fire Engineering in Beijing South Railway Station, The Arup Journal 1/2011, London, England, pp.21-24.
Chen, J., Cheng, V., Chong, K., Dodd, G., Guoet, D. et al. 2014. Fire Safety in Shenzhen Stock Exchange, The Arup Journal 2/2014, London, England, p.77.
Dixon, A., Ferguson, A., Lane, B. and Wardak, R. 2010. Case Studies: Beijing Olympics Water Cube in Human movement and safety: New approaches to facilities design,
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