Earthquake and Post-Earthquake Fire Performance

Issue 82: Earthquake and Post-Earthquake Fire Performance

By Brian Meacham, Ph.D., P.E., FSFPE, Haejun Park, Ph.D. and Jin-Kyung Kim

Advancements in seismic analysis and design methods, building code provisions and mitigation technologies have significantly reduced the potential for structural collapse and associated loss of life as a result of earthquakes. However, damage to and losses associated with nonstructural components and systems (NCS) and post-earthquake fire remains a concern.

 

For example, in the 1994 Northridge, CA earthquake, NCS damage was reported to have accounted for 50% of the $18.5 billion loss associated with building damage,¹ and NCS damage was reported to account for the majority of losses in the 2010 Maule earthquake in Chile.²

 

Since all active and most passive fire protection systems are considered NCS, this is a significant concern for post-earthquake fire performance of buildings. This has been observed in numerous earthquakes, including the 1994 Northridge and 1995 Kobe earthquakes, where damage to fire sprinkler systems and fire doors was reported to be over 40% and 30% respectively.³

 

While building codes and standards have addressed several concerns that were highlighted in these events, such as improved requirements for sprinkler hangars and bracing, there has not been much focus on other areas, such as seismic performance of compartment barriers, doors and stairways, which form important parts of egress systems.

 

The implications of such omissions were seen the 2010 and 2011 Christchurch earthquakes, for example, where interior stairs collapsed and impeded safe evacuation.⁴ This not only impacts the ability of occupants to escape, but the ability of first responders to enter buildings and conduct rescue and firefighting operations.

 

To better understand the extent of the problem, and in particular to characterize and predict the potential damage to NCS during earthquakes and post- earthquake fires, a full-scale five-story building specimen was constructed, equipped with various NCS and contents, and subjected to a series of earthquake motions and post-earthquake fires. Referred to as the "BNCS Project," this project was led by researchers at the University of California, San Diego (UCSD), Worcester Polytechnic Institute (WPI), San Diego State University (SDSU), and Howard University, and included a large number of governmental and private sector participants, sponsors and supporters. Experiments were performed on the large, high performance outdoor shake table (LHPOST) at the Englekirk Structural Engineering Center at UCSD. A photo of the test building specimen is shown in Figure 1.

 

Figure 1 - Test Building Specimen

The BNCS project was successful in providing data and insights into earthquake and post-earthquake fire performance of buildings. Details can be found at the project website, the WPI website and in associated project reports^5-7 and papers.^8-13 In addition, a 30-minute documentary produced by UCSD-TV provides an overview of the project and its outcomes in the context of designing earthquake resilient hospitals.

 

 

From a fire protection perspective, damage was observed to a variety of fire and life safety systems as a result of the earthquake motions. This included damage to exterior façade systems (impacting compartmentation), interior wall and ceiling systems, doors, the stairway, the elevator, rigid gas piping system, and the structure. Some photos that illustrate the damage are provided in Figures 2-7.

 

Figure 2 - Ceiling Damage	Figure 3 - Façade Damage	Figure 4 - Wallboard Damage
Figure 5 - Stair Damage	Figure 6 - Elevator Door Damage	Figure 7 - Structural Damage

 

The building specimen was outfitted with an automatic sprinkler system, including riser, branch lines, drops and heads, using a range of components, including steel and CPVC piping, flexible and rigid drops, and featuring flexible couplings and seismic bracing. Designed to current codes and standards,^14-15 and given the small footprint, the sprinkler system sustained no damage from the earthquake motions.

 

Following the earthquake motion tests, and given the various damage states as shown in Figures 2-7, a series of six room-scale fire experiments were conducted. Ranging up to about 2 MW in size, heptane pan fires were used to assess the potential for smoke and flame spread. These fires were generally less than 10 minutes in duration.

 

Fire size and duration limitations were imposed on the project due to site and environmental concerns, meaning multi-compartment fires and fire-induced impact on the structure were not permitted. Nonetheless, smoke spread between compartments was observed both horizontally and vertically. Vertical smoke spread occurred via the elevator shaft, since the doors had failed in the open position. Also, gypsum board that enclosed the elevator shaft was damaged, and smoke spread through the void space between metal studs. Flame extension was observed between compartments and outside of window openings, as depicted in Figure 8.

 

Considering that this was a small fire – about the size of a small loveseat burning – it is easy to visualize how much damage could occur with a building full of combustible material and numerous pathways for fire to spread. A large, unimpeded fire, coupled with damage to the structure, as observed on Floor 2, could lead to local or global collapse. Future efforts look to model such scenarios based on the damage observed in the tests.

Figure 8 - exterior view.

While limited in scope and configuration, the experiments were valuable in highlighting a number of concerns and issues which need to be addressed to increase the post-earthquake fire and life safety performance of buildings, particularly when developing post-earthquake fire scenarios and appropriate mitigation strategies. These include:

• As illustrated in Figures 2-4, joints intended to be static (e.g., wall corners, wall-ceiling connections, façade connections) were displaced by the ground motion, creating breaches in compartment barriers, which allowed the spread of smoke and flame. As such, seismic performance of interior and exterior barrier components should be considered, including performance of fire stop materials at joints, wall and ceiling systems, doors and windows.

• As illustrated in Figures 5-6 – and as also observed in actual earthquakes, including the 2011 Christchurch earthquakes⁴ – egress components can become compromised, which in turn impacts the ability and time required for occupants to egress or for the fire service to gain access. Seismic performance of egress components should be considered, including the potential for loss of one or more stairs, elevators, or exit access routes due to damaged doors, walls and ceilings. Selecting some design fire scenarios with one or more exits unavailable, for example, would seem prudent.

• Severe damage was observed for some structural connections, such as the one shown in the Figure 7. While the structure did not collapse from this damage, the structure had to be shored prior to the fire testing. In a real event, such damage, coupled with loss of gypsum board cover and an ensuing fire, would put the structure at risk of failure due to fire. Therefore, seismic performance of the structure should be considered, including the potential for loss of protective cover (e.g., gypsum board, ceiling systems), spalling (concrete), and connection integrity, all of which have implications under fire conditions.

• While the sprinkler system performed well in these tests, displacement was observed, and damage could have resulted if flexible couplings and other seismic components had not been used. Also, with some breaches of non-rated HVAC ductwork observed (during fire tests), this is a potential concern as well. As such, seismic performance of active fire protection systems should be considered, particularly in buildings which do not have systems that meet current or recent seismic requirements.

• A rigid steel pipe system, reflective of a fuel gas pipe, suffered a broken connection during the motion tests. Such a break in an occupied building could present an additional source of fuel to any post-earthquake fire. As such, fuel gas and other systems, which could add fuel if damage, or present ignition hazards, should be carefully considered during scenario analysis and design.

While the above may seem obvious, it is not clear that such factors are adequately considered by either seismic engineers or fire protection engineers in the design of buildings in earthquake prone areas. It is hoped that thesis work towards development of a conceptual model for bridging the gap between performance-based seismic and fire engineering will be a start in the right direction.¹⁶

 

Acknowledgements

 

The authors gratefully acknowledge the many BNCS project sponsors, in particular the SFPE Educational & Scientific Foundation, the California Seismic Safety Commission, Hilti Corporation, Arup and WPI.

Brian Meacham, Ph.D., P.E., FSFPE, and Jin-Kyung Kim are with Worcester Polytechnic Institute, Haejun Park, Ph.D. is with Olsson Risk & Fire.

 

References

1.Kircher, C., "It Makes Dollars and Sense to Improve Nonstructural System Performance”, Proc. ATC 29-2 Seminar on Seismic Design, Performance, and Retrofit of Nonstructural Components in Critical Facilities, Applied Technology Council, Redwood City, California, 2003.
2.Miranda, E., Mosqueda, G., Retamales, R., & Pekcan, G. "Performance of Nonstructural Components during the 27 February 2010 Chile Earthquake," Earthquake Spectra 28: 453-471, 2012.
3.Sekizawa, A., Ebihara, M. & Notake, H. "Development of Seismic-induced Fire Risk Assessment Method for a Building,” Fire Safety Science – Proceedings of the Seventh International Symposium, International Association for Fire Safety Science, London, 2003.
4.Wilkinson, S., Grant, D., Williams, E., Paganoni, S., Fraser, S., Boon, D., Mason, A. & Free, M. "Observations and Implications of Damage From the Magnitude 6.3 Christchurch, New Zealand Earthquake of 22 February 2011,” Bull Earthquake Eng. 11: 107-140, 2013.
5.Chen, M., Pantoli, E., Astroza, R., Ebrahimian, H., Mintz, S., Wang, X., Hutchinson, T., Conte, J., Restrepo, J., Meacham, B., Kim, J., & Park, H. BNCS Report #1: Full-scale structural and nonstructural building system performance during earthquakes and post-earthquake fire - specimen design, construction and test protocol. Structural Systems Research Project Report Series, SSRP 13/9. University of California San Diego, La Jolla, CA. (Forthcoming).
6.Pantoli, E., Chen, M.C., Astroza, R., Ebrahimian, H., Mintz, S., Wang, X., Hutchinson, T., Conte, J., Restrepo, J., Meacham, B., Kim, J., & Park, H., "BNCS Report #2: Full-Scale Structural and Nonstructural Building System Performance During Earthquakes and Post-Earthquake Fire - Test Results." Structural Systems Research Project Report Series, SSRP 13/10. University of California San Diego, La Jolla, CA. (Forthcoming).
7.Kim, J., Meacham, B. & Park, H. "Full-Scale Structural and Nonstructural Building Systems Performance during Earthquakes and Post-Earthquake Fire: Fire Test Program and Preliminary Outcomes," Worcester Polytechnic Institute, Worcester, MA, 2013.
8.Hutchinson, T., Restrepo J., Conte J. & Meacham, B. "Overview of the Building Nonstructural Components and Systems (BNCS) project,” Proceedings, ASCE Structures Congress, American Society of Civil Engineers, Reston, VA, 2013.
9.Meacham, B., Kim J. & Park, H. "Shake Table Testing of a Full-Scale Five-Story Building: Fire Performance Tests,” Proceedings, ASCE Structures Congress, American Society of Civil Engineers, Reston, VA, 2013.
10.Pantoli, E., Chen, M., Wang, X., Hutchinson, T., Meacham, B. & Park, H. "Shake Table Testing of a Full-Scale Five-Story Building: Seismic Performance Of Major Nonstructural Components: Egress Systems, Facades,” Proceedings, ASCE Structures Congress, American Society of Civil Engineers, Reston, VA, 2013.
11.Wang, X., Ebrahimian, H., Astroza, R., Conte, J., Restrepo, J. & Hutchinson, T. "Shake Table Testing of a Full-Scale Five-Story Building: Pre-Test Simulation of the Test Building and Development of a Nonstructural Components and Systems Design Criteria,”Proceedings, ASCE Structures Congress, American Society of Civil Engineers, Reston, VA, 2013.
12.Kim, J., Meacham, B., Park, H., Hutchinson, T. & Pantoli, E.," Fire Performance of Full-Scale Building Subjected to Earthquake Ground Motion: Test Specimen, Ground Motions and Seismic Performance of Fire Protection Systems,” Fire Safety Science - Proceedings of the 11th International Symposium, International Association for Fire Safety Science, London, 2014.
13.Park, H., Meacham, B. & Kim, J., "Fire Performance of Full-Scale Building Subjected to Earthquake Ground Motion: Fire Test Program and Outcomes,” Fire Safety Science - Proceedings of the 11th International Symposium, International Association for Fire Safety Science, London, 2014.
14.NFPA 13, Standard for the Installation of Sprinkler Systems, National Fire Protection Association, Quincy, MA, 2010.
15.California Building Code, California Building Standards Commission, Sacramento, CA, 2010.
16.Kim, J.K., A Conceptual Framework for Assessing Post-Earthquake Fire Performance of Buildings, MS Thesis, WPI, Worcester, MA (in progress).

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