March 19, 2013 by Canadian Underwriter
Structural damage to buildings from earthquakes can have a negative impact on fire safety performance, suggest the results from a study in the United States.
Researchers in the Department of Fire Protection Engineering at Worcester Polytechnic Institute (WPI) and the University of California, San Diego (UCSC) conducted the study last year, sponsored by the National Science Foundation and a group of industrial partners.
For the study, a five-story building was constructed on top of a large outdoor, high-performance shake table at UCSD’s structural engineering school.
The building included a working elevator, a full-size interior staircase, heating, ventilating and air conditioning system components, electrical equipment, fire protection systems, and a mock medical suite, intensive care unit, medical storage room, server room, and residential space, WPI noted.
“The third floor was configured for fire testing, including complete partition walls and ceiling systems, firestop materials at joints and through partitions, a fire door, a fire sprinkler system, and a smoke detection system,” according to WPI.
The researchers conducted simulated earthquakes, ranging from 6.7 on the Richter scale, to 7.9 magnitude, while a team of engineers from UCSD monitored the buildings performance from a range of sensors.
After each simulated quake, the WPI researchers looked at the state of fire systems in the building and conducted live fire tests to see if structural damage compromised those systems, such as by allowing smoke or flames to pass through compartments.
“They ignited pans of heptane, a liquid fuel that burns hot enough to simulate a fully engaged compartment fire,” WPI explained.
“Using temperature probes and video cameras, they assessed how damage from the simulated earthquakes affected the ability of the active and passive fire protection systems to contain fires and prevent the spread of smoke.”
Some of the findings from WPI included:
“Structural damage on the second and third levels was significant; while the building didn’t collapse, it had to be shored up to support gravity loading prior to the fire testing.
Damage to the building’s interior and exterior wall and ceiling systems created openings through which smoke and flames could spread; debris from the walls and ceilings became obstacles that would have hampered the evacuation of occupants or the movements of firefighters.
A number of doors were unable to be opened or closed (open doors allow fire to spread; stuck doors can cut off escape routes or hinder the movements of first responders).
Access to the upper floors was cut off when the staircase became detached from the landing and distortion of the elevator doors and frame on some levels made the elevator unusable. During the fire tests, smoke and hot gasses entered the elevator shaft through the open doors, spreading smoke to other floors and raising temperatures to dangerous levels.
Most of the active and passive fire protection systems, including the sprinkler system, the heat-activated fire door, fire dampers, and fire stop materials, performed well.”
“When the ground stops shaking after a major earthquake, the damage may have just begun,” Brian Meacham, associate professor of fire protection engineering at WPI and principal investigator for the post-earthquake fire study noted in a statement.
“Historically, post-earthquake fires have been as devastating if not more devastating, than the seismic events that preceded them,” he added. “In fact, the largest peacetime urban conflagrations (in San Francisco in 1906 and in Tokyo in 1923) were post-earthquake fires. More recently, fire caused significant damage following the 1995 Kobe, Japan, earthquake.”
The complete report from the study is available on WPI’s website.
Image credit: University of California, San Diego