Shifting seismic zones call for new bracing solutions.
June 12, 2013
|The U.S. Geological Survey will complete its next program in 2014 and will likely show an increase in the number of seismic regions worldwide, meaning seismic requirements in nonresidential and multifamily building codes will be tougher than ever in regions found to have seismic activity. Photo credit: ©istockphoto.com/Sharon Meredith|
As a result, geographic surveys include more complete data, which create a clearer picture of the likelihood of seismic activity in given regions. The U.S. Geological Survey will complete its next program in 2014 and will likely show an increase in the number of seismic regions worldwide.
What does this mean for fire protection engineers? Seismic requirements in nonresidential and multifamily building codes will be tougher than ever in regions found to have seismic activity. The burden is on fire protection design professionals, engineers and contractors to choose fire-protection systems and bracing solutions that meet seismic requirements and perform well during actual seismic events. Choosing the right solutions is perhaps even more critical in urban areas just discovering the potential for seismic activity.
As urban areas have continued to grow, the damage caused by earthquakes and related seismic activity has increased substantially. Damage is not only measured in terms of structural collapse, but also — and more importantly — in loss of human life. Tremors can cause accidental ignition, and as a result destructive fires are common in urban settings after an earthquake. Structural damage to a fire sprinkler system can cut off water supplies necessary for fire suppression.
According to actual field performance and lab tests by a nationally renowned engineering, architectural and materials testing firm, some CPVC fire sprinkler systems can and have outperformed steel piping during and after seismic events. CPVC piping faced, and passed, one of its toughest tests when an earthquake with a 7.5 magnitude on the Richter Scale hit San Salvador, El Salvador. Just seven months prior, the American embassy had been retrofitted with a CPVC system. Despite massive structural damage, the piping remained largely intact and operational during and after the earthquake.
When a fire sprinkler system requires seismic bracing, several factors must be considered. NFPA 13 addresses sprinkler system design, installation and acceptance testing; hanging and bracing systems; underground piping; and seismic protection in line with SEI/ASCE 7. NFPA 13, Chapter 9, Section 3 delineates the current requirements for selecting seismic bracing products. As a general rule, a thorough review of system specifications should be made to determine a product’s suitability for use with any sprinkler system, including the stress a bracing system may place on CPVC pipe.
When bracing piping without a UL-listed system, NFPA 13, Chapter 1.7.1 offers an alternative to the written standard. It reads:
“… nothing in the standard shall be intended to restrict new technologies or alternate arrangements, provided the level of safety prescribed by the standard isn’t lowered.”
In short, this provision suggests new technologies shouldn’t be prohibited from use as long as they provide an equal amount of protection for the particular application. A qualified design professional is ultimately responsible for reviewing and confirming the compliance of “alternate arrangements.”
Seismic regions are reviewed regularly and an area not requiring bracing today could change in the next completed survey. In order to ensure proper system operation, professionals must follow manufacturers’ design and installation instructions for seismic bracing systems and piping systems.
If choosing an “alternate arrangement” as allowed by NFPA 13, Chapter 1.7.1, the authorities having jurisdiction must review the arrangement prior to installation of the system. For added assurance, obtain written approval from the AHJ.
Gary Johnson is a 20-year employee of The Lubrizol Corp. and serves as business manager — Americas in the Global Fire Protection Systems business. He also is a member of NFSA’s Suppliers and Manufacturers Council, QA and Residential committees, IFSA’s board of directors, NFPA’s 13 D/R Technical Committee and is PPFA Product Line Committee Vice Chairman.