How to engineer systems in mixed-use buildings: Fire and life safety
When working on mixed-use buildings, engineers must address many needs in one building. Fire and life safety issues are discussed here.
Mark Crawford, Principal engineer, Southland Industries, Las Vegas
Christopher M. Kearney, PE, LEED AP, Project manager, exp, Maitland, Fla.
Brian McLaughlin, Associate, Los Angeles, Arup
CSE: What unique fire suppression systems have you specified in mixed-use buildings?
McLaughlin: Mixed-use buildings will often incorporate wet-pipe automatic sprinkler, pre-action sprinkler, and gaseous suppression systems. Unique approaches are often employed as a means to provide fire protection in-line with the intent of the code, while not meeting the prescriptive guidelines. For example, a recent project strived to omit sprinkler protection above a certain ceiling height because sprinkler effectiveness was deemed marginal due to the extremely large volume, steep ceiling geometry, and specific use of the space. On another project, pre-action sprinklers systems were employed throughout the entire building due to the owner’s design to minimize accidental water damage. The approach to fire suppression must combine code requirements, design intent, and owner project needs to reach a suitable level of protection that addresses the objectives of all stakeholders.
Crawford: The Venetian Condo Tower in Las Vegas was designed as a 50-story, 661-ft high-rise. The structure was to contain parking, retail, assembly, and condominiums. The NFPA 14, Standard for the Installation of Standpipes and Hose Systems, 350 psi pressure limitation would require an intermediate pump mid-level within the tower on traditional fire standpipe systems. The alternate design, done in conjunction with the Clark County Fire Department (CCFD), used pressures near 500 psi. The design concept was also presented at the 2010 NFPA conference in Las Vegas and has been adopted by CCFD as an acceptable alternate standpipe design method. The design offered more leasable space and overall project cost reduction.
Kearney: Double interlocked pre-action systems, gas suppression systems, carbon dioxide systems, fixed water spray systems, deluge systems, high- and low-expansion foam systems, and water mist systems.
CSE: What unique egress, mass notification, or emergency communication systems have you specified into mixed-use buildings?
McLaughlin: As mixed-use developments strive to become more interactive for the patrons’ experience, public address systems of varying sophistication are becoming more commonplace. Because these systems are often designed to ensure audibility throughout the occupied spaces, they become a prime candidate for integration to the fire alarm and evacuation strategy. However, because the public address equipment is often not listed for fire alarm duty, a comprehensive strategy must be developed to demonstrate to all stakeholders that this type of system can be effective.
CSE: What are some important factors to consider when designing a fire and life safety system in a mixed-use building? What things often get overlooked?
Kearney: Important factors include: water flow volumes and pressures, whether an auxiliary water supply be required by code, whether water is allowed in the special use areas like the data center, whether a gas suppression system preferred, whether a fire pump is needed and whether it’s above the flood plain, and whether it is directly accessible by the fire department.
McLaughlin: It is important to consider the facility operation as a whole, while also incorporating special provisions for specific uses. For example, a fire in a hotel guest room tower may not need to sound an alarm in the adjacent casino depending upon how the hotel egress strategy impacts the casino operation. Alternatively, if multiple towers are situated atop a common parking podium, there may be a need to alarm and notify the towers’ floors and begin the evacuation process. I think the most often overlooked issues are the conversations that should be occurring with the various authorities having jurisdiction. In large mixed-use developments it is imperative to ensure that the fire and life safety system operates in a manner that meshes with the responding emergency personnel operations.
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