MS in Fire Protection Engineering
College of Engineering
Frederick Mowrer and Christopher Pascual
The purpose of this report is to perform a two-part analysis of Tucson Student Housing’s fire protection design components. The two-part analysis consists of a prescriptive analysis, and a performance-based analysis. The purpose of the prescriptive-based analysis is to verify Tucson Student Housing meets or exceeds applicable construction standards. The prescriptive based analysis reviews the fire resistance of building elements, flammability of interior finishes, wet suppression system, fire alarm system, voice evacuation system, and occupant egress requirements. The performance-based analysis evaluates the performance of Tucson Student Housing’s fire protection systems when subjected to specified design fires. The design fire scenarios used in the analysis use design guidelines from the NFPA Life Safety Handbook. The focus of the performance-based analysis is to apply fire scenarios to ensure that fire protection systems and features meet the demands of the fire scenarios.
Tucson Student Housing is a new multi-use residential high rise in Tucson, AZ. Tucson Student Housing is composed of the following major sections: The enclosed garage provides parking spaces for 143 vehicles over two below grade floors. The parking garage has elevator access, and two stairwell exits that discharge to the public right of way. The Enclosed Garage floors are classified as Storage Occupancy Low Hazard Storage S-2 (IBC 311.3). The first floor consists of multiple occupancies with Retail Shops and Assembly Areas for Residents. The first floor consists of social lounges, study lounges, Office Administration areas, an exercise room, residential space, retail space, and mechanical/electrical area. The 1st floor consists of mostly of Assembly space, and residential space. A portion of the 1st floor dedicated to commercial retail is currently built as a shell only for future use. The occupancy types on the first floor include: Business Occupancy (IBC 304.1), Assembly Occupancy A-2 (IBC 303.3), Residential Occupancy R-2 (IBC 30.4), Mercantile (IBC 309.1), and Storage Low Hazard S-2 (IBC 311.3). The Residential Units span all above grade floors. Residential units are concentrated between floors 2 through 8. Each floor has approximately 18 units. The Residential floors have elevator access, and access to two stairwells that discharge to grade level. The occupancy type for residential floors is Residential Occupancy R-2 (IBC 30.4). The rooftop is used in Tucson Student Housing as an Assembly space. The Pool is an Assembly Occupancy A-4 (IBC 303.5), with a calculated roof top occupant load of 447 occupants.
There is one area of interest in the prescriptive design, the roof of the Tucson student housing building met egress requirements. However, the calculated occupant load of the Roof is 447 occupants, at the calculated load only two exit stairs are required. If the occupant load exceeds 501 occupants, the requirement increases to three exit stairs. It is recommended occupant entry is managed using a card access system to ensure occupant load does not exceed 500 occupants. The performance analysis determined prescriptive fire protection measures performed as designed during the vehicle fire scenario in design fire scenario 1. Design fire scenario 1 for the Tucson Student Housing was based on a vehicular accident occurring in the parking garage. The accident would result in one of the two cars igniting. The location of the accident in the parking garage is important because the purpose of the design fire is to reduce the available exits. When the number of exits is reduced from two to one, will occupants still be able to egress the floor to grade level. This design fire scenario follows the design criteria of NFPA 101 design fire scenario #2. The first step in designing the fire was to determine the heat release rate of a burning vehicle. The performance analysis determined prescriptive fire protection measures performed as designed during the vehicle fire scenario in the parking garage. Available safe egress time (ASET) exceeded required safe egress time (RSET). The required safe egress time was established using two methods. The first method was a hydraulic first order analysis, and the second method was a computer-generated egress simulation. The hand calculations determined RSET for the parking garage fire to be 1.29 minutes or 77.4 seconds. The computer-based simulation model determined an RSET value of 4.18 minutes or 251 seconds. Available Safe Egress Time was determined using smoke detectors to measure the spread of smoke at a height of 2.5 meters above the floor. Using this criterion, it was determined that the first smoke detector activated at approximately time 8.1 minutes or 486 seconds. This analysis showed that occupants can exit before tenability criteria failed and the model in the performance-based design showed sprinkler activation at 215 seconds. The egress model determined all occupants were able to egress into the exit stairwell at 251 seconds, well before the smoke layer descended below 2m above the floor within 30 meters of the nearest queued occupant.