MS in Fire Protection Engineering
College of Engineering
Frederick Mowrer and Christopher Pascual
This report describes the building code compliance of a military aircraft hangar. The facility is evaluated for both prescriptive code compliance and for a performance-based compliance via the use of design fires analyzed with computer programs Fire Dynamics Simulator (FDS) and occupant egress analyzed with Pathfinder software as well as hand calculations utilizing Excel.
The prescriptive code analysis is done based upon a combination of Unified Facilities Criteria, International Building Code, and NFPA 101 codes and standards. Prescriptive compliance was checked against the building non separated occupancies of S-1 and B. The building was evaluated for building construction type IIB. The separations, fire ratings, egress component sizing and spacing, fire alarm, and fire suppression systems were all evaluated.
The building is compliant with all the prescriptive standards. All the building systems and construction details were prescriptively compliant with the building codes of record.
The performance-based design has objectives of verifying that the as designed building configuration and occupancy will be provided with an environment for the occupants that is reasonably safe from fire. The objectives were compared to tenability criteria limits of 1,400 ppm of CO concentration, temperature limit of 60°C, and a visibility limit of 10 meters. The building egress time was evaluated with a stairwell inaccessible due to the fire being near the stair door on the 2nd floor of the facility. The hangar areas of the building were evaluated for asset protection of the aircraft housed within. The asset protection analysis involved verification of when the alarm and suppression systems dealt with the fire and determining the highest heat release rate achieved and flame height developed for a pool fire that is generated during the 65 seconds between ignition and the aircraft silhouette being covered by high expansion foam.
The final analysis from FDS shows an ASET of 330 seconds. The final analysis of RSET utilizing Pathfinder and assumed premovement times of 162 seconds and egress time of 186 seconds, indicates an RSET time of 348 seconds. The building does not provide an environment where the ASET is greater than the RSET. The analysis evaluated in this report is very conservative in nature and does not account for occupant reactions to the fire beyond egressing such as closing the door of the room of origin or pulling a pull station prior to the sprinkler setting off the alarm. Due to this the ASET and RSET values are very conservative in their application and any adjustment to the modeling will lead to a greater difference between the ASET and RSET. The performance-based design meets the goals presented since the worst case scenario and it shows that the ASET is within 5% of the RSET. With a reevaluation of the modeling utilizing less conservative tenability criteria and taking into account the reactions of trained facility occupants it is possible to have the ASET become greater than the RSET. This should be evaluated in the future.
The asset protection analysis shows that an evaluated maximum fuel spill of 30 gallons can generate a 48 MW fire with a 10 m flame height. The 10 m flame height will impinge upon the fuselage height of approximately 1 m and under wing height of approximately 2.5 m. The aircraft will sustain damage during the fire.