Innovation Award of Excellence: Performance-Based Structural Fire Design of Tall Buildings
Ali Ashrafi
Principal
Thornton Tomasetti, Inc., New York City
Ron Klemencic
Chairman & CEO
Magnusson Klemencic Associates, Seattle
Better Safety, Reduced Material Costs: A Performance-Based Structural Fire Design Approach
The performance of a tall building under fire loads is a critical consideration for the design team. The objective of this peer-reviewed exercise was to compare prescriptive and performance-based designs for a building in terms of safety in fire as well as design, cost, and aesthetic implications. The PBSFD evaluated different performance objectives, as well as adjustments to passive fire protection and structural design to achieve the target performance. The design was for a “generic” Type I-A mixed-use, 50-story building, with approximately 20,000 square feet (1,858 square meters) per floor, representative of a common high-rise building design in the US. The building frame is steel at the lower 30 office floors, transferring to concrete framing at the upper residential floors, through a series of steel transfer trusses. Two important components of the building were considered for PBSFD: a typical bay of the steel frame of the lower 30 floors, and the transfer trusses. The team developed a series of design scenarios corresponding to varying performance objectives under uncontrolled fire exposure.
The study showed that a combination of modest structural modifications and adjustments to a code-standard quantity of fireproofing provides the designer with the best means to achieve performance goals for tall buildings. Importantly, PBSFD does not mean more expensive design. With modifications to the structure and fireproofing, a building might benefit both from better safety and reduced material costs. The design showed a reduction of up to 42 percent in fireproofing quantity. In addition, the reduced fireproofing can lower the labor cost and the installation time, compress the construction schedule, and even reduce the carbon footprint.
Ron Klemencic is speaking on behalf of SEI and Charles Pankow Foundation.
