Seismic Performance of a Fire-Exposed Moment-Resisting Frame

Abstract

Major earthquakes in urban areas often lead to building fires. Such earthquakes frequently damage buildings’ water sprinkler systems and diminish or strain firefighting capabilities. In such scenarios, buildings get exposed to fire for a long period of time, resulting in damage of spray-on-fire resistive materials. Consequently, steel frame temperature may reach as high as the maximum fire temperature, which subsequently cools slowly to ambient temperature. If the building frame does not deform severely after such a fire event, it is usually rehabilitated for continued occupation. The performance of such a fire-exposed steel building during a future earthquake is not known. This study investigates the seismic performance of a fire-exposed steel frame by performing finite-element analyses incorporating fire-exposed steel material properties. The simulation responses demonstrate vulnerability of fire-exposed steel buildings. A novel but startling observation made is that under seismic loading, a fire-damaged steel frame may form a soft-story mechanism at the story of fire exposure because of plastic hinge formation in the column instead of in the beams.