Post-earthquake fire performance of steel moment frame building columns

Sprayed fire resistive material (SFRM) is an integral part of structural fire protection for multistory steel building construction. SFRM is intended to thermally protect structural steel elements during a fire. Damage to the SFRM can compromise the efficacy of the SFRM and lead to elevated temperatures in the steel substrate and thus a reduction in strength and stiffness of the steel.;The broad objective of this research is to evaluate the efficacy of sprayed fire resistive material in steel moment frame building structures in the event of a post-earthquake fire. The focus of the work is the axial load behavior of a steel column in a fire as influenced by damage to the SFRM in the beams adjacent to the columns.;The scope of this work includes four tasks: (1) tensile plate tests to investigate the bond of SFRM to steel plates at various levels of post-yield strain in the plates; (2) cyclic loading tests of beam-column assemblages with SFRM to determine earthquake induced damage to the SFRM; (3) nonlinear finite element heat transfer analyses to determine the fire-induced temperature distribution in the beam-column connection region due to damaged SFRM on the beam; and (4) nonlinear finite element structural analyses of the strength of the columns, at the elevated temperatures determined in Task 3, due to fire and damaged SFRM.;For well-designed, strong column---weak beam moment frame steel structures in earthquakes, it is likely that steel yielding will first occur under the action an earthquake causing drifts of about 1%, and consequently debonding of the SFRM will occur. Under the design earthquake causing story drifts of 3% to 4%, tearing in the SFRM at the locations of buckling of the beam flanges occurs. The tears separate the SFRM in to sections that can then fall away from the connection, exposing the steel at those locations.;The SFRM damage patterns studied in this research lead to significant increases in column temperatures under the action of a standard fire load, and thus contribute to important reductions in steel yield strength under the action of 90 minute and 2 hour standard fires.