Fiber-based model for earthquake-induced collapse simulation of steel frame buildings

Earthquake-induced collapse risk assessment of steel frame buildings requires the use of simulation models that can realistically replicate dynamic instability of frame buildings. Such models for steel columns should consider the coupling between the axial force and flexural demands. In end columns, the axial load demand variations due to dynamic overturning effects may be considerable. Other important aspects to be considered are the cyclic hardening prior to the onset of local buckling; the column post-buckling behavior under various axial and lateral loading histories. The potential of utilizing different steel materials should also be considered. This paper proposes a component model that simulates the hysteretic behavior of steel columns utilizing hollow structural sections at large deformations. A fiber-based approach is adopted that combines an equivalent engineering stress-strain constitutive relation assigned to a fiber crosssection within a pre-defined plastic hinge length of a force-based beam-column element formulation. The pre- and post-buckling behavior of the equivalent engineering stress-strain relation is defined based on uniaxial cyclic coupon tests and extensive stub column finite element analyses. The effectiveness of the proposed model in simulating the steel column behavior is demonstrated through comparisons with steel column collapse experiments as well as frame simulation studies validated with shake table collapse tests.