Modeling of steel frame structures in fire using OpenSees

The OpenSees framework has been extended to deal with frame structures under fire conditions. OpenSees is an object-oriented, open source software framework developed at UC Berkeley and has so far been focused on providing an advanced computational tool for analyzing the non-linear response of structural frames subjected to seismic excitations. New classes defining time-dependent temperature distributions in the cross-section of members have been created and OpenSees material classes have been modified to include temperature dependent properties based on the Eurocode. New functions and interfaces have been added into existing element and section classes to calculate the member actions due to arbitrary thermal loading taking into account material degradation with increasing temperature for non-linear analyses. This paper reports on a number of benchmark tests to ascertain the performance of the new codes implemented in OpenSees for beams, frames, and plate structures. The analysis procedures being developed for structures exposed to fire in OpenSees will make it easier for users to define temperature-dependent material properties and allow for arbitrary non-uniform temperature distributions across and along an element by interfacing a fire and heat transfer analysis module also being developed for OpenSees. This work will also enable the modeling of earthquake damaged structural frames subjected to a subsequent fire.