Numerical Investigation of Steel Moment-Resisting Frame with RBS Connections Under Fire Conditions

Recent earthquakes indicate that the welding connections of steel moment-resisting frames (SMRFs) are so brittle. Then, huge damages are generated by cracking the weld between beam flange and column face. After ۱۹۹۴ Northridge and the ۱۹۹۵ Kobe earthquakes, reduced beam section (RBS) connections were proposed to reduce the damages by forming a plastic hinge outside the panel zone. Thus, the great effect of seismic performance and ductility of the panel zone, RBS moves the formation of plastic hinge at a suitable distance from column face. In this regard, in order to evaluate the behavior of SMRF with RBS connections under fire conditions, four types of steel frame connections including RBS with radial, rectangular, triangular and trapezoidal cuts were modeled in ABAQUS software. Due to the fact that fire is an unpredictable phenomenon, both in terms of size and fire load, it has special complexities. The fire load was simulated either by a steady state method to reach a fully-developed fire or by a transient state method following the standard temperature–time curve. The results of this study showed that by increasing temperature of the heated area, the transferring of plastic hinge is conducted better. Meanwhile, based on the obtained outputs of displacement-time coefficients, Frame-RBS-۰۱ sample had the most ultimate strength compared to other samples up to ۷۴۸.۳۴ ° C temperature and the least ultimate strength is related to the Frame-RBS-Rectangle-۰۲ sample up to ۵۲۶/۹۰ ° C temperature.

Keywords:

Steel moment-resisting frame (SMRF) , RBS connection , Fire , ABAQUS software