Thermal creep behavior of shear tabs in fire using modified burgers model

Abstract

A mechanical model is developed to predict the time-independent (fast) and time-dependent (due to thermal creep) force-rotation characteristics of shear tab connections subjected to fire. The time-independent behavior of the connection is modeled using a group of springs that can predict the rotational stiffness and the strength of the connection when subjected to fire temperatures. A modified Burgers model is incorporated in the mechanical model to include the thermal creep effect. The modified Burgers model is composed of linear springs and viscous dashpots that can predict the time-dependent behavior of the shear tab connection before and after beam-column contact, and bolt bearing. The proposed model shows excellent agreement when compared with experimental results and finite element (FE) simulations. Furthermore, isochronous curves are developed to study explicitly the effect of different parameters, on the strength and rotational capacity of shear tab connections. The proposed model can be considered an important step toward the inclusion of thermal creep in fire design of shear tab connections.