Thermal creep effect on the behavior of flush end-plate connection under prolonged transient heating conditions

Abstract

The properties of steel material become dependent on the temperature and duration of heating during a fire event. Thermal creep strain of steel is a time-dependent inelastic deformation that becomes significant under constant load and high temperatures. The goal of this study is to understand the thermal creep effect on the behavior of beam-to-column flush end-plate connections subjected to transient fire conditions. Finite element (FE) models were developed and validated against experimental work available in the literature. FE parametric studies were conducted to study the overall response of the connection with and without the explicit consideration of thermal creep. The parameters include: heating-cooling rate, beam length, load ratio, plate thickness, bolt size, and thermal creep effect in bolts. A mechanical model was developed to predict the flush end-plate connection behavior subjected to fire temperatures. The proposed model is based on geometrical components and material properties of the connection. This model is able to predict the thermal beam axial forces including the effect of beam mid-span deflection. The proposed model is also able to predict the time-dependent behavior of the flush end-plate connection where thermal creep strains are incorporated in slow heating rates. This work shows the importance the including the effect of thermal creep strains in designing flush end-plate connections subjected to prolonged heating conditions.