Numerical study on masonry-infilled steel frames under vertical and cyclic horizontal loads

Abstract

Although there are many researches on infilled steel frames with welded beam-to-column connections, however, few studies were undertaken to investigate the behaviour of these infilled structures but with other common connection types (extended endplate, flush endplate and header plate connections), particularly under combined vertical and horizontal loading. In this paper, firstly, a simplified numerical model of infilled steel frames under cyclic loading, considering the interactions between frames, infills and beam-to-column connections' components, was constructed. The model results were compared with experimental data for cyclically-loaded infilled frames, showing good agreement. Using the verified model, a parametric study on infilled steel frames with five different beam-to-column connection types, under vertical and cyclic horizontal loads, was performed. Several parameters, including vertical load level, infill thickness and vertical load application method, were investigated. The results showed that increasing the level of vertical load (uniformly distributed on the beam) minimised the difference in performance between the frames with welded connections and those with bolted connections. Under vertical loads of 0, 16% and 24% of the columns' axial capacity, the horizontal ultimate load of frames with header plate connections, was, respectively, 73%, 86% and 91% of that of frames with welded connections. Hence, when the infilled frames are subjected to relatively high levels of vertical load, utilising header plate connections may be a viable alternative to using welded connections. Furthermore, a simple analytical method for predicting the stiffness and load-carrying capacity of masonry-infilled steel frames (with different connection types) under vertical and horizontal loads, was proposed.