Influence of Opening Ratio and Position in Infill Wall on Constitutive Law of Equivalent Compression Strut

Abstract

Infill walls are widely used in any building to create a separation between spaces intended for different purposes. In general, partial openings exist in infill wall with different opening ratio and position due to architectural considerations, functional needs and aesthetic concerns. In current practice, buildings are considered as bare frames ignoring infills and openings. However, infill walls and partial openings may significantly affect the seismic behavior of structures. Equivalent compression strut model is frequently used in modelling of infill walls for structural analysis. Accordingly, the force-displacement (F–D) relationship of equivalent compression strut is quite important in nonlinear analysis of infilled frames. In particular, opening sizes and position are essential parameters in order to properly constitute F–D relationship of infill wall with openings simulated by means of an equivalent compression strut. In this study, F–D relationship of equivalent compression strut is determined for different opening ratios and positions in infill wall considering three different F–D relationship models available in the literature. The maximum strength of equivalent compression strut and the corresponding displacement, the compression cracking force and the corresponding displacement, the residual strength and the axial compressive stiffness of the strut are compared and discussed for different constitutive F–D laws. It is found that force values of F–D relationships decrease as opening ratio increases. However, displacement values are not generally effected by opening ratio or position. Furthermore, openings upon the diagonal are more influential on F–D relationships of equivalent compression strut in comparison to other opening positions.