Contribution to numerical modelling of concrete- masonry interface In concrete framed structures with masonry infill

Abstract

Masonry infills have long been used as interior partitions and exterior walls in buildings. They are usually treated as non-structural elements, and their interaction with the bounding frame is often ignored in design. Nevertheless, infill contributes strength to a structure and will interact with the bounding frame when the structure is subjected to strong lateral seismic loads, when the infill is stressed due to movements of an overlying slab or any other case of in-plane or out of plane lateral loading. This interaction may or may not be beneficial to the performance of the structure, however, and it has been a topic of much debate in the last few decades. The interaction of the infill is governed by the relative stiffness and strength characteristics of each individual component and most importantly the interface characteristics that decide the degree of composite action. An interface is a special contact plane on which nonlinear relations between stresses and displacement discontinuities are present. Very often initiation and propagation of cracks along these interfaces are the cause of failure of the relevant structures. Similarly, in the case of concrete framed masonry assemblages, the bond between the masonry and the concrete frame is a weak link, through which failure is possible. Therefore to simulate this behaviour, interface elements with a suitable constitutive model can be utilized. This paper explores finite element models developed to simulate the behaviour of concrete- masonry interface of masonry infill. In this study, brick-concrete couplets were mathematically modelled, using commercially available software ANSYS. The adopted numerical strategy consists of simplifying the concrete-masonry-mortar interface to a zero thick interface, modelling the brick units and the concrete units with three dimensional solid brick elements and modelling the bond using zero thickness interface elements with a cohesive-zone model (CZM) for mixed-mode fracture based on damage mechanics introduced by Alfano and Crisfield(2001).