Seismic evaluation of reinforced concrete buildings including effects of masonry infill walls

A comprehensive study to evaluate the seismic performance of reinforced concrete (RC) buildings including unreinforced masonry (URM) infill walls is outlined. The study is performed in three sequential parts: (1) shake-table experiments, (2) computational modeling and (3) reliability-based performance evaluation. A hypothetical prototype building with RC frames, RC floor slabs and URM infill walls is considered. A reduced-scale test structure is constructed to represent a substructure of the first story of the prototype building and the relationship between the demand parameters of the test structure and those of the prototype substructure is established using pre-test computational modeling of the prototype and the test structures. Shake-table experiments are conducted on the test structure to evaluate its dynamic properties and seismic responses with and without the effect of the URM infill walls. Based on several preliminary tests and the results obtained from the pre-test computational modeling of the test structure, shake-table motions and their sequence of application are selected. The results of the shake-table experiments in terms of global and local behavioral observations of the test structure and the effects of the URM infill wall on the behavior and dynamic properties of the bounding RC structure are discussed. Several post-test computational modeling approaches to represent the URM infill walls and their interaction with the surrounding RC frames of the prototype building are evaluated by comparing their results to those obtained from the experiments. Moreover, a detailed finite element (FE) model of the test structure is constructed and validated using the results of the shake-table experiments. Using this validated FE model, several computational simulations are performed to understand the in-plane and the out-of-plane responses and their interaction for RC frames with URM infill walls subjected to bidirectional seismic loading. Realizing the importance of effects of bidirectional loading on the infill walls, a three-dimensional (3D) strut and tie (SAT) model is formulated for practical representation of the combined in-plane and out-of-plane failure surface in conventional structural analysis computational platforms. Finally, the prototype building is considered to demonstrate a framework for practical reliability analysis of RC buildings containing URM infill walls. This is conducted using a refined computational model of the prototype building benefiting from the earlier experimental and computational studies conducted on the test structure. Defining the limit states in terms of the capacity loss of the URM infill wall, fragility functions are determined using the reliability analysis for the prototype building subjected to near fault ground motions in a wide range of hazard intensities.