Studies on Masonry Infill Modelling and it’s Implementation in RC Building

Abstract

Masonry has been widely used in the construction of non-engineered buildings due to its local availability and relatively less cost. Now-a-days modern buildings comprising of Reinforced concrete (RC) frames use masonry as an infill wall. A newer class of masonry infills using Fly Ash bricks and Autoclaved Concrete Blocks are rapidly replacing conventional Red Clay bricks. Generally, masonry infill walls are considered as a non-structural element in design methodology due to the complexity in the prediction of the behavior of infill walls under lateral load. Masonry infill with RC frame was found to have significant lateral stiffness, strength, overall ductility, and energy dissipation capacity from numerous experimental investigations. However, it causes several undesirable effects under seismic loading like short-column effect, soft-story effect, torsion, and out-of-plane collapse, etc. Therefore, it is important to study the behavior of infilled RC Panels under lateral load so that contributions from masonry infill can be included in the analysis and design of RC buildings. Present study is conducted in two parts, firstly numerical investigation on masonry infilled RC panels with red clay bricks, fly ash bricks, and AAC blocks is conducted to assess the capability of different macro models of masonry infill and secondly, single strut macro modelling is implemented with medium-rise RC building for seismic analysis. Numerical investigations with single, double, and triple strut are carried out for single storey RC Panel with red clay bricks, fly ash bricks and AAC blocks for which experimental results were available within linear limit as well as masonry infilled RC Panel with single, double and triple strut are studied by nonlinear static analysis. It was found that single strut modelling of masonry infill offers highest lateral load resistant among all macro models and reduces internal forces in beam and column elements of the RC Panel. However, two strut and three strut models of masonry shows better distribution of internal forces among masonry infill, beam and column elements of RC Panel. Six-storey RC infilled building modelled with macro model using ETABS software. The building is analysed and designed under gravity and lateral loading. It has been observed that time period of building reduced by 1.65 times as compared to bare RC frame and thus base shear of the building increases by 1.32 times. However, top displacement of the building reduces by 25%, maximum inter-story drift reduces by 40% and reduction in longitudinal reinforcement is about 25-30% as compared to bare RC frame.