Seismic Performance of Unreinforced and Reinforced Brick Masonry Structures by Numerical Modelling for Design Optimization

Abstract

Most of the residential houses are constructed with unreinforced brick masonry in many earthquake-prone regions. These structures are not safe against seismic loading. In absence of proper guidelines, researchers have recommended the use of reinforced brick masonry considering broader seismic parameters. Most of the time, the seismic demand is much less than the provided strength even with the use of minimum stiffeners cross-section, concrete strength and reinforcement re-bars. Thus, generalized cross-section of stiffeners is proposed. This practice does not consider all seismic parameters and ultimately engineers recommend stiffeners of heavy design to ensure safety. To overcome this problem, there is a need to correlate the seismic demand with the stiffeners design. The design optimization of reinforced concrete (RC) vertical and horizontal stiffeners in brick masonry structures using a diagonal approach is important. In this research work, the proposed design of RC vertical and horizontal stiffeners is validated numerically in accordance with governing seismic parameters i.e. I = 1 and T < 0.7 second. The purpose of this effort is to ensure both structural safety and economy at the same time. A total of 50 numerical models of brick masonry structures are developed and analysed in SAP2000 for different seismic parameters. The seismic performance of unreinforced brick masonry structure (UBMS) and reinforced brick masonry structures (RBMS) is studied in terms of principle critical stress (PCS), maximum top displacement (in-plane) and prediction of crack propagation. The behaviour of different RBMS are compared with that of UBMS. As anticipated, RBMS (with proposed stiffeners) performed better than UBMS for respective seismic loadings. In RBMS, the PCS of both walls (i.e. wall with openings and solid wall) are reduced up to 68% compared to that in UBMS. The maximum top displacement (∆) of RBMS in wall with opening and solid wall are decreased up to 33% and 37%, respectively, compared to that of UBMS. The length and number of cracks in RBMS are less compared to that of UBMS for all soil profile types and seismic zones. It is concluded that the proposed optimized stiffeners in RBMS meet the required seismic demand for that particular combination of seismic loadings. Based on these results, the proposed diagonal approach for design of vertical and horizontal stiffeners in brick masonry structures is safe and economical.