The effects of brick wall and RC tie variables on the seismic performance of low-rise confined masonry buildings

Abstract

An extensive parametric investigation is carried out to determine the effects of different RC tie system and brick wall variables on the performance of confined masonry walls and buildings. The variables considered include: the number of storeys and adjacent walls, the walls aspect ratio, thickness and compressive strength of masonry walls, presence of openings, the RC tie system dimensions, compressive strength and detailing of the longitudinal and transverse reinforcements. The main aim of the investigation is to verify the efficiency of some of the prescriptive code recommendations and to provide a basis for further descriptive guidelines for low-rise confined masonry buildings. Among the major conclusions, it is found that the main affecting parameters are those of the masonry walls themselves. When the walls have sufficient shear capacities, due to lower aspect ratio, higher compressive strength and wall thickness and lack of, or small openings, the flexural demand on the tie system is small and its elements act mainly as axially-loaded tie elements. Therefore, the least affecting parameters are those of the tie system's reinforcement detailing. However, when the masonry walls are weak in shear (low masonry strength and large openings), the demand on the tie system increases, to the point that instead of acting as an integral part of the wall, it acts similar to a weak, moment-resisting frame having infill masonry walls, for which it has not been designed. The scenarios that this will happen include: the wall aspect ratios AR > 2, the masonry compressive strength, f′m < 5.0 MPa and the ratio of length of opening to the length of the wall, Ol/Wl > 0.5. To avoid such behaviour, it is also suggested that the tensile stresses in the longitudinal bars of the RC tie elements be limited to 0.6fy.