Effect of Shear Wall Openings on the Fundamental Period of Shear Wall Structures

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An-Najah National University
A common approach in resisting lateral forces is the use of reinforced concrete shear walls in low-rise and mid-rise buildings. These walls represent the main elements to resist the lateral forces due to their large strength and stiffness. However, such walls may contain many openings like doors and windows due to functional requirements, and this may largely affect the overall lateral stiffness of them. It is thus of prime importance to quantify the effect of openings on the dynamic performance of the shear walls. To generate data on the effect of openings on the fundamental period of shear walls, finite element analysis using SAP2000 structural analysis program is used as a main source in this study after verifying the results by comparing them to theoretical equations proposed by Hsiao in 2014 and hand calculations of period using Rayleigh’s method. Finite element analysis is made first by using linear elastic analysis at the wall level with different central window opening sizes, and for different wall heights. Then, multi-floor typical shear wall buildings with different central window opening sizes are studied for various numbers of floors and different stiffness ratios of walls to columns. The results are compared to ASCE7-16 code equations for estimating the fundamental period of shear wall structures. After conducting this study, it is found that the openings in concrete shear walls have a major effect on the fundamental period and on the lateral stiffness of shear-walled structures. Central window opening ratio of 3% is the maximum ratio that can be neglected safely in a one floor building, and this ratio increases by increasing the number of floors. Door opening ratio of 65% converts the solid wall to behave as a frame. The effect of wall openings on the fundamental period of shear wall structures depends on the height of the building and on the deflection mode of the shear walls, where it is either shear or flexural deflection mode. Finally, statistically regression is used to fit an equation for estimating the increase in the fundamental period of the shear – walled regular structures due to openings in the shear walls. Such an equation is quite useful in the conceptual design phase of buildings. The final results are discussed by conducting comparisons between finite element results and the fitted equation results.