ISSN 2303-4521 Periodicals of Engineering and Natural Sciences Original Research Vol. 9, No. 3, August 2021, pp.494-508 © The Author 2021. This work is licensed under a Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/) that allows others to share and adapt the material for any purpose (even commercially), in any medium with an acknowledgement of the work's authorship and initial publication in this journal. 494 Study of effect of shear wall in the seismic response of the existing buildings Mohammed A. Elwi 1 , Wameedh Gh. Abdul Hussein 2 1,2 Civil Engineering Department, University of Technology, Baghdad, Iraq ABSTRACT In Iraq, it has been observed that an increase in seismic activity, and that most existing buildings are not seismically designed and that can suffer serious damage or collapse, thus causing loss of life. In this paper, a numerical simulation of the experimental laboratory sample on the subject of non-seismically designed buildings and methods of strengthening them was performed using a seismic strengthening technique using an infill RC wall in order to maintain the risk of earthquakes. This study was carried out through the work of verifying the numerical and practical model by matching the results of laboratory work with the results of numerical analysis using the analysis finite element analysis method (FEAM) by Abaqus CAE 2019 software and then using the model to study the effect of openings in the infill RC walls and the extent of its impact on the response of the building. The practical model is a full four-story building tested laboratory in Elsa, Italy using pseudo dynamic test (PSD). The experimental model is a sample of not seismically design buildings (gravity design only) and ways to improve them by adding new RC walls with different contact details to the existing building. The goal of the experimental test was to study the effectiveness of adding RC infill walls with two types (North and South) infill RC walls, including designing it and the contribution of two types of dowels that connect the new infill walls to the existing RC building. In other words, it’s a way of strengthening by converting selected bays into RC walls with two types of reinforcement and connection between new infill RC walls and existing builders called (north and south) frames. The results of analytical modeling show that the percentage of differences in X- Direction of top story displacement between Abaqus software and Experimental tested at ELSA results are 2.47% in positive and 3.12% for negative X direction, which refer to a very good similarity and accurate building simulation. Keywords: Numerical Simulations, Strengthening techniques, Infill RC Walls, North Frame, South Frame, RC Infill Wall, Abaqus CAE2019 software. Corresponding Author: Asset. Prof. Mohammed A. Elwi Civil Engineering Department, Technology University, Baghdad, Iraq. E-mail: mohammed.a.elwi@uotechnology.edu.iq 1. Introduction FEA is a helpful tool for finding solutions to many engineering problems. It is fundamentally a process where a continuum with finite degrees of freedom in which corresponds to be a congregation of elements (or sub- regions) each with unknowns specified finite numbers [1]. Design building according to the specifications of the seismic codes provides capabilities to resist earthquakes without collapsing, the seismic loading calculation is an important part of the structure designing procedure. During earthquakes, the structural parts of the building must have sufficient capacity to withstand lateral loads and thus comply adequately when increasing pressures and being able to increase life safety. Two types of seismic retrofitting, are known as a global and local modification [1]. Fig.1 shows types of retrofitting techniques.