The presence of infill walls within the plane of the frames significantly alters their structural properties, causing notable differences in strength, stiffness, internal forces, and other characteristics of a frame with an infill wall compared to frames without infill walls. This difference in performance has been observed not only in various theoretical and experimental studies by different researchers but also in different earthquakes. Therefore, if the effects of infill walls are confirmed in the design of infilled frames, they cannot be disregarded, and must be considered in the analysis and design process. In this study, the seismic behavior of reinforced concrete frames with cement block infill walls is evaluated using the three-spring modeling method. This method has demonstrated acceptable accuracy in validation studies, showing consistency between numerical results and experimental data. In the solving process using nonlinear static analysis, fiber plastic hinges are used in the beam and column elements. As well as validating the methods used based on reliable experimental results and ensuring the accuracy of numerical calculations, a parametric study was conducted on 27 models of reinforced concrete frames, both without infill walls and with solid and hollow cement block infill walls. These models were analyzed for three different structures with 3, 6, and 9 stories, with a fixed story height of 3.4 meter and a span-to-story height ratio of 1.5, 2, and 2.5.
The results indicate that, compared to models without infill walls, the presence of infill walls significantly increases the stiffness and strength of the structure. The average increase in initial stiffness for the three-story, six-story, and nine-story structures with different span lengths, and hollow cement block infill walls, is 10 times, 5 time, and 3 times greater, respectively, compared to structures without infill walls. For structures with solid cement block infill walls, the increases are 20