Effect of Arrangement of Masonry Infill Walls, Shear Walls and Steel Bracings on the Story Drift and Stiffness Irregularity

Abstract

Irregularities in structures, such as soft story irregularity, might make them vulnerable under lateral forces such as earthquake. One solution to this problem is a suitable use of infill members. In this study, the effect of masonry infill walls, shear walls and steel bracings on the soft story irregularity and story drift of a 10-story building is evaluated. The building has its first two stories not infilled, and the remaining stories fully infilled with masonry infill walls. Fourteen models of different infill situation divided into three groups were studied. In the first infill group, the 1stand 2ndstories were fully infilled with masonry infill walls, shear walls and steel bracings. In the second infill group, infill members were used in the center of the building. In the third group, infill members were placed in some portions of the exterior surface of the building. Moreover, two more models were developed to overcome the excess of the permissible values of partially infilled models using shear walls by changing the thickness of the shear walls. The models were analyzed using ETABS analyzing software. The results showed that arrangement of infill members has remarkable effect on the soft story irregularity and story drift. They also showed that symmetry in the elevation of the building has great impact on the performance of the building against stiffness irregularity and lateral displacement ofthe structure. The most applicable solution for the stiffness irregularity and story drift problems in the studied building is partially infilling the exterior surfaces with steel bracings or shear walls. With these infilling methods, the interior parts of the first two stories will be empty and can be used for different purposes since the infilling is only applied in the exterior surfaces of the building.