Seismic Analysis of Torsional Irregularity Attributed to Shear Walls Location in Multi-Story Building- Case Study

Abstract

Nowadays, the investigation for the behavior of irregular structure during earthquakes become one of the most pressing demands for the design of multi-story buildings, it is a result to the evolution of design approaches towards the concept of showing the complexities and irregularities in the shape of the buildings Architecturally. Normally, the columns and shear walls for the building are providing the rigidity to resist the earthquake forces. Therefore, the judicious choice for size and location of these elements within the configuration of building story plan is important. This study is focusing on one type of structural irregularity related to the location of shear walls in story plan and how can this contribute to the structural response during earthquake. Three models have been analyzed for 10 typical story building, the first one is the base model (regular) where the group of shear walls located in the center of the typical plan while the second one is for the building when the walls shifted to the edge in X direction and the third model is for the case where walls are located at the corner of the building (shifted in X and Y direction). the performance of these frames has been evaluated as per the procedures described in (Uniform Building Code) UBC 97 code as well as the criteria to obtain the results for story drift, story displacement, time period, base shear, and overturning moments. Shifting the group of shear walls from center of the story plan to different locations created irregular frame for the models therefore the amplification factor has been used wherever the torsional irregularity is observed. All the results have been studied, analyzed, and compared in detail by plotting the data or arranging them in tables. It was noted in irregular models that the vertical elements are exposed to forces bigger than the regular model. The torsional irregularity for structure produced the bigger biaxial forces on the columns located further from the shear walls position, therefore, changing the size and shape of these elements might be required. Alternatively, it might need to add shear walls in the areas exposed to significant forces to minimize the effect of torsion on the structure.