A numerical study on seismic behavior of plan irregular buildings

The shape, size and geometry of the building affects critically its seismic performance. Buildings with simple geometry in plan had performed well during the past strong earthquakes. But buildings with plan irregularity are more vulnerable and expected to be experienced more damage during seismic excitation. In this study, an eight story reinforced concrete regular building having a typical 6 bay x 6 bay frame with plan dimensions of 36 x 36 m and twenty four irregular buildings with different irregularities of +, C, O, H, ┴, L and Z shapes were examined. The structures were modeled using a finite element method and evaluated by both nonlinear static and dynamic analyses. Three-dimensional structural models were utilized for the analysis. Capacity curves, variation of storey displacement, and roof displacement, base shear time history were computed for the regular and irregular buildings. The analysis of the results showed that the regular building had considerably greater capacity in comparison to the irregular buildings due to the fact that irregularity caused decreasing the capacity of the buildings and the structures were more doubtful when they were more irregularities. Moreover, the displacement demands of the buildings were sensitive to type and amount of irregularity, especially at roof level.