Seismic elastic performance of L-shaped building frames through plan irregularities

Abstract

The trends of irregular building construction have rapidly increased due to aesthetic and limited availability of land. Past studies have shown that the structures with configuration irregularity are damaged under strong ground motion. Structural irregularities are important factors which decrease the seismic performance of the structures. Buildings having structural irregularities result in the uneven distribution of the story drift, excessive torsion, etc. according to the irregularity type and may fail during an earthquake. One such form of irregularity is the presence of re-entrant corners and torsional irregularity that causes stress concentration due to sudden changes in stiffness and torsion amplification in buildings. In this context, the present study evaluates the effect of plan configuration irregularity when subjected to the varying angle of the input response spectrum. For this, one regular and six different L-shaped RC building frames were modeled for numerical analysis. The analysis was done through an equivalent static lateral force method and response spectrum analysis (dynamic analysis). The structural responses were measured in terms of story displacement, inter-story drift ratio, torsional irregularity ratio, torsional diaphragm rotation, normalized base shear force, and overturning moment. The results indicate that buildings with plan configuration irregularity are more sensitive to the varying angle of the input response spectrum as compared to the symmetrical building model. The significant increase in seismic response demand was observed when the finite element models were subjected to a 135-degree angle as compared to the zero-degree angle of seismic incidence. In addition, the study shows that the fundamental time period of structure based on standard code shows a lower value as compared to a finite element approach. It is concluded that to account for the irregularities present within the buildings, current code provisions are insufficient and should be amended.