The level of damage in irregular structures is more compared to regular structures. In this study, L shaped RC buildings are investigated with and without steel bracings in different positions in frames. The response spectrum analysis has been done by using ETABs software. The two cases considered, case I and case II for understanding the effect in inverted V bracing in L shape building. Case II shows the suitable seismic parameters when bracing is used properly. Interstory drift, displacements, base shear, fundamental time period, torsional irregularity ratio and the capacity ratio of the columns are evaluated. It is also noticed that adding the steel bracing decreases the inter-story drift, displacements of the structure effectively. The torsional irregularity ratio of each 12 models are studied carefully. The capacity ratio of the selected columns is studied to understand the performance of the columns while using the steel bracing in the buildings. The steel bracings are effectively used as retrofitting in L shaped buildings if the position of bracings are considered in the frames appropriately. While designing irregular buildings with steel bracings, the torsional effect should be checked.

Retrofitting of the existing buildings helps to reduce the serious damages under the strong ground motions. In retrofitting techniques, steel bracings are used to resist the lateral load effectively. In this study, the author aimed to investigate the four-story RC frames without and with steel bracings to understand the seismic performances of the buildings. The authors select the V bracings having 7 different thickness of steel bracings ( t= 2.5, 4, 6, 8, 10, 14 and 20mm) and observed the effect in seismic behaviors of the structures in terms of maximum story displacements, inter-story drift (ISD), base shear, fundamental time period (FTP) and capacity curves. In addition, it observed the failure behaviors of the structures. To study the seismic behaviors, the response spectrum analysis and nonlinear static analysis are performed in ETABs software. The result indicates that V bracing improves the seismic performances of the RC frames as well as improves the strength capacity and stiffness of the buildings. Adding bracing in RC frames decreases the top story displacements and inter story drift of the buildings. To get the expected failure mechanism in the braced frames and suitable uniform energy dissipation behaviors, the bracings are designed in such a way that the RC columns should be the main line of defense in the dual systems. Expected failure mechanism is obtained when stronger column, weak beam and weaker bracings design philosophy is used and it is only possible when the columns are designed to resist at least 50% lateral base shear in dual systems. A suitable thickness of bracings which is economical and structurally good should be selected.

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