Effect of using off-center bracing system on the capacity curve of a reinforced concrete building.

This study investigates the variation in the capacity curve of an eight story reinforced concrete (RC) building before or after applying off-center bracing system. The case study structure had the same floor plan (3x4 bays) with varying bay length. The external and the internal bays are 3 m and 4 m spans, respectively. The off-center bracing system comprised of three main members. Two of them were non-straight diagonal elements and connected at a certain point in the frame bay while the third one was connected from this point to the corner of the frame. This arrangement introduced different eccentricity parameters. In the current study, four different eccentricity parameters varying from 0.2 to 0.8 and nine different sizes of brace member with an outer diameter ranged from 80 to 240 mm were used. The brace members were selected as circular hollow section (CHS). Thus, a total of 37 different cases were considered in this study. All structural models were subjected to the nonlinear static pushover analysis. The effect of the eccentricity in the off-center bracing together with brace member size on the seismic performance of the strengthened building were evaluated. The comparative analysis indicated that the lateral load carrying capacity of the structure was very sensitive to the amount of eccentricity. Increasing the eccentricity from 0.2 to 0.8 dramatically reduced the capacity of all case studied structures. Keywords: Eccentricity, Off-center bracing, Pushover analysis, Reinforced concrete building, Seismic response.