Seismic Strengthening of Weak Column Reinforced Concrete Exterior Frames Using Joint Bracing Struts

Abstract

There have been many seismically vulnerable buildings with non-seismically designed reinforced concrete buildings in the northern area. This study presents a test of three externally reinforced concrete beam-column joints under cyclic loading. The first specimen was a strong beam-weak column exterior frame. The remaining two frames were the same as the first frame, but with joint bracing made of either rectangular hollow steel or non-shrinkage mortar-infilled hollow steel. The test results showed that the specimen without bracing failed due to severe diagonal cracking, which rapidly reduced the lateral load; the maximum load is 15.02 kN. The rectangular hollow steel and non-shrinkage mortar-infilled hollow steel bracing respectively increased the cyclic load by 64.86% and 157.27% in average compared with that of the specimen without bracing. All specimens had diagonal cracks around the joint area. At the ultimate state, local buckling of the bracing strut close to the weld between the bracing strut and steel plate was found.