Abstract
A new seismic retrofitting method for existing R/C buildings by using a circular hollow section (CHS) bracing is proposed. In the proposed method, a reinforcing frame composed of an H-section peripheral frame and pin-ended CHS bracings is placed on the outer surface of an R/C frame and connected to the R/C with mechanical anchors and high strength mortar. Experimental studies were carried out to evaluate the reinforcing effect. A single tube brace and a tube-in-tube brace, which is restrained not to buckle by the outer tube, are applied as a reinforcing brace. For comparison, H-section braces are also applied to proposed and conventional method. All the specimens are 1/3-scale models for one story-one bay substructure frame of an R/C building. In the experiment, the horizontal shear loads were cyclically applied to specimens under a constant vertical load. Through the experimental results and analytical results, an effectiveness of the proposed method is discussed. The horizontal load carrying capacities of specimens are agreed with predicted values approximately for the reinforcement of R/C frames.
