Experimental study on seismic retrofit for existing R/C building by using CHS bracing

摘要

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. An FLD (Force Limiting Device), which is restrained not to buckle by the outer tube, is applied mainly as a reinforcing brace. For comparison, single tube braces and H-section braces are also applied to the proposed and conventional method. The proposed connection can transfer the shear force of the brace to the R/C frame. Consequently, the horizontal load carrying capacities of specimens agree with predicted values approximately for the reinforcement of a ductile R/C column. The design efficiency of the reinforcing frame for the brittle R/C column is also discussed.