STRENGTH OF JOINT IN SEISMIC RETROFIT USING OUTER-FRAMEFOR EXISTING RC BUILDINGS

摘要

In a seismic strengthening of existing reinforced concrete (RC) buildings, it is important to estimate thecapacity along the connection between the additional component and the existing frame. In case of thestrengthening with new outer frames, researches are insufficient on the required quantity of anchors in theconnection to transfer shear and to resist eccentric moment. Therefore, an experimental study and elastoplasticanalyses were carried out to investigate the effect of anchors on the behavior of existing RC framesstrengthened by new outer frames.One-span and one-third scale specimens simulating an existing frame strengthened by a new outer RCframe with steel braces were tested under static and cyclic loading reversals. Friction type dampers wereincorporated into the braces to make the resistance generated by the new frame stable. Main parameter ofthe test was quantity of anchors connecting both frames. Based on the test results, specimens wereanalyzed by nonlinear frame analysis. Moreover, parametric analyses by changing quantity of anchorswere conducted to investigate adequate quantity of them.From the test and the analyses, the followings were concluded. The quantity of anchors could bedetermined appropriately according to the recommendation by Japan Building Disaster PreventionAssociation for the retrofitting inside the existing frame, provided that the capacity of a new outer frameshould be estimated exactly. Assuming incomplete composition between the new outer RC frame and theinner steel frame was desirable to estimate their capacity safely in the design. Sufficient anchors should beplaced in the beam and be concentrated in high shear areas in order to transfer the shear to the new outerframe effectively.