Experimental Study for Making Easily to Recovery of RC Piers Damaged by Earthquakes

Many reinforced concrete (RC) piers have cut-offs where the number of rebars in the longitudinal direction are reduced according to the cross-sectional force. When such piers, the cover concrete in the intermediate section of RC piers can fall off in large earthquakes. Usually RC piers receive damage at their bases when large earthquakes lateral force act. Thus, for RC piers set in a river or those with deep-set bases, it can be that recovery work after earthquakes would require huge temporary construction facilities and result in large expenses and work time (Fig. 1). If damage can be made occur above the water surface and the ground level where recovery work can be easily done, more reasonable aseismic design of RC pier structure including recoverability can be achieved. In this research, we carried out cyclic loading tests using 3 specimens having cut-offs. We studied which position of piers will yield and failure occurred based on the cyclic loading tests. We set a flexural performance ratio (ratio of bending moment to flexural yield strength) at the rebar cut-off point. This ratio is the quantitative value that controls damage in the intermediate section of the frame. As a result, the difference in yield position and bending fracture due to difference in a flexural performance ratio, and difference in position of between yield and flexural fracture due to reinforce the inner spiral rebar of the cut-off point were clarified.