LATERAL LOADING TESTS ON RC FRAMES REINFORCED BY STEEL ARCH: For reinforced concrete apartment house

Recently the earthquake resistance of public buildings such as schools has progressed, but seismic diagnosis and seismic retrofitting of private apartments have not progressed. So we deal with an apartment which was built before 1981, and propose the seismic reinforcement method for it. Now we reinforce the apartment on the balcony and common corridor, because it is required to do seismic reinforcement construction of apartment at the out of the private area. We created RC frame, reinforcement method was attached steel arch in RC frame. Reasons for attaching steel arch reinforcement are as follows. 1) It has less influence on traffic lines compared with brace reinforcement 2) The curved portion of the arch can smoothly transmit the horizontal force from the girder to the column to the lower part of the building. 3) Spiral reinforcement isn't set between the RC frame and steel arch, in order to reduce the decrease of the opening height when the residents take refuge. The purpose of experiment is set in confirming the effect of reinforcement by steel arch. Two 1/4-1/5-scale RC frames were tested cyclic lateral loading. Next they were reinforced by steel arch. And the reinforced them were done experiment. We obtained the following conclusion from this experiment. 1) The initial stiffness of specimen after reinforced by steel-arch increased about 70% than it of specimen before reinforcement. The strength on R=0.5% of specimen after reinforcement increased about 80% than it of specimen before reinforcement. The hysteresis energy of specimen after reinforcement increased about 50% than it of specimen before reinforcement. 2) The initial stiffness of specimen with arch-corner-plate was 18% higher and the strength of specimen with arch-corner-plate was 13% higher, than specimen without arch-corner-plate. 3) In the case of reinforced by steel-arch, the maximum load was reached in the vicinity of R=0.8%. The shear cracking occurred in the column. The lateral load decreased but the load at maximum deformation at the initial cycle of R = 2.0% was 8-17% less than maximum load. The large reduction in yield strength were not observed. 4) Axial force and bending moment of the steel-arch became large at the curved portion, and they can be dispersed by attaching the arch-corner-plate. 5) Hysteresis energy of specimen after reinforcement on maximum load was Approximately 4 times than specimen before reinforcement on R=0.5% load. And Hysteresis energy of specimen after reinfo