塑性ヒンジ発生位置を制御した鉄筋コンクリート梁の構造性能

<p>　Recently, various studies have been conducted to prevent joint hinging failure of reinforced concrete beam-column joints. In particular, there are many experimental studies related to hinge relocation method. However, most of these are tested by interior and exterior beam-column joint subassemblages specimens, few experimental studies with only beam members have been carried out. </p><p>　In this study, flexure and shear tests were conducted to clarify the structural performance of reinforced concrete beam with plastic hinge relocation method, to further improve the seismic performance and to ensure quality and productivity in the construction of high-rise RC buildings. Specimens were ten 1/2-scale reinforced concrete beams with relocating plastic hinge region at the both ends of beam. The main test parameters were shape of cross section (T-shape half precast, rectangular), method of relocating plastic hinge away from the stub face (connecting main reinforcement at the beam ends having different diameters or different strength using mechanical splices, cut-off of main reinforcement using anchorages), distance from the stub face of relocated critical section, shear span ratio, and amount of transverse reinforcement. </p><p>　As a result of the tests, it was found that crack patterns, failure modes, load-deformation relationship and plastic deformation capacity were affected according to the parameter. This paper studies the strain and stress distribution of longitudinal bar, deformation component of the member, evaluation method of restoring force characteristics and failure mode for use in practical design. The analysis and discussion of test results lead to the following conclusion: </p><p>(1)　The characteristic and position of relocated plastic hinge of beam can be controlled as designed by the two methods considered in this study.</p><p>(2)　The restoring force characteristics can be evaluated taking into consideration the effect of the relocation of critical section by using evaluation formulas currently in use.</p><p>(3)　The failure mode can be estimated by comparing the shear margin and the bond stress margin. Provided that both of these are greater than 1.0 brittle failure can be prevented after flexural yielding.</p>