Shizuo Hayashi

EARTHQUAKE-RESISTANT PROPERTY OF PREFABRICATED HIGH-STRENGTH CONCRETE PILE

This paper presents results from experimental studies of a prefabricated high-strength concrete (PHC) pile that suffered brittle failure at the pile head during the 1995 Hyougoken-Nanbu earthquake. The specimens, which were representative of typical pile heads, were tested under reverse cyclic loading and a constant axial load. Conclusions are provided, including the findings that: 1) when properly reinforced with longitudinal deformed bars and lateral reinforcement, PHC pile can exhibit stable hysteretic behavior and significant ductility, and 2) the deformation capacity can be evaluated using the section analysis, in which the concrete confinement provided by the lateral reinforcement is incorporated.

LATERAL STRENGTH EVALUATION OF SEISMIC STRENGTHENED FRAMES BY STEEL BRACES WITHOUT DOWEL ANCHORS

We have developed the anchorless retrofitting method of our previous research, and clarified the shear transmission mechanism in retrofitted frames. The strength of retrofitted frame without anchors is composed of the column punching shear strength, shear friction between the existing reinforced concrete girders and steel frame, and the column shear strength. In this paper, we considered the shear friction between the existing reinforced concrete girders and steel frame, and evaluated the shear friction as a coefficient multiplying the punching shear strength of the column. We performed FE analyses using concrete strength and span as parameters, and found that the ratio of the shear friction to story shear shared by steel brace is 0.35.. The method of evaluating the lateral strength of retrofitted frame without anchor was proposed, the average ratio of calculated values to experimental values was to be 1.33. We confirmed the safety of the proposed evaluation method.