13th World Conference on Earthquake Engineering Vancouver, B.C., Canada August 1-6, 2004 Paper No. 4
MECHANICAL BEHAVIOR OF REINFORCED CONCRETE BEAM-COLUMN ASSEMBLAGES WITH ECCENTRICITY Tomohiko KAMIMURA1, Hiroyasu TAKIMOTO2, and Shinya TANAKA3
SUMMARY Experimental work was carried out to study the mechanical behavior of interior beam-column subassemblage with the eccentricity between beam axes and column axes. Test specimens are four wall girder-wide column joints with large beam depth and two beam-column joints which beam depth is the same as column depth. The variables of the test series in girder-column joints are eccentricity, column longitudinal reinforcement ratio, and joint lateral reinforcement ratio. The variable of the test series in beam-column joints is eccentricity only. The mechanical behavior of beam-column subassemlages with one-sided eccentricity is discussed from the experimental results, and the ultimate strength of each test specimen is estimated using the proposed equation. The failure mode of girder-column subassemblages with eccentricity, which were designed so that shear failure in joint after wall girder and wide-column flexural yielding should form in no consideration of eccentricity, was column torsional failure. The ultimate strength of wide column under combined torsion and shear increases with the amount of column longitudinal reinforcement and joint lateral reinforcement. Proposed equation for predicting the ultimate strength of columns under combined torsion and shear approximately gives an agreement with the test data of girder-column subassemblage. The beam-column subassemblage with eccentricity was the same failure mode as that without eccentricity and failed in joint after beam flexural yielding because of the small eccentricity. Therefore, the ultimate strength of joint can be calculated by considering the effective width and using proposed equation for the ultimate strength of joints under combined torsion and shear. INTRODUCTION The reinforced concrete school building of four stories with the eccentricity between narrow wall girder axes and wide column axes at Hakodate College in Japan was heavily destroyed by the 1968 Tokachioki Earthquake. From the investigation of the destroyed building, it is suggested that the heavy eccentricity between columns and beams caused torsional moments in the columns and joints, causing severe damage.
1
Professor, Shibaura Institute of Technology, Tokyo, Japan E-mail:
[email protected] Graduate school, Shibaura institute of Technology, Tokyo, Japan E-mail:
[email protected] 3 Graduate school, Shibaura institute of Technology, Tokyo, Japan E-mail:
[email protected] 2
Therefore, the investigation is needed for the influence of the eccentricity among the axes of members on the mechanical behavior of beam-column subassemblages subjected to lateral loading. The objects of this study are to give consideration to the mechanical behavior of interior beam-column subassemblage with one-sided eccentricity, and also to estimate the ultimate strength of columns and joints in such a subassemblage subjected to torsional moment. OUTLINE OF EXPERIMENTAL WORK Fig.1 shows an eccentric beam-column joint in typical structures. In this paper, the seismic behavior of eccentric wall girder-wide column joints and beam-column joints, which beam depth is the same as column depth, without floor slabs and transverse beams is discussed. The inflection poi