Behavior of Reinforced Concrete Beam-Column Joints With Eccentricity

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Title: Behavior of Reinforced Concrete Beam-Column Joints With Eccentricity

Author(s): O. Joh, Y. Goto and T. Shibata

Publication: Special Publication

Volume: 123

Issue:

Appears on pages(s): 317-358

Keywords: beams (supports); columns (supports); ductility; eccentricity; failure; joints (junctions); reinforced concretes; shear properties; torsion; Structural Research

Date: 1/1/1991

Abstract:
Geometrical configurations of reinforced concrete beam-column joints in actual building structures are quite varied because the configurations depend upon the number of structural members connecting the joints, the shapes of cross section of the members, the eccentricity among the axes of members, and so on. Focusing the interest mainly on the eccentricity from these factors, studies on seismic behavior of reinforced concrete interior beam-column joints in one-way frames with eccentricity are carried out with a classificatory examination, an investigation of a building destroyed by a strong earthquake, and a survey of previous studies and the authors' experiments. 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. From the survey of three previous experiments in which one-sided eccentric joint specimens with wide columns and deep beams were subjected to lateral loading, it is shown that effective width and/or torsional moment should be considered for calculating the strength and stiffness of frames. Experimental results indicate that such eccentricities caused twisting of the columns and joints, resulting in reduction of the shear strength of the members. From the results of the classification examination and of the authors' tests in which five beam-column subassemblages with several types of eccentricity and beam width were subjected to cyclic lateral forces, it is observed that joints with one-sided eccentric beams suffer larger torsional moment around column axes, narrowing the effective joint width. Therefore, the shear cracking stress and the deformability of joints are reduced.