Modeling of Three-Dimensional Failure Mechanism in Reinforced Concrete Beam-Column Joints Subjected to Tri-Directional Earthquake Motions

点击翻译按钮获取中文摘要

Complicated stress flows develop in reinforced concrete beam-column joints in moment resisting space frames subjected to bi-lateral and varying axial loads. There is no common finding yet on failure mechanism of R/C beam-column joints, whereas some ideas are proposed such as the shear failure caused by crush in joint panel concrete or the flexural failure caused by diagonal crack opening in a joint panel. Therefore, shear resisting mechanism in three-dimensional beam-column joints was studied through static loading tests in which bi-lateral load reversals were afforded, focusing on the bond performance along longitudinal beam and column bars passing through a beam-column joint and the shape of a beam-column subassemblies. Three half-scale R/C three-dimensional beam-column joint specimens were tested ; two interior joints with four beams and one exterior joint with three beams. In one interior joint specimen bond along beam bars was improved by welding three ring plates with steel thick … More ness of 7 mm in a joint panel, and in another interior joint specimen bond along beam and column bars was eliminated within a joint panel. Bi-lateral loading was so controlled that the path of story displacement at the top of a column traced the line with 45-degree inclination to longitudinal direction of a specimen. All specimens failed in joint shear. Severe crush of concrete was observed at four corners of a beam-column joint region. Conclusions drawn by the study are indicated below.(a)Shear strength of the interior joint specimen with improved bond along beam bars in a joint panel was enhanced by 25 percent greater than that without bond along beam and column bars in a joint panel.(b)Shear capacity decayed remarkably after attaining shear strength in exterior joint specimen with three beams due to the progress of concrete compressive damage within beam-column joint region into which beams do not frame.(c)It was pointed out from test data, e.g., strain of joint lateral hoops and column longitudinal bars, that three-dimensional force-carrying mechanism in a beam-column joint panel was influenced by the difference of stress fields around a joint panel. Less