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

在双向变轴力作用下，钢筋混凝土抗弯空间框架梁柱节点存在复杂的应力流动。目前，关于梁柱节点的破坏机理还没有统一的认识，提出了节点板混凝土受剪破坏或节点板斜裂缝张开引起的弯曲破坏等观点。为此，通过双向加载的静力试验，重点研究了梁柱节点纵向钢筋的粘结性能以及梁柱节点的截面形状，研究了三维梁柱节点的抗剪机理。进行了三个半比例R/C三维梁柱节点试件的试验研究，两个内节点为四根梁，一个外节点为三根梁。在一个内节点试件中，通过焊接三个钢厚环板来改善梁筋沿梁筋的沿着粘结 ...更多信息 在一个接缝板中，7 mm的厚度，以及在另一个内部接缝试样中，在接缝板内消除了沿梁和柱钢筋的沿着粘结。双向加载的控制使柱顶部的层位移路径与试件的纵向倾斜45度。所有样本均在联合剪切中失败。严重的混凝土压碎观察到在四个角落的梁柱节点区域。研究得出的结论如下。（a）沿节点板中的梁筋沿着粘结改善的内部节点试样的抗剪强度比沿节点板中的梁筋和柱筋沿着粘结的内部节点试样的抗剪强度提高25%。（B）三梁节点试件在达到抗剪强度后，受剪承载力显著衰减，这是由于梁柱节点区混凝土受压损伤的发展造成的。(c)It从测试数据中指出，例如，梁柱节点板三维受力机理受节点板周围应力场差异的影响。少

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