Shear Behavior of Reinforced Concrete Beam-Column Joints Subjected to Bi-Lateral and Varying, Axial Loads

点击翻译按钮获取中文摘要

Two three-dimensional interior beam-column joint subassemblage specimens removed from a reinforced concrete space frame were tested to investigate failure mechanism in a joint panel under bi-lateral and axial loading. The anchorage ability of beam bars within a joint was chosen as a test parameter. Steel plates were placed at the beam critical sections in one specimen to carry directly the anchorage reaction force from beam longitudinal bars to the joint panel concrete. Slabs were not placed in both specimens for simplified path of load transfer. Concrete compressive strength was 23 MPa. Result of the plane beam-column joint specimen tested last year was compared with that of three-dimensional specimens to research on the effect of transverse beams to joint behavior. All specimens failed in joint shear. Following conclusions are drawn from the test.(1) Horizontal load carrying capacity for three-dimensional specimen with beam bar anchorage plates at beam critical sections and cracked t … More ransverse beams was enhanced to 1.1 times that without anchorage plates and 1.3 times that for plane specimen without transverse beams.(2) Joint shear capacity was enhanced by confining action due to anchorage plates against the out-plane expansion of joint core concrete. On the other hand, anchorage plates at beam critical sections caused bond deterioration along beam bars within a joint because development length of beam bars was limitted equally to a column depth by the plate.(3) Transverse beams framing into a joint contributed to enhance joint shear strength by the restriction to both expansion and damage of joint core concrete. Confining force by transverse beams to joint concrete was one fourth approximately of tensile force of longitudinal beam bars in loading direction.(4) The shape of bi-directional interaction in joint shear capacity was regarded as not circle but square under bi-lateral loading in three-dimensional subassemblage specimens. This means that safety to earthquake excitations can be maintained for reinforced concrete beam-column joint in actual frames by designing joints to shear forces in each direction independently. Less