Experimental Study On Seismic Behavior Of Abnormal Reinforced Concrete Frame Interior Joint With Abrupt Beam Section

The beam-column joint is an important part of structure. Now with more and more large cross, large-scale, high-level structures of complex shape, abnormal reinforced concrete frame interior joints with abrupt beam section (later referred to as "abnormal joints") are greatly appeared. However, China's current code for such joints are only from the experience or conceptual sense, which is lack of adequate experimental basis and theoretical analysis. Therefore, to insure the abnormal joints's safety when the earthquake is happened,it is urgent to research on abnormal joints of reinforced concrete,discuss the failure mechanism and influence factors. It is of greatly theoretical and practical value on the study of such abnormal joints.Relied on the seismic tests of three 1/3-scale abnormal interior joints model, this paper discussed seismic performance, destruction and damage characteristics of the process of such joints, also analyzed the joint's seismic behavior under changed the size of beam cross-section. Based on the test results the paper proposed:1.The beam size is the most important factor affecting the capacity and the seismic performance of abnormal joint, the distinctly affecting is the change of small beam size.2.The shear strength of abnormal joint is is provided by an equivalent diagonal compression strut, based on this a new analytical model has been developed to predict the shear force vs. shear distortion response of joints, the model calculation agrees well with the experimental results, the simplified calculation formula has been gived for calculate shear strength.3.Select strong and weak joints under the test, based on the mechanism of equivalent diagonal compression strut analyzed the elevation difference of beam that impacted the shear strength of thisjoints. The results showed:the elevation difference of beam is a decisive factor for the shear strength of joints;get the shear strength curve of strong and weak joints under a ratio between the beam elevation difference and the column height; the paper suggested to calculate shear strength by edge joint5tion difference of beam large the column height. 4.Based on parameter analysis, the abnormal joints can be proposed divided into two types by the ratio between the beam elevation difference and the column height.