Experimental Investigation On Seismic Behavior Of Abnormal Joints With Changed Beam Section In Reinforced Concrete Frame Structures

With the development of socio-economic the needs of architectural features and special craftof industrial plant structure, abnormal joints (with changed beam section) widely appeared in all kinds of building structure. An abnormal beam-column joint can be defined as a joint with beams of different depths. In this type of connection, the top beam bars are arranged with passing through the joint and the bottom beam bars are ancored with a 90 degree hook in the joint. So its characteristics of the force is obviously different from normal joint. The treatment of such joint given by our country's current concrete code just from normal joint's experimental data or sense of the concept and lack of adequate experimental basis and in-depth theoretical analysis. So working on this kind of abnormal joint has theoretical values and practical useful values.This dissertation focuses on the situation on above, test 4 reinforced concrete frame joint(variable beam section joint) about there seismic performance. Through the analyses of the anti-shear properties in the joint core, working on the factors of beam section changing, the axial compressive ratio, reinforcement in the joint core and so on, the dissertation has discussed the working mechanism and the failure modes of the abnormal interior joints: Controlled by the small core area, the anti-shear capacity of abnormal joints is rest with concrete strength, size and reinforcement of the small core area. Due to the diffusion of stress; the big core area works on the small core area with restraining effect, and the restraining effect is reflected on the area ratio of the big core and the small core, namely the restraining coefficient. Joint through the beam reinforcement premature degradation in bonded combination of the earthquake would adversely affect performance. It will increase the portfolio of hysteresis curve of the pinch shrink, reducing the energy capacity of specimens, to reverse the initial stiffness loading components decreased significantly. Discussed the joint's ant-shear capacity checking formula at the situation that when the height of the small beam is bigger or smaller than the big beam. Stirrup in core area yield unevenThrough the analysis of working mechanism and failure modes of interior abnormal joints; referencing to the general joint design method, taking the complete crack as the design rule, the dissertation has put forward with advises and useful design formulas for the aseismic design of this kind of joints, in the hope of supplying reference for aseismic design in engineering.