The Research On The Seismic Behavior Of The Interior Top-of-Column Joints Of R.C Frames Strengthened By Carbon Fiber

Reinforced concrete beam-column Joints are important elements in the frame structures. It connects the beam and column, transverses and distributes the inertial forces, also it makes the structure's deformation compactable in components. The earthquakes happened in the world have proved that the structure will be severe destroyed when the joints damaged. Earthquakes are often happens in our country, so as to reduce the losses of earthquakes, it needs to repair and retrofit the current buildings, especially retrofitting the frame joints. So to do some research about the frame joints' retrofitting is necessary.Because the joints locate in the crossing of the beams and columns, the details and forces acting on the joints are very complicated, so it is hard to repair and retrofit these inadequate performance joints. From the previous research level in domestic and abroad, about this new retrofitting technique's research mainly focus on the simple elements' repaired, such as the beams' and columns' moments and shear resistance strengthening. About the beam-column joints retrofitting there is little study, especially on the joints having slabs and lateral beams. So such technique is a significant one which deserves further investigation.In this paper, the numerical simulation of six interior beam-column joins, which is under a platitude load to verify two seismic retrofit methods for interior, will be described. By the comparison of numerical results between the control and strengthened specimens in aspect of damage mode, ultimate load, stiffness, ductility and other fields, this paper analyzes the main seismic performances of strengthened joints and finds the best seismic retrofit method by CFRP sheet, analyzes the performance of the strengthened mechanism of the frame structure joints by CFRP. Based on the calculated formula of joints' shear resistance capacity in current national regulation, bring forward a coefficientη_f to regard the core concrete's strength hardening and the area increase of inclined strut. A simplified formula to calculate η_f is put forward.