Research On Seismic Performance Of Mechanically Connected Precast Concrete Frame Joints

In the process of industrialization and modernization of the construction industry in china,the precast concrete frame structure has become a hot spot of research in the construction industry because of its characteristics of being suitable for standardized design,matching the development prospects of informatization,and being more green and environmentally friendly.Among the main categories of precast concrete frame joints,precast wet connection joints have been widely used with higher feasibility and safety redundancy.However,the current precast wet connection joints in the process of further industrialization have the problems of high pricisionrequirement,inconvenient construction in the joints area,and difficulty in cost control,which reduces the advantages of precast frame structures in engineering applications.On the basis of meeting specifications and actual needs,it is of great practical significance to improve the connection mode of joints.In order to further improve the construction efficiency and control the construction accuracy,the application scenarios of mechanical connectors in the connection of precast beams and columns were studied.Two set of precast wet connection joints were designed.One of which is the bottom bars of precast beams bent and anchored,and the precast columns are connected by sleeve grouting and mechanically respectively;One of which is the precast beams and columns are all mechanically connected.The seismic performance test research,numerical simulation analysis and restoring force model research have been carried out in this paper.The main work and conclusions are as follows:（1）According to the classification standards of precast wet connection joints and dry connection joints,the precast joints that have been studied are classified,and the common structural forms and working characteristics of the two types of joints are sorted out.Combined with the current research and application status at home and abroad,the research progress of joints with different connection methods are discussed.（2）Cyclic loading tests were carried out on the two kinds of precast wet connection joints and the cast-in-place comparative joint specimen.The test results show that: when the bottom bars of precast beam is bent and anchored,the specimens of mechanically connected precast column exhibit better seismic performance than the specimens of precast columns connected by sleeve grouting.For the joitns of precast beams and columns are all mechanically connected,the connection of additional U-shaped steel bars in the joint area has a better effect on improving the seismic performance of the joint,which can achieve satisfactory seismic performance of the cast-in-place specimen.（3）Based on the finite element software Open SEES,more detailed numerical analysis model was established,which include Beam-Column Joint joint element and Pinching 4uniaxial material constitutive,Reinforcing Steel reinforcement material constitutive and Bond＿SP01 bond slip constitutive models.The comparative analysis between the simulation results and the experimental data shows that the established numerical analysis model can better consider the effect of steel bar sliding under the cyclic load of the joint specimen.The parametric analysis results show that the axial pressure has little effect on the seismic performance of the joint;with the increase of the shear-span ratio,the skeleton curve of the joint changes significantly.（4）By using the method of test data fitting,the skeleton curve model and restoring force model of the precast frame joint with bottom bars of precast beams mechanically connected are established.The calculation results are in good agreement with the test results,and the established restoring force model can accurately reflect the hysteretic characteristics of the precast frame joint with bottom bars of precast beams mechanically connected.