Research On Performance Of Prestressed Precast Concrete Frame With Ductility Joints

Prefabricated assembly technology is an effective way to achieve building industrialization requirements.Assembled concrete frame structure is a popular structural form that meets China’s national conditions and has broad application prospects.The research of fabricated concrete frame joints is a key issue to promote the development and application of such structures..The overall performance of the traditional wet connection is generally equivalent to the cast-in-place structure,but its low degree of assembly is not suitable for the development needs of the industrialization of the building,and the traditional dry connection has poor integrity.In order to improve the seismic performance of prefabricated structures and adapt to the development trend of industrialization of buildings,this paper proposes a form of prestressed fabricated concrete frame ductile joints based on the summarization of domestic and foreign scholars’ research achievements.In the nodal area,through the pre-buried PVC pipe in the column,the steel with better ductility at the yield point is inserted into the energy dissipation rod.The prefabricated beam is connected to the energy dissipation rod through the reduced-diameter threaded sleeve to form a ductile connection system.The lower energy-consuming member first yields plastic deformation,thereby avoiding damage to other components.The prestressed tendon is used as a node assembling method and provides a self-resetting capability.Combining the prestressed nodes with the energy-consuming components to form a new type of hybrid connection node will have broad development prospects in China and have considerable research value.The main research content of this paper is as follows:(1)In-depth understanding of the research and development status of prefabricated prefabricated concrete structures,as well as the classification and summarization of prefabricated prefabricated joints.Aiming at the existing problems,a prestressed assembled concrete frame ductile node is proposed.(2)The basic situation of the seismic performance test of the prestressed assembled concrete frame ductility joints is introduced in detail,including the structure of the joints,the working mechanism,the design scheme,the construction process,and the test loading and measurement scheme.(3)A full-scale experimental study was conducted on two preloaded concrete frame ductile mid-nodes and a cast-in-place comparative mid-node.The MTS hydraulic servo loading test system was used to push and pull the two actuators to apply reverse symmetric low-cycle reciprocating vertical loads to the nodes.With reference to the common cast-in-situ concrete joints,the seismic performance of fabricated joints is evaluated synthetically by comparing the stiffness,energy dissipation capacity,ductility,and deformation recovery capability of the prestressed assembled concrete frame ductile joints.(4)Using OpenSees finite element analysis software to model the prestressed fabricated concrete frame ductility nodes.The mechanical properties and hysteresis characteristics of the test pieces were studied and compared with the test results.Finally,the main parameters affecting the performance of the node are: concrete strength grade,beam reinforcement ratio,energy dissipation rod diameter,and axial compression ratio.The above research shows that the prestressed assembled concrete frame ductility node basically achieves the same cast-in-place and is even stronger than cast-in-place design expectations.Compared with cast-in-place joints,the prefabricated joints have higher initial stiffness and higher ultimate bearing capacity.Under large displacement loading conditions,the prefabricated beam and post do not show obvious damage and have excellent self-return capability,which helps to reduce the post-earthquake repairments.The energy dissipating rods arranged in the column are superior to those arranged on the beam end,and the bearing capacity,energy dissipation capacity,and ductility are all improved.The nonlinear finite element software OpenSees can simulate the mechanical behavior of beam-column joints under low cyclic loading.