Test On Seismic Performance Of Step-terrace Frame Structures With Sliding Support Connection In The Upper Ground

Step-terrace frame strucures constructed in mountain areas exist natural vertical and torsional irregularity,causing the loading and deformation features as well as failure patterns different from ordinary moment frames supported on flat ground.The way how to improve irregularity and failure patterns is the key problem need to be solved for the seismic behavior of step-terrace frame structures.The way how to avoid the upper embedding lateral force resisting members always failure prior to other members is the direction what design theories of step-terrace frame structures pursue.In this study,bi-directional sliding support connection is introduced into the stepterrace frame structures,the reduced scale of the model is 1/8,and the seismic performance is analyzed in the study.The seismic performance of step-terrace frame structures with different grounding modes and different lateral stiffness ratios is studied by means of the elastic response spectrum analysis and dynamic elastoplastic time history analysis with the PERFORM-3D software.In this study,the main work and conclusions were summarized as follow:(1)The designing of the shaking table test of step-terrace frame structures with sliding support connection.Based on the equipment conditions and test purposes of the shaking table,the design parameters of the prototype structure of the shaking table test are determined,and the reduced scale model of the five-layer and three-span frame with sliding support connection,whose similarity relation is 1/8,is established.The study determines the material of the test model.The material test,model structure design and model construction are carried out,and the loading scheme and measurement points arrangement of the test are finally determined.(2)The analysis of the shaking table test of seismic performance of step-terrace structures.The main test phenomena of the elasticity,elastoplasticity and failure stages of the model under the action of earthquakes are measured and analyzed.And the structural failure characteristics,dynamic characteristics and evolution rules,acceleration response,maximum relative displacement response of each layer,inter-layer displacement angle and maximum torsional angle along slope are also analyzed.The test results show that step-terrace frame structures with sliding support connection have no significant improvement in terms of structural failure,dynamic characteristics and evolution,deformation and stress characteristics.(3)The validity and reliability of the PERFORM-3D reasonable modeling results are verified by comparing the test values and simulated values of the seismic response indexes of the test prototype structure.The elastic response spectrum analysis and dynamic elastic-plastic time history analysis method are used to supplement the threedimensional angle structural performance analysis of the two frame models with or without sliding supports.The stiffness ratio of the story is controlled to be constant and the lateral stiffness ratio is controlled to change in equal amplitude,then the elastic-plastic behavior of the frame structure with lateral sliding support connection and fixed ground is analyzed.Through the analysis of indexes of the structure,such as the displacement angle between layers,the layer shear force and the column reinforcement strain,it is found that the seismic performance of step-terrace frame structure with sliding support connection is not as good as that of the ordinary frame structure with sliding support connection,so the sliding support connection must not be used lightly.This conclusion is obviously different from the current national regulations that the upper grounding vertical member can use the sliding support connection to form the upper grounding sliding release type when there are few upper grounding parts.When the lateral stiffness ratio is about 1.856,the provision of a lateral sliding support connection at the upper grounding position can relatively reduce part of the interlayer displacement angle and layer shearing force of the step-terrace frame structure,share the force of the upper grounding column,and improve structural component damage.