Shaking Table Test And Finite Element Analysis Of GFRP Reinforced Concrete Frame Structure

One of the main diseases of reinforced concrete structures,when steel bars are corroded,using FRP(Fiber Reinforced Polymer)bars instead of steel bars for concrete structures,is part of the effective methods to solve the problem of steel corrosion.At present,most of the researches on FRP reinforced concrete structure at home and abroad focus on the mechanical performance of beam and column members,and there are few types of research on the overall seismic performance of FRP reinforced concrete structure.In addition,most of the seismic performance studies have adopted quasi-static test methods,and there are few studies using dynamic test methods.It is necessary in order to analyze the seismic behavior of FRP reinforced concrete structure model by seismic wave excitation with a vibration table.Based on the study of the mechanical properties of GFRP(Glass Fiber Reinforced Polymer)bars,a three-layer,two-span 1/4 scale frame model was designed and produced with GFRP bars at the main base of the beam and column.Four seismic waves were selected,and the model was subject to one-way,two-way and three-way seismic wave excitation under 27 working conditions with four different acceleration peaks.The acceleration response of each floor of the model under different working conditions was obtained and further processed by data processing.The displacement response of each floor of the model and the displacement angle between the layers is obtained.The seismic behavior of GFRP reinforced concrete frame structures are studied in combination with experimental phenomena.Then the finite element model of GFRP reinforced concrete frame structure is established to simulate the other working conditions which are not completed due to the limited conditions of the test.The main research results are summarized as follows:(1)Analysis from the experimental phenomenon: in the process of frame model from frequent earthquakes to rare earthquakes,the number and width of cracks keep increasing,which indicates that the damage of model structure gradually accumulates under the action of the earthquake,and the stiffness keeps decreasing.However,the model remains intact after the eighth-degree rare earthquake,and there is no GFRP bar fracture phenomenon,which indicates that the model can meet the seismic fortification concept of ‘no collapsing with robust earthquake'.(2)Analysis from the response acceleration of model structure: under the action of the same peak acceleration,the acceleration response of model structure caused by different seismic waves is different,indicating that the acceleration response of structure is not only dependent on the size of the peak acceleration of mesa input but also related to the spectral characteristics of seismic waves.In addition,the model's acceleration amplification coefficient in the last two processes is less than that in the first two processes,because the model's structural stiffness degrades,and the earthquake effect is difficult to be uploaded.(3)Analysis from the response of model displacement: in the first three processes,the displacement amplitude of each floor of the model increased slightly,while in the case of eighth-degree rare earthquake,the displacement amplitude of each floor of the model increased greatly due to the severe degradation of structural stiffness.In addition,the displacement responses of the floors caused by single,double and triple waves in the first two processes are little different,while the displacements of the floors caused by the triple waves in the latter two processes are significantly larger than those of the single and double waves.The displacement indicates that the multi-directional seismic damage is much higher than the one-way seismic action when subjected to large earthquakes.(4)Analysis from the inter-story displacement angle: since the first layer is relatively high and the shear force is the largest.The maximum displacement angle between the model layers is mainly concentrated in the first layer.In addition,it is concluded that the inter-story displacement angle of GFRP reinforced concrete frame structure will be greater than the inter-story displacement angle of reinforced concrete frame structure under the action of the same seismic wave by combining the testing phenomenon,the mechanical properties of GFRP bars and the limit value of inter-story displacement angle of reinforced concrete structure.In seismic design,the inter-storey displacement angle limit of GFRP reinforced concrete frame structure should be greater than that of reinforced concrete frame structure.(5)Analysis from the finite element: the finite element analysis of 30 working conditions was completed on the basis of the experiment.The similarity between the finite element simulation results and the experimental results reached about 80%,it can be possible to conclude that it is feasible to use finite element analysis to simulate the shaking table test.In addition,the finite element simulation was used to complete the seismic action under the three working conditions which were not completed in the test,and the seismic performance of GFRP reinforced concrete frame structures are studied through data analysis.