Finite Element Analysis Of Seismic Performance Of High-Strength Concrete Composite Core Columns Confined By Multiple Hoops

In the commercial development of the subway cover in high intensity areas,the large column grid frame structure is generally used.In the design,it is essential to ensure that the frame column still has sufficient seismic reserve under strong earthquakes for the safety performance of the large column grid frame structure.High-strength concrete is generally used to improve the vertical bearing capacity of frame columns,but with the increase of concrete strength grade,its brittleness increases significantly,which is not conducive to structural seismic resistance.In this paper,high strength concrete is used to improve the compressive strength of the column.At the same time,multi-layer longitudinal bars and stirrups are added in the core area to form multiple composite core columns,so that the column has multiple seismic defense lines to ensure that the specimen still has sufficient longitudinal bearing capacity after the failure of the outer longitudinal bars and concrete.The main research work of this paper is as follows :(1)Taking EC-DC-100 multi-composite core column specimen of high strength concrete as an example,the parameters required for the steel model and the concrete model for modeling were calculated,and the modeling process was introduced.The influence of different factors on the simulation results was discussed.(2)On the basis of experiments,ABAQUS was used to simulate the mechanical properties of multi-composite core columns,and the “element deletion method” was used to analyze the crack morphology and failure mode of the specimens.The simulated failure process is in good agreement with the test.The quantitative indicators are further verified to verify the reliability of the selected model.The results show that the current model can effectively simulate the mechanical properties of high strength concrete multi-core columns under low cyclic loading.(3)On the basis of the above,the expansion simulation was carried out to study the influence of different factors on the seismic performance of the new column.The results show that :(1)When the stirrup spacing is 100 mm and 150 mm,the stirrup spacing has little effect on the seismic performance of the specimen,but with the increase of the stirrup spacing to 300 mm,the cumulative energy consumption of the specimen is51%?75% lower than that of EC-DC-100.(2)With the increase of axial compression ratio,the bearing capacity of the specimen increased by 9.6%–39.5%,but after the peak load,the concrete ring of the specimen broke seriously and the brittleness was obvious.The cumulative energy consumption of the specimen with high axial compression was 18.9%–62.5% lower than that of EC-DC-100.(3)Increasing the reinforcement ratio in the core area can effectively improve the bearing capacity and ductility of the component,and improve the energy dissipation performance of the specimen.The cumulative energy dissipation of the specimen EC-DC-24+10-100 is 23.7%?47.3% higher than that of the other specimens with low reinforcement ratio.(4)Different from traditional concrete columns,the change of stirrup form in the core area has a great influence on the seismic performance of multiple composite core columns.Among them,the stirrup form of outer circle and inner circle has a significant effect on improving the seismic performance of the core column specimen,while the stirrup form of outer circle and inner circle and inner spiral is unfavorable to the seismic performance of the specimen.(5)When the area of inner core and interlayer confined concrete is within a certain range,the seismic performance of multiple composite core columns decreases by 9.8%–13.4% with the further increase of the area of inner core and interlayer confined concrete.