Research On Seismic Behavior Of Precast Confined High Strength Concrete Columns With Different Stirrup Ratio

As an important member,columns play an important role in the structure.The ductility of concrete columns can be improved by placing high-strength concrete under constraint.With the development of building industrialization,prefabricated structure has been popularized.So far,there are few studies on the seismic behavior of the precast confined high-strength concrete columns.The stirrup ratio is the main factor that affects the seismic performance of confined concrete columns.Based on this,this paper studies the seismic performance of precast confined high-strength concrete columns with different stirrup ratio.The main achievements are as follows:(1)Five specimens of precast confined high strength concrete columns and one specimen of cast-in-place high strength concrete columns were designed and manufactured,the low cycle cyclic loading tests were carried out on them.The differences of seismic performance between cast-in-place and precast confined high strength concrete columns under the same conditions were compared.The effects of stirrup ratio on hysteretic curve,skeleton curve,stiffness degradation,strength attenuation,ductility and the influence of performance and energy consumption of precast confined high strength concrete columns were studied.The results show that:(1)the failure mode of the specimens is bending failure.(2)When the precast confined high-strength concrete column is damaged,the sealing layer is broken,there is a small amount of relative slip between the reinforcement and the grouting material,the ultimate displacement angle is between 4.9 and 5,the displacement ductility coefficient is between 4.92 and 5.15,and the ductility is good.(3)Under the same conditions,the horizontal bearing capacity of cast-in-place and assembled columns is not much different.The hysteretic curve of cast-in-place columns is relatively full.The peak value of horizontal bearing capacity of assembled columns declines slowly,the strength declines slowly,and the rigidity degenerates more smoothly.(4)After meeting the concrete design specifications and the stirrup volume ratio reaches a certain value,increasing the stirrup volume ratio does not significantly increase the bearing capacity,but improves the ductility.(2)The finite element model is established,and ABAQUS software is used to simulate the test specimen,and the correctness of the finite element model is verified by comparing with the test results.Then,using the established finite element model,the finite element extended parameter analysis of 16 precast confined high-strength concrete columns is carried out to further analyze the influence of stirrup ratio on the seismic performance of precast confined high-strength concrete columns.The results show that when the stirrup volume ratio is small,increasing the stirrup volume ratio can significantly increase the horizontal bearing capacity and reduce the rate of stiffness degradation;after that,increasing the stirrup volume ratio will not significantly improve the horizontal bearing capacity,but improve the ductility.(3)Based on the experimental results and simulation results,according to the existing calculation methods,the restoring force model of precast confined high-strength concrete columns considering the influence of stirrup ratio is proposed.The skeleton curve of the restoring force model is determined by the statistical regression analysis of the test data.