Earthquake Damage Model Of High Strength Steel Tube Ultra High Performance Concrete Column

Concrete-Filled Steel Tube(CFST),which combines the advantages of concrete and steel tube,has greatly improved its bearing capacity,stiffness,ductility,and seismic performance,and is widely used in high-rise and large-span buildings.With the improvement of engineering construction requirements and the continuous application of high-strength materials,some scholars proposed to combine ultra-high performance concrete(UHPC)and high-strength steel tube to form ultra-high performance concrete filled high strength steel tube(UHPCFHST).However,the existing research mainly focuses on the axial compression of high-strength steel tube ultra-high performance concrete columns.The research on the seismic performance of the composite structure is insufficient,and the research on the seismic damage determination of the structure is less.Buildings constructed with high-strength materials should pay more attention to the safety performance of the structure.Therefore,the research on the seismic damage determination of high-strength steel tube ultra-high-performance concrete columns is of great significance.In conclusion,to make the research on the seismic performance of high-strength steel tube ultra-high performance concrete columns more comprehensive,15 UHPCFHST specimens are designed for low-cyclic reciprocating(loading)tests and numerical simulation.The main research works is as follows:(1)The low-cyclic reciprocating tests of 9 square and 6 circular sections of high-strength steel tube ultra-high performance concrete columns were completed to study the influence of section form,axial compression ratio,and shear span ratio on the seismic performance of the specimens.The research results show that the hysteretic curve of high-strength steel tube ultra-high performance concrete columns under low-cyclic reciprocating load mainly shows three stages: elastic stage,elastic-plastic stage,and the falling stage after the ultimate bearing capacity.When the axial compression ratio is increased properly,the horizontal bearing capacity of the specimen will be improved,but the bearing capacity of some specimens will not change obviously or even decrease if the axial compression ratio is increased continuously,but the specific threshold of axial compression ratio change needs further study;Reducing the shear span ratio can effectively improve the horizontal bearing capacity of the specimen,but it will make the bearing capacity of the specimen decrease faster after the peak load;The horizontal bearing capacity of the square section specimen drops faster than the circular section specimens’.(2)Referring to relevant specifications,based on experimental research and structural nonlinear theory,combined with finite element software ABAQUS,considering the constraint effect of steel tube,the finite element modeling method of high-strength steel tube ultra-high performance concrete column is determined,and the low-cycle reciprocating load numerical simulation analysis of high-strength steel tube ultra-high performance concrete column is carried out,and the test and numerical simulation results are compared from the aspects of failure mode,hysteretic curve,and peak load,The reliability of the modeling method and the selected material constitutive relation is verified.On this basis,a lot of numerical analysis has been carried out to provide sufficient data support for the establishment of the damage model.(3)Based on the research conducted by the project team,this article proposes a seismic damage model for high-strength steel tube ultra-high performance concrete using experimental and numerical simulation results.The model uses the obtained combination coefficient and loading path factor to calculate the damage index D of the specimen at the time of failure,and D’s mean,variance,and coefficient of variation are calculated to be 0.9751,0.0012,and 0.0361,respectively.In addition,by calculating the damage factors of some specimens based on the experimental specimens,a damage curve is obtained,and it is shown that this damage model can better reflect the damage situation of the structure at various stages in combination with the experimental situation.