Study On Multi-level Mechanical Properties And Stable Bearing Capacity For Concrete-filled Steel Tubular Arch Bridge

As an important transportation infrastructure,concrete-filled steel tubular(CFST)arch bridge will cause huge loss of property and negative social impact in the event of instability and damage.Therefore,it is essential to ensure the stability and safety of CFST arch bridge structures.In this paper,the Heshan Hongshuihe CFST arch bridge is used as the engineering background,and the material constitutive relationship of the CFST arch bridge and the stable bearing capacity of the members and structures are studied systematically from the"material level","component level"and"structural level".The research results have certain reference significance for the design of the similar CFST arch bridge structure and the optimization of the later structure.The main research contents and research results are as follows:(1)Considering the influence of axial compression deformation and lateral deflection for the distance change on both ends of the CFST components,at the same time,the"secant algorithm"is introduced to adaptively adjust the iterative parameters,and an improved fiber model method is proposed.The load-deformation curves are calculated by combining the test database of axial compression and eccentric compression,comparing with the traditional fiber model method,and the rationality,superiority and applicability of the improved fiber model method established in this paper are verified.(2)The material constitutive relationship correction model and bearing capacity failure criterion of circular CFST members are established.Firstly,considering that the steel tube in the CFST has different mechanical properties under different stress states,the constitutive model of the steel tube is modified.Then,according to the large-scale experimental data,the expressions of core concrete peak stress,residual stress section coefficient and hoop effect reduction factor are established by regression analysis,based on this,a modified constitutive model of the core concrete is established.Further,according to the limit state of the bearing capacity,and considering the different mechanical properties of different types of steel,the adaptive bearing failure criterion of the CFST members is established.On this basis,according to the improved fiber model method of this paper,the ultimate bearing capacity and load-displacement curve for axial compression,eccentric compression and pure bending members of the circular CFST are calculated.Finally,the accuracy and applicability of the material constitutive relationship and bearing capacity failure criterion of circular CFST members are verified by comparing with the large-scale test data,material constitutive relationship and bearing capacity failure criterion of the circular CFST members.(3)A higher precision calculation model for the flexural capacity of the circular CFST members is established.Firstly,the influencing factors of plasticity development coefficient of CFST members are analyzed,and using the traditional fiber model method,the plasticity development coefficient model of the circular CFST members is proposed by the mean of regression analysis,Based on this,the calculation model for the flexural capacity of the circular CFST members is established.Then,combing with the pure bending test database,the model in this paper can achieve the highest calculation accuracy by comparing with the calculation models collected in specifications.Furthermore,introducing the influence of the stability,based on the improved fiber model method,the homogeneous generalized yield function(HGYF)of the circular CFST members is established by regression analysis.Finally,the bearing capacity of the member is calculated by HGYF,and the calculated results agree well with the experimental results.The accuracy and rationality of the HGYF established in this paper are verified.(4)The linear elastic iterative method-elastic modulus reduction method(EMRM)is used to analyze the stability bearing capacity of CFST arch bridges.Firstly,the linear elastic iterative method-EMRM for the analysis of the stability bearing capacity of CFST arch bridges is established by using the HGYF established in this paper.By comparing with the model test arches shows that the EMRM has higher computational accuracy,computational stability and computational efficiency.Then,the application analysis of the actual engineering structure is carried out with the Heshan Hongshuihe CFST arch bridge as the background.The force performance analysis under the main load conditions of the whole bridge and the parameter analysis under the temperature load conditions are carried out,the research results can provide reference for the design parameters of similar arch bridge structure.Finally,based on the established HGYF,the stability bearing capacity of Heshan Bridge under the basic load combination is analyzed by the method of EMER,and the safety of Heshan bridge at both the component and structure levels is evaluated,which can lay a foundation for subsequent structural optimization.