Research On Shrinkage And Creep Of Concrete Filled Steel Tube (CFST) And The Effects Of Mechanical Property For Tied Arch Bridge

Concrete filled steel tube(CFST)is the best combination of two materials, and have been extensively used for civil engineering structures. To all problems that the current research status of CFST on concrete filled steel tube test datas and field datas are still few, and the mechanism research of existing issues have been most lacking. The paper investigated shrinkage and creep of mechanism combining system for CFST and its effect on the mechanical behavior of steel tube concrete tied arch bridge. Research methods can be conducted in four ways: pilot study, theoretical analysis,numerical simulation and field test. The research work includes six parts.(1) On the basis of a large number of domestic and foreign literatures,the system for shrinkage and creep of CFST are summarized,then experimental are studied and theoretical is analyzed,numerical calculation and field studies of the present situation are summerized.(2) The article focuses on core concrete,then the tests of restricting expansion and contraction were implemented. At the same time, the shrinkage performance of new test model by homemade core concrete was tested under different admixtures and curing method.(3) 51 pillar creep tests and 11 pillar shrinkage experimental tests have been carried out with three years. Shrinkage and creep laws for CFST development under different steel ratio, different stress ratio and different dosage of expansive agent.The mathematical model is obtained for creep and shrinkage matching with the test results.(4) The mechanism of core concrete creep is analyzed by SEM and RapidAir, microscopic mechanism under different dosage of expansion agent and curing condition was observed. Immanent cause for macroscopic shrinkage and creep of CFST was demonstrated by microscopic morphology and pore structure, and furthering the mechanism of steel pipe concrete shrinkage and creep.(5) Take an actual structure for example, the method of numerical simulation are used for analysing the differentiation of creep and shrinkage for different national standard.The tied arch bridge was analyzed under different creep action,the internal force and deflection of arch rib and suspender and tie beam were carried. The effect is obtained quantitatively for creep on tied arch bridge.(6) The stress change of the core concrete and steel tube is tested and analyzed under the effect of different creep continued of CFST in filed. The internal force distribution and stress relaxation is analyzed quantitatively.