Experimental Study And Theoretical Analysis Of Mechanical Behavior Of Steel-Concrete Joint Section Of Hybrid Girder Cable-Stayed Bridge

There are many large span hybrid cable-stayed bridges have been built or under construction at home and abroad, but the design and structure of each hybrid-stayed bridge steel-concrete joint section in the main beam are different from each other. Because there is no detailed design statement of the cable-stayed bridge steel-concrete joint section in the bridge design codes at home and abroad, so the design consideration is not clear and definite. In steel-concrete composite structure, the shear connector can make implement cooperation work between steel and concrete which are great differents in the material property, so it is very important. In present, there are many works study the shear capacity and shearing stiffness of shear studs, but they are more centering on push-out test of single or several shear studs, and less centering on the mechanical behavior of the shear studs in the steel-concrete joint section of the main beam, so it is very important to analyse the mutual action mechanism among shear stud, steel and concrete, and research the calculation method of the steel-concrete joint section in the main beam of the hybrid-stayed bridge.Based on the model test of the steel-concrete joint section in the main of the large span hybrid cable-stayed bridges and carrying capacity and shearing stiffness test of shear studs at home and abroad, two different structure styles main beam steel-concrete joint section model test and research are carried out. The comparison research on the experiment measured result and the numerical calculation results shows that the numerical calculation tallies with the experiment result, and the reasonable finite element analysis can accurately reflect the forced state of the test model. According to the experiment measured result and numerical calculation results, the rationality of the design of the main beam steel-concrete joint section in real bridge is verified. The following main contents are studied and some impotant results and conclusions have been achieved as follows:1. Taking the shear stud commonly used in steel-concrete composite structure as research objects, the specimen of single shear stud steel reinforced concrete is designed and constructed, and the push-out test is done. Through push-out test, the force characteristics, load-slippage rule, failure mechanism of single shear stud in joint section are studied, the shear capacity and shearing stiffness of single shear stud are calculated. After the the method to simulate the interface between steel and concrete in steel-concrete composite structure is investigated in finite element software, the finite element calculation model is established to study the mutual action mechanism among shear stud, steel and concrete. The comparison analysis between the experiment measured result and numerical calculation results shows that the reasonable finite element calculation can accurately calculate the ultimate bearing capacity and load-slippage curve of single shear stud, this finite element calculation method makes up the deficiency that the ultimate bearing capacity of single shear stud can only be achieved by push-out test.2. The huge rate models of Nanchang Yingxiong Bridge and Wuhan ErQI Changjiang River Bridge main beam steel-concrete joint section is designed and constructed, and the static experiments are done. The static experiments of the models of the two bridges main beam steel-concrete joint section under three load conditions that they are respectively scenarios of service limit state load, design ultimate limit state load and 1.4 times design ultimate limit load state are carried out, the stress distribution, load bearing capacity, force bearing and deformation behavior of the two bridges main beam steel-concrete joint section which have two different structure styles are reseached under the three load conditions.3. After the the method to simulate the interface between steel and concrete of main beam steel-concrete joint section is investigated in finite element software, the finite element analysis is done for the two different structure styles of main beam steel-concrete joint section ahout the two bridges above mentioned. The comparison analysis between the experiment measured result and numerical calculation results shows that the finite element calculation result tallies with the experiment result, and the reasonable finite element calculation can accurately reflect the forced state of the tset model.4. According to the shear stud push-out test result, main beam steel-concrete joint section model test result and related finite element analysis result above mentioned, taking that there are no influences on force characteristics of the different styles main beam steel-concrete joint section of the two bridge above mentioned as prerequisite, the main beam steel-concrete joint section is simplified in the finite element analysis. Nonlinear simulative calculation of the simplified model is done, the effect of the different degree of binding between steel and concrete on the force characteristics of crowded shear in the simplified model is studied, the force mechanism of the steel-concrete joint section simplified model is researched.5. Combining with the shear stud push-out test result, main beam steel-concrete joint section model test result and related finite element analysis result, the effect caused by the interface slip between steel and concrete on the compressive strength and bending strength is researched, and this paper puts forward the formula to calculate the strain of the steel and concrete in steel-concrete joint section under axial force or moment loading in the condition that the interface slip occurred between steel and concrete.