| The steel-UHPC composite structure is a new type of structure which combines the steel members and the UHPC components together through the shear connector.Compared with the traditional combination structure,the application of UHPC can improve the ductility and stiffness of the whole component,delay the expansion of the cracks,and have a positive effect on the improvement of the structure life.In the steel-concrete composite structure,it is very important to ensure the connection between the interfaces.The PBL shear connector has been widely used in the key parts of the bridge because of its good bearing and fatigue properties.This paper first introduces the development of composite structure,UHPC and PBL shear connector.Then 12 HSSFC and 12 UHPC specimens are designed,and then tested to destruction.According to the experimental results,the load slip curves were obtained,the failure modes and failure mechanisms were described,the main work includes the following contents:(1)The effect of the strength of concrete,the diameter of the reinforcing bar and the number of holes on the static performance of the PBL shear connector is studied through the experiment.The study shows that the concrete strength has a significant influence on the static performance,but the influence trend of the steel diameter will vary with the strength grade of the concrete.(2)In order to study the stress characteristics of each stage in the shear bond load-slip curve,analyzing the characteristics of the load slip curve of PBL shear connector in detail.At the same time,the formula of shear stiffness,ductility index and ultimate bearing capacity of each specimen is derived based on the EC4 standard calculation.The comparison with the experimental results shows that the agreement is good.(3)Based on the stress characteristics of each stage of load slip curve,combined with the influence factors of the ultimate bearing capacity,MATLAB is used to fit the dimensionless full curve calculation formula of HSSFC specimen.According to the beam theory of elastic foundation and the shear stiffness of the UHPC specimen with the theory of Euler-Bernoulli and the Timoshenko beam theory,this kind of test piece is given.The comparison of the total curve calculation formula with the experimental results shows that the two formulas have higher accuracy.(4)By collecting the the experimental data of PBL launched by domestic and foreign scholars in recent years,and then analyzing the influence of concrete strength,hole diameter,diameter of perforated steel bar,thickness of open plate steel plate and reinforcement ratio on static energy of PBL shear connector to compare with the test data of this paper.(5Introducing the nonlinear theory of finite element and the general situation of finite element model,then the calculation and analysis of the model are carried out by ABAQUS.The results of the finite element calculation are ideal by the contrast analysis of the stress cloud and load slip,which are in agreement with the actual situation. |
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