| Shear connectors is the key component to ensure the steel beam and concrete slab to work together, and stud connectors are most widely used in steel-concrete composite structures. Numerous researches had been conducted and great achievements had been gained by researchers all over the world. At present, shear capacity and load-slip curve are mostly obtained from push out tests while load transfer mechanism between stud and concrete is seldomly investigated. The regression load-slip based on test results is lack of certain theoretical basis. Shrinkage and creep of concrete plate would make additional burden on the composite beam and stud connectors, even produce a large number of slip, severely weaken the service behavior of composite beam. Based on the 12th five year national science and technology support plan-"New Urban Composite Structure Bridge Time-Dependent behavior and Dynamic Performance Research" (2011BAJ-09B02-02) project,the load-transferring mechanism between stud and concrete and the effective height of stud were investigated by experiment research, theoretical and refined numerical analysis, the calculation method of stud force and load-slip curve were proposed. Lastly, the effect of shrinkage and creep of concrete plate on composite beam mechanical behavior was analyzed through the refined numerical model. Detail contents are summarized as follows:(1) Experimental research on stud shear connector and refined numerical analysis11 push out specimens were tested to investigate the effect of stud length, stud diameter, the layout of reinforcement and stud quantity on shear behavior of stud shear connector. Refined numerical model was established for test specimens, which can consider the contact between the stud and concrete and nonlinearity of the material etc. and showed good correlation with test results.(2) Theoretical calculation method and refined numerical analysis of studs considering interaction between stud and concreteThe internal force equations of stud were established and the reaction coefficient of concrete and yield displacement were analyzed by existing achievements and numerical analysis. The internal force of studs and load-slip calculation method were proposed based on elastic foundation beam theory. The internal moment, shear force and deformation were analyzed by the proposed equations. The load-slip curve was divided into two types according to the failure mode, including concrete crushing and stud failure.(3) Load transfer mechanism and effective height of shear stud connectorThe failure mode of push out specimens, the interaction of studs and concrete, load transfer mechanism were investigated by refined numerical model. Then, the effect of compressive strength of concrete, stud diameter and stud height on shear behavior were further analyzed.The effective stud height of φ19 stud under different concrete compressive strength was determined by Mises stress. This value were 4.42d,4d,3.68d,3.42d respectively when the concrete compressive strength were 20MPa,30MPa,40MPa,50MPa.(4) Investigation on time-dependent behaviors of steel-concrete composite beam based on refined numerical modelRefined numerical model of composite beam was constructed in combination with beam test, in which solid element was adopted for studs instead of spring element and the contact between studs and concrete was taken into account. The prediction of proposed model reached a good agreement with test results.The mechanical behavior difference between beam test and push out test was discussed using the refined numerical model. The result showed that the shear force at stud root in beam was smaller than push out test specimen while the uplift force was larger at stud root in beam. Consequently, the shear force at stud root was weakened by the uplift force.The effect of different degree of shear connection on composite beam mechanical behavior was investigated as well as shrinkage and creep of concrete plate based on the refined numerical model. The deflection of mid-span, shear force of stud root and interface slip were further analyzed. |
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