| Aiming at the problems of low tensile strength,self weight and easy cracking of concrete slab near shear connectors in traditional steel-concrete composite beams,it is proposed to form steel-UHPC composite beams by combining Ultra-High Performance Concrete（UHPC）with steel beams to improve the crack resistance of components and reduce the stress level of components.The problems of traditional composite beams are improved by using the excellent mechanical properties and good durability of UHPC.At present,there are many studies on steel and conventional concrete composite beams in China and abroad,and the research on steel-UHPC composite beams is still in its infancy.In this paper,the mechanical properties of steel-UHPC composite beams are studied through numerical simulation and theoretical analysis.The main work is as follows:（1）Study on shear resistance of stud.The push-out test of steel-UHPC composite members based on stud connection was established by ABAQUS,and the displacement-load curve,shear capacity,shear stiffness,ductility and deformation performance of studs in UHPC were analyzed.The relevant parameters were analyzed based on the FEA model.The results show that the failure mode of stud connectors in UHPC is shear failure of stud;the height of stud has little effect on shear performance,shear performance of studs is mainly affected by stud diameter,followed by the tensile strength of the stud,and they are positively correlated;based on the finite element results,the existing formula for calculating the shear capacity of studs is improved,and it is verified that the formula can effectively calculate the shear capacity of studs in UHPC.（2）Study on shear resistance of channel steel.The push-out test of steel-UHPC composite member based on channel steel connection was established by ABAQUS.The displacement-load curve,shear capacity,shear stiffness,ductility and deformation performance of channel steel in UHPC were analyzed,and the relevant parameters were analyzed based on the fine finite element model.The results show that the failure mode of channel steel connector in UHPC is shear failure of channel steel web;the height of channel steel has no effect on the shear performance.The increase of the thickness of channel steel web and flange helps to improve its bearing capacity,but has little effect on the stiffness.The increase of channel steel length can significantly improve its shear performance;based on the theory of elastic foundation beam,a formula for calculating the shear stiffness of channel steel connectors is proposed,and it is verified that the formula can effectively calculate the shear stiffness of channel steel connectors.（3）Comparative study on flexural performance of steel ordinary concrete composite structure and steel UHPC composite structure.The numerical analysis models of steel ordinary concrete composite structure beam and steel UHPC composite structure beam with stud as connector are established,and their flexural properties are compared.The results show that using UHPC instead of ordinary concrete can significantly improve the bearing capacity of composite beams,significantly reduce the deflection under the same load,and show superior mechanical properties;the modified reduced stiffness method in this paper can better calculate the deformation deflection of steel UHPC composite beam;under the same load,the relative slip between steel beam and UHPC is about 70% less than that of ordinary concrete,which is more in line with the plane section assumption of composite beam.（4）Analysis of bending performance parameters of steel-UHPC composite structure.The main parameters affecting the bending performance of steel-UHPC composite beams were discussed.The results show that the diameter of studs and the shear connection degree have a great influence on the mechanical properties of composite beams.The bearing capacity of composite beams with large diameter studs and complete shear connection is improved in both elastic and plastic stages,and the interface slip is significantly reduced.The increase of the yield strength of the steel beam and the thickness of the lower flange have obvious effect on the bearing capacity of the composite beam,and have little effect on the interface slip.The increase of concrete strength has little effect on the bearing capacity of composite beams,which can reduce the interface slip to a certain extent.The increase of concrete thickness can obviously improve the bearing capacity of composite beams,and has little effect on the interface slip.Figure[63];table[18];reference[86]... |
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