Test And Finite Element Analysis On Flexural Performance Of Steel And UHPC Composite Beam

Based on the excellent mechanical properties and ultra-high durability of UHPC,the concrete in steel and concrete composite beam is replaced by UHPC to form steel and UHPC composite beam,which can further improve the crack resistance of the structure and greatly reduce the self weight of the structure,thus making the structure more widely used.In this paper,steel and UHPC composite beam is taken as the research object.Through model test,theoretical analysis and finite element analysis,the flexural behavior of steel and UHPC composite beam is explored.The main work and conclusions are as follows:(1)The flexural behavior tests of one ordinary reinforced UHPC beam and three steel plate UHPC beams were completed.The test results show that there is restraint between steel and UHPC in steel and UHPC composite beam.And reducing the stud spacing can enhance the restraint between steel and UHPC,effectively reducing the interface slip between steel and UHPC,slowing down the deceleration rate of structural stiffness.This can improve the bearing capacity of the structure.(2)The crack distribution of steel and UHPC composite beam is different from that of ordinary reinforced UHPC beam.The cracks of ordinary reinforced UHPC beam are distributed densely,while the cracks of steel and UHPC composite beams are mainly distributed near the area where the studs are located.And the number of cracks are far less than these of ordinary reinforced UHPC beams.And the first crack of steel and UHPC composite beam does not start from the bottom of the beam,but occurs 30 ～ 40 mm away from the bottom of the beam.(3)Referring to the equivalent method of stress curve in the calculation of ordinary concrete and considering the contribution of UHPC in tensile zone to the bearing capacity of structure,the formula of ultimate bending capacity of steel and UHPC composite beam is derived.Then,the theoretical calculation results are in good agreement with the experimental data,and the average error is 4%,which verifies the correctness of the formula.(4)In the finite element simulation analysis,there are three ways to simulate the stud in the composite beam: tie constraint,embedding constraint and face-to-face contact.The calculation results of the finite element model with the face-to-face contact are in good agreement with the measured values,which can better reflect the deflection,strain and slip law of steel and UHPC composite beam.Therefore,the simulation method of face-to-face contact can be used as a reasonable way to simulate the finite element analysis of steel and UHPC composite beam.And the simulation method of face-to-face contact should be adopted to simulate the finite element analysis of steel and UHPC composite beam.(5)Based on the finite element model calibrated in Chapter 3,change other parameters of the model to further understand the influence of different parameters on the bending performance of steel and UHPC composite beam.The influence of each parameter on the ultimate bearing capacity of steel and UHPC composite beam is: the strength of steel > the compressive strength of UHPC > the spacing of stud> the tensile strength of UHPC > the length of stud.In addition,in the structural design,attention should be paid to the selection and arrangement of shear-bending studs,while pure-bending studs can be relatively weakened.