| Composite beam with cast-in-place concrete slab has the advantages of good integrity and flexible shape arrangement,but it needs a large amount of wet work and temporary support.Composite beam with precast concrete slab can save formwork and support,thus effectively improve construction efficiency and engineering quality.Through static tests and finite element parameter analysis,the flexural behavior in negative moment region of prefabricated composite beams with studs as shear connector were investigated.The main research contents are as follows:(1)The effects of stud arrangement patterns(uniform arrangement and group studs arrangement),the longitudinal spacing of stud and stud groups on the flexural behavior in negative moment region of prefabricated composite beams were studied through the static failure test of 6 prefabricated steel-concrete composite beams.The experimental results showed that the failure modes of all specimens included partial buckling of mid-span steel beams and severe cracking of concrete slab.Compared with specimen PCB4,PCB5 and PCB6 with the same shear connection degree,the maximum relative slip of PCB1,PCB2 and PCB3 increased by 139.6%,58.0% and 212.5%,respectively.This indicates that,compared with the uniform arrangement of stud,group studs arrangement could reduce the relative slip at the interface between steel beam and concrete slab.The ultimate load-carrying capacity difference of each specimen was within 6.2%,which indicates that the arrangement pattern of stud and the spacing of stud have little influence on the ultimate load-carrying capacity of prefabricated composite beams with complete shear connection.Both of the two arrangement patterns of stud can transfer the longitudinal shear force between the steel beam and the concrete slab effectively,so that the composite beam can work well together.(2)Based on the tests,22 finite element models were established by using ANSYS nonlinear finite element analysis software.The influences of multiple parameters such as reinforcement ratio of longitudinal reinforcement and height of steel girder web on the flexural behavior of prefabricated composite beams in negative moment region were studied.Numerical analysis results showed that with the ratio of longitudinal reinforcement increases from 1.3% to 3.0%,the ultimate load-carrying capacity of composite beams shows a trend of increase,but the biggest increase amplitude is only 4.7%.The reason is that with the increases of the longitudinal reinforcement ratio,the shear connection degree of composite beams decreases,so the increase amplitude of the ultimate load-carrying capacity is not obvious;As the steel flange width increases from110 mm to 200 mm,the ultimate flexural capacity of the composite beam increases by 45.0%.As the height of the web increases from 156 mm to 196 mm,the ultimate flexural capacity of the composite beam increases by 22.7%.It is concluded that with the increases of flange width or web height,the flexural stiffness and ultimate bearing capacity of the prefabricated composite beam could be significantly improved under the condition of satisfying the height-thickness ratio limits.(3)Based on the results of test and finite element simulation analysis,the flexural capacity of the composite beam specimens with different stud arrangement patterns was analyzed by using the plastic design method regulated by current standard.The calculated results agree well with the results of test and numerical analysis,and the calculated results were inclined to safety.It indicates that the current standard can be used to calculate the flexural capacity of prefabricated composite beams in negative moment region.Based on the test results,a mathematical model of section stiffness degradation with bending moment in negative bending moment region was proposed.The research results of this paper can provide reference and basis for the design and calculation of such prefabricated composite beams. |
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