Study On Flexural Behaviors Of Composite Beams With Segmented Precast Concrete Slabs

The fully prefabricated steel-concrete composite beam(PSCCB)consists of the steel beam,precast concrete(PC)slab,and shear connectors.The PC slabs have to be prefabricated in segments and assembled on-site due to the constraints of the processing site and transportation conditions.At this point,gaps will be formed between the PC slabs of the PSCCB,the presence of which will have a direct impact on the flexural performance of the PSCCBs.In order to solve the above problems,this study designed seven PSCCBs and carried out a study on their flexural performance under static and repeated loading.Parametric analysis was conducted on the flexural performance of the PSCCBs,and a deflection calculation method suitable for PSCCBs using segmented precast concrete slabs was proposed.The main research contents of this paper include:(1)Four fully assembled PSCCBs were designed for the static loading tests,which included three PSCCBs with segmented PC slabs with different shear connection degrees and one PSCCB with a monolithic PC slab.Test results show that all specimens suffered bending failure,with only local concrete crushing occurring near the gaps.While comparing with the beam with a monolithic PC slab,the segmentation of the PC slab reduced the initial stiffness of the composite beam by 16.2%,slightly affecting the ultimate load-carrying capacity but significantly increasing the deformation capacity of the composite beam.The mid-span deflection at ultimate load for the beams with segmented slabs is72.0% higher than that with monolithic PC slab.While adopting the segmented PC slabs,the reduction in the shear connection degree from 1 to 0.65 reduces the initial flexural stiffness of the PSCCB by 35.7%.(2)Numerical models of 52 assembled composite beams were established using ABAQUS software.Analysis shows that the flexural performance of the beams with segmented PC slabs is mainly affected by the length of the middle PC slab;the PC slabs on both sides contribute less to the flexural performance of the PSCCBs before the adjacent PC slabs contacted while being crucial in maintaining the load carrying capacity of the beams after contact.Changing the gap widths slightly affects the initial stiffness and ultimate load capacity of the PSCCBs,but significantly increases the deflection of the PSCCBs at ultimate load: the ultimate load at a gap width of 5.0 mm is only 4.4% lower than at a gap width of 1.0 mm,but the ultimate displacement increases by 123.0%.(3)Three PSCCBs with segmented PC slabs were designed for repeated loading tests,and static loading was carried out at the end of the repeated loading until the specimens failed.The test results show that the steel beams were strengthened,the gap width was significantly shortened,and the specimens accumulated a maximum residual deflection of 34.5 mm after repeated loading.In the subsequent static loading,the beams with segmented slabs exhibited similar flexural performance to that of the beam with a monolithic PC slab.Repeated loading increased the initial flexural stiffness and yield strength of the PSCCBs and reduced the deformability and ductility of the composite beam,but had little effect on the ultimate load-carrying capacity of the composite beam.After repeated loading,the initial stiffness of the specimens increased by a maximum of 46.6 %,while the displacement ductility coefficient decreased by46.7 %,35.6 %,and 30.0 %,respectively,with decreasing shear connection degrees.(4)A method for calculating the mid-span deflection of PSCCBs using segmented PC slabs under serviced load is proposed.The results of the deflection calculation of the PSCCBs based on the proposed equation are in good agreement with the finite element models,indicating that the method can be used for the prediction of the mid-span deflection of PSCCBs using segmentd PC slabs.