| Shear connectors are a key component to ensure that steel and concrete can work together effectively in steel-concrete composite structures.Currently commonly used shear connectors are studs and PBL shear connectors.PBL shear connector has been widely studied and applied because of its advantages such as large bearing capacity,good ductility,and excellent fatigue performance.However,there are no reports about the influence of PBL shear connectors on the mechanical properties of steel-UHPC composite bridge decks at home and abroad.Based on this,this paper is based on the National Natural Science Foundation of China "Super-Long Span High-Performance Material Cable-Bearing Bridge Structure Design and Wind-induced Catastrophe Theory and Method"(Project Approval Number: 51938012),with the Danjiangkou Reservoir Bridge as the engineering background.In order to clearly configure the longitudinal mechanical properties of PBL shear connector steel-UHPC composite bridge deck,especially the structural performance of wet joints,this paper studies the test parameters of the type,number and wet joint type of the steel-UHPC composite bridge deck.The impact of longitudinal tensile performance,so as to provide a reference for engineering applications.The main research contents completed are as follows:(1)The test parameters are shear connector type,number of shear connectors and wet joint type and the PBL shear connector with main and auxiliary notches proposed by the team as the prototype,seven partial full-scale model specimens of steel-UHPC composite bridge decks were designed and produced,and static load axial tension tests were carried out on the composite plate specimens.The results show that compared with the stud shear connector,the steel-UHPC composite bridge deck equipped with PBL shear connector has better overall tensile performance.The initial crack strength of PBL specimen increases less than that of the stud specimen,but the stiffness after cracking increases significantly.The nominal tensile strength of PBL specimen at the crack width of 0.05 mm is improved compared with that of the stud specimen.Compared with the corresponding stud specimens,the initial crack strength of PBL seamless and flat wet joint specimens is only increased by 3.6% and 5.1%,respectively,the stiffness after cracking is increased by 52.7% and 63.2%,and the nominal tensile strength is increased by 3.3% and 10.0%,respectively.Increasing the number of PBL shear connector s can increase the initial cracking strength and post-cracking stiffness of the steel-UHPC composite deck slightly,but can effectively increase the nominal tensile strength of the composite bridge deck.When the number of PBL shear connectors increases from one to three,the initial crack strength,nominal tensile strength and post-crack stiffness increase by 20.0%,61.0% and 28.6%,respectively.The crack resistance of the rectangular-tooth wet joint specimen is significantly better than that of the flat wet joint specimen.The initial crack strength,the nominal tensile strength and the rigidity after cracking of the rectangular-tooth wet joint specimen are increased by 55.3%,66.2% and 53.3% respectively compared with the flat wet joint specimen;The nominal tensile strength of joint interface can be greatly increased by increasing the reinforcement ratio of joint interface.(2)Based on the finite element model of the steel-UHPC composite bridge deck test specimen verified by the test results,the parameter analysis of the thickness of the perforated plate,the reinforcement ratio and the spacing of the PBL shear bond is carried out.The results show that the initial crack load and ultimate load of the composite salb are not significantly affected by the thickness of the perforated steel plate and the spacing of the PBL shear connectors.However,the stiffness of the composite slab after cracking increases as the thickness of the perforated steel plate increases and the spacing of the PBL shear connector decreases,and the setting of the main notch of the perforated steel plate has little effect on the longitudinal tensile performance of the composite slab.When the thickness of the perforated steel plate is increased from 6mm to 8mm,10 mm and 12 mm,the cracking load of the composite plate increases by 0.2%,0.3% and 0.4%,respectively,and the stiffness after cracking increases by 6.0%,10.7% and 15.2%,respectively.The ultimate load has been increased by 0.2%,0.5% and 0.7% respectively.When the spacing of PBL shear connectors decreases from 600 mm to 400 mm and 200 mm,the cracking load of composite slabs increases by 0.7% and 1.4%,and the post-cracking stiffness increases by 9.4% and 20.2%,respectively.The ultimate load of composite plate increases by about 1.0% and 1.9%,respectively;The reinforcement ratio has a significant effect on the stiffness and ultimate load of the steel-UHPC composite bridge deck after cracking,and has a small effect on the initial cracking load.When the reinforcement ratio is increased from 2.0% to 2.8% and 4.0%,the cracking load of the composite slab increased by 0.3% and 1.3%,the stiffness after cracking is increased by 46.3%and 113.5%,and the ultimate load is increased by 4.7% and 11.3% respectively;For the flat wet joint composite slab specimens,the cracking strength and ultimate load of the composite slab increase slightly with the increase of the reinforcement ratio of the joint section.The stiffness of the composite slab after cracking is significantly affected by the reinforcement ratio of the joint section.When the reinforcement ratio of joint section increases from 2.0% to 2.8% and 4.0%,the cracking strength of composite plates increases by 8.4% and 14.7%,the post-cracking stiffness increases by 50.8% and 115.5%,and the ultimate load increases by 4.6% and 12.2%,respectively;For the rectangular-tooth wet joint specimens,the lateral length d of the rectangular-tooth wet joint has little effect on the initial crack load and ultimate load of the composite slab with the rectangular-tooth wet joint.The post-crack stiffness and the ultimate load of the composite slab increase with the increase of the lateral length d of the rectangular-tooth wet joint.When the side length d of the rectangular-tooth wet joint increases from 100 mm to 200 mm and 300 mm,the crack load of the composite slab increases by 1.2% and 1.6%,the post-crack stiffness increases by 10.9% and 43.7%,and the ultimate load increases by 0.7% and 0.8%,respectively.The side length l at the end of the rectangular-tooth wet joint has little effect on the initial crack load of the rectangular-tooth wet joint composite slab.The rigidity after the cracking and ultimate load decrease with the increase of the side length l at the end of the rectangular-tooth wet joint.When the edge length of rectangular-tooth wet joint end increases from 200 mm to 300 mm and 400 mm,the cracking load decreases by 0.1% and 0.8% respectively,the post-cracking stiffness decreases by 6.4% and 10.0% respectively,and the ultimate load decreases by 0.2%and 2.9% respectively. |
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