Mechanical Properties Of Steel And Alkali Activated Ultra High Performance Concrete Lightweight Composite Deck

With the wide spread of orthotropic steel bridge,the fatigue damage of steel bridge deck and the cracking of pavement layer gradually appear in the service process,which is due to the lack of stiffness of steel bridge deck.The use of ultra high performance concrete(UHPC)as overlay,combined with steel bridge deck is an effective solution to solve the problem of insufficient stiffness of steel bridge deck.Based on the steelUHPC composite slab,this paper proposes a composite bridge deck structure with alkali-activated UHPC as overlay,which can provide more environmentally friendly solutions for the problem of insufficient stiffness of steel bridge deck.At present,there is no mature research on the mechanical properties of alkali-activated UHPC.Therefore,in order to explore the feasibility of alkali-activated UHPC strengthening steel bridges,it is necessary to study the mechanical properties of the combined structure.Therefore,this paper intends to study the bending performance of steel-alkali-activated UHPC composite plate and the shear performance of studs in alkali-activated UHPC by combining model test,theoretical analysis and numerical simulation.On this basis,the influence of reinforcement ratio,protective layer thickness and other factors on the bending performance of composite plates and the influence of the length and diameter of studs on the shear performance of studs are analyzed,which provides reference for the application of alkali-activated UHPC in practical engineering.The specific research contents of this paper are as follows :(1)The alkali-activated UHPC materials were studied.The alkali-activated UHPC was prepared according to the mix proportion of relevant literature.The effects of modulus and dosage of activator,fly ash and steel fiber content on the performance of alkali-activated UHPC were fully considered.On the basis of the optimal mix proportion,considering that factors such as workability in the mixing process increase the water-binder ratio,a more economical natural condition maintenance is selected in the maintenance system.(2)The bending performance of composite plates was studied.Eight composite slabs with the same section size were designed and four-point bending tests were carried out.The mid-span load-deflection curves of eight specimens were obtained.The effects of loading mode,reinforcement ratio,protective layer thickness,shear connection degree and transverse reinforcement position on the flexural capacity of lightweight composite slabs were analyzed.The results of each specimen were simulated by ABAQUS finite element software.Finally,according to the plastic calculation method of conventional composite beams,the flexural bearing capacity of composite plates is calculated.(3)Eight push-out specimens with the same cross-section size were designed and push-out tests were carried out to study the shear performance of the studs.Eight pushout specimens with the same cross-section size were designed and push-out tests were carried out.The load-slip curves of the studs in alkali-activated UHPC were obtained.The effects of the height and diameter of the studs in alkali-activated UHPC on the shear capacity of the studs were analyzed,and the finite element simulation of the test was carried out with ABAQUS.Finally,according to the bearing capacity formula of studs in the specification,the shear bearing capacity of studs in alkali-activated UHPC was verified.