Material Characteristics And Fatigue Properties Of Anti-cracking Ductile Pavement On Steel Bridge Deck

Due to the advantages of light weight,high bearing capacity and fast construction,steel bridges have become one of the preferred types for the construction of bridges and grand bridges.However,by combining with existing engineering applications,many steel bridge structures are facing increasingly prominent pavement diseases due to the uneven distribution of local forces acting on the deck system,negative surface bending moments,hot spot stress of welds,environmental temperature and overload,which are extremely harmful to road performance and even to the safety and durability of the main structure.In order to improve the status of steel bridge deck and enhance the service life of the overlay,the strain-hardening cementitious composites(SHCCs)are proposed for pavement structure design.Due to the excellent deformation ability,crack resistance and fatigue resistant ability of SHCCs,it provides an effective way to solve the disease problem of steel deck overlay.The main research works are as follows:On the basis of traditional SHCCs' design theory,proportioning design was carried out with polypropylene(PP)fiber,hydrophilic polyvinyl alcohol(HPVA)fiber,and raw materials used in ordinary concrete.The long-term performance of the SHCCs was verified by chloride ion penetration test,carbonization test,and steel corrosion test.Micro-scale observation of fiber and hardened cement paste was carried out by field emission environment scanning electron microscopy(SEM).The effects of the fiber interface form and the raw material composition on the microstructure of hardened cement paste were described.The compressive tests on cubes of different sizes were carried out for different mixtures The influence of the fiber type and the dosage on the size effect in uniaxial compression was analyzed.The dimensional effect and the size conversion factor for cubic specimens of different sizes were obtained,and the cubic specimen with the edge length of 100 mm was recommended as the standard specimen for the compressive strength test of this type of material.The four-point bending test method was used for analyzing the mechanical properties of the material subjected to bending load,and the inapplicability of SHCCs bending toughness characterization using the existing concrete standard was demonstrated.Finally,a characterization method of bending toughness to meet different fiber types,fiber dosage and bearing stage of SHCCs was proposed.The pavement layer model members with different cross-section thicknesses were designed and loaded,and the influence of cross-section thickness on the bearing characteristics of the pavement layer was analyzed.Through the loading test of steel bridge deck composite members with 60mm thick SHCCs cast in place,the feasibility of steel bridge deck pavement design using anti-cracking ductile SHCCs was verified.The fatigue loading test of SHCCs-steel bridge deck composite members was carried out.The Weibull fatigue life probability distribution equation of cement-based materials was used for analyzing the fatigue life probability distribution of composite members.The S-N fatigue life prediction model of composite plates under different stress levels was established.The finite element method was used for verifing the fatigue load of the steel bridge deck pavement structure,and the improvement effect of SHCCs pavement on the steel bridge deck and asphalt concrete pavement was analyzed.