| Aiming at the current situation of severe fatigue cracking of existing Orthotropic-Steel-Decks(OSDs),this paper improves the conventional Steel-UHPC lightweight composite deck structure and uses steel strips to specifically stren gthen the tensile properties of the UHPC bottom surface,thereby preventing the steel decks from con-tinuing fatigue cracking.Studs act as shear connectors to resist interface slip of UHPC and steel decks.At the same time,because the steel strip is adher ed to the cracked steel plate by organic glue,the interface shear resistance is more complicated.In this paper,in order to further study the interface static and fatigue shear perfo r-mance when severely cracked steel bridge decks are reinforced by UHPC,the fol-lowing tasks were mainly completed:(1)The static properties of studs in UHPC and the effects of adhesive steel strips on the shear performance of studs are studied by push-out tests.Fifteen specimens were conducted.The test parameters included stud diameter,interface treatment,and loading method.According to the test force model,a three-dimensional fine finite element analysis model was proposed.The parameters analysis that contains weld form,short stud diameter,short stud height,and UHP C strength is conducted by using the ABAQUS explicit analysis method.The test and analysis results show that:i n-creasing the diameter of studs can significantly improve the shear capacity and shear stiffness of short studs;interfacial bonding can increas e the initial shear stiffness of short studs and has almost no effect on the shear capacity;(Monotonic loading and cyclic loading),short stud height and UHPC strength have baraly effect on the shear performance of short studs;The shear capacity of short studs simulated welds(elastic and plastic welds)in FEM increases by 93%and 48%than that of short studs are not simulated;the maximum slip of all test pieces does not exceed 4mm,and the design can be designed according to the elastic connection.(2)Combining the test data and the results of finite element analysis,a calcul a-tion formula for the shear bearing capacity considering the contribution of welds is proposed.Meanwhile,a total of 68 sets of relevant experimental data collected at home and abroad are compared with the theoretical values of the calculation fo rmula for the shear load capacity of studs in UHPC proposed in this paper.The ca lculation formulas in this paper have higher accuracy and adaptability;Then,load-slip curve prediction formula taking account of stud diameter is proposed.Finally,the average secant stiffness of 0.3P_u and 0.4 P_u on the load-slip curve is taken as the shear stiff-ness of the studs in UHPC.(3)The fatigue push-out test was conducted to study the effect of sticking steel strips on the fatigue and shear performance of studs in UHPC.The results indict that the fatigue life is 3.36 million times under a nominal shear stress amplitude of 108.4MPa.Because interface bonding is broke,the shear stiffness of the test specimen de-creases rapidly under the first 500,000 cyclic loadings.Then fatigue crack grows sta-bly and fatigue failure occurred.The failure modes are the superposition of two modes:stud and steel plate shearing,while the UHPC board has basically no obvious damage.Finally,taking the Yichang Highway Yangtze River Bridge as the enginee r-ing background,the ABAQUS software was used to esta blish a shell-solid multi-scale finite element model with cracks to evaluate static and fatigue performance of studs.The calculation results show that static and fatigue properties of studs both meet the design requirements. |
