Research On Steel-RPC Composite Bridge Deck Wet-joint Mechanical Property

The bending stiffness of Steel-RPC(Reactive Powder Concrete) composite bridge deck is obviously larger than that of the orthotropic steel bridge deck, the Steel-RPC composite bridge deck can improve the shortage of fatigue cracking in bridge deck and damage with asphalt pavement in orthotropic steel bridge plates. Due to the fast hardening speed of RPC, some large bridges have difficulty of large areas pouring concrete in the longitudinal direction and transverse direction, so there will exist a wet-joint where the steel fiber can’t be continuous, resulting a reduction of bending resistance. Under the condition of negative moment, the wet-joint may crack, if the crack width is not properly controlled, it will affect the service life of the structure. So it is important to control or prevent the concrete crack in the wet-joint of composite bridge deck in design. A new structure of wet-joint whose shape is a dovetail will be used in the thesis, based on the characteristics of the dovetail which can transfer the bending moment, the local stress of wet-joint can be optimized, at the same time, with help of a high ratio of reinforcement, the crack width will become smaller. Combined with the results of theoretical derivation, FE simulation and experimental research, the behaviors of composite beam wet-joint under negative moment, concrete crack mechanism and the development of stiffness in normal using stage are studied. The main contents and conclusions are as follows:(1) Static model tests are conducted on simly-supported steel-RPC composite beam under negative moment. The study gives the regulation of the structure stress, deflection and the development law of concrete crack. Meanwhile, the static model test validates that the mechanical interlocking effect of the wet-joint and the ratio of reinforcement are the main elements to influence the crack width. Using the results of the finite element simulation to compare with the results of experiments, the result indicates a good agreement.(2) Through experiment research and numerical simulation analysis, preliminary proved the main factors which influence the crack width include the dovetail tenon bevel angle, reinforcement ratio and thickness of protection cover of reinforcing bar, these factors are consistent with the no-slipping theory. The method provides a basis for calculating crack width.(3) Based on the no-slipping theory, and according to the numerical simulation and experimental data, considering the beneficial effects of mechanical interlock of the dovetail bevel edge, a regression analysis is carried on to modify the influencing factors. The formula of crack width which is applicable to composite bridge deck that containing a dovetail wet-joint has been established.(4) Considering Constraint effect of dovetail to the section stiffness, using effective stiffness method to have a research on the composite structure, putting forward the theoretical calculation formula of stiffness which can be adapted to a steel-RPC composite bridge deck that contains a dovetail wet-joint.