Experimental Study On Fatigue Behavior Of Reinforced Concrete Bridge Deck Under Linear Loading

Bridge structure is an indispensable part of traffic construction,but in recent years,bridge accidents are common,resulting in adverse social and economic impact.Reinforced Concrete(RC)bridge deck,as an important component of bridge structure,bears the vehicle load directly.Therefore,RC deck is easier to be fatigued under cyclic loads of vehicles.Therefore,it is particularly important to study the fatigue performance of RC bridge deck.Many scholars at home and abroad have studied the fatigue performance of RC bridge deck for a long time.They think that there are many factors affecting the fatigue performance of RC bridge deck.Among them,the load form of RC bridge deck is one of the important factors affecting the mechanical properties of RC bridge deck.The previous research found that the fatigue performanee of RC bridge deek is mostly based on the fixed-point test.There are some differences between this loading mode and the actual wheel moving load on the bridge deck.Therefore,this paper designs a linear loading scheme which is closer to the actual load on this basis.Firstly,the punching shear tests of RC bridge deck with different strength grades are carried out.By observing its failure state,the relationship between the steel strain,concrete strain,central deflection and load is measured,and then the influence of concrete strength on the punching shear performance of RC members is studied.On the basis of punching shear test,three RC bridge deck members with the same size,reinforcement and casting conditions and different concrete strength grades are tested under linear load fatigue,and the influence range of linear loading frame is further studied.During the test,the formation of crack morphology and crack width,central deflection of RC plate,strain of steel bar and concrete and residual strain were observed and recorded.The relationship between various factors and loading times was analyzed.The main conclusions are as follows:(1)Concrete strength has certain influence on punching shear capacity of RC bridge deck.Improving concrete strength can improve punching shear capacity and slab stiffness of RC bridge deck.Therefore,the influence of concrete strength of bridge deck should be taken into account in punching shear design of RC bridge deck,but the relationship between strain of steel bar and concrete at compressive side and concrete strength is inversely proportional during punching shear test.(2)Different from punching failure of bridge deck,fatigue failure under linear load forms the main crack along the direction of loading frame,and forms a triangular area near the edge of support.Moreover,the steel bars at the center of the lower part of the linear loading frame are all fractured,and the section is smooth without necking.(3)The fatigue life of slab specimens can be effectively improved by increasing the strength of concrete and the loading range of linear loading frame at the same stress level.Most of the cracks in linear fatigue tests have been formed during the first 10,000 cycles of loading,and the crack development of RC slabs mainly shows the development of crack width with the loading.On the whole,the change of crack width value is also concentrated in the first 30,000 fatigue loads,and then the change is more stable,which lasts until the RC plate is on the verge of failure.(4)The cracks of C30 bridge deck during punching test and fatigue test are restrained to a certain extent due to the addition of steel fibers.