Research On Static And Fatigue Performance Of Coarse Aggregate UHPC Continuous Bridge Deck

In the traditional steel-concrete composite girder,the ordinary concrete bridge deck has high self-weight and unsatisfactory tensile performance,which restricts its application in longspan steel-concrete composite girder cable-stayed bridges and cable-bearing bridges.UltraHigh Performance Concrete),as a cement-based composite material with ultra-high strength,ultra-high toughness and high durability,can effectively solve the problems of self-heavy and unsatisfactory tensile properties of traditional concrete bridge decks.The wet joints of UHPC bridge decks are easy to crack.Based on the coarse aggregate UHPC continuous bridge deck structure,this paper proposes a new type of gusset plate type coarse aggregate UHPC continuous bridge decks,and has passed the fatigue test,static test and numerical analysis.The fatigue performance and static performance are studied by the method of and theoretical analysis.The main work and research results are as follows:(1)Research on strengthening structure of UHPC continuous bridge deck wet joint.In this paper,the five-span coarse aggregate UHPC continuous bridge deck structure is taken as the research object.The wet joint of the bridge deck is set in the positive bending moment area in the middle of the span,and the negative bending moment area is cast as a whole.Shear nails and thin plates are used at the bottom of the wet joint The steel plate is set up with a new wet joint structure to explore its crack resistance,reveal the crack resistance mechanism of the joint plate bridge deck,find out the failure mode,and propose a design method for shear connectors and joint steel plates.After 10 million times of variable amplitude fatigue loading,The bottom steel plate in the positive bending moment area of the specimen did not have any damage such as large and irrecoverable slippage,which verifies that the structure of the gusseted bridge deck is reasonable and has good fatigue strength.The static load test results show that the joint plate bridge deck improves the crack resistance of wet joints by 59.3%,and the flexural bearing capacity of normal sections by 61.3%,the static load failure in the positive bending moment zone starts from the yielding of the bottom steel plate shear nail,and the strengthening of the connection between the bottom steel plate and the coarse aggregate reactive powder concrete can further improve the ability to resist the positive bending moment.(2)Study on bending fatigue properties of coarse aggregate UHPC continuous bridge deck.In this paper,the equivalent load and stress amplitude of the actual bridge are used to load,and its fatigue crack resistance performance is investigated.The performance of the moment zone under fatigue load,the fatigue test results show that the fatigue of UHPC is mainly related to the upper limit stress.When the upper limit stress is less than 0.4～0.45 times the initial bending crack strength of UHPC,the UHPC bridge deck will not appear fatigue cracking;When the upper limit stress is higher than 0.7 times the initial bending crack strength of UHPC,fatigue cracks will appear in the UHPC bridge deck,but the cracks will not continue to develop,and the decrease in stiffness can be ignored;when the upper limit stress is higher than 9Mpa,fatigue cracks will continue to develop,but not Fatigue failure will occur.(3)Study on static bending performance of coarse aggregate UHPC continuous bridge deck.Taking the five-span coarse aggregate UHPC continuous bridge deck structure as the research object,the method of full-scale test,numerical simulation combined with theoretical analysis is used to reveal the stiffness and internal force redistribution law of the bridge deck during the loading process,and systematically and comprehensively grasp the entire loading process of the bridge deck.The research results show that: the coarse aggregate UHPC bridge deck may suffer from negative moment failure and positive moment failure.It ends with the crushing of concrete in the compression zone;the whole process of static loading occurs three times of moment redistribution with the characteristic points of cracking in the negative bending moment zone,positive bending moment zone,and reinforcement yielding in the negative bending moment zone;referring to the limit of continuous beams The calculation method of the load,and the calculation method of the ultimate failure moment of the continuous bridge deck is proposed;According to the test results and the calculation results of the finite element model,the empirical calculation formula of the flexibility coefficient under the symmetrical load in the linear elastic stage is obtained by comprehensively considering the two factors of the mid-side-span load ratio and the load spacing.