Study On The Performance Of UHTC Locally Reinforced Simple Supported Continuous Bridge Wet Joint

With the advantages of clear force,high degree of assembly,rapid construction and low cost,the Simple-Supported Continuous Bridge is widely used in medium and small bridges of highways.However,the problems such as lack of durability and crack resistance of the wet joint structure of the Simple-Supported Continuous Bridge are gradually exposed in a long run service,which seriously affects the service performance of the Simple-Supported Continuous Bridge.In response to such problems,many scholars have been focused on the wet joint force from the construction process optimization,prestressed arrangement and the use of steel fiber concrete and other measures,but the effect is not satisfactory.Based on this,from the perspective of improving the mechanical property of wet joint materials,this paper introduces a type of Ultra High Toughness Concrete(UHTC),which is superior to high-strength slightly-expanded concrete,steel fiber high-performance concrete to locally Reinforced of the wet joints of the Simple-Supported Continuous Bridge,to solve the wet joints of premature damage problem fundamentally.The main research contents are as follows:(1)According to the theory of closest packing and fiber-reinforced toughening,it explored the feasibility of developing an ultra-high fracture toughness concrete with simple preparation,good workability,and excellent comprehensive performance.It evaluated the applicability of the ultra-high performance concrete to the common concrete flexural member sensitive parts of the force-Section tension zone.(2)In view of conventional technology and natural curing conditions,through optimizing the material components of ultra-high performance concrete,and combined with mechanical properties tests such as construction workability,compressive strength,flexural strength,tensile strength,shrinkage cracking resistance and flexural toughness,the ultra-high toughness concrete mixed with steel fiber and polypropylene fiber which super high strength and super high fracture toughness and suitable for locally reinforced wet joint of the Simple-Supported Continuous Bridge has been prepared.(3)Based on the two-point symmetric loading test method,the bending performance of three ultra-high toughness concrete local reinforced composite beams was tested,and were investigated of the mode of post-embedded,load-deflection curves,strain distributions of cross-section and bearing capacity of the composite beams,which in the condition of different UHTC thicknesses.Based on this,the formula for calculating of the cracking moment,yield moment and ultimate bending moment of UHTC composite beams is established by applying analytical method,and the calculated results agree well with the experimental values.(4)Through the study of ultra-high toughness concrete on mixing,pouring and curing construction technology,the construction method for locally reinforced the wet joints of the ultra-high toughness concrete of the Simple-Supported Continuous Bridge was put forward.Based on the finite element software of MIDAS/Civil,established the bridge space grillage analysis model,and combined with field measurement data.The results show that the bond between UHTC and normal concrete does not slip,and the structure of wet joint is good.(5)Based on the analysis theory of the normal section bearing capacity of prestressed members,combined with the force transfer mechanism of ultra-high toughness concrete and ordinary concrete composite beams.The ultimate bearing capacity analysis model of prestressed ultra-high fracture toughness concrete locally Reinforced composite beam is established by analytic method,and the influence of UHTC thickness on the bearing capacity of prestressed UHTC composite beam is discussed.The results show that the reasonable thickness of UHTC layer is 0.15 h≤t≤0.4 h.