Study On Static And Fatigue Properties Of Wet Joins Of Orthotropic Steel-UHPC Composite Bridge Deck

Orthotropic steel bridge deck is widely used in steel structure Bridges.A lot of engineering practice shows that fatigue cracking and pavement damage of steel bridge deck are the important reasons restricting its development.In order to solve these two problems,it is an effective solution to connect Ultra High Performance Concrete(UHPC)and steel bridge deck into a composite bridge deck structure with common stress by using bolts.In the construction process of orthotropic steel-UHPC composite bridge deck,the UHPC layer is usually cast in sections and connected by wet joints.However,wet joints are the most prone to crack in composite bridge deck,and systematic research is lacking.Based on the static and fatigue properties of UHPC wet joints,theoretical and experimental studies were carried out to determine the mechanical properties of different wet joint interface treatment modes and structural forms in orthotropic steel-UHPC composite bridge panels,and a real bridge was taken as an example to evaluate the anti-crack performance.The specific contents include:(1)Study on bonding behavior and tensile constitutive model of UHPC-UHPC joint interfaceThrough four-point bending test,the interface bond properties of UHPC-UHPC joints under four different interface treatments were determined.Based on the deflection and bottom strain data measured in the test,the effects of percussion drilling,high-pressure water gun gouging and interface agent on the interface bond strength were analyzed,and the reasonable interface treatment was determined.Based on the load-span mid-bottom strain curve,the tensile stress-strain curve of the interface bond performance was obtained by backward analysis,and then the tensile bilinear constitutive model of the interface bond performance under different interface treatment methods was fitted.Based on the constitutive model,a numerical simulation method for the bonding behavior of UHPCUHPC joint interface was established.(2)Study on static crack resistance of wet joints of different construction forms and evaluation of crack resistance of wet joints of real BridgesBased on the reasonable joint interface treatment method,five groups of wet joint composite beam specimens with different construction forms were designed,and four-point flexural tests were carried out on them.By comparing the deflection,reinforcement strain,crack development and other basic performance indexes of the five groups of specimens,the strengthening effect of different structural forms on wet joints was clarified.Based on the tensile bilinear constitutive model of bond interface,the reinforcement stress of joint section of five composite beams was numerically analyzed,and the formula for calculating crack width of wet joint section was deduced.Finally,based on the theory of crack width calculation,the nominal allowable tensile stress of wet joints of different structures is calculated,and the crack resistance of wet joints of a double-deck cable-stayed bridge is evaluated.(3)Study on fatigue crack resistance of wet joints under typical structureIn order to explore the fatigue performance of wet joints under typical structural forms,fatigue tests were carried out on two composite beam specimens with rectangular wet joints and welded steel plate wet joints.The variation law of deflection,variation law of reinforcement and crack development law were measured through the tests,and the fatigue crack resistance performance of wet joints under typical structural forms was discussed and verified.