Research On Performance Of Stud Connectors For BFRC Steel-Concrete Composite Bridge Deck In Marine Environment

There are problems of concrete deck cracking and lifting in the negative moment area of steel-concrete composite bridges,especially the long-span bridges of steel-concrete composite structures built in coastal areas also face the marine salt spray environment.It not only causes steel corrosion,but also deteriorates the service environment in which the concrete is located.Basalt fiber is used to prepare high performance concrete because of its excellent properties,wide range of raw materials and low carbon and environmental protection.Chopped basalt fiber reinforced concrete is widely used in concrete bridge decks.In this paper,C80 highstrength concrete is used as the benchmark,and five kinds of fiber volume dosage are set for the performance test of concrete base.The optimal dosage of basalt fiber was comprehensively judged by taking basic mechanical properties,shrinkage rate properties,and chloride ion corrosion resistance as characterization parameters.And the early age shrinkage model of basalt fiber reinforced concrete is proposed.At the same time,the basalt fiber concrete was used as the base material to explore the pull-out performance and stress mechanism of stud connectors under different aspect ratios and different corrosion rates.Combined with Mohr’s circle theory,the strength factor of ultimate tensile bearing capacity of concrete cone failure is determined,and the CCD model is modified to establish a more widely applicable model of failure bearing capacity of concrete cone.The main research findings include:(1)The basic mechanical properties of concrete showed a trend of first increasing and then decreasing with the increase of basalt fiber content.When the fiber content is between 0%and 0.6%,the shrinkage and chloride ion corrosion resistance of concrete are significantly improved with the increase of fiber content,and the effect of basalt fiber on shrinkage in the early stage is better than that in the later stage.When the fiber content is 0.3%,the comprehensive performance of C80 high-strength concrete is the best.(2)The content of water-soluble chloride ions in concrete increases gradually with the growth of salt spray erosion,and the relationship between the content of chloride ions and the depth from the erosion surface of the specimen is a quadratic function.Basalt fiber has stable performance and can effectively improve the resistance of concrete to chloride ion corrosion.(3)There are two modes of concrete cone failure and pin necking failure of the stud connector under the pull-out load.Ductile failure of high-strength concrete stud connectors at lower aspect ratios.The concrete cone failure mode exhibits brittle tensile load-displacement behavior,and its ultimate tensile bearing capacity increases nonlinearly with the increase of depth.(4)The cohesive force,friction force and mechanical occlusal force of the stud connector do not exist at the same time during the drawing process,and the ultimate tensile bearing capacity of the stud only depends on the mechanical occlusal force of the two.Combined with concrete properties and Mohr’s circle theory,concrete tensile strength is the most suitable strength factor for predicting the failure of concrete vertebral bodies of stud connectors.(5)The rust expansion of the stud causes the concrete to form a radial through crack in the center of the stud,and the concrete splitting failure mode appears in the stud connector.When the corrosion rate is large,the pull-out bearing capacity of the connector drops sharply,and the tensile ductility of the connector is improved.