Experiments And Theoretic Research On Steel-Concrete Composite Beams Considering Interface Slip And Uplift

Steel-concrete composite beam is a kind of new-type composite member that depend on the connector made steel and reinforcement concrete slab composite and work together. Despite of steel-concrete composite beams have comparatively broad research in home and abroad, but there still are a lot of technology difficult problems in theory and actual application. In the dissertation, the behavior of interface slip and vertical uplift effect for steel-concrete composite beams are analyzed by means of specimen tests and theoretical analysis. The main works and results are as follows:1.11 simple supported specimens under positive or negative bending moment and 3 continuous members were designed taking the degree of shear connection as main factor. In order to measure the interface relative slip between the steel and concrete slab, the Double-directional Embedded Electronic Steel-Concrete Slip Transfers were placed in these 14 specimens. Electronic strain gauges were installed on the stud to test the force of uplift. The displacement instruments were respectively installed on the same section of steel and concrete slab to measure the vertical uplift displacement. Electronic strain gauges were also installed on the steel shape flanges, webs and concrete. The change of the mechanical behavior, interface slip and vertical uplift of the 14 specimens in the whole process of loading was fully observed.2. By the summarizes and the whole analysis with experimental results of the 14 specimens, the interface slip and vertical uplift distributions were obtained and the influence of the factors such as degree of shear connection, the distribution of stud and the way of loading was further studied. The level resist slip and vertical resist uplift stiffness coefficient of the stud are obtained by experimental analysis.3. Theoretic expressions for calculating the stress of interface vertical uplift of steel-concrete composite beams are developed, and the force of uplift subjected by the stud can be obtained by proper integral in the space of the stud. The values from this theoretical method are in good agreement with experimental results. It provided a basis for the further study on the resisted uplift of the stud. Based on the vertical uplift effect and section optimization principle, the range of rational steel ratio was presented for the steel-concrete composite beams.4. A reduced stiffness method is adopted by the Code for Design of Steel Structures (GB50017-2003) in calculating the deformation of steel-concrete composite beam. But it has some limitation which was proved by experimental results and theoretic analysis. Theoretical calculating expression about deformation of steel-concrete composite beams is presented in which the interface slip and vertical uplift effect are taken into account in the same time. The results calculated by this method has a good agreement with those obtained from experiment. A simple utility formula for stiffness which satified engineering design is proposed.5. Elastic and limit bending capacity which influenced by the interface slip and vertical uplift were analyzed. A simple method was presented in calculating the bending capacity with taking the interface slip and vertical uplift into account. By conducting the degree of influence of slip stiain on average strain of a member section, some parameters of corrected even section were calculated, which made the corrected even section more reasonable.6. Based on the test results and theoretic analysis, the concrete slab obviously contributed to the shear capacity of steel-concrete composite beams whether it subjected sagging moment or hogging moment. The interface slip and vertical uplift have little influence to the shear capacity of the steel-concrete composite beams. The formulae are derived for the shear capacity with consideration of the contribution from concrete flange. The predicted values are in good with the experimental results.