Experiments And Theoretic Research On Behavior Of Continuous Composite Beams

Steel and concrete composite structure has both the advantages of steel structure and concrete structure. It has been widely used on the project circle in recent years. Steel and concrete composite beam is a kind of new-type beam that depend on the connector made steel and reinforcement concrete slab composite and work together. Despite of steel and concrete composite beams have comparatively broad research in home and abroad, but there still are a lot of technology difficulties in theory and actual application. With the further application of continuous composite beams which the concrete of negative moment bending drawn crack, reduce the stiffness of negative moment bending section.It's more and more outstanding to influence the function of this structure. So this paper research on one simply supported composite beam and three continuous composite beams that two steps are equal.According to the experiment of composite beams,the results show that the longitudinal reinforcement and the steel can work effectively if sufficient shear connection is provided.This article investigate the destroy mechanism, destroy law and the process of crack;define the loading-deflection curve of mid-span, the slip curve of interface between the steel and concrete , the loading-width of crack curve and strain curve of mid-support along the profile height; make a analysis and summary that the different factors influence bearing capacity and ductility of composite beams consider its shear connection degree and the arrangement of shear connector.Based on the theory of elastic analyes,the calculation formula of interface slip of steal and concrete and deflection of mid-span about simply supported composite beams under symmetrical load and concentrated load can be established. The results of calculation and testing are concrasted. Comparing experiments and theory , the stiffness of negative moment bending should be reduced. Assume of flat section when the concrete cracked , through establishing the balance relation of sectional mechanics, the crack moment and crack load can be got. Finally,contrasting the law of crack of concrete beam,considering the major factor of composite beam,the formula of the crack width have been established which considering the bending curvature,crack height and the distance of crack.This paper will be helpful to the further experimental researchs and theoretic studies on the flexural behavior of continuous composite beams.