Effect Of Sliding On Mechanical Behavior Of Concrete-Partial-Filled Steel Box Continuous Composite

The steel-composite structure is an anti-bending member formed by shear joints between steel and concrete slabs.Under the action of positive bending moment,the concrete slabs are pressed and the steel beams are pulled.The materials can give full play to their respective properties.Under the action of negative moment,the concrete slab is cracked and the steel beam is compressed.Partial backfill steel box-concrete continuous composite beam is filled with concrete at the lower part of the steel box in the negative bending moment area.The backfill concrete is restrained by the steel box,and its stress characteristics are similar to that of the concrete-filled steel tube column.Therefore,the continuous composite beam of partially filled steel box and concrete is composed of concrete panel,steel box girder of partially filled concrete and shear connector.Slip is an important factor affecting the mechanical properties of composite beams such as stiffness and bearing capacity.In this paper,the symmetrical concentrated load test of 6 partially filled steel box-concrete continuous composite beams were carried out,and the influence of relative slip on the mechanical properties of composite beams was studied by combining theoretical analysis and ANSYS simulation.The main achievements are as follows:(1)Three failure modes,load-deflection curve,load-slip curve and load-strain curve of composite beams were obtained through static test study of 6 partially filled steel box-concrete continuous composite beams,recording test process and observing test phenomena.According to the analysis results,the distribution law of slip and the stress performance and deformation characteristics of composite beams were summarized.(2)The slip of composite beams under the action of positive and negative moments is analyzed theoretically by means of analytical method and superposition principle.The concepts of slip strain and slip are introduced,the principle and mechanism of relative slip are analyzed,the micro element model of relative slip of composite beam is established,the relative slip differential equation and slip strain differential equation of composite beam are derived,and the distribution law of relative slip and slip strain is obtained.The slip calculation formula and slip strain calculation formula of continuous composite beam are obtained by superposition method,and the slip analysis of continuous composite beam with different shear connection degree and different middle support reinforcement ratio is carried out.(3)ANSYS was used to conduct finite element analysis of 6 partially filled steel box-concrete continuous composite beams.Through finite element simulation,the deflection finite element value is basically consistent with the measured value,and the difference between the two data is not big in the mechanical performance of each stage.The error between the finite element value and the measured value is small,which can reflect the sliding behavior of the continuous composite beam.