Study On The Flexural Performance Of Steel Box-concrete Composite Slabs With Different Structure

The concrete-filled steel box composite slabs composed of steel box and concrete,have the advantages of high load-bearing capacity and good stress performance.However,there has been relatively little research on the bending properties of the concrete-filled steel box composite slabs.Therefore,this thesis conducts experimental research and finite element analysis on the concrete-filled steel box composite slabs with different structures based on existing research.The main research content and results are as follows:(1)Five concrete-filled steel box composite slabs and one empty steel box specimen were tested for flexural strength using the thickness of the steel box and the presence of PBL stiffeners as parameters.The study aimed to investigate the failure modes,working mechanisms,and flexural performance of different concrete-filled steel box composite slabs.The results showed that: the internal filling of concrete can effectively prevent serious local buckling of the steel box,and the flexural bearing capacity of the concrete-filled steel box composite slab is significantly higher than that of a pure steel box.Non-equal thickness concrete-filled steel box composite slabs exhibited better flexural strength,and under the same steel content,the flexural strength of non-equal thickness concrete-filled steel box composite slabs with a ratio of upper and lower steel plate thickness less than 1 was higher than that of equal thickness concrete-filled steel box composite slabs.The load-bearing capacity of the concrete-filled steel box composite slabs with PBL reinforcement can effectively slow down the local buckling of the steel box roof,which can improve the flexural bearing capacity of the component,but the improvement is not significant.(2)Using the ABAQUS finite element software to perform numerical simulation on the test specimens,the finite element analysis results were compared with the experimental results,and the agreement between the two in terms of failure state,moment-deflection curve,and experimental results was high.This indicates that the material constitutive models,element types,mesh partitioning,interactions,boundary conditions,and other factors used in the model are suitable for finite element analysis of concrete-filled steel box composite slabs with different configurations.(3)Based on a finite element model,a sectional optimization analysis was carried out on the upper and lower non-equal thickness concrete-filled steel box composite slabs.The research results showed that within a certain range,the smaller the ratio of the thickness of the upper and lower steel plates,the greater the ultimate bending capacity of the component.Under the same steel content ratio,the steel box and concrete in the non-equal thickness concrete-filled steel box composite slabs with a thickness ratio of less than 1 bear more bending moment than the equal thickness concrete-filled steel box composite slabs.The calculation results of the bending capacity based on plastic theory are in good agreement with the results of the finite element simulation,and the optimal sectional formula under a certain steel content ratio is obtained by using the ultimate bending moment as the objective function.(4)Based on the finite element model,parameter analysis was carried out on steel-concrete composite slab with PBL stiffener,and explores the influence of steel strength,concrete strength,PBL stiffener thickness,PBL aperture diameter and PBL aperture spacing on the bending capacity of the steel-concrete composite slab.The research results show that the steel strength has a greater influence on the bending capacity of the steel-concrete composite slab,while the concrete strength and PBL stiffener have a smaller influence.This thesis recommends that the thickness of the PBL stiffener should be consistent with the thickness of the steel box,and the relative aperture diameter should be 0.5,and the relative aperture spacing should be 2.0.