Experimental Study On Cracking Behavior Of Concrete-Partial-Filled Steel-Box Composite Continuous Beams

Steel and concrete is the main construction material of structures.Different materials have their own advantages and disadvantages in physical properties and mechanical properties.If only one kind of material is used to construct the structure,the structural performance will be greatly reduced.The traditional steel-concrete composite structure,is in some way to combine these two kinds of materials to work together,avoid weaknesses,make the best use.Concrete-partial-filled steel-box composite continuous beam(PFCSCB)which has an innovation in the form of cross section,is based on the traditional steel-concrete composite beam.Dividing the steel box into two chambers and filling concrete in the lower chamber to make up a steel tube confined concrete structure,which can greatly improve the continuous beam stress performance and it's bearing capacity.The cracking of composite continuous beam concrete slab causes the decrease of stiffness and the decrease of durability of the PFCSCB.Therefore,knowing the mechanical properties of composite beams in the negative moment region,researching the main influence factors of concrete cracking,so as to control the cracking of concrete are still key problems in the research of continuous composite beam.Combined with the project granted by national science foundation of China(NO.51168011,NO.51108109),the stress characteristics,concrete crack and control method under short-term loads are studied in service stage for composite beams,the main contents and conclusion are as follows:(1)This experiment completed the static loading test of 6 composite continuous beams The curves of load deflection and load strain curves of continuous beam under different reinforcement ratio and shear connection degree are plotted with experimental data.The characteristics and distribution of cracks in concrete wing plate are summarized.(2)Analyzing the causes of the cracks in the concrete wing plate,the main influencing factors and their influence on crack resistance.The theoretical formula for calculating the cracking moment of concrete wing plate is derived by using the elastic theory,Then the calculated values were compared with the experimental results after the theoretical calculation of cracking moment completed.The results are in good agreement.(3)Studying the crack width in the concrete wing plate of the negative moment zone.Considering the influence of reinforcement ratio and arrangement of the studs on the crack width.According to the test results,calculation formulas of crack width are analyzed and verified.The calculation methods of "Code for design of highway reinforced concrete and pre-stressed concrete bridges and culverts(JTG D62-2012)" and " the calculation method of steel-concrete composite structure design specification(DL/T 5085-99)" in the linear phase are the most appropriate.(4)Using ANSYS software to compete the elastic-plastic finite element analysis of the whole process of the composite continuous beam.The simulation test curves and the measured values fit well,and the experimental phenomena are also corresponding to the simulated cloud images,which shows that ANSYS solid modeling,analysis and calculation is effective and reliable.