Research On Pure And Combined Torsion Behavior And Also Its Damage Of Steel-concrete Composite Beams

Based on the analysis of some problems about the common steel-concrete composite beam,this article puts forward a new type of steel-encased composite beam.Compared with traditional composite beams,the new type of steel-encased composite beams have the advantages of improvements in the flexural capacity,the fire-resist capacity and the comprehensive economic index of the beams,and the convenience of construction process.In the project,steel - concrete composite beam in the torsion condition is many,also mostly is at the compound condition.In the domestic and foreign,the composite beam's the research is turned to be less,therefore the new steel-encased composite beam which carries on the torsion research has the important practical significance and the broad project application prospect.This article is based on the new composite beam's anti-curved performance research,to conduct the experimental study and the theoretical analysis of its torsion performance.The details are as followings:1.The 2 steel-encased concrete T section composite beam's pure torsion experiment and 3 steel-encased concrete T section composite beam's combine torsion experiment were completed,The composite beam's torque-ratio of torsion,the load-deflection curves, relational curve of section strain were obtained.We studied this new steel-encased concrete composite beam's destruction shape,worked mechanism and the crack development and the distributed situation under pure torsion and combine torsion.2.In the foundation of experimental analysis,theoretical analysis of the steel-encased concrete T composite beam's dehiscence mechanism under pure and combined torsion is conducted.On the basis of elasticity plastic theory,the formula about cracking torsion of pure torsion and combined torsion are presented;and using spatial truss model with variable angle,formulas for ultimate torsion strength of pure torsion and combined torsion are presented.Through torsional stiffness of composite beams have been studied,we inferred torsional stiffness formulas of their beams cracking to ultimate bearing capacity and ultimate destruction.Base on the relevance of composite beams under combine torsion were carried out,we respectively inferred related equations of composite beams in the big or smalltorsion-bending ratio and combine torsion,we analyzed shear connector design method of straight line composite beams under combine torsion.In the reasonable supposition's foundation,by straight line composite beams under combine torsion equivalent to circular arc curved beam,through theory,Put forward a practical shear connector design method of composite beams under combined torsion.3.We analyzed the fracture states of composite beam's structure and also researched its damage-destruction mechanism and interweaves the nature of concrete in the course of its force.Based on experiment,and according to theories of damage mechanics and also use software ANSYS,analyzed mechanical behavior of this new type steel-encased concrete composite T section beams the whole process from load to destruction,and contrasted with calculation result of concrete damage model,they are proved fit together.4.Finally,conclusion and study expectation of this new type of steel-encased concrete T section composite beam are advanced according to the results of test research,theoretical analysis and computer simulation.