| Fiber Reinforced Polymer (Fiber Reinforced Polymer, FRP) has been widely appliedin the field of civil engineering for the characteristics of high strength, light weight,anti-fatigue, corrosion resistance and convenient construction, and its unique superiorityhas been shown in reinforcement of concrete structures especially. The related research inchina and other countries presented that the effects of higher strength of FRP is limitedbefore the yield of tensile reinforcement or tension edge of steel structure when using ofthe FRP sheet to strengthen member in bending in steel structure and reinforced concretestructure. Its high strength can be brought into play only when the yields of tensilereinforcement in the concrete beam or tensile zone of steel structure.This problem can be solved effectively by combining the traditional prestresstechnology with FRP reinforcement technology, which can improve the structure bearingcapacity and stiffness further and reduce the deformation of beam. The fatigue failurecan be reduced, and tensile strength of the FRP fabric can be fully applied and materialutilization rate can be improved by introducing compressive stress into the tensile zone.The excellent tensile properties of steel and superior compressive property of concrete canbe full used by combination beams.At present, the research is stillless in using of CFRP sheet to reinforce steel structureof beam and composite beams of steel and concrete, therefore, force analysis has beenmainly studied on the prestressed CFRP sheet to strengthen steel-concrete compositebeams.Based on the analysis of domestic and foreign research on reinforcement concretestructure and steel structure by using of CFRP, the method has been put forward tostrengthen steel and concrete composite beams by using prestressed CFRP sheets, thestress analysis of it has been conducted, and calculation formula has been found aboutultimate bearing capacity of prestressed CFRP sheet and steel-concrete composite beams.The conclusions are as follows:Stress analysis has been given to steel-concrete composite beam: normal stressanalysis of section; shear stress analysis of section; analysis of the ultimate bendingcapacity (including the plastic neutral axis in steel beam flanges and in steel beamscontaining web). This can increase the stiffness of the structure and increase the stabilityand integrity.Stress analysis has been given to reinforced steel and concrete composite beams by prestressed CFRP sheet:The stress which effected by several factors is considered in stress analysis of crosssection: the internal forces re-distribution between combination of beam and steel beam iscaused by long-term load effects (concrete creep) and self-stress of internal compositebeam induced by temperature changes and hardening and contraction of concrete.The ultimate flexural bearing capacity analysis: according to the structurecharacteristics of reinforced steel-concrete composite beam and conditions of stress byprestressed CFRP, two kinds of failure modes has been analyzed. One of it is steelyielding, concrete crushing, CFRP sheet breaking; the other is steel yielding, concretecrushing, CFRP sheet does not tensile failure. Through analysis the results can be foundthat the higher tensile properties of CFRP can be used better by prestressed CFRP sheets,and it can effectively improve the bearing capacity of steel and concrete composite beams.An example of simulation analysis has been given by using of the finite elementsoftware to verify the result of theoretical analysis and the correctness of the theoreticalanalysis has also been proven through the analysis.It has been proved that the strength limit and flexural capacity limit have been improved by reinforced composite beam by contrast the strengthened beam and non-strengthened beam with the calculation results of finite element. |
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