Experimental Study On Flexural Behavior Of SMA/FRP Reinforced Concrete Beams

Fiber reinforced composite(FRP)has excellent mechanical strength、physical and chemical properties,and is widely used in engineering reinforcement.Since the initial strength is difficult to request,the idea of prestressing is used to obtain a good early force effect.At present,due to the cumbersome operation of the mechanical tensioning device,the application of FRP is limited.The shape memory effect of the shape memory alloy(SMA)is used to generate the recovery deformation.The two materials are combined in a certain way,and the temperature is applied to the activation region,Prestressing can be introduced in the composite zone by the action of temperature on the activation zone.In this study,through the experiments of 7 beams,by comparing the bearing capacity,deflection variation and crack development mode of each test beam,the force mechanism and failure mode are revealed,and the calculation formulas of bearing capacity and deflection are optimized.The FRP-reinforced concrete beam can greatly improve the bending capacity of the test beam.The test results show that the bearing capacity increases by 22%~32.9% in the range of 0~300MPa.Directly pasting the FRP-reinforced beam has less impact on the cracking load,but the FRP strengthened beam can be increased by 53.3% after the prestressing.It can be seen that the prestressing application can effectively improve the crack resistance of the beam.The stiffness of reinforced concrete beams is improved after FRP reinforcement.Especially after the prestressing,the reduced deflection is more obvious under the same load level.The reinforcement also limits the development of cracks,making the distribution of cracks more dispersed at the bottom of the beam and improved normal use of the beam.According to the analysis of FRP strain level,the application of pre-stress is more effective to show the high-strength effect of FRP.The strain response level is different from the initial pre-strain level。In this paper,the SMA-FRP composite reinforced concrete beam test is also carried out.The basic material performance test shows that the temperature can make the single SMA wire get the maximum recovery stress of 383.9MPa.According to the shape memory effect of SMA,the pre-stress level can be effectively controlled by prestrain and temperature.In this paper,a new method of FRP and SMA segmentation is adopted.By pre-bonding and fixing the two-stage composite zone,it is possible to introduce pre-stress in the intermediate composite zone through the recovery effect of the SMA wire in active zone.The two test beams strengthened by the composite material increased the cracking moment by 13.3% and 33.3% at the early stage of the load,and the rigidity increase level was small due to the uncovered pure curved section,and the bearing capacity was only increased by 4.9% and 8.5%.The use and arrangement of SMA has opened up the idea of pre-stress introduction mechanism,made up for the existing knowledge and engineering defects,and further explored the application of new materials on bridges,and achieved the effect of structural stress improvement.