Bonded Prestressed Carbon Fiber Reinforced Steel Beams Of Experimental And Theoretical Studies

Compared with the traditional strengthening technology using Carbon Fiber Reinforced Polymer (CFRP), the strengthening technology using Prestressed CFRP has a series of merits.But bonded prestressing CFRP reinforced technology are easy to stress detachment, heat softening, Fear of aging to degum, and time-consuming maintenance and so on. For that reason, This article would make some relevant theoretical research about unbonded prestressed CFRP reinforced steel beam.And would make a Experimental study on prestress loss by using our project team invention "the parallel pole type of anchorage device and method about flexible flake material " and" the way of using parallel stems to impose Prestresse on fiber sheet". the main achievements are as follows:1. we derived calculating formula for the stress increment of the prestressed carbon fiber based from deformation method of coordination and the energy method respectively.And analysis derived from the formula:pre incremental is the linear relationship with the external load when the steel beam is in the elastic stage of work;also prestressed increment is pro portional to the deflection of the middle of span. We can verify the two points above by the finite element calculation.2. By the finite element analysis, the yield load and ultimate load of steel beams are increased when steel beams are reinforced by the external prestressed carbon fiber,and the margin of increase is increase with the prestress.3. Based on composite beam theory and the theory of plastic design, formula of the yield flexural capacity of steel beams before and after loading is put forward.Comparing with the theoretical results and the results of finite element analysis, both are in good agreement. 4. Using the approximate differential equation based on deflection curve, virtual energy principle and stationary potential energy principle to solve the advance opposite deflection of steel beam. The example calculation results of the three methods are close to the lab testing. It proves that the three methods are accurate.5. According to the features of deflection change of steel beam under the load, which has been reinforced by prestressed CFRP, respectively, give the deflection formulas of the middle of span before and after the steel beam yield. By comparing results of the example calculations and FEM,show that they are very close.6. Test and analyze the stress losses after exerting pretension to CFRP sheet. The categories of prestress loss are listed as follows:the loss caused by deformation of the device, the loss caused by CFRP's stress relaxation, the loss of the temperature change, Loading under long-term effects, the loss caused by deformation of interaction between bolts and steel beam, and the loss of steel elastic compression caused by Internal force incremental of prestressed CFRP.And put forward the calculation formulas of effective prestressed in prestressed exert stage and use stage and some values about prestress loss.