The Research Of Flexural Behaviors Of RC Beams Strengthened With CFRP Under Secondary Loading

In the actual project of RC beams strengthened by carbon fiber sheets,secondary loading factors need to be considered as calculating the stiffness of RC beams strengthened by carbon fiber sheets because of the loading is generally difficult to be dismounted completely. The studies include the following:1. Seven beams had a load span of 2600 mm and a rectangular cross section of 200 mm wide and 200 mm high, including one contrast beam. By using the weights and lever loading system, the tests simulated the condition of secondary load on the RC beams strengthened by carbon fiber sheets with relatively high accuracy.2. Experimental results validate the plane assumption. At the same amount of carbon fiber sheets, direct reinforcement beams crack width is less than secondary loading beams. The more carbon fiber sheets, the smaller crack width is smaller. With the increase of the amount of carbon fiber sheets, yield load increased. The initial load has little effect on the yield load and ultimate load. At the same amount of carbon fiber sheets, the stiffness of direct reinforcement beam is larger than the secondary loading beams.3. Based on analyzing the stiffness changes on the cross-section of the reinforced concrete beams strengthened by carbon fiber sheets with secondary load, and through theoretical analysis and experimental statistics, this paper established the method of calculating the short-term stiffness on the rectangular section of the reinforced concrete beams strengthened by carbon fiber sheets with secondary load. After making a contrastive analysis of the calculated results with experimental data and the results of other calculation methods, it turned out that the formula enjoys good accuracy.4. By using the finite element software ANSYS, we simulate the whole process of the tests Simulation and experimental values were compared and analyzed. The results showed that the average of the ratio of simulated values and measured values is similar, indicating that the simulation results with a certain accurary. Meanwhile, in order to verify the correctness of the formula of stiffness, 45 finite element simulation beams were operated. The results showed that the analog value and the value of the formula is similar, indicating that this model can provide a reference for the actual project of RC beams strengthened by CFRP under secondary loading.