Theoretical Analysis And Experimental Research On Torsion Of RC U-shaped Beam

U-shaped beam is a new type of upper structure form in urban rail transit bridges, which has been applied more and more in rail transit in our country so far. Compared with the traditional box-beam, T beam, U-shaped beam has high utilization rate, beautiful appearance, low cost, and can effectively reduce noise pollution. But because the U-shaped beam are thin-walled open section, the stress is complex, especially the torsional bearing capacity calculation method of problem, and there is no relevant discussion in the present specification. Therefore, the study of U-shaped girder torsional performance is necessary.This paper adopts the research method of combining theory and model test for reinforced coagulation, the torsion problem of U-shaped beam thematic research, comprehensive theoretical and experimental research results, draw the following conclusions:1. According to Vlasov of open thin-walled torsion theory, and based on the similarity formula of bending and torsion, we come up two formulas,one is suitable for the cracking and ultimate torsion bearing capacity of the thin-walled open section of U-shaped beam within the constrainted conditions.2. According to the engineering background of U type beam,we design the 1:4 scale test model and test program.3. Through six reinforced concrete under constraint torsion of U-shaped beam model test results of pure torsion and bending and twisting with the theoretical calculation results of the comparison research, verified the correctness of open thin-walled U-shaped beam under the action of constrained torsion of the correctness of the cracking and ultimate torque formula.It can provide technical support for further engineering application of U-shaped beam.In this paper, aiming at the fixed constraint conditions of open thin-walled U-shaped beam, respectively by pure torsion and bending under the action, puts forward the calculating formula of the cracking and ultimate torque theory, based on tests of 6 beams to prove the correctness of the formula, in the end it can provide technical support for the engineering application of U-shaped beam in the future.