Static Load Test Research On U-Shape Beam Of Urban Rail Transit

With the rapid development of urban rail transit of China, the U-shape beam is an increasing concern by a diversity of advantages, such as low building height, high cross-section use efficiency, beautiful shape, good noise reduction result and etc.U-shape beam has asymmetric webs and remove the transverse prestressings when compared with traditional channel girders. Engineers pay more attention on strength, stiffness, crack resistance and ultimate bearing capacity of the U-shape beam under loading conditions. At present, U-shape beam is less common used in urban rail transit of China, and neither mature nor specified experience in design can be formulated.In this paper, the natural vibration frequency, linear and nonlinear behavior of U-shape beam are numerically simulated through the analysis of three-dimensional finite element model building by software ANSYS. By comparing the experimental values with the calculated values, the results show that:1. The measured value of the vertical fundamental natural vibration frequency is 4.31 Hz, which is greater than the calculated value 3.78Hz. It shows the vertical stiffness of the structure suffices the requirement of design.2. The structure behaves linear elastically under horizontal effect of design load with good strength and stiffness.3. Under the maximum shear load condition, shear behavior of the structure suffices the requirement because no inclined crack develops. But the test value of the maximum tensile stress at the edge of the beam is slightly above the calculated value.4. Under the carriageway slab local load condition, the carriageway slab has good crack resistance because no longitudinal crack develops.5. Under 1.2 times design load, the structure still has good strength and stiffness. The crack resistance suffices the requirement because there is no visible crack.6. Tthe structure starts behaving in plastic stage under horizontal ultimate bearing capacity load at effect of 1.6 times design load. The strain, displacement and load are nonlinearity related to a certain degree. The experiment value of ultimate bearing capacity load is 2.7 times design load, which is as same as calculated value. It shows that the ultimate bearing capacity load of the U-shape beam should be no less than 2.7 times design load.