Theoretical And Experimental Study Of Secondary Moment On Concrete Frame Beams With External Pre-stressed Tendons

Because of its advantages to resolve the lacking of stiffness of concrete beam, to nicely control the development of the cracks and deflection, and also because of its nice economy in use, external pre-stressed concrete has been widely used in engineering include long span frame structure. The pre-stressed concrete application areas are becoming wider and wider, but until now days, the cognition about the behavior of such structure under loads is not enough for the realm of pre-stressed concrete of all the world. Also the mechanical properties and the computing method of secondary moment and the third moment of the hyperstatic structure under external pre-stressed force are not recognised universally .Through the experiment of one frame beam and relevant simulating in the soft of ANSYS, the author analyzes the mechanical properties of external pre-stressed concrete frame beams, and proposes some suggestion and results. Based on the national and foreign research and applications about pre-stressed concrete, combining with the experiment on pre-stressed concrete, this paper detailedly researches about one experimental frame beams: discusses basic structural performances of beams during the load process, and then obtains data such as deflection, steel strain, concrete strain and ultimate moment for further research. And also analyzes load-bearing capacity, stress increment of bars,concrete and tendons with different external force of tendons. non-linear analyses is conducted to acquire overall realizations of the external pre-stressed concrete beam's performance. Finite element method in the soft of ANSYS which takes the influence of non-linear factors into consideration is carried to depict the load-deflection curve. Referring relevant code and theory, establish different analyzing and computing methods about the third moment and secondary moment of the hyperstatic prestress effect of external prestressed frame concrete structure. The result of the test indicates the stress of concrete fits the assumption of flat section, and the internal nonprestressed steels have yielded and the external pre-stressed tendons haven't yielded at the state of ultimate carrying capacity. Also present that the hyperstatic prestress effect of hyperstatic structures has little change during the whole loading stages.