The Finite Element Analysis For Temperature Effect Of Railway Bridge Pier

For the exothermic performance of the hydration and exposing in the natural environment, bridges are inevitably affected by the surrounding temperature, sunshine as well as cold wave from the initial construction stage to the service stage, which may produce temperature effects to the structures. But these temperature effects were usually simplified for that people could not calculate them precisely. With the development of science and technology, more and more bridges cracked or even collapsed have been confirmed for the inadequate consideration of temperature effects. Currently, there are in-depth studies on the temperature effects of box girder at home and abroad, however, there are relatively less studies about the temperature effects of the railway pier. Therefore, to make the thorough and metiulous research for the temperature effect of the railway hollow pier is necessary and meaningful.This dissertation takes a scientific research task about scientific research and experimental validation of Niujiaoping two-lane extra large bridge in Xiangyu railway as the backdrop, and specifically analyzes the effects of the piers induced by hydration heat, sunshine and cold wave, moreover, it compares the results with the experimental outcomes. In this dissertation, the main contents and conclusions are as follows:(1) Compute thermodynamic parameters reversely from the temperature field.(2) Under the heat conduction finite element method, the three-dimensional model was built in the finite-element analysis software ANSYS. And calculated results were compared with experimental results, also thermal stress analysis was conducted, temperature distribution characteristics as well as thermal stress developing laws were obtained. Moreover, measures to prevent cracking were proposed.(3) Using ANSYS FEM program, a systematic study was conducted on the various parameters that affected temperature difference between inside and outside concrete in the course of the trial , such as stratified pouring, intermittent time of concrete, form removal time and so on. And conclusions were drawn, which provided certain reference for the arrangements of construction.(4) According to the trial, we use finite element analysis program to conduct temperature field and thermal stress analysis of the pier under sunshine, and compared the outcome with experimental results. Based on the computing theory of thermal stress, we use analytical methods to calculate, and compared with the results of finite element analysis, which lead to the temperature field distribution characteristics and the development laws of temperature stress.(5) The analysis of pier models with different thickness obtains the temperature field and temperature distribution characteristics of pier models with different wall thickness: temperature distribution is uneven in the thickness direction; usually the temperature difference distribution along the wall thickness direction is an exponential curve. Along with the increase in thickness, the temperature difference as well as the compressive stress of outer wall has also increased. Meanwhile, the existence of the air vents lead the temperature of the inner wall surface higher than the temperatures in the middle of the wall, thus the tensile stress of inner wall is not the biggest, and even becomes compressive stress sometimes.(6) Combined with provisions in the code, we use optimization design of the senior analysis in ANSYS to design the diameter as well as the layout of the air vents, and the optimal scheme is as follows: diameter of air vents is 0.20 to 0.30 meter, staggered arrangement, and the distance between the air vents is 4.5 to 5 meters, which provide some references for the design and construction.(7) According to the reverse test method in simulating cold wave by internal heating, ANSYS was used to simulate the test and analytical method was used in calculation. By the comparing analysis of the results, it comes to the conclusion that cracking of concrete surface caused by the cold wave happens at about 20°C . Meanwhile, the simulation of cold wave occurred during construction shows that the ultimate tensile strength of concrete is low during its early age state. If a cold wave happens, the possibility of surface cracking is lager.