The Study Of Temperature Field And Thermal Stress For Concrete Girder Bridges

When calculating thermal stress in concrete girder bridge, large difference is found between the result gotten by present method and the data derived by actual measurement. The three aspects which influence the calculated result of thermal stress are studied:Temperature field. The leading factors which influence the temperature field of bridge structure by solar radiation are analyzed, and the transient thermal analysis is performed. As a result, a method of accurately simulating the distributing of temperature field is gotten. The analysis of an example is carried out to show that by using this method- the bridge temperature field can be gotten at random time, and is closer to the practice than the temperature field in present code, so thermal stress based on it is more exact.Thermal self-restraint stress. By using the three-dimensional assumption of plane, and changing the mode of thermal load and the restraining force's state, the method for calculation of thermal self-restraint stress where the global property is considered is put forward. Several examples are analyzed to compare the result calculated by this method with the result gained by other methods. The comparisons prove this method is correct, and show that when the thermal self-restraint stress in concrete girder bridge is calculated, the three-dimensional modal should be used, the stress-strain interaction between transverse and longitudinal should be considered, and the mode of thermal load in accord with practice should be applied, consequently the calculated result will be closer to the real value.Thermal secondary force. In statically indeterminate structure affected by temperature, thermal secondary force exists, and it is the base of calculating thermal secondary stress. The secondary force in continuous beam is analyzed by using equivalent load, which converts thermal load into general load. The thermal secondary force in non-uniform beam is compared with the force in uniform beam, and the difference between each other is found: in non-uniform beam, the secondary force, due to the inequality of curvature in each section which is brought about by temperature, exists.In short, thermal stress is studied from three points of view, and the reason, the difference exists between the thermal stress result gotten by present method and the data derived by actual measurement, is analyzed, and the new methods are put forward to iron out the difference, which make the calculated result closer to the real value.