Study On Temperature Field And Temperature Effect Of Steel-Concrete Composite Beams

In recent decades,the steel-concrete composite beam has been widely used in bridge engineering.The steel-concrete composite bridges exposed to natural environment will bear dramatic temperature gradients,by the influence of sunlight and ambient temperature,which leads to the thermal stress and induced uneven stress distribution,concrete cracking,bearing displacement and so on.Therefore,the temperature field and thermal effects of steel-concrete composite bridges in the natural environment should be underscored in a wide range.The main research contents and conclusions of this thesis are as follows:1.The thesis aims to study the influence of various parameters on the temperature field of composite beams via an analysis of the sensitivity related to temperature field parameters of typical steel-concrete steel plates and steel box composite beams so that the response functions of each actors influencing temperature field can be derived.The experiment draws the following conclusions: the daily temperature differences and convection coefficient are the main factors influencing the composite beam temperature distribution,while the concrete thickness and the daily ordinals are secondary influencing factors.By fitting the analytical data,the mapping relations between the different influencing factors and temperature field characteristics are obtained.It is recommended that in the steel-concrete design in different regions,the temperature field calculation base able to reflect the regional characteristics should be adopted.2.An analysis on the temperature field of the composite beam is conducted in the four representative cities for the further analysis of the temperature field characteristics of the composite beams in different regions.Based on this,the most unfavorable temperature field model is selected to establish the thermal-structural coupling analysis model to analyze the stress and deformation of the composite beams under the temperature load.The main conclusions are as follows: There are huge differences between the distribution and specification of temperature inside the concrete during the four cities.In the code,the temperature forms a broken line pattern that gradually decreases from the top plate to the bottom plate.In the finite element analysis,the maximum temperature of steel-concrete composite beam occurs within the concrete,displaying the anti-"C" distribution mode.Due to the temperature difference,the tensile stress of the concrete is large,which should be attached importance to in engineering practice.3.Based on the design scheme of Lancang River Bridge on Sichuan-Tibet Railway,the temperature field analysis and temperature effect analysis are carried out.Based on the basic theory of temperature stress from Academician Nie Jianguo,the paper engages in the exploration of the calculation method of vertical stress from concrete temperature gradient.The main conclusions are as follows: there is a temperature gradient inside the concrete;the temperature of the steel beam changes little vertically.There is a temperature difference between the steel beam and the concrete.The vertical stress distribution of the concrete is uneven,there is a stress gradient inside the concrete.The internal temperature gradient serves as the main factor influencing the concrete temperature stress.