Study On Temperature Field And Temperature Effect Of Long Span Concrete Filled Steel Tube Arch Bridge

Because of its excellent structural performance,simple construction method and beautiful structural alignment,concrete-filled steel tubular arch bridge has been widely used in the background of infrastructure construction in China,and its span has been constantly broken through.With the extensive use of targeted research public relations,the research on the performance and technology of concrete-filled steel tubular structure has made great progress.However,due to the obvious regional and structural characteristics of the bridge temperature problem,the research on this aspect is still lacking,and the theoretical research is relatively slow.In particular,the continuous breakthrough of the current span brings about large pipe diameter,high-grade concrete and complex bridge site environment,which makes the research on the temperature field and temperature effect of large pipe diameter and long-span CFST arch bridge very urgent.In this paper,the long-term temperature monitoring test of large-diameter concrete-filled steel tube specimens is mainly used,supplemented by the finite element numerical simulation method to analyze the arch rib temperature field and temperature effect calculation parameters,so as to provide reference for the follow-up researchers to study the temperature problem of large-diameter concrete-filled steel tube arch bridge.The main contents of this paper are as follows1.The research status and research methods of concrete-filled steel tube arch bridges and their temperature problems are summarized,and the heat exchange calculation theory and boundary conditions are analyzed to provide theoretical guidance for the calculation of temperature distribution and temperature effects of the bridge.2.The calculation parameters and influencing factors of the hydration heat release temperature effect in the process of mass concrete pouring are studied.When calculating the temperature effect of mass concrete hydration heat release,the influence of temperature on the elastic modulus of concrete cannot be ignored.Based on the equivalent age theory,a composite exponential elastic modulus prediction model that takes into account the temperature effect is used to calculate the hydration thermal stress.In the initial stage of cooling,the concrete produces a large hoop tensile stress of about 3MPa,which may cause the risk of cracking of the concrete.Due to the confinement of the steel tube,the concrete exhibits compressive stress in the radial direction.The calculation of the factors affecting the thermal stress shows that lowering the temperature of concrete entering the silo,such as adding ice water,can better improve the tensile stress caused by the exothermic heat of hydration.3.The temperature distribution,temperature effect,bonding interface stress and parameter sensitivity of concrete filled steel tube under sunshine and other temperature loads are studied.The results show that the maximum tensile stress of the concrete in the radial direction reaches 1.48 MPa and the maximum tensile stress in the circumferential direction reaches 2.06 Mpa under the action of sunshine temperature load,which is greater than the C60 concrete tensile design value 1.96 Mpa.The concrete cracks under the action of periodic temperature risk.The maximum tensile stress of the bonding interface between steel tube and concrete exceeds 1.22 MPa,and the thermal stress of the interface bonding is positively correlated with the wall thickness and negatively correlated with the pipe diameter.4.In order to study the method of calculating the temperature effect of the concrete-filled steel tube arch bridge,a long-term temperature monitoring experiment was carried out on a full-size concrete-filled steel tube specimen.On the basis of experiments,combined with calculation and analysis,the closing temperature,effective temperature value and temperature gradient model of the concrete-filled steel tube arch bridge are studied.The study shows that the closing temperature is more reasonable to be calculated according to the recommended formula of the "Code for Design of Concrete-filled Steel Tubes for Highways";The temperature gradient model of the arch rib makes recommendations.5.Calculate and analyze the temperature effect of the concrete-filled steel tube arch bridge during the operation stage.The results show that the temperature has a significant influence on the bridge,and the influence of the temperature effect on the arch toe section is more prominent than that of other sections of the arch rib.