Non-Uniform Temperature Field And Thermal Effect Of Steel-Concrete Composite I-Girder Bridges Under Solar Radiation

The temperature field and thermal effects play a significant role in the safety and durability of the steel-concrete composite I-girder bridge.This dissertation investigates the non-uniform temperature field and temperature effect of steel-concrete composite I-girder bridge under solar radiation.It focuses on model testing,numerical simulation development,sensitivity analyses of temperature actions,temperature gradients analyses during the construction stage and thermal effects evaluation.The main research works and results are as follows:(1)The temperature distribution test on a steel-concrete composite I-girder segment was carried out.The time history and spatial distribution characteristics of composite I-girder temperature distribution were investigated,which provides the basis for validating the longterm numerical thermal simulation model of bridge temperature field under solar radiation and parameter calibrations.(2)The theoretical model for the temperature field of the bridge under solar radiation was established.A finite element model with the self-compiled shadow recognition method with ABAQUS user subroutine DFLUX was proposed to simulate the temperature field.The fine long-term simulation of the temperature field of composite I-girder bridge under solar radiation was realized.The temperature variations and temperature actions of FEM were compared against the measurements for 15 months from a composite girder segment,providing the validation of the developed method and model.(3)Based on the Euler-Bernoulli hypothesis and the assumption that linear expansion coefficients of steel and concrete are equal,the temperature actions indexes of any twodimensional composite I-girder bridge temperature field were derived.The temperature actions indexes correspond to the thermal effects and are independent of each other.The numerical model’s accuracy and precision were verified by comparing the temperature actions between measured and simulated results.The time distribution pattern of composite I-girder bridge temperature actions were identified,and the most unfavorable time of each temperature action index was revealed.(4)The influence of 11 factors,such as seasonal,geographic,thermal and geometric parameters on the temperature actions of composite I-girder bridge was analyzed using Python parametric modelling and script post-processing.The parameter combinations of the most unfavorable temperature actions of the composite I-girder bridge were determined.(5)The vertical and horizontal temperature gradient patterns and values corresponding to the maximum temperature deformation in the construction stage were analyzed and proposed based on the most unfavourable equivalent linear temperature difference of composite I-girder bridge.The coupled thermal-stress numerical calculation model considering the bridge’s nonuniform temperature field under solar radiation was established,using a sequentially coupled method of temperature field and stress field.Taking the plateau and alpine region as an example,the coupled thermal-stress response of composite I-girder under the non-uniform temperature field was analyzed.A simple calculation method of temperature deformation of composite Igirder bridge was proposed based on the temperature actions indexes.