Thermo-mechanical analysis of extreme thermal loads on a flax fiber composite sandwich footbridge

In this study, a framework is proposed to perform a thermo-mechanical analysis under an extreme thermal weather event. The objective is to evaluate the temperature-induced responses as they represent a critical factor in the durability and safety of bridges. The 15 m flax fiber composite sandwich footbridge case study used for validation is instrumented with 82 fiber Bragg grating (FBG) sensors and 8 thermocouples, and it is located in Almere, the Netherlands. The structural response is evaluated under an extreme weather condition obtained through an extreme value analysis (EVA) on an hourly 18-year dataset of solar radiation and air temperature. A peak-over-threshold (POT) strategy is adopted to extract extreme values. The extremes are fitted by a generalized Pareto distribution (GPD) to obtain the 50-year temperature and global solar radiation. The framework combines environmental data, point-by-point solar radiation analysis with sun sheltering, 3D transient heat transfer, and a sequentially coupled (one-way) mechanical analysis in Abaqus. The thermal simulation accuracy is first verified against in-situ measurements. Subsequently, the extreme thermal load is applied and quantified. The results prove that the resultant stresses are significant (up to 26 %) concerning the compressive, tensile, and shear characteristic strength of the lamina.