Hybrid concrete/fibre-reinforced polymer (FRP) composite structural systems are increasingly used in civil engineering, yet current design provisions do not define procedures for determining the maximum and minimum service temperatures required to account for temperature-dependent material properties. This study presents a methodology for predicting service temperature ranges and thermal gradients through a synthetic thermal load that integrates geographical location, structural orientation, analytical solar-radiation formulations and geometric self-shadowing. The method condenses environmental variability into representative exposure patterns within numerical modelling frameworks, enabling estimation of temperature limits for FRP and hybrid systems under service conditions. The methodology is developed and assessed based on calibrated numerical models of a hybrid sandwich panel system composed of glass fibre-reinforced polymer (GFRP) box profiles, a polyurethane foam core and a steel fibre-reinforced self-compacting concrete (SFRSCC) topping, complemented by a parametric investigation across different European locations. A pedestrian footbridge formed by GFRP I-profiles and an SFRSCC deck is analysed as an application example to illustrate the use of the proposed approach in practice, highlighting the influence of solar-exposure asymmetry and the role of self-shadowing in predicting realistic thermal states. Results indicate that the synthetic thermal load provides a robust estimate of maximum temperatures and thermal gradients without leading to over-design, while minimum-temperature predictions depend more strongly on the adopted air-temperature limits. The findings support the ability of the methodology to capture thermal extremes and annual thermal evolution within the investigated framework, offering an efficient approach to define service temperature ranges in FRP composites, including hybrid concrete–FRP structures. • A synthetic thermal load is proposed to define service temperatures in FRP structures • Solar radiation, orientation and self-shadowing are explicitly accounted for • The method predicts realistic maximum temperatures and thermal gradients • Numerical results show safe-oriented estimates without over-conservatism • A hybrid GFRP–concrete footbridge application demonstrates practical relevance
Filho et al. (Fri,) studied this question.