EXPERIMENTAL AND NUMERICAL ANALYSES ON THE THERMAL DISTRIBUTION WITHIN HYBRID FRP SANDWICH PANELS UNDER DIFFERENT CLIMATIC CONDITIONS
Topic(s) : Material and Structural Behavior - Simulation & Testing
Co-authors :
Marco A. ABREU FILHO (PORTUGAL), João M. PEREIRA , Miguel AZENHA , José SENA-CRUZ (PORTUGAL)Abstract :
Fibre-reinforced polymers (FRP) show valuable features for civil engineering applications and have been the subject of extensive studies to enhance the understanding on their mechanical properties and structural behaviour in recent years. However, the response of these structures to temperature variations are often oversimplified. External structures are subject to daily, seasonal, and annual environmental thermal conditions that influence their behaviour. The non-uniform temperature distribution resulting from temperature variations cause the structure to undergo thermal stresses. In addition, in some cases temperature fluctuations can exert a more significant influence on the structural response than external operational loads, becoming one of the main factors leading to deformations. This issue has been identified by the CEN WG4.T2 project team (accountable for the development of the CEN/TS 19101:2022 "Design of fibre-polymer composite structures" published in November 2022) as an urgent problem to be addressed.
This work was carried out to develop and refine numerical models of FRP structures under controlled climatic conditions, allowing accurate prediction of thermal distribution in response to environmental thermal loads considering the effects of radiation, convection, and conduction. The validation of these models involved a meticulous analysis of experimental results, focusing on the thermal analysis of hybrid FRP sandwich panels, composed of a glass-FRP (GFRP) box structure and a polyurethane (PUR) foam core, complemented by a top layer of steel fibre reinforced self-compacting concrete (SFRSCC).
The experimental phases progress through five stages. In Stage I, specimens experience controlled temperature conditions, stabilizing at 20 °C and 40 °C. For Stage II, the analysis of the temperature distribution involves subjecting specimens to cycles from -15 °C to 40 °C. Stage III introduces radiation with a high-pressure sodium lamp with a UV to IR spectrum, cycling between 12 hours of exposure and 12 hours of non-exposure, maintaining a constant temperate of 20 °C. Stage IV combines lamp exposure with temperature cycles, involving ten cycles (-15 °C to 40 °C), synchronizing activation of the lamp with temperature increase (12 hours exposure) and deactivation with temperature decrease (12 hours non-exposure). The study culminates in Stage V, subjecting specimens to outdoor tests under real environmental conditions in the city of Guimarães, Portugal. The instrumentation consisted of six PT100 temperature sensors placed in the middle of the length of the panel and along the central axis of the cross-section, as shown in Figures 1 and 2.
Numerical simulations demonstrated a very relevant agreement with experimental results (see Figures 1 and 2), validating the efficacy of the models. This comprehensive investigation provides insights into the thermal distribution over hybrid FRP sandwich structures subjected to environmental thermal loads.
This work was carried out to develop and refine numerical models of FRP structures under controlled climatic conditions, allowing accurate prediction of thermal distribution in response to environmental thermal loads considering the effects of radiation, convection, and conduction. The validation of these models involved a meticulous analysis of experimental results, focusing on the thermal analysis of hybrid FRP sandwich panels, composed of a glass-FRP (GFRP) box structure and a polyurethane (PUR) foam core, complemented by a top layer of steel fibre reinforced self-compacting concrete (SFRSCC).
The experimental phases progress through five stages. In Stage I, specimens experience controlled temperature conditions, stabilizing at 20 °C and 40 °C. For Stage II, the analysis of the temperature distribution involves subjecting specimens to cycles from -15 °C to 40 °C. Stage III introduces radiation with a high-pressure sodium lamp with a UV to IR spectrum, cycling between 12 hours of exposure and 12 hours of non-exposure, maintaining a constant temperate of 20 °C. Stage IV combines lamp exposure with temperature cycles, involving ten cycles (-15 °C to 40 °C), synchronizing activation of the lamp with temperature increase (12 hours exposure) and deactivation with temperature decrease (12 hours non-exposure). The study culminates in Stage V, subjecting specimens to outdoor tests under real environmental conditions in the city of Guimarães, Portugal. The instrumentation consisted of six PT100 temperature sensors placed in the middle of the length of the panel and along the central axis of the cross-section, as shown in Figures 1 and 2.
Numerical simulations demonstrated a very relevant agreement with experimental results (see Figures 1 and 2), validating the efficacy of the models. This comprehensive investigation provides insights into the thermal distribution over hybrid FRP sandwich structures subjected to environmental thermal loads.