Pultruded GFRP tubes with liquid-cooling system under combined temperature and compressive loading

An active fire protection system, liquid-cooling, was applied to pultruded GFRP tubes subjected to combined thermal and mechanical loading in order to maintain material temperature below the critical glass transition temperature. The use of an appropriate flow rate enabled endurance times of up to 3 h at full serviceability loads to be achieved, even in the most severe scenario of compressive loading. Building code requirements concerning fire exposure – normally for a fire endurance of up to 2 h – can therefore be met. The experimental results evidenced not only the temperature – but also the time-dependence of the load-bearing capacity. Previously proposed thermal response and strength degradation models were further validated by the experiments. Since the applied models were derived from kinetic theory, the experimentally observed time-dependence could be well described.