Thermal Response Modeling of Column Experiments

In this chapter, thermal response results were presented from full-scale experiments on cellular FRP beams and columns with and without liquid-cooling. The structural members were subjected to ISO fire curve and mechanical loading simultaneously until a stop criterion (water leakage or structural failure) or after the planned fire exposure duration. 

For the noncooled members, a fire resistance up to 57 min was achieved for beams and more than 30 min for columns. It was shown that the closed cellular cross section could prevent the rapid heating of the webs, which further continued to stabilize the face sheet on the cold side against budding, while the face sheet on the fire side rapidly lost stiffness and strength. Closed multicellular cross sections 

For the water-cooled beam and column specimens, after an increase of temperature in the first 20 min, temperatures progression approached a nearly steady-state condition in the following 70-100 min and a fire resistance time of more than 2 h could be achieved, satisfying the code-required 90 min fire resistance for most buildings. In the water-coohng system, the flow rates used were modest and apph-cable in real buildings. The increase of water temperature was small and the outlet temperatures remained well below boiling. 

A one-dimensional thermal response model was developed to predict the temperature of FRP structural members subjected to fire. Complex boundary conditions can be considered in this model, including prescribed temperature or heat flow, as well as heat convection and/or radiation. The progressive changes of thermophysical properties including decomposition degree, density, thermal conductivity, and specific heat capacity can be obtained in space and time domains using this model. Complex processes such as endothermic decomposition, mass loss, and delatnina-tion effects can be described on the basis of an effective material properties over the whole fire duration. 

Although the experimental verification was based on polyester resin reinforced with E-glass fiber, this model appears to be applicable for other kinds of composite materials, if the necessary material parameters are determined. 

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