Finite element model for the steel-polymer composite floor filled with phase-change amorphous polymers at elevated temperatures

In this study, a steel-polymer composite floor filled with PU, an amorphous polymer with irregular polymer chains, was introduced. Because these sandwich-type floors have significant structural performance at ambient temperatures, actual buildings in Korea selected them as floor members. In addition, the fire behavior of composite floors has been investigated in several studies. However, it is highly complicated to define an analytical model for the behavior of the floors owing to the phase changes of the amorphous polymers. Therefore, a finite element model considering the phase change of the polymers is proposed in this study. The proposed model considers the composition of the polymers depending on the phase changes at elevated temperatures, as defined by material and furnace heating tests. Next, several factors, such as porosity, volumetric expansion of polymer gasification, and phase-change temperatures, were investigated to model the material properties. The analysis results from the proposed model considering the factors were compared with the furnace heating tests to obtain reliability. Porosity generally influences the structural fire behavior of composite floors, whereas the volumetric expansion of gasification partially influences the structural fire behavior after gasification. In addition, the entire phase-change temperatures provide information on the structural fire behavior depending on each characteristic, and the gasification temperature particularly provides information on the start time for large expansion owing to gasification. Finally, the fundamental behavior of the composite floors at elevated temperatures is defined by the investigations, and this can be used to predict the structural fire behavior of new steel-polymer composite floors filled with new amorphous polymers that will be improved or have different properties with finding the factors to derive the thermal expansion coefficients.