Thermal Contact Conductance-Based Thermal Behavior Analytical Model for a Hybrid Floor at Elevated Temperatures

Abstract

Hybrid floors infilled with polymeric materials between two steel plates were developed as a prefabricated floor system in the construction industry. However, the floor’s fire resistance performance has not been investigated. To evaluate this, fire tests suggested by the Korean Standards should be performed. As these tests are costly and time consuming, the number of variables were limited. However, many variables can be investigated in other ways such as furnace tests and finite element analysis (FEA) with less cost and time. In this study, furnace tests on heated surface areas smaller than 1 m2 were conducted to investigate the thermal behavior of the hybrid floor at elevated temperatures. To obtain the reliability of the proposed thermal behavior analytical (TBA) model, verifications were conducted by FEAs. Thermal contact conductance including interfacial thermal properties between two materials was adopted in the TBA model, and the values at elevated temperatures were suggested based on thermo-gravimetric analyses results and verified by FEA. Errors between the tests and TBA model indicated that the model was adequate in predicting the temperature distribution in small-scale hybrids. Furthermore, larger furnace tests and analysis results were compared to verify the TBA model’s application to different sized hybrid floors.

Fire Design Equation for Steel–Polymer Composite Floors in Thermal Fields Via Finite Element Analysis

“…The contact surfaces between two materials are related to physical factors, such that the thermal contact conductance at elevated temperatures can be altered by physical properties such as residual mass. The residual mass at elevated temperatures can be obtained from thermal gravimetric analysis (TGA) obtained from previous study [11], as shown in Figure 2. The reduction ratio of thermal contact conductance at elevated temperatures agrees with the pattern of the TGA results, and the value of the thermal contact conductance at ambient temperatures is 250 W/m 2 such that the thermal contact conductance at elevated temperatures can be altered by physical properties such as residual mass.…”

“…Owing to this feature, polymers, which are elastomers that have large failure strains on the composite floors, were targeted to exhibit strong bond strengths in the early development stage. To investigate the fire resistance performance of composite floors, fire-resistant polymers have been developed, thus enhancing fire resistance [11]. However, conducting fire tests based on Korean Standards (KS) was very difficult in Korea [12][13][14].…”

“…These limitations indicate that efficient studies requiring lower costs and less time are needed, such as small-scale tests or analytical studies. Consequently, using finite element methods and small-scale furnace tests, analytical studies were conducted to investigate the fire behavior and fire resistance of steel-polymer composite floors [11,15]. The performance of fire resistance was evaluated using small-scale furnace tests and alternative fire-severity methods [15].…”

“…The performance of fire resistance was evaluated using small-scale furnace tests and alternative fire-severity methods [15]. A thermal-contact, conductance-based thermal behavior analytical model for the composite floors was developed and verified using furnace test results [11]. The temperature distribution of the composite floors at elevated temperatures is a prerequisite that determines mechanical properties depending on the temperature.…”

“…The validation of the finite element model that had already been obtained from various-scale fire tests was achieved again by comparing it with full-scale fire tests based on the KS. [11] The thermal behavior analytical model for steel-polymer composite floors focuses on thermal contact conductance, which is the contact issue between polymers and steel. Thermal contact conductance is defined by an invisible gap and contact surfaces.…”