Fire Spread of Thermal Insulation Materials in the Ceiling of Piloti-Type Structure: Comparison of Numerical Simulation and Experimental Fire Tests Using Small- and Real-Scale Models

Abstract

Large-scale fires mainly due to the ignition of thermal insulation materials in the ceiling of piloti-type structures are becoming frequent. However, the fire spread in these cases is not well understood. Herein we performed small-scale and real-scale model tests, and numerical simulations using a fire dynamics simulator (FDS). The experimental and FDS results were compared to elucidate fire spread and effects of thermal insulation materials on it. Comparison of real-scale fire test and FDS results revealed that extruded polystyrene (XPS) thermal insulation material generated additional ignition sources above the ceiling materials upon melting and propagated and sustained the fire. Deformation of these materials during fire test generated gaps, and combustible gases leaked out to cause fire spread. When the ceiling materials collapsed, air flew in through the gaps, leading to flashover that rapidly increased fire intensity and degree of spread. Although the variations of temperatures in real-scale fire test and FDS analysis were approximately similar, melting of XPS and generation of ignition sources could not be reproduced using FDS. Thus, artificial settings that increase the size and intensity of ignition sources at the appropriate moment in FDS were needed to achieve results comparable to those recorded by heat detectors in real-scale fire tests.

Numerical Validation of the Two-Way Fluid-Structure Interaction Method for Non-Linear Structural Analysis under Fire Conditions

“…where 𝜃 is the surface temperature of the steel member, 𝑘 is the correction factor for the shadow effect, 𝐴 /𝑉 is the section factor for the unprotected steel member, 𝑐 is the specific heat of steel, 𝜌 is the mass density of steel and ℎ is the net heat flux. The steel temperatures at the three points in Figure 12 were calculated using two methods and compared with the experimental data of the steel surface, as shown in Figures [16][17][18]. The steel temperatures calculated by the heat transfer equation show a similar rising curve slop at three measuring points with the experimental data during the initial period (0-150 s).…”

“…The FDS developed by the National Institute of Standards and Technology has been widely introduced in fire engineering divisions for modeling various fire scenarios [14]. Many studies have validated the FDS [11,[15][16][17][18][19]. The FDS can accurately calculate the values of gas-phase environments, such as temperature, heat flux, velocity and species concentrations, in a variety of fire simulations by comparison with experimental databases [20,21].…”

Influence of Wooden Compartment’s Fuel Moisture Content on Time to Flashover: An Experimental and Numerical Study

“…Similar approaches have proven valuable in fire investigations, as seen in [38]. However, when conducting a comparative analysis of thermal insulation on a small scale versus a large scale, certain phenomena like the melting of XPS and the generation of ignition sources could not be replicated using Fire Dynamics Simulator (FDS) as per the study [39]. This suggests that many studies, when comparing small and large scales, encounter issues that cannot be fully modeled.…”

Characteristics and Mechanism of Fire Spread between Full-Scale Wooden Houses from Internal Fires

“…Fire spread in full-size buildings have been studied mainly considering the material [39], geometry [39], ventilation [40], boundary properties [26,41,42], and wood structures [43,44]. Their studies have systematically analyzed how these factors affected the spread of fire in full-scale buildings.…”