Yoshifumi Ohmiya

Characteristics of merging occupants in a staircase

The purpose of this study was to investigate the effects of merges on crowds in a staircase and the ease of merging with variations in crowd density, directions of merge, and whether the door joining a hallway to a staircase was opened or closed. The results led to the following conclusions: 1) merging is easier at lower population density; 2) merging is easier if the direction of the merging crowd is same as the direction of the crowd in the staircase; and 3) merging is easier if the door is initially opened, and the evacuation speed is decreased by 30% when the door is initially closed.

Effect of a Facing Wall on Façade Flames

If a fire occurs and spreads in a building, fire plumes ejected from the openings may cause fire spread to upper floors and neighboring buildings. In particular, flames ejected from an opening were investigated by many researchers [1-5]. However, most of their works focused on temperature distribution of fire jet plume and heights of the flames issuing from the opening. Although some researchers examined heat transfer from ejected flames to facade wall [6], their studies did not cover situations where there was an opposite wall. In the present study, a series of small-scale experiments having a facade wall and an opposite parallel wall representing an adjacent buildings were carried out in order to investigate flame heights, heat flux to the facade wall and to the facing wall, and temperature distribution of ejected flame from an opening. The following phenomena were examined: 1) the heat release rate at which flames occurred from the opening and 2) the temperature distribution in ejected flames and the heat flux from ejected flames with and without an opposite wall [7].

Effect of Aggregate on Mechanical Properties of Ultra-High Strength Concrete Exposed to High Temperature

Concrete structures exposed to fire produce changes in their internal structure, resulting in their service life reduction due to the deterioration of its strength and performance capacity. The deterioration level are dependent on the temperature, exposure time, concrete mix proportions, aggregate property, and material properties. This study was performed to evaluate the thermal behavior of ultra-high strength concrete for the parameters of water to cement ratio (compressive strength), fine to total aggregate ratio, and maximum coarse aggregate size. At room temperature and , tests of ultrasonic pulse velocity, resonance frequency, static modulus of elasticity, and compressive strength are performed using cylindrical concrete specimens. The results showed that the residual mechanical properties of ultra-high strength concrete heated to is influenced by variation of a water to binder ratio, fine to total aggregate ratio, and maximum coarse aggregate size.

Algebraic Equations for Calculating Surface Flame Spread and Burning of a Cubical-Shaped Polyurethane Foam Block

This work presents a simple algebraic method for calculating heat release rate (HRR) considering the three-dimensional flame spread and burning over a cubical-shaped polyurethane foam block. Flame spread area is calculated by flame spread velocity toward multiple directions over top and side surfaces. Burnt-out area is calculated by projected area of the burnt-out portion onto original top and side surfaces. Mass burning rate per burning area is calculated by radiation from flame to each burning surfaces. HRR is calculated by multiplying burning area with mass burning rate and heat of combustion. The calculated results were compared with experiments. In cases of the cubical shape or wide shape, HRR is predicted fairly well until peak HRR. In case of tall blocks, the calculated peak HRR was smaller than experiments due to HRR per unit area over vertical surface was under estimated.

Experimental Study on the Effect of Frame Height of Bed Mattress upon Fire Behavior in Compartment

This paper aims to find out the distinction of bed mattress fire behavior (mainly, surface flame spread of mattress) in compartment compared to non-compartment condition and to investigate the effect of the frame height of bed mattress upon the smoke layer in compartment. Toward this purpose, a series of full-scale bed mattress tests with different frame heights were conducted according to ISO 12949. The results in compartment were measured in terms of factors such as heat release rate, total heat release, surface flame spread of bed mattress by thermocouple, and temperature of smoke layer, where some results were compared with non-compartment condition. Compared to non-compartment, compartment result clearly shows the difference of skyrocketing tendency in HRR and THR depending on different frame height. Flame spread in the bottom surface of mattress reached to the opposite edge faster than the top surface’s flame in compartment. This phenomenon is a unique distinction in bed mattress only in compartment since it did not occur in non-compartment. In addition, this phenomenon increasingly appeared in higher frame of bed mattress in compartment. Moreover, commonly through all of five frame heights (0, 115, 215, 315, and 515 mm), most of temperatures in thermocouples near the ceiling part of compartment showed higher temperature value than thermocouples near floor of compartment, and higher frame condition increased higher temperature of smoke layer in compartment. Therefore, it could be inferred that even if the bed mattress consists of same materials, higher frame of bed mattress is able to cause the fire behavior in compartment to be more severe as compared to non-compartment. In addition, higher frame height under bed mattress may indicate the volume of thermal convection in airflow. Even, considering the estimation results on radiative heat flux, frame height would affect on the radiation emitted from smoke layer in compartment.

Verification Methodology of Vertical Fire Spread to the Upstairs Room via Openings and Facade Wall

The authors conducted an ISO 13785-2 modified large-scale facade fire tests in Tokyo University of Science and tentatively proposed the draft for the calculation method for vertical upstairs fire spreading based on those fire test results, prior to this study. And in this research, several modifications were carefully added to past calculation methods, especially regarding the calculation of temperature in the fireroom, detailed method of unifying multiple openings on the same floor for calculation, and the criteria for the occurrence of upstairs fire spreading. Detailed calculation methods are proposed for two different situations depending on the existence of an eave above the opening at the fireroom, respectively. Also, two different criteria for verification of vertical upstairs fire spreading were proposed, one of which is based on the maximum heat flux to the upstairs room (Method 1), while the other is based on the integrated value of heat flux over time of fire duration (Method 2). Using this newly modified calculation method, the effectiveness of 90 cm spandrel and 50 cm eave is demonstrated, respectively, in terms of practically preventing the occurrence of vertical upstairs fire spreading. Improved verification calculation methods (both Methods 1 and 2) are applied to four exiting office buildings in Japan and seven rooms of fire origin considered. Verification methods using calculation proposed in this study are proved to be able to practically evaluate the occurrence of vertical upstairs fire spreading, especially regarding noncombustible facades with openings in there.

Study on Fire Plume Behavior in Vertical Shafts of Buildings

Model experiments are conducted on a vertical shaft with openings installed uniformly in the vertical direction along the vertical shaft and on a vertical shaft where one opening is present in the bottom floor and another one floor above. Study of these models helps to elucidate phenomena such as the stack effect by working from fundamental knowledge of the behavior of hot airflows in vertical shafts. The following results were obtained: (1) the temperature distribution within the vertical shaft decreases from the lower part toward the upper part inside the vertical shaft, and (2) \( \Delta {T}_{s,F}/{T}_{\infty } \) and \( {Q}_{z_F}^{*} \) have a largely proportional relationship, independent of the opening conditions and the position of the fire source. Furthermore, a prediction formula for the temperature distribution inside the vertical shaft is derived from the results.

Analysis of Combustion Expansion and Heat Release Rate During Combustion of Mattress Installed at Different Heights

Combustion experiments were performed on single-size pocket coil mattresses in order to gain an understanding of their combustion behavior with the aim of evaluating the fire risk of mattresses. Experiments were performed by varying the installation height of the mattresses above the floor from 0 to 515 mm and also by installing a pool filled with water beneath the mattresses to suppress combustion of molten droplets of mattress material on the floor. The results show that combustion of the constituent mattress materials that melted and dripped onto the floor promotes combustion of the mattress, accelerates the spread of the fire, and increases the maximum heat release rate (HRR). Furthermore, we attempt to quantitatively evaluate the heat release rate during combustion separately for the combustion of the mattress and the pool fire that burns on the floor from molten droplets. Although the history of heat release rate where it reaches a peak could not be reproduced, the heat release rate history corresponding to combustion expansion could be reproduced to some degree. Effects such as the promotion of mattress combustion by the pool fire on the floor need to be considered.

Experimental Study on Confluence of the Emerged Flames Ejected from Two Adjacent Openings

A considerable number of studies on emerged flames have been done in the past. However, since these studies were implemented using a single opening, the same conditions applied to multiple openings in close proximity to each other are yet to be determined.

Flame Spread Mechanism through Analysis of Fire Behavior of Bed Mattress by the ISO 12949 Test

Abstrct This paper aims to explain and analyze the test results of the fire behavior of real-size bed mattress products when subjected to an open flame burner system with a total heat supply of 27 kW according to the ISO 12949 method. These results were analyzed in terms of the heat release rate, flame height, temperature, and flame-spread rate using an equation. A normal bed mattress without any fire retardant treatment has a peak heat release rate (HRR) of more than 3 MW before 300 s. After ignition, only a few minutes are allowable for the evacuation of the occupants, making it important to prevent the ignition of the bed mattress or to adopt a retardant bed mattress. The flame heights measured by analyzing a video showed good agreement with the mean flame height estimated from the dimensionless HRR calculated using the burning area in an experiment with a non-flame retardant bed mattress. Finally, the mean flame-spread rate interpolated from the measured temperature rising data at several points on the bed mattress in an experiment with a non-flame retardant bed mattress was consistent with the proposed calculation model.