Insights into ignition of a premixed flow impinging on a hot surface are important from a fire-safety point of view. This paper theoretically discusses the critical conditions for ignition of a stagnation flow near a surface heated at a constant power. A one-dimensional, diffusive-thermal model is developed, and a shooting method is used to numerically obtain a steady-state solution for a given heat flux at the solid surface. It is found that there are three solution branches when the heat flux is within a certain range. The upper branch corresponds to a gas-phase combustion solution, and the lower branch to an extinguished solution, whereas the middle branch to a solution with weak (but not negligible) reaction. When the heat flux exceeds the upper limit of the three-branch range, there exists only the upper solution, meaning that ignition always occurs. The result indicates that there is the critical heat flux for ignition, agreeing with previous experimental observations. Asymptotic analysis is additionally conducted to analytically obtain the critical condition for ignition.

Deformation behavior of concrete structures exposed to fire heating is influenced by amount of water release of the cement hydrate. In this study, elevated temperature tests for measuring the mass loss of concrete cylinders are carried out and water release property of the cement hydrate in the concrete up to 800 °C is discussed. The evaporation occurs remarkably above 100 °C. The rate of evaporation increases proportionally to the water content between 100 °C and 200 °C. The release of gel water from C-S-H continues up to 500 °C. The rate of dehydration increases proportionally to the gel water mass between 250 °C and 500 °C. The release of water from cement hydrate hardly occurs between 600 °C and 800 °C under heating condition at 1.5 °C/min.

This paper presents a comprehensive experimental study on the mechanism of merging of fire whirls and the estimation of flame height. In the experiment, a tubular device made of 16 guide plates with adjustable angles was used. Tests were conducted using multiple fire sources arranged symmetrically on the circumference of the bottom of the device. When the guide plate angle was narrow, it was found that a fire whirl merges at a small separation distance. The complexity of the formation of the merged fire whirl was determined by the competition between the combustion enhancement due to the associated air and the enhancement of the inflow between the fire sources, which clearly differed from the characteristics of the merged flame in free space. Furthermore, on the basis of the result that the Froude model can be applied even to the merged fire whirl, a model formula for the flame height of the merged fire whirl was proposed. As a result, it was obtained that the useful information for determining the generation condition related to the fire whirl through the merging of multiple fire sources and the height of the flames.

We investigated post-earthquake fires that occurred in the 2016 Kumamoto earthquake. As a result, we found 18 post-earthquake fires occurred in the 2016 Kumamoto earthquake. Fires in the 2016 Kumamoto earthquake were caused mainly at electric wiring devices and power supply units for emergency. In addition, this survey shows that hindrances to firefighting operations or heavy damage of buildings caused by earthquake resulted in heavy fire damage. The ignition rate was lower than that of the Great East Japan Earthquake. In the Kumamoto earthquake, two initial fire extinguishing cases were successful, but the success rate of the initial fire extinguishing is not so high.