Tsukasa Tomabechi

Analysis of Snow-Related Disaster in Hokkaido

SYNOPSIS The purpose of this study was to obtain basic data for disaster prevention. We investigated cases of snow-related disaster that occurred in Hokkaido. The following results were obtained. 1) A proportional relationship was found between the number of snow-related disaster reported in newspapers and the number of such accidents reported to police ; the former was about one-third of the latter. Thus, this relationship can serve as an index of snow-related disaster in Hokkaido. 2) Examination of police records showed that most of the snow-related disaster occurred in cities during daily life activities. Moreover, many of the victims were people over 60 years old, indicating that the occurrence of snow-related disaster is a problem especially for elderly people living in snowy regions. 3) Many of the snow-related disaster occurred during the removal of snow and ice from buildings or the removal of roof snow, and such accidents dramatically increased in years of heavy snowfall. Thus, the occurrence of snow-related disaster is greatly affected not only by meteorological conditions such as amount of snowfall but also by residential area planning and by the construction design of individual buildings. 4) It was found that, in contrast to the immediate increase in the number of snowrelated traffic disaster following an increase in the amount of snowfall, the number of snow-related disaster begins to increase at about 10•`20 days after an increase in the amount of snowfall.

Evaluation and Maintenance of Snow Sliding Performance of Coated Steel Roofing Used for Sloped Roof

屋根上積雪の規則的な滑落処理を継続的に行う勾配屋根に用いる屋根用塗装鋼板の長期的な滑雪性能の評価および維持の手法について検討している。勾配屋根に用いる葺材は紫外線による化学的劣化と滑雪による機械的劣化が生じ,年数の経過に伴って材料表面の性状が変化する。実際に使用されていた屋根用の塗装鋼板における滑雪性能の経年劣化曲線には,初期劣化の後に18年経過頃まで滑雪性能が殆ど変化しない期間が長く存在する。なお,この滑雪性能の経年変化は,屋根雪と屋根葺材との凍着強度および摩擦係数で評価した。このことから,長期的な滑雪性能を評価する場合は,滑雪性能の経年劣化曲線に基づいて行うことが有効と考える。さらに,その劣化曲線を考慮して,屋根の滑落機能の維持保全を計画する必要がある。従って,屋根葺材の滑雪性能の耐久寿命を推定するには,材料の劣化機構に対応する劣化外力の影響を考慮する必要があると言える。本研究により,勾配屋根に適用できる材料設計手法の基本概念が提示された。

Fundamental Study on the Evaluation of Snow Load on the Roof of a Membrane Structure

Membranes have high transmissivity within the visible-light range and are used in buildings to create a bright interior space. In regions with heavy snowfall, various means are used to remove snow from the roof of membrane structures in order to maintain a bright interior space during winter. However, the current evaluation of snow load on the roof of membrane structures is the same as that used for buildings from which snow removal is not frequently carried out. This is thought to be due to the current small number of membrane structures in regions with heavy snowfall and to insufficient clarification of the effectiveness of methods for removing snow from roofs. In this study, we conducted interviews with building managers as well as on-site surveys with regards to snow accumulation on the roof of membrane structures for the purpose of collecting data that may be used as a basis for appropriate evaluation of snow load on the roof of membrane structures in regions with heavy snowfall. Furthermore, from the survey results, we estimated the most effective roof design for snow removal, and, using this roof design, we performed membrane structure analysis that took into account snow load on the roof. The results showed that for a membrane structure, a V-shaped roof of membrane panels is effective for reducing snow load on the roof.

On the present situation of escape facilites during winter

The purpose of this study is to obtain basic data for making future plans of construction and disaster prevention. We did research by questionnaire in towns and cities of a heavy snow area to know the conditions of their escape facilities in the winter season. Additionally we did further research on three cities in Hokkaido both by a spot survey and by an interview to the officers of their fire stations. It came to be clear through our reserch that the administrative guidances and measures, as well as the laws and ordinances concerning escape facilities, should be reconsidered in a very cold snow area.

Regarding surface properties and snow-sliding performance of deteriorated steel sheet for roofing

Careful consideration was given to the change in the snow-sliding performance of coated steel sheets roofs due to deterioration in snowfall area. Samples of the steel sheets that had deteriorated were collected from those actually used as roof coverings in Sapporo City.As a result of these experiments, the dynamic friction resistance of those sheets which have been used for five years or more is on the upward trend. And no marked change can be found until fifteen years. After that, as irregularities on the outer surface increase, the above resestance has become much more larger.