著者

中楚 洋介 立山 耕平 山田 浩之 川口 健一

出版者

日本建築学会

雑誌

日本建築学会構造系論文集 (ISSN:13404202)

巻号頁・発行日

vol.84, no.766, pp.1525-1532, 2019 (Released:2019-12-30)

参考文献数

14

被引用文献数

1

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Finishing materials installed at the building surface closest to the living space of people often fall down and harm the life, body or property. Ceiling collapse especially occurs by the various reasons, e.g. the rain leaking, dew condensation, wind, traffic vibration, on a daily basis. In addition, the ceiling collapse tends to occur in the region where the seismic intensity is over five lower during earthquakes. The authors propose the quantitative evaluation method to assess the degree of risk of the ceiling collapse by comparing the impact force and the proper human tolerance. So far, we dropped the various ceilings having commercial size of 910 mm square from one to twenty meters high using the guide wires to hit to the dummy head remaining horizontal and measured the impact force with the load cell installed underneath of the dummy head. However, the experimental conditions are constrained. Therefore, the examination regarding the efficiency of ceiling size and impact angle is insufficient. To do the parametric study by the numerical analysis, the material properties of the finishing material in a wide range of strain rates are needed. However, few reports are available on the material properties of the finishing materials. In this study, a series of compressive tests, i.e. quasi-static tests, dynamic tests and impact tests by split Hopkinson pressure bar method, at various strain rate from 10-5 to 103 s-1 were conducted to examine the strain rate effect on the compressive property of the representative finishing materials: gypsum boards, calcium silicate boards and rock wool sound absorbing boards. The results obtained from this study are following: 1) The X-ray CT images show the internal structure of the finishing materials. The porosity of the gypsum boards is about 25%, and it was also slightly observed in the rock wool sound absorbing boards. On the contrary, it was found that the calcium silicate boards were the solid material with no void. 2) It was revealed that all materials used in this study have the strain rate dependence of the compressive strength at the strain rate from 10-4 to 103 s-1. In addition, it was found that the strength drastically rose at the strain rate of about 102 s-1, although it is not confirmed that the strain rate dependence is attributed to the material itself or its foam, i.e. open cell structure. 3) The constants for Cowper-Symonds constitutive equation (dynamic constants) of the representative finishing materials were identified by least-squares method based on the compressive test results. Due to this, it can be expected to improve simulation accuracy in the future.

著者

立山 耕平 成毛 志乃 佐々木 寿 福井 拓哉 山田 浩之

出版者

特定非営利活動法人 日本火山学会

雑誌

火山 (ISSN:04534360)

巻号頁・発行日

vol.65, no.2, pp.41-51, 2020-06-30 (Released:2020-07-06)

参考文献数

26

被引用文献数

1

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In recent years, casualties caused by the impact of ballistic ejecta from sudden phreatic eruptions have drawn much attention, as observed with Mt. Ontake in September 2014 and Mt. Moto-shirane in January 2018. Hence, improvement of evacuation facilities (shelters) that protects against ballistic ejecta is expected as a forthcoming volcanic disaster prevention initiative. In many cases, the utilized evacuation facilities are outfitted by strengthening existing facilities such as mountain huts. Therefore, it is necessary to understand the baseline impact resistance against ballistic ejecta of the existing mountain huts. In the case of Japanese wooden buildings, Japanese-style rooms with tatami (Japanese-style thick straw mats) are often used. In this study, we focused on the impact resistance of tatami used for flooring. We conducted tests which simulated the impact of ballistic ejecta on various types of tatami, in order to assess the penetration limit of tatami. Three types of bodies of tatami (tatamidoko) were prepared: straw tatamidoko, non-straw tatamidoko type III, and straw sandwich tatamidoko. The projectile was simulated ballistic ejecta with a diameter of 128mm and a mass of 2.66kg, made using a vitrified grinding wheel. This object was launched at a speed of 22 to 69m/s using a pneumatic impact test apparatus. From the impact test, non-straw tatamidoko type III did not prevent penetration, even at an impact energy of 0.63kJ. Therefore, if non-straw tatamidoko type III was to be used in a mountain hut, it cannot be expected to protect against ballistic ejecta. On the other hand, the minimum energy of penetration of straw tatamidoko and straw sandwich tatamidoko were 4.9 and 4.1kJ, respectively, and they had sufficient impact-resistance against ballistic ejecta compared to the mountain hut roof. Thus, it was shown that the downstairs of straw tatamidoko and straw sandwich tatamidoko can be designated as “a safer place in the building”.