砂防学会誌
Online ISSN : 2187-4654
Print ISSN : 0286-8385
ISSN-L : 0286-8385
62 巻, 6 号
特集:土砂災害対策施設とその効果
選択された号の論文の13件中1~13を表示しています
口絵〈観測の現場を訪ねて-19〉
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論文
  • 片出 亮, 香月 智, 嶋 丈示
    2010 年 62 巻 6 号 p. 3-14
    発行日: 2010/03/15
    公開日: 2014/02/01
    ジャーナル オープンアクセス
    This paper proposes a simplified estimation method for redundancy of steel check dam, and its related design method. The estimation method uses a parameter defined as “elemental index”. The mathematical significance of the elemental index is proved in this paper, from the view point of structural degree of indeterminant. Using typical model of 6 steel check dams, this paper discusses the relationship between the elemental index and structural redundancy. First, each structure is evaluated by the proposed elemental index. Secondly, the effect of elemental index on collapse load is discussed. Thirdly, residual collapse load ratio associated with the structures removed some elements is checked and its relation to respect elemental index is discussed. And, the positive relationship between the residual collapse load ratio and the elemental index is found. Based on above discussion, this paper proposes the modified allowable stress design method, i.e., the allowable stress is reduced for low elemental index structure. The modified design method tends to adapt to the lager section area or section modulus of important members of less elemental index structures, in order to complement the insufficiency of redundancy of structure. In order to evaluate the effect of proposed design method from the view point of upgrading the probability of residual collapse load, two dimensions hazard map for falling gravels and fragility curve for each elemental character are produced, respectively. The probability of an elemental failure is calculated by using both the hazard curve for position of a member and the fragility curve for resistance of a member. Finally, it is found that the proposed method properly upgrading the residual collapse load for low elemental index structure.
  • 武澤 永純, 内田 太郎, 田村 圭司
    2010 年 62 巻 6 号 p. 15-23
    発行日: 2010/03/15
    公開日: 2014/02/01
    ジャーナル オープンアクセス
    Many structures, such as housing, building, bridges etc., were damaged by the Hyogo earthquake in 1995. At that time, it was tried to evaluate seismic resistance of Sabo dam. However, at that time, earthquake observation records for Sabo dam was not exist, so the adequate analysis of seismic resistance could not be carried out. While, recently, many seismic responses of Sabo dams were observed. Thus, we evaluated seismic resistance using two observation records (small and medium earthquakes). At first, we examined the applicability of seismic response analysis to evaluate seismic resistance of Sabo dam. Results showed that the seismic response analysis can explain seismic response characteristics of Sabo dam, although elastic coefficient of ground and damping factor of ground have to be fitted to observation record. Then, we examined effects of size of earthquake on values of these fitted parameters and showed that seismic response characteristics of the Sabo dam on the medium earthquake can be reenacted using parameters which were fitted from observation record of small earthquake. Based on these analyses, it can be thought that at least, the concrete gravity Sabo dam has enough seismic resistance with the earthquake that corresponds to 6 upper of JMA Seismic Intensity.
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