後, 水道施設耐震基準が改定され, 相当の大きな地震動を考慮することになったが, 大きな地震動に対する水管橋の動的挙動についてはほとんど報告されておらず, 動的解析の適用方法, 評価方法については十分に検討されていないのが実態である.
本論文では, 以前に設計・施工された2つの斜張形式水管橋の振動実験によって求められた固有振動特性 (振動数と振動モード) と減衰定数の結果と, その結果を踏まえて行った非線形動的解析の結果について報告するものである.

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On Jan. 17, 1995, a large and shallow earthquake (M=7.2, focal depth =14 km) occurred in Kobe and the surrounding area, resulting in a tremendous disaster. Nojima fault, one of the active faults of the Rokko Fault System that strikes NE-SW and is dominated by right-lateral offset, was activated in association with this earthquake, and is identified as a seismogenetic fault for the Kobe earthquake, although there must have been other seismogenetic fault activity to account for the severe damage in the Kobe area. Repeated activity of the Nojima Fault since ca. 20 ka BP is described by Mizuno et al. (1990).
The surface appearance of this earthquake fault can be traced for about 10 km on the west coast of the northern part of Awaji Island. This fault is characterized by right-lateral offset, up to 1.8 m, accompanied by veritcal displacement up to 1.3 m. The upthrown side is mostly the southeast side of the fault, indicating that this fault activity has been responsible for the formation of the hilly land of Awaji Island.
The fault plane dips steeply southeastward, indicating that this fault is a high-angle reverse fault. Clear striation upwards to the right, on the fault plane is a composite result of strike-and-dip slip movement. Only at Nashimoto is the northwestern side uplifted. The surface deformation appears as prominent overhanging fault scarps at most localities along the fault, cutting through the lower to middle Pleistocene Osaka Group. However, at Nashimoto, where the fault displaces unconsolidated alluvial sand and gravel, a flexural scarp was formed. In addition to the fault scarp, many secondary features related to this faulting have appeared, including en echelon cracks, a minor pull-apart basin, and tectonic bulges. These features were mapped in detail by several groups immediately after the earth-quake (e. g. Nakata et al., 1995; Lin et al., 1995; Awata et al., 1995; Ota et al., 1995). Furthermore, trenching work to understand the previous fault activity has been done. The recurrence interval is estimated to be ca. 800 years by Suzuki et al. (1995). The newly exposed fault scarp provides an opportunity for the study.of the fault retreat process which is described in a companion paper by Azuma et al. Coastal uplift, up to ca. 55 cm, also occurred on the upthrown side, .which suggests that eastern side (except at Nashimoto) was absolutely uplifted at the time of the 1995 earthquake.
Damage to houses on Awaji Island is rather localized only on or around the Nojima Fault. Old wooden houses with, heavy roof tiles on the fault were particularly severely damaged. However, damage to new houses built with light materials, or concrete houses was not so severe, even if they were located very close to the fault. Many houses collapsed at Toshima or Gunge, where the fault trace was rather unclear or not found at all. This may be caused by lithological factors, because these settlements are located on the coastal alluvial lowland.

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For the purpose of finding the factors of slope collapses from the characteristics of the distribution of them in the Rokko Mountains triggered by the 1995 Hyogo-ken Nanbu Earthquake, we have extracted some frequency characteristics from the seismograms and performed the morphometry and the frequency analysis of the microtremors. Then we have tried to set them in correspondence to the distribution of the slope collapses.
The results are as follows:
1) It is presumed that the maximum acceleration of the Hyogo-ken Nanbu Earthquake was about 300-400 gal in the Rokko Mountains and its predominant frequency was 1 Hz or less.
2) The principal shock has excelled in the direction perpendicularly intersecting with the principal axis of the Rokko Mountains. This may have affected the direction of the surfaces of slope collapses.
3) The distribution of the aftershocks corresponds well with that of the slope collapses. Therefore, it is possible that the distribution of breaking energy on the fault plane is refrected in that of the slope collapses.
4) It is possible that the difference in the degree of weathering between the Rokko granite and the Nunohiki granodiorite is refrected in the distribution of the slope collapses.
5) To take a wide view, the slope collapses have occurred frequently in the areas where the faults existed densely.
6) The slope collapses tend to occur frequently at the ground where the vibration of a frequency band of 6-7 Hz is easy to be amplified. Therefore, the earthquake motion did not produce resonance in the ground.
7) To take a local view, a correlation between the topographical factors-elevation, inclination and irregularity-and the distribution of the slope collapses is not found. However, in the areas in which slope collapses have occurred frequently, a rate of slope collapse area increases with inclination.
8) It is considered that slope collapses have occurred frequently in the areas which satisfied the above 3) -6) simultaneously.

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における建物被害の研究は, 自治体による建物被害調査データや建築研究所がGIS化したデータなどに基づいて行われており, ほとんどが甚大な被害を受けた神戸市以東の地域を対象としている. しかし, この地震ではこれ以外の地域でも大きな被害を受けており, より広域の地震被害を評価することは重要と考えられる. 筆者らは, これまでに明石市の建物被害データ基づいて構築したデータベースを用いて建物被害分析を行っている. 本研究では, 既往の研究報告がされている神戸市灘区の建物被害に基づいて構築された建物被害関数を用いて, 明石市の建物被害から地震動分布の逆推定を行った.

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Seismic performance of 3 to 6 story steel buildings are investigated based on the damage survey and PGV estimation during the 1995 Hyogo-ken Nanbu earthquake. Major findings are as follows. First, damage levels of exterior walls such as mortar walls and ALC panel walls are classified schematically and their correspondence to structural damage is investigated. The damage ratio functions, which indicate relationships between PGVs and damage ratios for damage levels of structure or exterior walls. From the comparison of damage ratio functions, the moderate structural damage is comparable to the complete loss of property value and the damage level of ALC panel walls is reduced by the improvement in seismic performance of steel structures by the amendment of the Building Standard Code in 1981.

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We determined the maximum slip vector on the surface fault associated with the Hyogoken Nanbu, western Japan, earthquake of January 17, 1995. The surface fault is dominantly strike slip with moderate to small amounts of vertical slip. A plane table map on a scale 1:100 was made at Hirabayashi, Awaji Island, where the maximum slip was observed. Using this map, directions and offsets of three artificial fault references were measured precisely. We successfully separated the two horizontal components of slip on the fault from these offset data, using a new method. The amount and direction of horizontal slip are 2.08^+0.08_-0.26m and 45.2°^+0.6_-6.5 (clockwise from the north), respectively, and the amount of vertical slip is 1.20±0.05m. The slip vector determined here, in conjunction with varying strike of the surface fault, may explain changes along strike in the nature of faulting (i. e., contractional on some segments and extensional on others).

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The Hyogoken-nanbu earthquake in 1995 has led to numereous slope failures both in Rokko mountain and Awaji island. The features of slope failures related to lateral faulting or horizontal acceleration by the earthquake are discussed, and their change by subsequent rainfall events are followed.
The earthquake has induced to the numerous slope failures at steep slope segments or near shoulders in dry state. The slip surfaces were shallow and plannar, suggesting that the failures were largely controlled by friction. The failed slopes were located almost at a particular site where the movement of fault or fault blocks made the landmass unstable. The situation is remarkable especially at east-faced slopes located at the northwest side of right-lateral faults, and at the east or north-faced slopes of the northeastern Rokko mountain.
An enlargement or renewed occurrence of slope failures by the subsequent rainfall events has occured in proportion to the number of slope failures due to the earthquake. The portions with intensive slope failures by the earthquake show also the subsequent enlargement and the renewed occurrence of the slope failures by the rainfall events. This means that the failures by the rain are supplementary to those by the earthquake, and also the tendency that they increase reciprocally to the number of the latter.

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本研究は, による宝塚市の建物被害データを用いて, 多角的観点から被害の特徴を検討し, 構造形式や建築年代などの建物特性を考慮した被害関数の構築を行ったものである. 具体的には, 震災直後に宝塚市が実施した固定資産台帳に基づく建物被害調査の結果を用いて, 構造形式・建築年代・地域分布等の観点から被害の特徴を検討した. さらに, 県内およびその周辺の強震記録と広域的な建物被害の関係より求められた地震動分布を用いて, 宝塚市の建物被害データによる構造形式・建築年代別の建物被害関数を構築した.

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では, 建物や地震動に関してこれまでにない豊富な情報が得られた. これまでの建物被害関数は, 過去の地震被害データに基づくもので精度の向上が必要であり, の建物被害データを取り入れることで, より精度の高い建物被害関数が構築できると考えられる. また, 建物被害関数を構築する際には地震動の面的な分布の推定が必要であり, 筆者らはこれまでに, 強震観測記録と低層建物の被害率から阪神地域の推定地震動分布を求めている. そこで本研究では, その推定地震動分布を, 西宮市が行った建物被害調査結果を用いて西宮市に関して再推定した結果の地震動分布と, 西宮市の建物被害調査結果より, 建築年代や構造などの建物特性を考慮した建物被害関数の構築を行った.

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についての強震記録は, 地域の地震動分布を求めるに充分なほどは得られていない. 本研究では, 神戸市の建物被害調査に基づくデータを用いて暫定的な建物被害関数を構築し, 構造・建築年代を考慮した地震動の再推定を行った. その結果, 建築年代ごとの建物分布の影響による推定誤差を減らすことができ, 精度の高い地震動を推定することができた. またこの地震動分布を用いて, 構造別・建築年代別の建物被害関数を構築した. これを用いて灘区全体における建物被害棟数を推定した結果, 実被害との誤差は平均で±1%であった. 以上の結果から, 本研究によって構築された建物被害関数は, の建物被害の状況をかなりの高精度で再現するものであり, 今後の被害推定等に役立つものと思われる.

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The Southern Hyogo Prefectural Earthquake (M=7.2, epicenter: 34.36°N, 135.0.2°E, depth =17.9km) occurred on January 17, 1995, and made the Nojima fault appear on the ground surface on Awaji Island. The Geographical Survey Institute surveyed the fault just after the earthquake on January 18-22 and February 13-17. The fault was a right-lateral fault with a reverse component. The maximum displacement measured on the ground along the fault was 1.7 meters in the horizontal (rightlateral) and 1.3 meters in the vertical direction in Nojima-Hirabayashi.
The detailed measurement of ground surface displacement around a fault has been only available in terms of the relative movement of one side of the fault against the other. The authors succeeded in measuring three dimensional displacement of 880 points around the Nojima fault by employing air photos taken before and after the earthquake.
The characteristics of the displacement are: l) on the west side of the fault, the maximum horizontal displacement is 3.4 meters and directed toward the east, but the amount and direction of the vertical displacement change in a complex manner; 2) the horizontal displacement on the east side is more than one meter and directed toward the south or southeast. In addition, large displacement can be found even in areas more than one kilometer from the fault line.
The displacement patterns around the fault are considered consistent with those caused by eastwest compression with eastward movement on the west side and southward movement on the east side:
The ground survey identified the southern end of the fault at Toshima. However, the horizontal displacement around the fault can be considered to show invisible continuation of the fault down to Tonouchi

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The number of recorded ground motion in the 1995 Hyogoken-Nanbu Earthquake was not large enough to estimate the detailed spatial distribution of ground motion. Yamaguchi and Yamazaki (1998) estimated the PGV distribution using the BRI's building damage data and the recorded strong indices. However the estimated PGV might be affected by the inventory characteristics of buildings in each district. Hence in this study, the PGV distribution was re-evaluated using the building damage data surveyed by Kobe City, in which structural type and construction period are provided. Using the re-evaluated PGV distribution, fragility curves considering detailed building information can be developed.

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After the Hyogoken-Nanbu earthquake on 17th January 1995, which brought about enormous damage to Hanshin area, many large span roof spaces were converted as temporary refuge spaces for numerous refugees. In this report the results of investigations, carried out by spatial structure researchers, of damage to large span roof structures of about four hundred and thirty school gymnasiums and public sports halls are summarized. Types of damage to large span roof structures are classified and distribution of damaged structures is shown. Special remarks are put on the damage to suspended non-structural elements, such as ceilings, lights and acoustic facilities.

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