Osamu Kiyomiya

Shear capacity enhancement of existing underground wall structures using postinstalled reinforcing bars

AbstractExisting underground structures constructed prior to the past few decades do not meet the present seismic design code; therefore, these structures do not have sufficient shear strength to withstand large-magnitude earthquakes and shear reinforcement is required. The reinforcement of these structures has not progressed due to the challenges associated with reinforcement methods. Thus, the authors propose a shear reinforcement method using postinstalled reinforcing bars to solve the previously mentioned problems. This method involves the insertion of reinforcing bars with mortar into drilled holes in reinforced concrete walls to achieve a shear bearing capacity similar to that of preinstalled stirrups. To verify the effectiveness of the method, several loading experiments on reinforced concrete specimens using monotonic and cyclic loads were conducted. This method provided a loading capacity that was 80% larger than the capacity provided by the preinstalled stirrups. Furthermore, finite-element anal...

Source Parameter Estimation and Stochastic Ground Motion Simulation Based on Recorded Accelerograms in Northwestern Vietnam

Estimated source parameters, path characteristics, and site parameters are used to simulate earthquake shaking waveforms in Vietnam. We used recorded accelerograms and point-source stochastic methodologies and included in our analysis empirical relationships between the duration of ground motion, seismic moment, and magnitude, and also those between corner-frequency, high-cut-off frequency, and moment-magnitude derived from earthquakes recorded in Vietnam and adjacent regions. Local site effects were estimated using horizontal-to-vertical spectral ratio methods. Simulated times series are compared with observed accelerograms from the 5.3 Dienbien earthquake in 2001, the first strong earthquake event to be recorded in Vietnam. Our synthetic time series of strong ground motion agrees well with both the observed waveforms and the response spectra, but suggests that PGA values obtained using current Vietnam codes may underestimate probable accelerations by 10–30%.

New type flexible joint for the Osaka Port Yumeshima Tunnel Osamu Kiyomiya

This paper describes a newly invented flexible joint called Crown Seal Joint for the immersed tunnel at Osaka bay. Crown Seal Joint can absorb larger deformation between tunnel elements than conventional flexible joints. Crown Seal Joint mainly consists of a rubber block and flanges reinforced by plastic fibers. Basic performance of the joint was made clear by experimental and analytical tests in this study. From the experimental results, it was confirmed that Crown Seal Joint exhibits excellent performance to absorb design deformation and always keeps its neutral position at the joint. By FEM analysis, intolerable distortion is estimated in rubber material. It was also made clear that Crown Seal Joint reduces resulting stresses in the joint induced by earthquakes and differential settlement

FIELD EXPERIMENTAL PROJECT OF FLAP-GATE BREAKWATER FOR TSUNAMI AND STORM SURGE PROTECTION

A flap-gate breakwater for tsunami and storm surge protection was previously developed through hydraulic model experiments and numerical simulations. In this study, applicability of the flap-gate breakwater through a field experiment is shown. Although the field experiment is carrying out at Yaizu fishing port in Shizuoka prefecture, Japan, some technical investigations have been obtained. Feasibility of maintenance and characteristics of age deterioration and corrosion will be verified through continuous experiments to be conducted in the future.

Stability analysis of the effect of soil settlement on a cable-stayed bridge in the mekong river delta

Soil settlement has a significant influence on cable-stayed bridges, especially in the Mekong River Delta, where most sites exhibit poor geological conditions. In this paper, the Can Tho Bridge was used as a prototype; two numerical models were generated using the details of the geometry, materials, and loads of the actual bridge. One model was used to evaluate the construction stage, and the other was used for the operational (or service) stage. Displacements of the substructure were applied to both models to discover their effect on the cables, an essential part of a cable-stayed bridge. The results showed that vertical displacements have a major influence on the stability of a cable-stayed bridge during the service stage. In addition, rotational and horizontal settlement creates unexpected effects that can neutralize the most critical working conditions of cable systems. However, soil settlement does not play a significant role in the construction stage.

HYDRAULIC MODEL EXPERIMENTS ON SLIDING STABILITY OF CAISSON BREAKWATER WITH GROUND ANCHOR FOR REINFORCEMENT

The rise of sea levels and the increase of wave forces which has been caused by global warming will cause the failure of breakwaters. The ground anchor for reinforcement is proposed as an anti-sliding method of caisson breakwaters. In this study, we conducted hydraulic model experiments with a scale of 1 to 30 model in order to investigate the sliding stability of caisson breakwaters with the ground anchor for reinforcement against wave forces. The results show that the caisson breakwater with the ground anchor for reinforcement increases the sliding resistance and reduces the sliding distance, and the larger the initial tension of the anchor is, the more effective as an anti-sliding method.

SHAKING TABLE TEST ON DYNAMIC BEHAVIOR OF CAISSON TYPE QUAY WALL WITH GROUND ANCHOR FOR SEISMIC REINFORCEMENT

アンカーで耐震補強された岸壁の耐震性は数値解析などで確かめられてはいるが，実際の地震時挙動を確認した事例は少なく，アンカーによる耐震補強効果について十分には明らかにされていない．そこで，グラウンドアンカーによるケーソン式岸壁の耐震補強効果を明らかにすることを目的として，大型水中振動台による模型振動実験を実施した．その結果，ケーソン変位抑制時のアンカーおよび岸壁の動的挙動を明らかにするとともに，ケーソン式岸壁にアンカーを適用した場合の留意点を指摘した．さらに，本実験を対象として，ケーソンの滑動，転倒および支持力について安定計算を行った結果，耐震補強によるケーソン安定性向上への貢献度がケーソンの破壊モードに応じて異なることが明らかになった．

Seismic Resistance Assessment of Multi-span Continuous Bridge in Vietnam by Dynamic Response Analysis

The response of the bridge subjected to seismic excitation can be evaluated by dynamic response analysis method. Vietnam is located at moderate seismic area; however, the seismic design has been introduced to secure the essential and important bridges. In this study, a typical concrete girder bridge in Vietnam (multiple frames in the longitudinal direction) is used to seismic resistance evaluations. These evaluations are performed by performing nonlinear dynamic response analysis on FEA method. It is found that the stopper and the rubber gasket influence on response of the bridge during Level 1 and Level 2 earthquakes.

Application of Numerical Analysis and Model Experiment on Seismic Design of Large Steel Celltype Quay Wall

The construction of a high seismic resistant quay, MC-3 began in February 2008 at Minami-Honmoku Pier of Yokohama Port. The large steel celitype quay with 24.5m in diameter and 32m in height is designed in conformity with the new technical standard for port and harbor structures revised in April 2007. Deformation and damage of structures must be evaluated accurately, based on performance-based design introduced to the new standard. Two-and three-dimensional finite element analyses and model shake table tests are conducted in this study, to evaluate performance ofthe quay during L2 earthquake.

EVALUATION OF COLLISION ANALYSIS OF SHIP TO PILE TYPE FENDER

船舶の橋梁への衝突による両者の被害を最小限にするため橋梁下部工に緩衝工が設置される. 緩衝工の設計では衝突時の船舶と緩衝工の挙動や損傷度合を推定する必要がある. 本報告では二質点系モデルおよび動的有限要素法により衝突解析を行い, 船舶と杭式緩衝工の挙動と被害を推定する. また, 両解析手法の違いによる衝突解析結果の比較を行う. 本研究の解析結果から, 船首変位や杭頭変位については, 両者の解析結果間で比較的一致することが確かめられた. ただし, 質点系モデル解析は, 衝突時の全体的な挙動を評価する上で有効であるが, 被害状況については十分追跡できない. 一方, 有限要素解析は, 衝突時の船舶の損傷過程の追跡, 緩衝工の発生断面力の評価および衝突位置による挙動の差を把握する場合に有効であることが確認できた.