Tsunami Force Research Articles

Comparison of Classical Tsunami Resistance Systems in RC Structure

The seismic performance response of reinforced concrete (RC) structures subjected to simultaneous Tsunami force and earthquake excitation is evaluated. Several classical resistance systems, such as bare frame, shear wall, steel brace, and dual systems, are employed in an eight-story RC building to resist these forces. The economic design of the systems is also considered. To satisfy the economic aspects, RC structures should utilize the minimum columns and beam size. Results show that the shear wall and bare frame systems failed because of their uneconomic properties compared with other resistance systems. On the basis of engineering and economical views, the dual system is accepted and commended among classical lateral resistance systems.

Stability of non-vertical waterfront retaining wall supporting inclined backfill under earthquake and tsunami

The stability analysis has been carried out for generalized non-vertical waterfront retaining wall supporting inclined backfill under combined action of earthquake and tsunami forces. Closed-form design solutions for factor of safety against sliding have been obtained using limit equilibrium method. For estimating seismic passive earth pressure and the wall inertia force, the pseudo-dynamic approach has been adopted. Different methods available in literature are used to estimate tsunami wave pressure and hydrodynamic pressure. It has been observed that parameters like seismic accelerations in both horizontal and vertical directions, time period, soil and wall friction angles, wall batter, ground inclination, pore pressure ratio, tsunami wave height have significant effect on the sliding stability of the waterfront retaining wall under combined action of earthquake and tsunami. Comparison of results with available results in literature for special case of vertical waterfront retaining wall supporting horizontal backfill has indicated a very good agreement. It is expected that the proposed design charts and tables presented in this paper will be helpful for the design engineers to design waterfront retaining wall against sliding mode of failure under combined action of earthquake and tsunami.

Performance of Bridge Girder with Perforations under Tsunami Wave Loading

Tsunami disaster poses a great threat to coastal infrastructures. Bridges without adequate provisions for earthquake and tsunami loading is generally vulnerable to tsunami attack. During the last two disastrous tsunami event (i.e. Indian Ocean and Japan Tsunami) a number of bridges were observed subsequent damages by tsunami waves. In this study, laboratory experiments were conducted to study the effects of perforations in bridge girder in force reduction. Results showed that significant amount of forces were reduced using perforations in girder. Approximately 10% to 18% force reductions were achieved by using about 16% perforations in bridge girder. Subsequent amount of force reductions revealed that perforations in girder are effective in reducing tsunami forces as perforations in girder let water to be passed through. Thus, less bridge damages are expected with the presence of perforations in girder during tsunami period. Keywords—Bridge, force, girder, perforation, tsunami, wave.

建物ビルに作用する津波力に及ぼす建物形状および津波作用方向の影響に関する研究

Tsunami evacuation buildings are considered as effective countermeasures against tsunami. The openings of buildings may reduce the tsunami force acting them, however, its effect may be influenced by inner configuration of buildings. Moreover, a tsunami direction is another important factor for tsunami forces. In this study, based on hydraulic experiments and numerical calculations, their effects on tsunami forces are investigated. The tsunami force after impact is found to be estimated by hydraulic pressure in different ways according to the size of openings, and for the buildings with large openings, it is confirmed to be considered forces acting on inner walls. In investigation of tsunami direction, the force due to obliquely incident tsunami can be determined by the tsunami acting area and effect of parry the tsunami.

陸上構造物に働く津波波力の時系列評価に関する研究

The tsunami force acting on a land structure generated by the run-up tsunami was generally evaluated from the maximum inundation depth of the passing run-up tsunami, which is estimated on the supposition that the structure does not exist. However, the maximum depth does not always accompany the maximum tsunami force, e.g., in the case that the inundation depth gradually increase. Therefore the time series evaluation of the tsunami force not with the maximum depth is required. In this study, the physical model experiment to examine the tsunami forces acting on a wall structure in time series was conducted. It is found that the time series of the tsunami force was expressed with the inundation depth and the velocity of the passing tsunami at the same moment.

Experimental study on tsunami risk reduction on coastal building fronted by sea wall.

This experimental study was conducted to idealize the efficacy of sea wall in controlling the tsunami forces on onshore structures. Different types of sea walls were placed in front of the building model. The tsunami forces and the wave heights were measured with and without the sea wall conditions. Types of sea wall, wall height, and wall positions were varied simultaneously to quantify the force reductions. Maximum of 41% forces was reduced by higher sea wall, positioned closer proximity to the model whereas this reduction was about 27% when the wall height was half of the high wall. Experimental investigations revealed that wall with adequate height and placed closer to the structures enables a satisfactory predictor of the force reduction on onshore structures. Another set of tests were performed with perforated wall placing near the building model. Less construction cost makes the provision of perforated sea wall interesting. The overall results showed that the efficacy of perforated wall is almost similar to solid wall. Hence, it can be efficiently used instead of solid wall. Moreover, overtopped water that is stuck behind the wall is readily gone back to the sea through perforations releasing additional forces on the nearby structures.

THREE DIMENSIONAL TWO-PHASE FLOW ANALYSIS OF TSUNAMI PRESSURES AND FORCES ACTING ON A BUILDING WITH OPENINGS

THREE DIMENSIONAL TWO-PHASE FLOW ANALYSIS OF TSUNAMI PRESSURES AND FORCES ACTING ON A BUILDING WITH OPENINGS

防潮堤背後の建物に作用する津波力に関する実験的検討

防潮堤背後の建物に作用する津波力に関する実験的検討

浮沈式大型津波シェルターに作用する流体力低減とその運動特性

After the Tohoku earthquake tsunami in Japan, many evacuating options from a huge tsunami, e.g. tsunami tower, large building, moving onto hill, stronger breakwater, underground shelter and small lifeboat, have been proposed in recent years. In this paper, the authors have proposed and developed one kind of a large-sized tsunami shelter with mooring that is capable of accommodating at least one hundred people or more to evacuate from a run-up tsunami. The optimization for the shape of the tsunami shelter was also examined using Particle method, Smoothed Particle Hydrodynamics. The tsunami force acting on the desired shape was compared with that on the basic shape, e.g. a rectangular shape. The proposed tsunami shelter could be one of useful options for evacuating from a huge tsunami attacking near coastal area.

CADMAS-SURF/3Dを用いた防潮堤背後の建屋に作用する津波力の検討

CADMAS-SURF/3Dを用いた防潮堤背後の建屋に作用する津波力の検討

VOF法を用いた東北地方太平洋沖地震津波の再現と建物の転倒メカニズムの解明

Some well-engineered reinforced concrete buildings collapsed due to the tsunami in the Tohoku-Pacific Coast Earthquake on March 11th, 2011. Understanding the tsunami forces and damage mechanisms of these buildings has become an urgent issue that demands prompt action from the tsunami resistant building design. In this study, a tsunami simulation using VOF method has been conducted to reproduce the tsunami in Onagawa city, Miyagi prefecture. Calculated tsunami elevations and inundation on shore showed good agreement with the recorded results. Tsunami loads acting on a collapsed building in the Onagawa port area were also discussed under considering the damaged situations of the building foundation and its piles in order to clarify the falling mechanism of the building.

津波形状がコンクリート鉄道橋りょうに働く流体力に及ぼす影響

Some bridges were failed by Tsunami at Great East Japan Earthquake. One of the reasons of the accident was the lack of useful method for evaluating the action of the bridges subjected to Tsunami. This means that there was no verification of the bridges caused by Tsunami. The authors have conducted experiments and numerical analysis in order to understand the Tsunami force applied to the prestressed concrete viaducts. This paper focused on the railway bridges having a large depth of beam compared with the road bridges, and also focused on the shape of Tsunami by controlling the wave period.

Experimental Study on Real-Time Tsunami Protection Structures

AbstractTwo kinds of new tsunami protection structures have been developed: a flap-gate breakwater named FLAPGATE, and a flap-gate seawall named No Energy and no Operation Rising Seawall (NEORISE). These structures are similar to the barrier employed in the Modulo Sperimentale Elettromeccanico (MOSE) Project in Venice. FLAPGATE and NEORISE can rise up and form a continuous wall by using tsunami forces in addition to buoyancy. Using the tsunami forces allows these structures to provide real-time tsunami protection. In this study, the capability and availability of these structures for real-time protection against tsunamis was examined and verified by a series of hydraulic model experiments. It was found that FLAPGATE and NEORISE rise up rapidly against tsunami wave attacks and have the capability of providing real-time tsunami protection.

Building Damage and Business Continuity Management in the Event of Natural Hazards: Case Study of the 2004 Tsunami in Sri Lanka

The Sumatra Earthquake and Indian Ocean Tsunami event on the 26 December 2004 has provided a unique and valuable opportunity to evaluate the performance of various structures, facilities and lifeline systems during the tsunami wave attacks. There are especially meaningful observations concerning the structural changes due to the tsunami forces, which open up a wide area of research to develop the mitigation procedure. The business restoration process of business companies in terms of buildings, facilities and lifelines have shown greater research interest. In this study, we investigated the restoration process of business sectors in East and South coastal region in Sri Lanka after the 2004 Indian Ocean Tsunami. A field survey was conducted in East and South coast of Sri Lanka, in order to study the affecting parameters to damage assessment in the restoration process of the business companies. The results of the questionnaire-based field survey are then compared with the statistical analysis results. Finally, the factors affecting the restoration process after the tsunami are identified. As a main conclusion, financial support could be the most important reason for delays in restoration. Moreover, it has been observed that the tsunami inundation level of higher than one meter may have had more effect concerning the damage to the structures and requires additional time for restoration than other areas.

2-PHASE FLOW ANALYSIS OF TSUNAMI FORCES ACTING ON BRIDGE STRUCTURES

The understanding of interactions between tsunami and structure is very important to consider tsunami countermeasures, though the interaction includes complex phenomena. For example, two-phase flow can be found when the tsunami hits a bridge structure with entrapping air beneath it. The air sometimes affects forces acting on the bridge, and the effect of entrapped air has to be taken into account to investigate the tsunami forces. This study is intended to investigate the tsunami forces acting on the bridge with using two-phase flow model. Three bridge models were tested in this study, where the slab bridge without girders beneath it, the slab with two girders, and the slab with three girders. The simulation results were compared with the results obtained from one-phase flow simulation, and also verified with experimental ones. This study revealed that, in the investigation of tsunami forces acting on the slab bridge without girder, the results of both one-phase simulation and two-phase one agree well with experimental results. In the simulation on the slab bridge with girders, the results from two-phase simulation correlate better with experimental results in comparison with the results from one-phase simulation. Furthermore, the entrapped air between girders highly affects the characteristic of uplift force.

津波作用下における浮沈式大型津波シェルターの運動と流体力に関する研究

In this paper, a floating tsunami shelter with mooring has been proposed and developed. The shelter is capable of accommodating at least three hundred people to evacuate from run-up tsunami. The floating tsunami shelter can be lifted by buoyancy when tsunami strikes on it. To investigate fluid force on the floating tsunami shelter, impact pressure and its motions such as heave, surge and pitch due to a run-up tsunami, some experiments were conducted and five tsunami shelters with different configurations was examined. The floating tsunami shelter, the type AF and the type B can reduce the tsunami force. The front shape in both types and the floating technique with mooring can avoid the tsunami force and strongly flow due to tsunami wave.

橋桁に作用する津波波力と津波流速の関係

Authors carried out hydraulic experiments to clarify the relationship between tsunami fluid force and tsunami velocity acting on a bridge deck subjected to surging breaker bores, plunging breaker bores, waves whose surface inclination is mild slope, and breaker bores with a bridge deck sets up under the still water level. Experimental results show the mechanism that the height of a bridge deck to a tsunami height with meanings of variation of surface inclination of waves causes a significant difference of wave velocity. In addition, it causes variation of Froude number, and leads differences of horizontal and vertical fluid forces acting on a bridge deck.

Three-Dimensional Tsunami Analysis for the Plot Plan of a Sodium-Cooled Fast Reactor Plant

As the practical evaluation method of the effect of tsunami on buildings, the formula of tsunami force has been used. However, it cannot be applied to complex geometry of buildings. In this study, to analyze the effect of tsunami on the buildings of sodium-cooled fast reactor plant more accurately, three-dimensional tsunami analysis was performed. In the analysis, VOF (Volume of Fluid) method was used to capture free surface of tsunami. At the beginning, it was confirmed that the tsunami experiment results was reproduced by VOF method accurately. Next, the three-dimensional tsunami analysis was performed with VOF method to evaluate the flow field around the buildings of the plant from the beginning of the tsunami until the backwash of that.

E212 Na冷却高速炉の建屋配置を対象とした3次元津波解析(OS8 軽水路・新型炉・原子力安全(5))

As the practical evaluation method of the effect of tsunami on buildings, the formula of tsunami force has been used However, it cannot be applied to complex geometry of buildings. In this study, to analyze the effect of tsunami on the buildings of sodium-cooled fast reactor plant more accurately, three-dimensional tsunami analysis was performed. In the analysis, VOF (Volume of Fluid) method was used to capture free surface of tsunami. At the beginning, it was confirmed that the tsunami experiment results was reproduced by VOF method accurately Next, the three-dimensional tsunami analysis was performed with VOF method to evaluate the flow field around the buildings of the plant from the beginning of the tsunami until the backwash of that.

津波避難ビル内部の空間形状に着目した作用津波力に関する実験的考察

津波避難ビル内部の空間形状に着目した作用津波力に関する実験的考察