Tsunami Force Research Articles

Tsunami Modelling and Run-ups along Indian Coasts

Abstract The Earthquake of Mw 9.3 on Dec 26, 2004 in the Andaman Sumatra subduction zone in the eastern Indian Ocean and the 27th November 1945 M8.0-8.2 Makran earthquake in the western Indian Ocean triggered tsunami causing large scale damage. Though, great tsunamigenic earthquakes are rare from the Makran subduction zone, the possibility of one off event exceeding M 8.0 cannot be overlooked. The record of historical tsunami has not been well documented, as there is very little data available from these two subduction zones, though few reports on tsunami impact on the Indian coasts are available. The devastating impact of 2004 Indian Ocean tsunami has generated great interest amongst the scientific community and changed the perception of the hazard associated with tsunami in the region. Several researchers from different parts of the world have worked in understanding and quantifying the tsunami propagation and inundation due to the 2004 Tsunami. In this paper different questions on the propagation of tsunamis over ridges, island, along the east and west coast, tsunami forces on different beaches and also the effect of varying bathymetry in the Indian Ocean have been discussed in the form of case studies.

Experimentally validated numerical models to assess tsunami hydrodynamic force on an elevated structure

Recently, the North American and Japanese authorities began combining the tsunami forces with other loads in their structural design guidelines. Nonetheless, due to the infrequent nature of tsunamis, the provisions may benefit from complementary insights on the qualitative and quantitative characterization of the extreme phenomena and their interaction with coastal structures. The goal of this paper is to explore reliable and relatively accessible computational techniques to determine pressures and forces due to tsunami-like waves on elevated structures. Hydrodynamic flow quantities are simulated for the tsunami-like waves using an Eulerian scheme (Shallow Water equations solved by the Finite Volume method), a Lagrangian scheme (Navier–Stokes equations solved by the Smoothed Particle Hydrodynamics method), and a coupled Eulerian Lagrangian modeling approach. The numerical solutions are validated against experimental data acquired from an experimental campaign performed at the large wave flume of the Hinsdale Wave Research Laboratory, Oregon State University. The correlations between the experimental data and the numerical solutions highlight the advantages and disadvantages of the simulation techniques used, contributing to increase the confidence levels in their use in determining tsunami forces for use in structural assessments and design.

Inelastic Displacement Ratios for SDOF Structures Subjected to Earthquake-tsunami Loadings

ABSTRACT This study investigates the inelastic displacement of structures subjected to earthquake-tsunami loadings. The relative intensity is defined as the ratio of the tsunami force per unit mass to the S a of the corresponding ground motion. The effects of the hysteretic model, soil condition, post-yield stiffness, damping, and relative intensity on the inelastic displacement ratios are investigated. The results show that, compared to earthquakes alone, earthquake-tsunami loadings can enlarge the inelastic displacement ratio demands, especially for higher relative intensities. A predictive model is developed by considering several parameters, which may be used in the framework of performance-based seismic design.

Catatan tentang Perencanaan Tembok Laut untuk Mitigasi Bencana Tsunami

Many coastal structures or structures in coastal areas were destroyed by a tsunami attack. Such destructions were due primarily to the fact that such structures were not designed to withstand a tsunami. Those which were designed to withstand tsunami force may also have been destroyed due to some damaging factors which were not included in the design. The damage of the coastal structures is one of the important factors that have caused casualties. Especially, when the destroyed structures were originally aimed to mitigate the area against tsunami, they may cause higher fatalities. Examples of such structures are sea walls in many parts of Japan which were destroyed by the 2011 tsunami. This paper discusses the important factors relevant to the damage of seawall as tsunami mitigation structure such as impact force due to tsunami front, hydrostatic force, and hydrodynamic force, debris force and scour due tsunami. The study was carried out based on literature about the damages of seawall as tsunami protection structures and laboratory experiment reports. The destructions to the structures were divided into three classifications namely instantaneous direct destruction due to impact and drag forces, slowly direct destruction due to drag force, and slowly indirect destruction due to scour. Finally, important aspects to be considered in the design of seawall as tsunamis protection were proposed.

Dynamic evaluation of jack-up platform structure under wave, wind, earthquake and tsunami loads

Nowadays, the demand for using jack-up platforms to carry out a large percentage of deep-water oil and gas exploration is steadily increasing. The response of jack-up platforms to the severe dynamic loads that may be encountered during the structure life is not examined enough. Therefore, this study attempts to investigate the response of jack-up platforms performance under the effect of dynamic loads due to wave, wind, earthquake and tsunami forces using the finite element method for two models with the lowest and highest hull elevations. The jack-up platform is located in the Gulf of Mexico. Earthquake accelerations are applied to the model in high and moderate seismic levels. In addition, tsunami waves are applied to the platform in three different directions at 0°, 45° and 90°. This study utilised Airy's linear wave approach to assess the surface elevations and wave kinematics. The reference wind velocity is 10 knots at 10 m over the mean water level. Results indicate that the dynamic response of the structure is affected by the height of the platform and by the increase of the platform hull elevation. The combination of the El-Centro earthquake, dead and live loads provides the major impact on the platform at the lowest (70 m) and highest (85 m) hull elevations. The comparison of all result proves that the jack-up platform hull under high earthquake intensity and tsunami waves with 45° has experienced maximum deformation. Moreover, raising the deck will increase the response of the dynamic load and displacements but will negatively affect the platform.

Experimental investigation of tsunami bore-induced forces and pressures on skewed box section bridges

Tsunamis in Indonesia (2004) and Japan (2011) severely affected communities bordering the Indian Ocean and Japan's east coast. Despite the plausible findings arising from the available studies, the research on the impact of tsunami bore forces applied to bridges of different designs is limited. This is because the estimation methods for tsunami-induced loads presented in the literature have mainly been developed for buildings and require careful adaptation to apply to bridges. The main focus of the present study is to experimentally examine the interaction between a tsunami bore and a box section bridge with different orientations to the direction of the incoming bore, bore strengths, and deck clearances. The experiments were conducted in a 15-m-long, 1.2-m-wide, and 1.2-m-deep wave flume. The forces and pressures applied to the bridge, the bore heights, and the velocities were measured. It was found that the skewed bridge deck is subjected to additional force and moment components, namely the cross-stream force (Fy) and the rolling and yawing moments (Mx and Mz). These components are non-existent for the unskewed bridge deck. Based on the experimental results, equations were proposed for estimating tsunami forces for a box section bridge deck.

Planning of the foundation a three-story building constructed on potential liquefaction area in Air Tawar Estuary of Padang City

The earthquake has become one of the most lethal problems in Indonesia, especially across the ring of the fire zone. On September 30th, 2009, an earthquake with a magnitude of 7.6 SR occurred, triggering tsunami and liquefaction. The liquefaction potential and tsunami forces need to be mitigated when an earthquake happens to reduce the risk. This study designs the building foundation that can endure the loads from an earthquake, tsunami, and liquefaction in the Air Tawar estuary of Padang City. The soil profile and liquefaction potential can be identified with CPT (Cone Penetration Test) data. After identifying the liquefaction potential, the upper structure was designed to consider the earthquake load and tsunami waves according to FEMA P-464 (2012). Afterward, design the foundation dimensions based on the ultimate load from the upper structure, wherein the amount of the settlement should be smaller than the tolerable soil settlement. The method used in the paper is taking the CPT data in the Air Tawar Estuary. After analyzing the liquefaction potential, making an upper structure design with ETABS 2016, recapitulate the maximum joint reaction to design the foundation that can withstand the ultimate load, and calculate the amount of soil settlement. Thus the design of the upper structure and lower structure take into account liquefaction. The amount of soil settlement obtained in the building design is still within the tolerance range of 9.79 mm, where the maximum limit of reduction is 32m.

Mitigation of tsunami bore impact on a vertical wall behind a barrier

Since tsunamis pose a threat to many coastal areas, the mitigation of tsunami forces is important in saving lives and reducing damage when a tsunami comes. Barriers are generally constructed to protect coasts from extreme waves including tsunamis. Although extensive research has been conducted to investigate tsunami forces on coastal structures, the effectiveness of defensive structures such as barriers, seawalls and embankments in mitigating these forces has not been studied thoroughly. This paper presents a series of physical experiments to investigate the effectiveness of barriers in reducing tsunami bore impact (and associated pressures) on a vertical wall. While horizontal forces and overturning moments on the wall can be significantly reduced if the barrier is high enough, low barriers can lead to larger horizontal forces and overturning moments than if the barrier were absent. Predictive equations are proposed for reduction ratios of horizontal forces and overturning moments, as well as other methods to estimate horizontal forces.

Physical assessment of wave forces on bridge girder impacted by potential tsunami hazard

ABSTRACT Bridges are one of the most susceptible structural elements that can be viciously impacted by tsunami disaster. During the latest few tsunami hazards, a number of bridges were affected severely due to the lack of proper incorporation of tsunami forces in design guidelines. Therefore, it becomes imperative to evaluate the stability of bridges through the analysis of tsunami-induced forces on bridge structures. In the present study, laboratory experiments were carried out to quantify the exerted tsunami forces on girder model. Broken waves along with unbroken waves were considered for the analysis purpose. The maximum horizontal forces were larger for the broken waves than the unbroken waves. Results showed that the initial impact forces were larger than the hydrodynamic forces for broken waves whereas the opposite was true for unbroken waves. Measured forces on girder model, located in higher position, were larger and increased with increasing wave height. Lower girder position showed better performance than higher girder position regardless of wave height. One predictive formula was proposed to estimate the horizontal wave pressure on the seaward side of girder using as input the wave height and girder height. The normalized wave pressure increased as tsunami wave height increased.

TINJAUAN GAYA TSUNAMI PADA JEMBATAN KRUENG RABA

Aceh Province is located in one of the earth's fault lines in Indonesia, which is an area prone to earthquakes and the potential for a tsunami disaster. Therefore, any planning of structures located on the coast must consider the potential for a tsunami to obtain a strong structure to withstand the forces affected by the tsunami. During the 2004 tsunami, many bridges were carried away by the tsunami. Both bridges made of concrete, as well as steel frame bridges, such as the Krueng Raba steel frame bridge, Lhoknga, the Krueng No bridge, the Meunasah Kulam bridge, and several other bridges. This study aims to analyze and calculate the force and load effects of the tsunami on the structure of one of these bridges, namely the Krueng Raba steel frame bridge, Lhoknga. The force and load of the tsunami effect (Ts) will be analyzed by adopting the Guidelines for Design of Structures for Vertical Evacuation from Tsunamis, 2012, namely: (1) hydrostatic force; (2) buoyant forces; (3) hydrodynamic forces; (4) impulsive forces; (5) debris impact forces; (6) debris damming forces; (7) lift force; and (8) additional gravity load from water retained on the bridge floor. From the results of this study, it is shown that each of the tsunami forces acting on the crew-raba Lhoknga bridge at the minimum tsunami height variable, 11 meters, which is the initial height of the tsunami touching the bridge's superstructure are: 94.866 KN hydrodynamic force; 142,299 KN thrust; 133,810 KN debris impact force; 14,244 KN debris dam force, and 34,018 KN lift force. Meanwhile, the maximum tsunami height variable, 25 meters, is 24634.934 KN hydrodynamic force; 36952,400 KN thrust; 720,591 KN collision force; 3698,939 KN debris blocking force; and 986,519 KN lift styles. The results of the analysis using computational methods, by inputting the magnitude of the tsunami forces to the bridge model, it can be seen that the ability of the Krueng Raba, Lhoknga steel frame bridge to withstand the forces and loads caused by the tsunami only up to a height of 14 meters.

Masonry structures subjected to tsunami loads: Modeling issues and application to a case study

Tsunamis are among the most dangerous natural disasters for coastal areas experiencing tsunami hazard. One of the major concerns in the assessment of strategies for the risk mitigation is to estimate vulnerability of structures and infrastructures. However, reliable approaches for the evaluation of the structural capacity under tsunami loads are nowadays not always available for all the types of structures, especially masonry. On this aim, the paper deals with the modeling issues of 3D masonry structures subjected to tsunami loads and the effect on the structural behavior of different modeling approaches. First, a brief state of the art on the available studies is presented regarding the evaluation of tsunami forces on buildings and the studies carried out on the determination of structural capacity.Then, an advanced structural analysis software based on the Finite Element Method (FEM) is used to analyze the influence of parameters such as load type, masonry type and interaction properties type. Finally, an application on a typical two-storey masonry structure subjected to tsunami load according to the actual codes is presented and discussed, providing recommendations on the assumptions to be made for the definition of a reliable numerical model.The findings of the numerical simulations revealed that the structural response is strongly influenced by the modeling approach defined for the masonry walls in terms of interaction properties and the type of connection between orthogonal walls. Moreover, it was observed that, as for the case of seismic analysis, when local behavior governs the failure, lower structural capacity is obtained, while in the case of global behavior governing the failure, higher structural performances are provided.

Study on anti-tsunami optimization design of bridge pier: A new type bridge pier

The surface of the bridge pier is divided into upstream surface and downstream surface. The tsunami force characteristics and generation mechanisms for regular piers, i.e. square, circular and diamond piers, as well as pressure distribution and flow field around piers are discussed. Results show that the upstream surface of the diamond pier is most beneficial to reduce water blocking effect and to lower runup at the stagnation point, which ultimately reduces the tsunami force on the upstream surface before tsunami bore reaches the downstream surface. Downstream surface of the circular pier is most beneficial for two branches of tsunami bore flow back and run up on the downstream surface, which generates larger negative tsunami force on downstream surface larger earlier, and ultimately makes entire tsunami force on circular pier smaller after tsunami bore reaches the downstream surface. Based on which, a new type pier is invented by combining the upstream surface of diamond pier and downstream surface of circular pier together. Further, the mitigation effect of new type pier is validated and the mitigation mechanism is explored. Among circular pier and the three piers of new type, N60 is proven to the best to reduce tsunami force.

Experimental investigations of tsunami loading on internal wall of a building with various openings and wall configurations

Previous studies demonstrated an introduction of building opening could decrease the tsunami loads on the external wall. However, tsunami waves flowing through the building opening could induce loads on the interior part. This study presented an experimental investigation of tsunami flow through a real building with opening. Three nominal wave conditions with wave overtopping and non-overtopping cases were tested to study its effects in combination with each configuration with opening sizes ranging from 15% to 35%. The tsunami-like wave pressures on an internal wall with varying locations were measured in the experiment. Finally, methodologies for estimating tsunami force on an internal wall were proposed. Results showed that the front opening size and the location of an internal wall significantly influenced the induced loads on the internal wall's front face. A new measure of the wake clearance angle was developed to best quantify each configuration. The maximum front face force on an internal wall manifested a linear trend with an increasing wake clearance angle up to a maximum force of approximately 4.8 times the hydrostatic force. Conversely, a dimensionless factor of front to back opening ratio was proposed, considering the effect of both front and back openings to determine the force on an internal wall's back face, where an increase in the front to back ratio tended to increase the maximum back face force in a non-linear trend.

Response of Coastal Structures against Tsunami Forces and Its Variation When Impact Load is Applied on Exterior and Interior Columns under Different Soil Conditions

The catastrophic tsunamis generated during Tohoku, Japan (2011), Indonesia (2004) and Alaska (1964) earthquakes caused severe damage to life and coastal structures and warned the coastal community on prepared and constructing safe structures against such events. Since most of the tsunamis are triggered by undersea earthquakes , it is necessary to establish analytical methods for obtaining the variation of response parameters when tsunami waves hit exterior and interior columns when the similar structure rests on different soils. In this paper, a G+9 storey coastal structure is chosen for the analysis and the response parameters like bending moments, shear forces, time periods, displacements and base shears are worked out considering with and without the effect of Soil Structure Interaction (SSI). From the results it is observed that the multi storied structure is more vulnerable when it rests on loose soil compared to when it rests on stiff soil or hard rock and when it is fixed at the base.

Numerical investigation on tsunami wave mitigation on forest sloping beach

An explicit one-dimensional model based on the shallow water equations (SWEs) was established in this work to simulate tsunami wave propagation on a vegetated beach. This model adopted the finite-volume method (FVM) for maintaining the mass balance of these equations. The resistance force caused by vegetation was taken into account as a source term in the momentum equation. The Harten–Lax–van Leer (HLL) approximate Riemann solver was applied to evaluate the interface fluxes for tracing the wet/dry transition boundary. This proposed model was used to simulate solitary wave run-up and long-periodic wave propagation on a sloping beach. The calibration process suitably compared the calculated results with the measured data. The tsunami waves were also simulated to discuss the water depth, tsunami force, as well as the current speed in absence of and in presence of forest domain. The results indicated that forest growth at the beach reduced wave energy loss caused by tsunamis. A series of sensitivity analyses were conducted with respect to variable parameters (such as vegetation densities, wave heights, wave periods, bed resistance, and beach slopes) to identify important influences on mitigating tsunami damage on coastal forest beach.

Fragility functions for a reinforced concrete structure subjected to earthquake and tsunami in sequence

Many coastal regions lying on subduction zones are likely to experience the catastrophic effects of cascading earthquake and tsunami observed in recent events, e.g., 2011 Tohoku Earthquake and Tsunami. The influence of earthquake on the response of the structure to tsunami is difficult to quantify through damage observations from past events, since they only provide information on the combined effects of both perils. Hence, the use of analytical methodologies is fundamental. This paper investigates the response of a reinforced concrete frame subjected to realistic ground motion and tsunami inundation time histories that have been simulated considering a seismic source representative of the M9 2011 Tohoku earthquake event. The structure is analysed via nonlinear time-history analyses under (a) tsunami inundation only and (b) earthquake ground motion and tsunami inundation in sequence. Comparison of these analyses shows that there is a small impact of the preceding earthquake ground shaking on the tsunami fragility. The fragility curves constructed for the cascading hazards show less than 15% reduction in the median estimate of tsunami capacity compared to the fragility functions for tsunami only. This outcome reflects the fundamentally different response of the structure to the two perils: while the ground motion response of the structure is governed by its strength, ductility and stiffness, the tsunami performance of the structure is dominated by its strength. It is found that the ground shaking influences the tsunami displacement response of the considered structure due to the stiffness degradation induced in the ground motion cyclic response, but this effect decreases with increasing tsunami force.

Investigation of Tsunami Hydrodynamic Loads Acting on A Slab Bridge

An analytical approach based on numerical simulation is performed to investigate the mechanism of a slab bridge damages caused by tsunami. This slab bridge was constructed in a parallel bridge structure with the adjacent highway bridge. Tohoku earthquake tsunami flooded and washed away this slab bridge. The CADMAS-Surf numerical model was used to determine the dynamic loads acting on the slab bridge subjected to a bore type tsunami. A series of hydraulic experiments were conducted, and the results were compared to the results obtained from numerical simulation. Numerical results showed good agreement with experimental ones in terms of water surface elevation, wave pressure and force. The validated numerical model was applied to the prototype scale of slab bridge that had 3D geometry. Simulation results showed that the tsunami flow fully overtopped the slab. The horizontal force was relatively smaller than the uplift force, however the total uplift force exceeded the dead load of the slab. This result meant that the tsunami flow uplifted the slab and washed the slab downstream. The effect of the existence of adjacent highway bridge on the characteristic of tsunami inundation and forces acting on the slab bridge is also discussed.

Tsunami force estimation for beachfront traditional buildings with elevated floor slab in Malaysia

ABSTRACTTsunamis have received increased worldwide awareness since their unprecedented occurrences in the Indian Ocean and Tohoku in 2004 and 2011, respectively. In this study, the impact of tsunami on a building with an elevated floor slab was investigated at a reduced scale of 1:100 and compared with that of a slab-on-grade building. Three nominal wave conditions were tested to study the effects of tsunamis on each building model type. The tsunami-like wave forces and pressures on the building model were measured in the experiment. Results showed that the existence of an elevated floor slab significantly reduced the horizontal force on building upon the impingement of the initial wave. When the nominal wave height was higher than the building model height, the wave-induced horizontal force was overestimated by the Japanese design method. The maximum vertical resultant force on the elevated building model manifested a linear trend with increasing wave-exposed height up to a maximum force of approximately 3.8 N when the building model was fully submerged. This study also presented a proposed methodology for tsunami force estimation of the front and back faces of a building with an elevated floor slab.

Experimental simulation of tsunami surge and its interaction with coastal structure

Following the tsunamis occurred in Japan (2011) and Indian Ocean (2004), investigating interaction between coastal structures and tsunamis became necessary. Although several attempts have been made to estimate the tsunami forces acting on the coastal structures, there still remain inconsistencies among the published design guidelines. This research includes an experimental study to investigate the interaction between a tsunami surge and a coastal structure. The tsunami surge was generated using a novel dam-break system, capable of generating higher tsunami surges than the previous simulations. The relations between surge velocity, surge depth, and surge-induced pressure on the structure were presented. In the surge-induced pressure–time histories, there were three identified force components, namely, run-up, impulsive and quasi-steady hydrodynamics. Furthermore, this research presents a comparison made between the experimental results and existing tsunami guidelines. The ratio of impulsive force to hydrodynamic force was found around 2.4 for each tsunami surge. The hydrodynamic forces were found to be higher with respect to those determined using the ‘Federal Emergency Management Agency’ FEMA P646 guidelines, whereas they were approximately in agreement with those obtained by FEMA 55. Moreover, the results showed that the ‘Structural Design Method of Building for Tsunami Resistance’ overestimates the impulsive force.

Tsunami Risk in Japanese Coast and Recent Mitigation Technique using Removable Breakwater

In this paper, the tsunami risk in the west coast of Japan is introduced. Especially, the inundation risk in Osaka city is discussed. Three visor gates are installed at the mouths of main rivers in the city. The gates are mainly installed to prevent the storm surge due to typhoons but they are effective to reduce the tsunami height at the mouth point of river. Though the gates are necessary to prevent the tsunami inundation, the stability against tsunami forces is not enough because the gates were constructed in 1960s. Therefore, the removable breakwater is now under consideration to reduce the tsunami force. The hydraulic experiment was carried out in order to investigate the applicability of the removable breakwater. The reduction rate by the breakwater was derived from the experiment.