Literature Review

Research Method: Literature Review

1.0

INTRODUCTION

There are several types of sea waves, which the force, speed and high of the waves are different (Table 1). Some of these waves are destructive to structures, and some are only minor waves which have no effect on structures. The force that induced by tsunami waves are much enormous and faster than other  waves. It doesn’t resemble the normal sea waves, because tsunami tsunami waves have a longer  wavelength, which generally consists of a series of waves with periods ranging from minutes to hours, with wave heights of tens of metres can be generated by large events.

WAVES

DESCRIPTION

TYPES 

A number of waves with different length.



Straight, long, powerful, and travel for great distance.



High waves with short wavelength and vertical eclipses.



Have powerful backwash



Dragging objects back to the sea.



Formed when there is a disturbance in between two masses of water with

Deep water 

Destructive

Internal

Kelvin

Shallow Water 

different density. 

Become turbulent and high waves when hit the shore.



Formed due to lack of the wind.



On Pacific Ocean sea.



High, wide, and warmer waves than the surrounding water.



In shallow waters at a depth less than 1/20 th of their wavelength.



Two types: Tidal.

o

Seismic / Tsunami.



Generated by intense wind in the sea.



It has low energy, but travel for a long distance, and break away from the

Surging (Wind-Driven)

o

shore. TABLE 1

Different type of ocean waves th

Source: Marine Insight, April 30 2011

Research Method: Literature Review

Tsunami waves are caused due to earthquakes occurred beneath the ocean. The speed of  the tsunami is extremely fast in open water, and then it will become increase in height significantly in shallow water, which causing dangerous and devastating effect to the shore it hits. Although the impact of tsunamis is limited to coastal areas, their destructive power can be enormous and they can affect entire ocean basins.

1.1

HISTORY OF TSUNAMI CASES

Throughout the history, several tsunami cases have been reported occurred in every parts of the world. Each time it occurred, it causes major losses to human lives and structures. Several  prevention and mitigation way have been produced to reduce the losses, but because of the devastating effect it brings, still major losses were reported. Some examples of the devastating effects of tsunami force when it occurred is shown  below in Table 1.2

LOCATION

DATE

CAUSES

EFFECTS

i. Sumatra, Indonesia

26

Earthquake with

December 

magnitude of 9.1 off the

2004

coast of Sumatera

50 m tsunami.

ii.

Several other countries affected

iii.

USD 10 Billion damages

iv.

23,000 people dead

i.

10 m high waves

ii.

18,000 people killed.

 North Pacific

11 March

Earthquake with

iii.

USD 235 Billion damages.

Coast, Japan

2011

magnitude of 9.0

iv.

 Nuclear emergency due to leaking on the nuclear   power plant

i.  Northern Chile

13 August

Series of two earthquake

ii.

1868

with magnitude of 8.5

iii.

21 m high waves. 25,000 deaths. USD 300 Million damages.

Table 1.2

Major tsunami occurrences and the effects.

Sources: Australian Geographic, March 16 th 2011

Research Method: Literature Review

Historical studies are important for future prevention method. These studies will give more data and knowledge in preparing engineers in designing a structure that can resists the tsunami loads. These studies also need to be done thoroughly so that the number of losses can be reduced in the future.

1.2

AIMS AND OBJECTIVES

The aims and objectives of these dissertations are 

To study and understand the waves force effects, the risk categories on structures, and the different failure modes on structures.



To summarize the way to quantify the force of tsunami affecting a structure and comparing the equations from other research that has been done.



To study in details the dynamic effects of the tsunami impact force on structure and the differences from static force.



To create a finite element modelling based on dynamic tsunami forces acting on structure.



To suggests way to strengthen the structure.

Research Method: Literature Review

2.0

LITERATURE REVIEW

As what have been described in the previous chapter, tsunami force causing very devastating effects on structure. According to history, billions of dollars were loss in one event of a tsunami attack. The total loss will also increase in re-building the structures again, and thus the importance of engineers needs to find a way for structure that can resists the tsunami force. Several factors can trigger the formation of tsunami waves. According to Federal Emergency Management Agency (FEMA), the factors that triggered tsunami are: 

Underwater Earthquakes.



Volcanic Eruption.



Submerged or aerial landslides.

According to history, majority of the tsunami was caused by the vertical displacement that occurred at the bottom of the ocean. Because of the displacement, it created a high speed over thousands of kilometre of tsunami waves (Palermo and Nistor, March 2008). But, to understand the forces that being induces by the tsunami, we need to understand the types of wave force and failure that will happen to structure under such loads. These types of  forces also were determined based on the location and types of the structure. Before the Chilean tsunami that occurred in 1960, dynamic pressure wasn’t taken into consideration when designing a structure to withstood tsunami attack. Dynamic pressure is more significant than static pressure in understanding the forces that being induced by the tsunami.

Figure 2.1

Japan Tsunami

Source: National Geographic, March 15 th 2011

Research Method: Literature Review

2.1

FORCE CATEGORY

The forces that induced by tsunami are categorised into several parameters. In defining the magnitude and application of tsunami-induced forces, these parameters are important to take into consideration (FEMA, 2008). 

Inundation depth.



Flow velocity.



Flow direction

And these parameters also depend on several other factors that are: 

Wave height.



Wave period.



Coastal topography.



Roughness of the coastal inland.

Categories of the forced that induced by tsunami are (Palermo and Nistor, March 2008):

2.1.1



Hydrostatic forces.



Buoyant forces.



Hydrodynamic forces.



Surge forces.



Impact forces.



Breaking wave forces.

Hydrostatic Forces

This force is generated by a slow moving wave acting perpendicular on a surface. This force is usually used on structure such as seawalls and dikes, but not being used for buildings. It is applied 1/3 from the base from pressure distribution, and this force is smaller than the drag and surge force in the case of broken tsunami waves. But, this force is important when coastal flooding from tsunami which is similar to rapid-rising tide occurred.

        

Fh  pc Aw

= Hydrostatic force = Hydrostatic pressure at centroid = Wetted area of panel

for

hmax > hw

else

hmax  hw

Research Method: Literature Review

hmax hw

= Maximum water height above the base of wall = Height of wall panel

2.1.2

Buoyant force

Buoyant force is come from the Archimedes principle. In case of tsunami-induced force, it is the vertical force acting through the centre of mass of a submerged body. The magnitude is considered equal to the weight of water volume that is displaced by the submerged body. This force has significant effect on the floor slab of structure, wood frame buildings, empty aboveground and below-ground tanks.

FB ρ g V

= Buoyant force = Density of water = 1000 kg = Gravity = Volume

2.1.3

Hydrodynamic force

  

It is also known as drag force. This force occurs as tsunami bore moves inland with moderate to high velocity and flows around structures. It is assumed to be uniform, which act at the centroid of area. This force is varies, because it depends on the shape of the structure where the flow occurred.

FD CD ρ A u

    

= Drag force = Drag Coefficient = Density of water = 1000 kg = Area = Flow velocity Width to Depth Ratio Drag Coefficient From 1 – 12 1.25 13 – 20 1.3 21 – 32 1.4 33 – 40 1.5 41 – 80 1.75 81 – 120 1.8 >120 2 Table 2.1 Drag coefficient value based on the width to depth ratio Source: Federal Emergency Management Agency (FEMA),2011

Research Method: Literature Review

2.1.4

Surge Force

This force is generated by the surge of the water from the tsunami bore acting on a structure. It depends on the geometry of the structural element and velocity of the tsunami. The magnitude of this force has four times more than the hydrostatic value.

  

In japan, another approach has been used to determine the surge force (Building Centre of  Japan). It is quite identical to the surge force equation. They adopted the equation made by Keulegan (1950).

     

Fs ρ g h  b u

= Surge force = Density of water = 1000 kg = Gravity = Height of surge = Base = Velocity

2.1.5

Impact force

√ 

The impact force came from the debris that has been collected by the tsunami bore and strike against buildings and structures. The debris can be as small as sand to as big as a ship, thus can induced very significant force on buildings, which will lead to structural failure and collapse. This force is being assumed as single concentrated load that act horizontally at the flow of the surface.

Figure 2.2

The debris that was drag by the tsunami

Source: The Guardian UK, May 1 st 2012

Research Method: Literature Review

There are several equations that have been developed to determine the impact force on a structure.

       ∫  

Which is based from the impulse-momentum approach.

The duration of the impact on a structure is depends on the type of the construction (FEMA). Type of Construction Duriation (t) of impact (sec, s) Wall

Pile

Wood

0.7 – 1.1

0.5 – 1.0

Steel

N/A

0.2 – 0.4

Reinforced Concrete

0.2 – 0.4

0.3 – 0.6

Concrete Masonry

0.3 – 0.6

0.3 – 0.6

Table 2.2

Duration of impact on type of materials of construction Source: FEMA CCM

American Society of Civil Engineering (ASCE) has developed other equation to determine the impact force.

FI m u CI CO CD CB R max Δt

  

= Impact force = Debris mass = Object impact velocity = Importance coefficient = Orientation coefficient = Depth Coefficient = Blockage Coefficient = Maximum response ratio for impulsive load = Impact duration = 0.03s

Research Method: Literature Review

2.2

RISKS CATEGORIES

To determine the categories of risks that can happened from tsunami’s, historical data need to be gathered and studied for more understanding and to have more accurate measure in reducing the risks. American Society of Civil Engineers (ASCE) has come up with a building code for   building and structures (Table 2.3 (a) and (b)) so the structure will not fail or collapse the second a tsunami wave forces hit the structures. But currently, there are no national standards for engineering design for tsunami effects that can be used. Because of this, the design risks of tsunami on coastal zone are still not clear  and broad for construction to follow from the design codes. So, as a result, the risks categories are being made in accordance to the structures importance and hazards it can bring if collapse or  fail (Table 2.3 (a) and (b)). For example, the nuclear plant in Japan that failed during the Japan tsunami in 2011, it has a disastrous effects to lives if it ultimately failed. So, these risks studies need to be followed to prevent for future tragedies.

RISKS

DESCRIPTION

CATEGORY

I

Building and other structures that has low risks to humans

II

All buildings and other structures except those listed on categories I, III, IV Buildings and other structures with potential to cause a substantial economic

III

impact and/or mass disruptions to of day-to-day civilians lives in the event of failure

IV

Buildings and other structures designated as essential facilities Table 2.3(a) ASCE 7 risks categories

Risks Use or Occupancy of Buildings and Structure

category for tsunami

Buildings and other structures that represent a low hazard to human life in the event of failure All buildings and other structures except those listed in Risk Categories I, III, and IV

I

II

Research Method: Literature Review

Buildings and other structures , the failure of which could pose a substantial risk  to human life, including, but not limited to: 

Buildings and other structures where more than 300 people congregate in one area



Buildings and other structures with day-care facilities with a capacity greater than 150



Buildings and other structures with elementary school or secondary school facilities with a capacity greater than 250



Buildings and other structures with a capacity greater than 500 for  colleges or adult education facilities



Any other occupancy with an occupant load greater than 5,000 based on

III

net floor area Buildings and other structures, not included in Risk Category IV, with potential to cause a substantial economic impact and/or mass disruption of day-to-day civilian life in the event of failure. Buildings and other structures not included in Risk Category IV (including, but not limited to, facilities that manufacture, process, handle, store, use, or dispose of such substances as hazardous fuels, hazardous chemicals , hazardous waste, or  explosives) containing sufficient quantities of toxic or explosive substances where the quantity of the material exceeds a threshold quantity established by the authority having jurisdiction and is sufficient to pose a threat to the public if  released. Buildings and other structures designated as essential facilities, including, but not limited to: 

Health care facilities with a capacity of 50 or more resident patients.



Hospitals and other health care facilities having surgery or emergency treatment facilities.



Fire, rescue, ambulance, and police stations.



Designated tsunami vertical evacuation refuges.



Designated emergency preparedness, communication, and operation centres and other facilities required for emergency response.



Power generating stations and other public utility facilities required in an

IV

Research Method: Literature Review

emergency. 

Aviation control towers and air traffic control centres.



Telecommunication centres.

Buildings and other structures, the failure of which could pose a substantial hazard to the community. Buildings and other structures (including, but not limited to, facilities that manufacture, process, handle, store, use, or dispose of such substances as hazardous fuels, hazardous chemicals, or hazardous waste) containing sufficient quantities of highly toxic substances where the quantity of the material exceeds a threshold quantity established by the authority having jurisdiction and is sufficient to pose a threat to the public if released. Buildings and other structures required to maintain the functionality of other Risk  Category IV structures. Table 2.3(b) ASCE 7 risks categories in details Source: American Society of Civil Engineers (ASCE), February 2011

2.3

FAILURE MODES OF STRUCTURES UNDER TSUNAMI FORCE

Under tsunami loads, building will fails and collapse. So, it is importance to know the types of  failure modes on a structure under this destructive force. These failure modes can be studied from previous tsunami’s tragedies and thus, engineers can improve and finding ways so that the structure won’t from failed under these conditions. From the Indonesian tsunami occurred on December 2004, three different types of  structural failure was observed which is sliding, overturning, and undermining through scouring (Dias and Mallikarachchi, June 2006). These failure modes are different on each structure,  because it all depends on the wave height (Table 2.4) and structure height.

Wave Height

< 2m

Structure Height

Types of failure

1 – 2 m

overturning

Image

Research Method: Literature Review

2 – 4 m

> 4m

Single-storey  building

Sliding

Multi-storey

Undermining through

 building

scouring

Table 2.4

Variety of structures behaved under tsunami loading Source: Dias and Mallikarachchi, June 2006

From historical tsunami’s event, engineers can study the failure modes that can occur  under the loads. From these studies, mitigation method can be developed and identified so that the structure can be more resistance to tsunami attack. Further studies need to be done to know more structural failure modes under tsunami loading. From the Tohoku tsunami tragedy, different types of failure modes were observed (Table 2.5). These failure modes are far more devastating, since it destroyed bigger, taller, and more reinforced structures than the structures in Indonesia tsunami. So, this types of failure modes need to be considered more when designing important structures.

Types of Structure

Two-storey reinforced concrete building

Failure Modes

Buoyant uplift

Image

Research Method: Literature Review

Three-storey steel building

Concrete warehouse

Lateral pushover 

Flow stagnation  pressurization

Combination of hydrostatic

Concrete wall

and hydrodynamic loading

Treatment Plant

Bore Impact

Table 2.5

Failure modes on reinforced structures

Source: Carden, Chock, Robertson, and Yu, December 2012

Research Method: Literature Review

2.3

PREVIOUS RESEARCH

There are several previous researched that has been done to studied the force that being induced  by the tsunami. These studies are important since it will create a more understanding and better  method in designing structure that can resists the tsunami loads in the future. For my work, I will look at two studies that have been made by S. Mizutani and F. Imamura, and D. H. Cammilleri. Both studies are important since it shows the force that induced by tsunami using different equations and methods.

2.3.1

Dynamic Wave Force of Tsunamis Acting on a Structure

Studies that made by S. Mizutani and F. Imamura focused more on structures along the coastlines such as seawalls and breakwaters, and done by doing hydraulic experiment. They introduced the types of wave’s forces acting on seawalls and breakwaters and categorised it into four which is dynamic, sustained, impact standing, and overflowing. They observed that the existence between impact standing and overflowing wave pressure have a very large value on short period of time at a local point. They also concluded that the impact standing value, due to collision of the reflected and incident waves is related to wave celerity and run-up height. They also proposed new equations to estimates the maximum value of kinetic, sustained, impact standing, and overflowing wave pressure. Below are the proposed equations from the observations.

2.3.1.1 Dynamic wave pressure

The dynamic wave’s pressure was developed by Fukui

et al.

in 1962, which is used to estimate

the maximum dynamic pressure applied on a structure. He empirically proposed this equation to determine the maximum dynamic wave pressure on structure.

Where

pdm c h H

ρω g

  

= maximum kinetic wave pressure = celerity = initial water depth = incident wave height = density of seawater  = acceleration of gravity

Research Method: Literature Review

K

= kinetic wave coefficient = 0.12

2.3.1.2 Sustained wave pressure

This formula considered that the maximum sustained wave pressure psm related to the maximum kinetic wave pressure pdm. This formula also taking into consideration the angle of slope of the structures.

    

2.3.1.3 Impact standing wave pressure

This formula was observed and it was concluded that impact of standing waves is related to the collision of reflected and incident waves. It takes into consideration the relationship between run-up height and sustained wave pressure, wave celerity and dynamic wave pressure.

   

             √  )     (   

2.3.1.4 Overflowing wave pressure

It was observed that the maximum overflowing wave pressure occurred when the overflowing wave collide on the back of the structure. They suggested several important parameters that is used in the equation.

Where:

pom Vm Hw

θH’

2 d

        = maximum overflowing wave pressure = maximum velocity = water depth on the crest = angle of the back slope = height of models

Research Method: Literature Review

2.3.2

Tsunami and Wind-Driven Wave Forces in the Mediterranean Sea

This paper was made by Denis H. Cammileri for the maritime engineering magazine. He studied and made comparison the impact of the force generated between the wind-driven waves and tsunami wave, and compared this with several methods. He uses several theories in obtaining the force for tsunami wave for his research such as Keulegan(1950) (Figure2.3), Morrisons (Figure 2.4), and Ambraseys (1962) (Figure 2.5) method. Since this is more on comparison  between two types of wave, I will focus more on the tsunami wave from this paper. He concluded that, tsunami wave are a non-breaking waves, which has higher energy when it strikes the shoreline than it does when it reaches certain distance. The tsunami wave also slows down, increase in height, and wavelength decreases when it approaches the land. By the models and calculations that he made, he suggested that the wave loading may be between 9 18 times the hydrostatic forces and this value doesn’t considered the effect of debris impacts on structure.

Figure 2.3

Figure 2.4

 

Kuelegan methods for shallow water relationship

    

Morrison method consists of two parts, drag and inertia force

Figure 2.5



Ambraseys method for tsunami intensity

Research Method: Literature Review