Earthquakes and their effects on buildings

Earthquakes and their effects on buildings Nicola Storgaard, Constructing Architect, 7th semster 2010 1 Preface This dissertation is a part of the...
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Earthquakes and their effects on buildings Nicola Storgaard, Constructing Architect, 7th semster

2010

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Preface This dissertation is a part of the curriculum for my final semester of the B.sc of architectural technology and construction management. It is written to understand the dynamics of a building during ground movement. To complete this report I have enlisted the help of my consultant Tommy Villadsen, and researched numerous amounts of literature on the subject. The idea of writing about the effects of an earthquake on a building comes from my interest in the subject. I myself have lived in Japan, and have witnessed waking up to a shaking building a numerous times. The report itself is divided into parts, to help the reader better understand the following chapters. The first part of the report focuses on the formation, and whereabouts of earthquakes,

Abstract As more and more people inhabit this planet, the inhabitants are forced to live in more dense cities, in tall buildings that must be able to offer them safety from the dangers that plague certain areas of the globe. Earthquakes are not only limited to the area around fault lines, but unknown fault lines, sleeping for hundreds of years pose a real danger to densely populated areas. Earthquakes can happen virtually anywhere on the globe, though not in the same kind of degree that the areas near famous faults experience them. Unfortunately some of these biggest cities in the world reside along some of the most dangerous fault lines. But due to this, lots of research about the effects of earthquakes on buildings has been done, which has made the modern high-rise buildings some of the safest places to be during an earthquake. This report focuses on the effects that earthquakes have on buildings, and what techniques can be used to limit the damage once the earthquakes hit.

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Acknowledgements I would like to thank the lecturers that have helped me through the past three years, teaching and guiding me through all the material necessary for this education. I would especially like to that the lecturers who taught statics and building construction during the past semesters, as without that knowledge, I wouldn't be able to get as good a start in writing a report about the effects of earthquakes on buildings. And of course, not to forget Tommy Villadsen, who is my consultant for this dissertation.

Contents Preface....................................................................................................................................................... 2 Abstract ...................................................................................................................................................... 2 Acknowledgements ................................................................................................................................... 3 1. Problem formulation ............................................................................................................................. 5 1.1 Definition .......................................................................................................................................... 6 Introduction ................................................................................................................................................ 6 2. Earthquakes .......................................................................................................................................... 8 2.1 What is an earthquake? ................................................................................................................. 8 2.1.1 Divergent boundaries .............................................................................................................. 8 2.1.2 Convergent boundaries ........................................................................................................... 8 2.1.3 Transform boundaries ............................................................................................................. 9 2.2 Seismic waves ................................................................................................................................ 9 2.2.1 Body waves .............................................................................................................................. 9 2.2.3 Surface waves.........................................................................................................................10 2.3 Predicting an earthquake ..............................................................................................................10 2.4 Earthquake early warning system (Japan) ..................................................................................11 2.5 Frequency and risks of earthquakes in Japan ............................................................................13 2.6 The threat to Tokyo........................................................................................................................13 2.7 Conclusion ......................................................................................................................................14 3. Ground movement and structures......................................................................................................15 3.1 Encountering different types of ground ........................................................................................15 3.1.1 Different types of substructure ...............................................................................................15

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3.1.2 Methods of limiting damage ...................................................................................................16 3.2 Earthquake simulation ...................................................................................................................16 3.3 Conclusion of the test ....................................................................................................................18 4. Earthquakes Design ............................................................................................................................19 4.2 A look into present day earthquake design .................................................................................19 4.2.1 Tuned liquid dampeners (TLD) ..............................................................................................19 4.2.2 Tuned mass dampeners (TMD).............................................................................................20 4.2.3 Taipei 101 ................................................................................................................................20 4.2.4 Reduced beam section (RBS) ...................................................................................................22 4.2.5 Self righting buildings .................................................................................................................23 4.3 Base isolation .................................................................................................................................24 4.4 Good and bad building design ......................................................................................................25 4.4.1 Simplicity..................................................................................................................................26 4.4.2 Soft storeys .............................................................................................................................26 4.5 Conclusion ......................................................................................................................................27 5. Understanding the forces on a building .............................................................................................28 5.1 Inertia forces...................................................................................................................................28 5.1 The dangers of frequency .............................................................................................................29 5.2 Tacoma Narrows Bridge ...............................................................................................................30 5.3 Diverting the forces of an earthquake safely ...............................................................................31 5.4 How shear forces work ..................................................................................................................31 5.5 Steel structure of an earthquake resistant building.....................................................................32 5.5.1 Special moment frames (SMF) ..............................................................................................32 5.5.2 Braced frames.............................................................................................................................33 5.6 Conclusion ......................................................................................................................................35 6. Building codes in Japan ......................................................................................................................36 6.1 John Milne (1850 - 1913) ..............................................................................................................36 6.2 The 1919 urban building law.........................................................................................................36 6.3 Building codes following the rebuilding of Japan after WW2 .....................................................38 6.4 Conclusion ......................................................................................................................................39 7. Conclusion ............................................................................................................................................40

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Figur 1: Seismograph during an earthquake ................................................................................................. 9 Figur 2: Diagram of the early warning system in Japan ................................................................................11 Figur 4: Japanese flyer of earthquake do´s and don´ts .................................................................................12 Figur 3: Early warning logo ..........................................................................................................................12 Figur 5: Magnification of earthquake destruction in loose soil.....................................................................15 Figur 6: Water counter balancing the forces of an earthquake ....................................................................19 Figur 7: Tuned mass damper .......................................................................................................................20 Figur 8: Floor plan of floor of Taipei 101......................................................................................................21 Figur 9: Picture of reduced beam section in Taipei 101 ...............................................................................22 Figur 10: Illustration of self righting building ...............................................................................................23 Figur 11: Base isolator v. fixed-base building ...............................................................................................24 Figur 12: Drawing of L-shaped building during an earthquake .....................................................................25 Figur 13: L shaped building designed for earthquake forces ........................................................................25 Figur 14: Frequencies for different sizes of buildings ...................................................................................28 Figur 15: Functions of a shear wall ..............................................................................................................31 Figur 16: Braced frames (http://www.fgg.uni-lj.si/kmk/ESDEP/master/wg17/l0500.htm) ...........................34 Figur 17: Seismic coefficient........................................................................................................................37

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1. Problem formulation How do you construct multistory buildings, so they are able to withstand the forces of an earthquake and protect the people inside? 1. What happens to a building when it is hit by an earthquake? 2. How does Japan cope with earthquakes in their major city Tokyo? 3. What are some of the building techniques available to eliminate structural damage? 4. Are there building codes specifically for earthquakes? 5. Are there any height restrictions on buildings in earthquake zones?

1.1 Definition 

Construct - Use earthquake resistant technology



Multistory buildings - Commercial and residential, minimum 3 stories



Withstand - resist the movement of the ground, and prevent collapse



Forces - Movement of the ground



Protect - Prevent any serious injuries to people inside the building

Introduction Taking on the subject Earthquakes and their effects on buildings, I wanted to investigate how an earthquake affects the structural integrity of a building. Since the subject is so large, and each earthquake affected area is different than the other, due to the different types of fault lines, I would have to narrow it down to one region. I figured that Japan would be an excellent country to find a case study, and examples on how to earthquake proof a building. Japan is well known for its frequent earthquakes, due to the fault that is part of the ring of fire. Because of the strength and frequency of earthquakes, they are also leaders in earthquake proofing technology. Also, they have been recording devastating earthquakes for the past four hundred years. This report focuses primarily on tectonic earthquake damage. Also, the buildings, and the stresses on buildings investigated, are the ones made from reinforced materials, like concrete and masonry. No wooden structures will be used in this report.

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In this first part of the report I will investigate what an earthquake is, how is occurs, and what geological forces are at work to create them.

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2. Earthquakes 2.1 What is an earthquake? The earth's crust is composed of two layers; the lithosphere which is Latin for rocky sphere, and is the solid part of the crust. And athenosphere which is molten rock. Earthquakes happen when stresses on the lithosphere occur as it floats on the athenosphere1. The earth's crust consists of fault lines throughout the globe, which experience different types of stresses. There are mainly three different types of faults found2. 1. Constructive plate margin/Divergent boundaries 2. Destructive plate margin/Convergent boundaries 3. Conservative plate margin/Transform boundaries 2.1.1 Divergent boundaries Here new crust is formed. The lithosphere moves apart, and upward moving magma forms new crust by as much as 2.5 cm a year. Earthquakes here occur at shallow depths of between 2 - 8 kilometers, and are relatively small. Larger earthquakes are uncommon near the divergent boundaries, as the plate here is thin, and stresses built up are not enough to cause larger earthquakes. 2.1.2 Convergent boundaries Convergent boundaries are the opposite of divergent boundaries. The general rule of tectonics is, that the same amount of crust formed at the divergent boundaries, must also be destroyed at the convergent boundaries. The earthquakes here are generally powerful, as a lot of pent up energy is created when the plates meet. Depending on where these convergent boundaries are found, the crust is destroyed differently. 

Oceanic - Continental convergence - The density of the oceanic plate is larger than that of the continental plate, which means that it gets pushed underneath the continental plate. Here the earthquakes are strong, and mountain ranges are formed where they meet.



Oceanic - Oceanic convergence - The older of the two plates gets pushed underneath the other.

1 2

http://www.wisegeek.com/what-are-earthquakes.htm Earthquake Resistant Design of Structures, by Pankaj Agarwal, Manish Shrikhande, p. 7

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Continental - Continental convergence - Here neither plate is sub ducted as both the crusts are formed of light rocks. Huge mountain ranges are formed here, like the Himalayas.

2.1.3 Transform boundaries Transform boundaries are the zones between two plates that slide horizontally. The majority of such faults are found on the ocean floor, but some can be found on land, like the San Andreas fault in California. The friction created by this kind of fault can release enormous amounts of energy, resulting in huge earthquakes. 2.2 Seismic waves During an earthquake you can encounter many different types of waves, but in general there are two categories to place these waves3: 

Body waves - These waves travel through the earth's inner layers.



Surface waves - Can only travel on the surface of the crust. Same principal as ripples on water.

2.2.1 Body waves Body waves consist of P-waves (primary waves) and S-waves (secondary waves). The first to arrive are P-waves, which move through the earth's inner layers faster than the Swaves. It can move through liquid and solid rock, and behaves similar to sound waves, as it pushes and pulls the rock that it travels through. Particles subjected to a P-wave move in the same direction that the energy is moving in, also known as the Figur 1: Seismograph during an earthquake

direction of wave propagation.

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http://www.geo.mtu.edu/UPSeis/waves.html Figure 1: http://wapi.isu.edu/envgeo/EG5_earthqks/eg_mod5.htm

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S-waves are felt after the P-waves. They move much slower, and can only travel through solid rock. The particles in their path are moved side to side, up and down, perpendicular to the wave propagation. 2.2.3 Surface waves Surface waves arrive after the occurrence of body waves, and have much lower frequencies. They are easily distinguished in a seismograph, as they create huge fluctuations. The damage caused to structures is mainly due to these kind of waves. The first kind of surface wave is called the love wave, named after the mathematician who worked out the model for this kind of wave. Love waves move in a horizontal motion, and move the ground side to side. The second type of surface wave is the Rayleigh wave, also named after the mathematician who predicted it by mathematical model. These waves roll along the ground, exactly like waves on the sea, and can be much larger than the other waves. Rayleigh waves move the ground up and down, side to side in the direction that the wave is moving. 2.3 Predicting an earthquake Unlike other natural disasters that warn us beforehand of the impending dangers, like hurricanes and volcanoes, earthquakes can be extremely hard to predict. Actually earthquakes are a warning sign of a volcanic eruption. In the hope of successfully predicting an earthquake, it is possible to look for patterns of activity. The most widely used theory surrounding plate tectonics, is the theory of dilatancy4. The theory is that when a rock is under pressure it expands, due to cracks opening up and enlarging the rock. The tricky part of this theory is, that it is hard to observe rocks when they are underground. To use this theory you have to employ other measures to get data to understand if the area is under stress. Scientists know that when a rock is under pressure, it transmits seismic waves in different frequencies, also the ground could start to uplift, and ground water pressure can change. Also the magnetic properties of a rock can change, and the electrical resistance can vary. Using these techniques can help understand if an area near a city is starting to store pressure in the ground. Another thing you can investigate is an area's history. It is possible to look at earth 4

http://www.geography-site.co.uk/pages/physical/earth/pred.html

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samples, to see how often an area encounters an earthquake, and the frequency of them occurring. This is a way to loosely predict when the next earthquake will occur, but it is still very important to monitor the ground, for changes. One farfetched theory in earthquake detection is the reaction of animals to the subtle changes in an area, probably due to magnetic fluctuations caused by expanding rock. The Chinese have observed that animals change their behavioural patterns just before an earthquake. Snakes have been observed to have surfaced from the ground during their hibernation period, to end up freezing to death. Domesticated animals like horses and cattle are said to be restless, and refuse to enter buildings5. Also people with common house pets have reported unusual behaviour from their animals.

2.4 Earthquake early warning system (Japan) As mentioned in the above sub-chapter, predicting an earthquake is almost impossible as you have to look for a series of anomalies regarding the surrounding area. Also earthquakes can have their epicentres far distances from a city, in areas that are not being monitored. An earthquake in the Japanese

Figur 2: Diagram of the early warning system in Japan

city Kobe, came from nowhere and unleashed destruction and devastation throughout the city. There were no warning signs to alert the public what was to happen. The inhabitants in Tokyo understand that the only means of protection are from properly built structures, and properly followed guidelines to follow when you hear the earthquake warning6.

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http://www.geography-site.co.uk/pages/physical/earth/pred.html Earthquake early warning, Kinkyu Jishin Sokuhou, 1 April 2009 Figure 2 and 4: Earthquake early warning, Kinkyu Jishin Sokuhou, 1 April 2009, http://www.jma.go.jp/jma/en/Activities/EEWLeaflet.pdf. 6

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From the moment an earthquake starts shaking the ground at the monitoring station outside the city, till it reaches people in the city can take between 0 - 15 seconds. Some people don't receive any warning at all. They are aware of an earthquake immediately when it starts. Monitoring stations are placed all over Japan, and work by picking up the faster moving P-waves. When a station picks up these faster waves, it immediately transmits its warnings to the media and disaster prevention organisations, who broadcast the warning to the public, hoping that people manage to brace themselves7. Figur 3: Early warning logo

Figur 4: Japanese flyer of earthquake do´s and don´ts

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Earthquake early warning, Administration Division, Seismological and Volcanological Department Japan Meteorological Agency, 10 August 2007 Figure 3: Japans Early warning earthquake logo.

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A properly reinforced and shake-proof building can only protect you from being trapped inside a collapsed building. During an earthquake there are other dangers, depending on where you are during the quake. If you are at home, or in a public building, you risk appliances and furniture topping over, falling on top of you, possibly crushing you. If you are outside in an urban area, you could potentially be killed by falling signs, facades, and other things falling off of buildings8. 2.5 Frequency and risks of earthquakes in Japan When designing a building in Japan an engineer has to be well aware of the risks posed by the sudden and unpredictable occurrence of earthquakes. Japan is a relatively small country, but yet experiences about 18% of all earthquakes on the planet, that are magnitude 7 or more9. The most dangerous fault lines are situated on the pacific coast of Japan, but the smaller and shallower faults are located throughout the country. In 2004 2005, earthquakes occurred from previously unknown faults, due to long recurrence periods10. This proves that you always have to assume that an earthquake could happen wherever you build.

2.6 The threat to Tokyo In 1923 a major 7.9 magnitude earthquake hit Tokyo and killed 143.000 people. The earthquake, also known as the Kanto earthquake, has hit the area approximately every 70 years, in the past 300 years. This means that Tokyo is soon due for another major earthquake. To understand how important it is to prepare a major city for an earthquake, you don't have to travel very far. In 1995 a major earthquake hit the city of Kobe in Japan. It too is situated in the vicinity of an active fault, and though it did prepare for an impending earthquake, it didn't prepare for one over a magnitude of 5. This resulted in major damage to the city, and made people realize that it was only a matter of time before something similar could happen to the capital11. In wake of the Kobe disaster an organization was established, called the Earthquake Research Committee (ERC), who developed seismic hazard maps over Japan from 1995 - 2005. Modelling has been used to understand the 8

Info from Japanese flyer of do´s and don´ts (figure 4) Japan: large-scale floods and earthquakes, By Organisation for Economic Co-operation and Development p. 191 10 Japan: large-scale floods and earthquakes, By Organisation for Economic Co-operation and Development p. 192 11 The Independent: Tokyo faces catastrophic earthquake risk, Richard Lloyd Parry, 1996 9

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effects on buildings according to their height and material, and research about how materials were effected in the Kobe earthquake have been implemented into the model. The information has been very useful for improving on the countries building codes12. 2.7 Conclusion In this chapter I am writing about the important information to know when you are investigating the effects that earthquakes have on structures. The general information about what an earthquake is, and how it is structured has been followed in this chapter, which helps to understand both how to warn people about an impending danger, and which vibrations are acting on buildings. We know from understand the different types of waves present during a quake, that it is the surface waves that are damaging to buildings. These waves move the earth both up and down, and side to side, and especially the Rayleigh waves are damaging, as they are stronger than the love waves. This chapter also looks into whether or not it is possible to predict an earthquake in a longer period before one happens. In Japan the population has just seconds to react to the sirens, and after that all they can do is duck for cover and hang on. If it was possible to predict a devastating earthquake before one struck, people living in vulnerable housing could have enough time to seek shelter somewhere else. What was discovered about predicting an earthquake longer back, is that it is possible to monitor the surrounding ground, and look for any alterations in the properties of the bedrock, which could indicate that the ground is experiencing an increase in stress. What I also understood from researching Japans warning procedures, is that they have an idea that an earthquake will hit, but it is impossible to predict it down to the day and hour.

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Risk assessment models, RMS, 2005

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3. Ground movement and structures 3.1 Encountering different types of ground When designing any structure in an earthquake prone area, one thing that has been be taken into account, is what type of ground the building will rest on. In earthquake prone areas this is extremely important, because you need different types of support for structures on different types of ground . It can be extremely hazardous to design a building without knowing if it will be built on solid ground, or loose ground, as both will react differently during ground movement. 3.1.1 Different types of substructure:13 

Stable, solid ground - Thought has to go into building on solid ground as the energy of even small earthquakes can be amplified by the structures built on it.



Fault line - The earth here can rip apart. Sometimes it is unavoidable due to expanding a city, or building in an area where the fault lines are not known about.



Loose gravely, sandy soil - The most dangerous ground to build on. During a quake, water is forced up through the loose soil, and liquefaction can happen, making the soil like quicksand. If a building isn't properly designed, even a small earthquake can cause it to collapse.



Coastal region - The biggest threat here is Tsunamis, triggered by an earthquake. The picture on the right shows how the magnitude of earthquakes can be amplified, if you build on soft sediments. Figur 5: Magnification of earthquake destruction in loose soil

When you are aware of the type of ground the building will sit on, you have to start making decisions based on what you know about which structure will best suit the type of ground, and how powerful the earthquakes are in the region. 13

Discovery Channel: http://dsc.discovery.com/guides/planetearth/earthquake/interactive/interactive.html Figure 5: http://www.tasaclips.com/animations/amplification_of_seismic_waves.html

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3.1.2 Methods of limiting damage: 

Reinforced building material - Reinforced with steel rods to increase the tensile strength of the material. Allows the material to deform while swaying, without crumbling apart.



Foundation anchoring - Prevents the building being shook off its foundation. Makes the building respond to the quake force in unison, and prevents the building from oscillating in different rates.



Base isolation - Absorbs the shock of earthquakes by allowing the building to slide back and forth on the foundation. Some of these buildings use counter weights placed in the top of the building.



Pile Foundation - Long pillars are constructed to bypass loose gravely soil, where liquefaction could be an issue, to anchor the building on firmer bedrock located under the dangerous soil.

3.2 Earthquake simulation By using an earthquake simulation program from the discovery channel, I have been able to construct a table showing the extent of the damage on buildings in different scenarios. I have learned that each type of ground has a preferred prevention style of building on top of it. Solid ground Types of prevention R FA BI

Magnitude 2 - 4.9 2 - 4.9 2 - 4.9

Scope of damage Minor Minor Minor

PF R FA BI PF R FA BI PF

2 - 4.9 5 - 6.9 5 - 6.9 5 - 6.9 5 - 6.9 7 - 9.5 7 - 9.5 7 - 9.5 7 - 9.5

Minor Structural damage Minor Minor Structural damage Collapse Collapse Structural damage Collapse

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By choosing the desired magnitude of the quake, building style and type of soil, I was able to see the result of each simulated earthquake, and place what I witnessed in a table. R FA BI PF

Reinforced Foundation anchoring Base Isolation Pile foundation

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Fault zone Types of prevention R FA BI PF R FA BI PF R FA BI PF

Magnitude 2 - 4.9 2 - 4.9 2 - 4.9 2 - 4.9 5 - 6.9 5 - 6.9 5 - 6.9 5 - 6.9 7 - 9.5 7 - 9.5 7 - 9.5 7 - 9.5

Scope of damage Minor Minor Minor Minor Structural damage Structural damage Structural damage Structural damage Collapse Collapse Structural damage Collapse

Magnitude 2 - 4.9 2 - 4.9 2 - 4.9 2 - 4.9 5 - 6.9 5 - 6.9 5 - 6.9 5 - 6.9 7 - 9.5 7 - 9.5 7 - 9.5 7 - 9.5

Scope of damage Structural damage Structural damage Minor Minor Collapse Structural damage Structural damage Minor Collapse/sink Collapse/sink Collapse/sink Collapse

Loose, sandy soil Types of prevention R FA BI PF R FA BI PF R FA BI PF

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3.3 Conclusion of the test After completing all the tests, and filling out the excel tables, I am able to get a complete overview of the test results, and can immediately tell that loose, sandy soil is extremely dangerous to build on if you experience a massive earthquake. Though I must add that with other building techniques it might be possible to save the building from collapse, as I have only tested with the basic kinds of prevention. The technique that fares the best is digging down to more solid ground, anchoring the building at a more solid layer of ground. The main course of collapse in this type of soil, during these large earthquakes it the liquefaction effect, which prevents the ground from being able to support the structure. Base Isolation seems to be the ideal choice to pick for the other types of ground, due to the way it counteracts the movement of the ground. The specifics surrounding this technology will be explained in chapter 4 of this report.

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4. Earthquakes Design 4.2 A look into present day earthquake design In this chapter I will focus on earthquake preventative design for high-rise buildings. That means buildings over three stories, and not made of timber. As most tall buildings are made from light, flexible building materials, like steel and glass, it is down to clever engineering to prevent them from oscillating

too violently.

Figur 6: Water counter balancing the forces of an earthquake

4.2.1 Tuned liquid dampeners (TLD) Japan was the first to start implementing Tuned liquid dampeners into buildings. This design is both cheap and very efficient to reduce the vibrations of an earthquake. What it is, is a tank of water in a specific size, according to the natural frequency of the building, that can be tuned to have the same frequency as the building by filling it to a specific depth. The baffles in the tank are there to prevent the tank itself from being resonant, as the water is sloshing back and forth during an earthquake. This is just a crude method of using water to act as an opposing force to the movements earthquakes. Another, more technical method, is the Tuned liquid column damper, which uses a U-shaped tube, but does the same as the tuned liquid dampener. A few of Tokyo's high-rise buildings use this technology today14.

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http://www.nd.edu/~tkijewsk/Instruction/solution.html Figure 6: http://www.nd.edu/~tkijewsk/Instruction/solution.html

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4.2.2 Tuned mass dampeners (TMD) The basic principle of the tuned mass damper is a system comprising of a spring (k), mass (m) and damper (c), attached to the structure. Like the liquid mass damper, it is tuned to the frequency of the building, and will resonate out of phase when the building sways. The damper uses the theory of inertia, which says, an object has a resistance to a change in its state of motion, which dissipates the energy in the structure through the damper,

Figur 7: Tuned mass damper

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usually in the form of heat . 4.2.3 Taipei 101 To see tuned mass dampening technology at its greatest you will have to travel south of Japan, to the island of Taiwan. There engineers have constructed one of the world's tallest buildings, which is not just famous for its style, but also for its technology. Like Japan, Taiwan is situated near the ring of fire, which is the most geologically active area on the planet. The building, called Taipei 101, not only has to withstand typhoon strength winds, but also has to survive major earthquakes. To explain this technology I will have to discuss the other methods which the building uses to combat swaying and movement, as the tuned mass damper is only one link in the chain. The building itself is a wonder of technology, as it is 508 meters tall, with 101 floors. Hence its name. The owners of the building, Taipei financial centre cooperation, originally wanted multiple smaller multi story buildings constructed on the lot, but all of the investoroccupants wanted to reside inside the tallest of the originally proposed buildings. This prompted the design to be what we know of today. The building resulted in being the tallest building of its time, by the shear amount of floor space needed to accommodate all who were interested16. The design of the building is based on local building culture, and that of bamboo, which is a slender plant with incredible strength. If you place an image of bamboo side to side with the building, you can see a striking likeliness between the two, as both are divided into 15

Tuned mass damper systems, 2002, chapter 4, p. 217 Figure 7: Tuned mass damper systems, 2002 16 Ingredients of high rise design Taipei 101, Leonard M. Joseph, Dennis Poon & Shaw-song Shieh, 2006, p. 1

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modules. Taipei 101 is designed with eight modules, to be exact. This design created some problems, as the building needed to be designed with lateral stiffness and strength incorporated into the design. Most buildings rely on a central core, to add additional stiffness to the building, but Taipei 101 is too tall to rely on just a central core alone. Other tall buildings have combated this problem by placing the lateral load resisting system on the buildings perimeter, but this would alter the bamboo like design of the buildings. The problem is that the modules on the building are narrow at the bottom, and flare out at the top, almost like a flower. If lateral support columns were installed, they would protrude outside the building on the narrow part of the module, and enter the building at the top where it is wider, and would take up valuable floor space. The designers and engineers went back to the drawing board and came back with an effective solution, to incorporate the lateral load resistant system into the bamboo design. What they came up with was sixteen core box columns, linked by outrigger trusses to the major outrigger columns on the building face. Under floor trusses are also incorporated to transfer horizontal perimeter moment frame shear. The frame of the building is constructed mainly of structural steel, as it

Figur 8: Floor plan of floor of Taipei 101

would lower the cost of the building, and importantly minimizes seismic forces, by keeping the building mass low. The main outrigger columns running vertically up the building get smaller as they run up the building, to make the building lighter for each module it goes up17. Now that the engineers have created reliable load paths down the building, geologists would have to investigate the soil which the building was to be constructed on. They found out that the soil underneath the 17

Ingredients of high rise design Taipei 101, Leonard M. Joseph, Dennis Poon & Shaw-song Shieh, 2006, p. 2 Figure 8: Ingredients of high rise design Taipei 101, Leonard M. Joseph, Dennis Poon & Shaw-song Shieh, 2006, p. 2

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building was comprised mainly of clay. To insure that the building would rest firmly during an earthquake, they calculated that they would have to drill holes, to make cast-in-place piers approximately 130 to 200 ft deep. By doing this the building would be able to rest firmly on soft rock18 Even though the building went through a total analysis of strength and stiffening, the steel structure and its central core were not enough to limit the swaying to an acceptable limit. What needed to be added to the structure was a tuned mass damper. The one installed in Taipei 101 occupies floor 87 - 91, and is the centrepiece of a public lounge. It resembles a giant sphere, and weighs in at 726 tons. That is approximately 0.26 percent of the buildings total weight. The sphere is suspended by four steel cables to act like a pendulum. By altering the length of the cables, you can alter the sway rate to match the building. Connected to the gigantic sphere are large dampers, that react to the push and pull of the pendulum. These dampers limit sway by converting the motions of the building into heat. 4.2.4 Reduced beam section (RBS) During previous earthquakes in other parts of the world, a weakness has been found within the modern steel structure that most tall buildings use today. In the wake of the Kobe earthquake, Steel to beam connections were found to have weakened, and yielding occurred within the connection. To eliminate this, sections are cut away from the beam near the connection, which causes yielding to occur within the beam, which increases ductility in the structure. Most importantly it moves the effect of yielding away from the connection itself. Taipei 101 is one of the structures using this technology today19.

Figur 9: Picture of reduced beam section in Taipei 101

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Ingredients of high rise design Taipei 101, Leonard M. Joseph, Dennis Poon & Shaw-song Shieh, 2006, p. 4 Ingredients of high rise design Taipei 101, Leonard M. Joseph, Dennis Poon & Shaw-song Shieh, 2006, p. 4 Figure 9: Ingredients of high rise design Taipei 101, Leonard M. Joseph, Dennis Poon & Shaw-song Shieh, 2006, p. 4 19

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4.2.5 Self righting buildings20 A new system is currently under development in Japan, claiming to hold a multi story building together during a magnitude 7 earthquake, and maybe even higher. This new earthquake proofing is supposedly so efficient, that when the quake is over the building will return to standing up straight on its foundation. The only damage occurring during the shaking will be confined to replaceable parts in the mechanism. Shake table tests of this new system have proven welcoming results, as it will enable inhabitants to return to their homes a lot sooner than in other buildings after an earthquake, as the structure incorporated into the building takes on the damage, instead of the building. This will lead to lower the costs of repair on damaged buildings, and enable people to return to their everyday lives faster. The way this system works is by installing steel braced frames around the exterior of the building, or in its core. The energy from the swaying of the building will be dissipated in the steel structure. To get the building to stand upright on its foundation after the shaking stops, steel tendons which are located in the centre of the braced frames, run from top to bottom, which become elastic during the movement of the building, go back to their original size. Installed in the bottom of the frames, where the bottom end of the cable meets the foundation, are the fuses. The task of these fuses are to prevent the rest of the building from sustaining damage. Their main design is to absorb the energy of the swaying, sustain damage, then be replaced. In Figure 7.1 you can see the fuses coloured in yellow. The utilization of this design is immense, as the steel frame not only can be incorporated into the design of a new building, but can be used

Figur 10: Illustration of self righting building

to retrofit an existing building that needs

20

Self righting buildings, Louise Bergeron. Figure 10: http://x-journals.com/2009/researchers-design-self-righting-buildings-that-survive-earthquake-test-instyle/.

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earthquake proofing. This is immensely cost efficient, as engineers don't have to worry about installing stiffeners or dampeners into the actual structure of the building. It is enough to install the steel frame on the exterior of the building21. 4.3 Base isolation The concept of base isolation is that as the ground moves, the building does not. Of course the base isolators under a building will never be able to totally eliminate the total forces of an earthquake on a building, but it will diminish the vibrations enough to avoid the worst kind of damage. Base isolated buildings use rubber base isolators to absorb the majority of the energy created by the tremors, and give the building a much needed flexibility. An otherwise shorter, stiff building is given the much needed flexibility it doesn't naturally have, whereas a taller building is naturally more flexible. Base isolators resemble large rubber pads and are suitable for hard, sturdy ground. They are not to be used on buildings that rest on softer soils22. This can be observed in the earthquake test in chapter 3.2.

Figur 11: Base isolator v. fixed-base building 21

The X-journals, Louise Bergeron, (http://x-journals.com/2009/researchers-design-self-righting-buildings-thatsurvive-earthquake-test-in-style/). 22 http://articles.architectjaved.com/earthquake_resistant_structures/seismic-base-isolation-technique-for-buildingearthquake-resistance/ Figure 11: http://articles.architectjaved.com/earthquake_resistant_structures/seismic-base-isolation-technique-forbuilding-earthquake-resistance/

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4.4 Good and bad building design There are certain ground rules as to how to construct buildings to avoid stress areas. The safest way to design a building is a single rectangular shape, as the vibrations of earthquakes move in all directions, and this can be a problem in L, or U-shaped buildings. Where the rectangles are connected, the forces of the earthquake moves them if different directions, crushing and pulling them apart, depending on the movement of the ground23. What figure 4 depicts, is that this certain shape of building is a bad construction during an earthquake because it is basically two rectangles jointed together at one spot. The problem with this is that each rectangle has its own free movement during an earthquake, or its own resonance period, and it forces the structure to Figur 12: Drawing of L-shaped building during an earthquake

move in such a way, that it could potentially destroy

the entire section of the building that is joined together. The advantage with rectangular buildings, is that the forces of an earthquake get more or less evenly distributed throughout the building. It is of course not a

Figur 13: L shaped building designed for earthquake forces

shape that cannot be used in earthquake prone countries, but if it is the wish of the designer to use this kind of shape, or the other U and H shapes, you must make the areas where two shapes connect independent from each other. That means that each section of the building is able to respond to the earthquake, without effecting the other section. This can be done by making the areas where they connect flexible, or by using dampeners. If this absolutely cannot be done, and the buildings have to connect, it is possible to reinforce them, or add additional stiffness to the gables with shear walls. This allows the building to act as a single structure24.

23

http://www.samco.org/download/reports/rules.pdf Figure 12: Own drawing 24 http://www.samco.org/download/reports/rules.pdf Figure 13: Own drawing

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When you design the layout of a building you have to understand how forces will act on it. You have to take into account that the vibrations of earthquakes move in all directions, and therefore have to be prepared to brace the building from all angles. Designing buildings to resist the lateral forces of an earthquake are similar to the forces you have to take into account when you design a building to withstand wind forces. The only real difference is the greater forces present during an earthquake, and the forces that move vertically. Now that the general look of the building has been discussed, and how the design can create some weak points where different shapes connect, we can look into how a building can be built up to withstand the forces of the earthquake that run perpendicular to the ground. This can be done by using shear walls, inner shear cores and cross-bracing25. 4.4.1 Simplicity Simplicity is very important in an earthquake zone, as complicated structures can affect the way that loads are dispersed equally, and it creates the need for a lot of unnecessary and complicated calculations. It lowers the risk of forgetting important calculations, such as the interactions of parts with different rigidity. It is important in a structure that will move during ground movement, that the energy dissipation in the structure should be high26. 4.4.2 Soft storeys Soft storeys are typically apartment buildings with parking garages or stores with large windows, placed on the bottom floor. They are called soft storeys because they cannot cope with lateral forces, and typically collapse due to weakness. They are categorized by having a stiffness of 70% or less of what the story above has. Because a soft story is usually a garage or retail space, it typically is located on the bottom floor of a building, which means that if that area of the building fails, the entire building comes down. In many earthquake zone areas, building codes are careful to classify soft storeys, and prohibit the construction of such weak designs in a building. Older buildings built before the tightening of the restrictions have the option to retrofit the building, to strengthen the weak story. This can be done by adding shear walls, and other strengthening details. Soft storeys are such a danger, that most insurance companies refuse to insure houses that have soft storeys27.

25

http://www.nasa.gov/worldbook/earthquake_worldbook.html http://www.fgg.uni-lj.si/kmk/ESDEP/master/wg17/l0500.htm 27 http://www.wisegeek.com/what-is-a-soft-story-building.htm 26

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4.5 Conclusion I have investigated the most used safeguards for buildings in this chapter, and can understand that to design buildings to be earthquake proof, you have to have a deep understanding of how the building will react during shaking. During my investigation for this chapter I noticed that a lot of the knowledge of how to limit dangerous movement in a building comes from information gathered from structures that have already collapsed. By learning from past mistakes engineers have been able to create models showing them how a building had weakened. This is how engineers were able to understand that metal structures had a dangerous flaw to them, that they were only aware of after the major earthquake in Kobe, where they noticed that many of the steel connections had given way. If a meticulous investigation into the collapsed structures had not been performed in the affected area, then this flaw would still be applied to buildings now. Also it is known that buildings must be as simple as possible, as you want to understand how the forces of an earthquake get dissipated through the structure safely. You have to have a clear understanding of the path that the stresses follow, so you can design a building that can safely transfer them to the foundation and ground. By using a soft story as an example, there is clearly no uniform design to the structure. The upper storeys are able to disperse the loads safely downwards, but as the soft story doesn't have the same stiffness as the rest of the building, it is unable to handle two forces acting upon it. Because we know that stiffness if very important in an earthquake resistant design (chapter 5), a change in the stiffness in a lower level of a building means that the frequency of that part of the building is different. As explained in chapter 4.4, it can be disastrous when one building is not built as a single unit with a unified resonance period. You have to work by the same theory when adding stories to a building. They have to have the same stiffness.

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5. Understanding the forces on a building In this chapter I discuss which forces are at work on a building during an earthquake, and how the forces are brought safely down the building, limiting the damage as much as possible. In the previous chapter I investigated the different methods of preventing too much movement and sway by using various innovations and designs, and also how the shape of a building can dramatically affect how the building responds during an earthquake. Now I will go deeper into the structure, to try and make sense of how these different movements present during an earthquake react in the structure of a typical high rise building. 5.1 Inertia forces Before investigating how a building handles the swaying movement of an earthquake, you have to understand which force in acting on the structure. The force acting on a building during ground movement is inertia. Inertia is not a real force, like when the wind pushes on a building, but an effect caused by an objects own inertia when it is on something moving. The best way to understand inertia is to picture a moving vehicle. When a car moves forward, it is not some invisible force pushing you back, but the back seat pushing you forward. You feel squeezed back in the seat because the car is accelerating, and your inertia is trying to keep you at rest28. What is acting on the building is called inertia (F) , or Newton's second law, as it is most commonly called. The equation for the second law of dynamics is F = m*a. The equation shows that the force acting on the building is equal to the mass times the acceleration. When the acceleration of the building increases, so does the force. The figure for the mass of the building will always be a constant, as the buildings mass never changes. It is import during the design stages of a building that the mass of the building is kept low, as a lower number (m) in the equation, will lower the value Figur 14: Frequencies for different sizes of buildings

of F. It is also possible to reduce the acceleration (a), by implying some of the

28

http://www.suite101.com/content/understanding-physics-of-inertial-forces-a129313 Figure 14: http://faculty.washington.edu/tpratt/frequencies.htm

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dampening techniques from the previous chapter. 29. The vibrations of an earthquake move in all directions, but the most damaging movement of the ground is when vibrations move parallel to the surface of the ground. This is dangerous for buildings because they are mainly designed to handle vertical gravity loads. How an earthquake effects a building is mainly down to its construction, like how well it can resist shaking. Also its dead weight has a lot of influence on its behaviour during an earthquake. One very important aspect to have in mind when you want to avoid damage to a building during an earthquake is the building's vibration period. Many things can affect this, such as its weight, height, stiffness, and its ability to absorb energy30. It is known fact that taller buildings have a tendency to have longer resonance frequencies. The rule of thumb is 0.1 x (the number of stories in a building)31. To define the frequency period, the frequency is the number of movements back and forth per second, and the period is how long one cycle (back and forth) takes. By counting the number of cycles, you can find the frequency (Hz), as seen in fig. 5.1. As the table shows, a smaller building has a higher frequency than a taller building. A taller building has more of a tendency to sway slowly from side to side. 5.1 The dangers of frequency The real danger to buildings, either short or tall, is the natural frequency of the building. When the vibrations of the ground and the vibrations of the building move in the same frequency, resonance occurs. This causes the building to move in its own natural frequency. The amplitude of the back and forth motion will increase for each cycle, as the vibrations exist. If the building gets to a point where the movement is too great for the structure to cope, the building will collapse32. The best way to illustrate this is to picture a child being pushed on a swing, as this acts like a pendulum. If you push the child in the natural interval of the swing (resonant frequency), the child will swing higher and higher. The swing absorbs a maximum amount of energy when you push it in phase with the swings own oscillations. The amount of force needed to push the child higher and higher is actually very small, and the same principle is for 29

http://mceer.buffalo.edu/infoservice/reference_services/buildingRespondEQ.asp Simplified building design for wind and earthquakes, by James Ambrose, Dimitry Vergun, p. 21 31 http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/earthquake_effects.html 32 http://www.intuitor.com/resonance/swings.html 30

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buildings. An earthquake doesn't necessarily need to be devastatingly large to cause a building to collapse. It only has to be large enough to make the building swing in its own oscillations. Taller buildings are prone to having smaller natural frequencies that shorter buildings. This is because buildings tend to have lower natural frequencies when: 

They are heavier



Are more flexible

The equation for natural frequency33:

F = Natural frequency (hertz) K = The stiffness of the building M = The mass of the building

5.2 Tacoma Narrows Bridge The natural frequency of a building is the most dangerous movement a building can undergo. One of the most famous cases of a structure falling apart due to vibrating in its own natural frequency is the Tacoma Narrows bridge. Opened to traffic on the first of July 1940; it was the third largest suspended bridge in America. Its life came to an end on the seventh of November 1940, after a 35 mile an hour wind (about 56 kilometres) pounded on it for three hours. A wind blowing at 35 miles an hour should not be able to cause the collapse of a bridge, but due to the lack of knowledge about forces, and the shape of the suspended part of the bridge, the moderate winds made it collapse. The speed of the wind unfortunately matched the natural oscillations of the bridge. Suspended bridges were pretty new in those days, and built with rigid structures strengthen by trusses, which allowed wind to pass through. The Tacoma Narrows bridge used plate girders instead,

33

http://www.ideers.bris.ac.uk/resistant/vibrating_build_natfreq.html

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which made the whole suspended part act like a giant wing, allowing the wind to act more easily on it34.

5.3 Diverting the forces of an earthquake safely Well built reinforced structures that are built for earthquakes have reliable load paths, that efficiently direct the loads posed on them safely to the foundation, where the loads can be transferred into the ground. To get these forces into the ground, careful consideration of the ground and floor plans must be made. There are two types of primary load paths. The horizontal load paths, and the vertical. The vertical load paths include Shear walls, braced frames and moment frames. The horizontal load paths include the roof, floors and foundation. 5.4 How shear forces work When loads run perpendicular to the main axis on a shear wall seismic forces cause an overturning moment, which courses tension at one end, and compression at the other. Shear walls must have a strong lateral strength to resist the horizontal forces that occur during an earthquake. If the wall is built strongly enough, the forces will continue down the load path. This could be another shear wall, column, slab, foundation, and so forth. Shear walls also have lateral stiffness, that prevents roofs and upper floors from excessive side swaying35.

Figur 15: Functions of a shear wall

Using shear walls is a very effective and highly used method of protecting a building from damage during an earthquake. It is frequently used in poorer countries, as it is relatively

34

http://www.vibrationdata.com/Tacoma.htm http://www.abag.ca.gov/bayarea/eqmaps/fixit/manual/PT07-Ch-3A.PDF Figure 15: Sheer walls, Timothy P. McCormick, P.E., p. 23 35

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inexpensive to apply to the design of a building. Normally the gables of the building will be one solid wall, with no openings.

5.5 Steel structure of an earthquake resistant building 5.5.1 Special moment frames (SMF) Moment frames are box shaped frames, that have special moment joints or connections. Its members and joints are able to withstand flexural and axial forces. The word moment, in SMF refers to the moment of inertia. In the case of inertia caused by earthquakes and not wind, the inertia that one should worry about is internal inertia coming from the ground. A good way to illustrate internal inertia, is to imagine a man riding a train which takes off fast. The sensation of being swiftly shaken from the ground up is internal inertia. Moment frame buildings are supposed to be able to slightly warp and bend during small earthquakes. It is important that they act almost like rubber bands. They are able to deform, but return to their former state. They are commonly used for low-rise buildings, as they are more expensive that the concentrically braced frames. When a large earthquake occurs, a moment frame building must sustain permanent damage. This might seem odd, as normally you would want to eliminate damage as much as possible, but to save the rest of the building the frame must bend and absorb energy without failing. A frame that is improperly built will be brittle and break, and not save the building from the forces. Special moment frames are one of two other types of moment frames (ordinary moment frames and intermediate moment frames). The only thing separating these types of moment frames, is their ability to handle different scales of earthquakes. OMF can only handle small tremors, while IMF can handle moderate earthquakes. SMF are the heavy duty moment frames, which must be used in high seismic areas. It has a high rigid standard, which the other frames do not36. In a steel special moment frame it is required that inelastic behavior occurs in beam to column joints, and at column bases. The deformation on the structure results in buckling of

36

http://www.wisegeek.com/what-is-a-moment-frame.htm

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these areas, and these areas only. Though, the beam to column connects must be able to transfer moment and sheer forces safe safely down the column, as too severe buckling of the steel in the beam/column connections can lead to a loss of strength in the steel37. In these connection it could be wise to employ the reduced beam sections, to help eliminate the yielding that occurs dangerously around the joint, and spread it out in the beam. 5.5.2 Braced frames Braced frames are one of the most efficient ways to protect against lateral loads. Braced frames are shown to have much higher resistance to lateral loads than moment frames, and have a superior quality of ductility. There are two types of bracing; internal and external. The external bracing is typically used during retrofitting of an existing building, to upgrade it to withstand the forces of an earthquake38. It is also commonly used as an architectural feature in modern skyscrapers, because of its esthetical purposes, as a main feature of the look of the exterior. 5.5.2 Special concentrically braced frames (SCBF) Concentrically braced frames are vertical truss systems that resist lateral loads through the axial forces in members. Concentrically braced frames belong to a group called dissipative structures. The level of energy absorption in these frames are similar to the energy absorption of moment frames. The SCBF is a good economical solution for medium to high-rise buildings. The seismic forces in this type of bracing systems are resisted by compression and tension. There are three main types of concentric truss bracings: 

Diagonal type - The horizontal earthquake forces are resisted by tension braces only. These bracings look like giant X´s.



Type V or L- Both tension and compression braces are used to resist the forces. These braces have a V or L shape.



Type K - This type of bracing is not recommended as it does not offer any ductile behavior.

37 38

Steel moment frames, Scott M. Adan, Ph.D., S.E., SECB and Ronald O. Hamburger, S.E., SECB. Seismic performance of RC frames with concentric internal steel bracing, M.A Youssef, p. 1

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5.5.3 Eccentrically braced frames (EBF) The eccentrically braced frame system is a lateral load resisting system for steel structures. It is basically a hybrid of a frame system and concentric truss bracing. They are highly attractive as a method for strengthening a building as they are extremely stiff, which excellent ductility and energy dissipation.

Figur 16: Braced frames (http://www.fgg.uni-lj.si/kmk/ESDEP/master/wg17/l0500.htm)

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5.6 Conclusion In this chapter I attempted to investigate the forces acting upon the building during an earthquake, and what the danger factors are, including the different methods for safely dispersing the forces. I found out that inertia plays a vital role, and it is mainly this force that engineers and architects must design the buildings around. In the previous chapters, including this one, I have learnt that there are many structural design and implementations one can do to protect the buildings from swaying out of control. One is the main structure of the building; It must be rigid and have a low mass. Also the acceleration must be controlled by using dampeners or some form of base isolation. The point is to limit the strength of the inertia effecting the building. Also designers have to create load paths which the energy can follow and be dispersed in the soil underneath the foundation. Combining what you know about inertia and the different techniques available to counter act the forces of an earthquake, it is pretty easy to construct a very strong and durable building.

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6. Building codes in Japan To help prevent buildings from collapsing during a seismic event authorities recognized that it is necessary to set rules and guidelines, to prevent unsafe buildings from being constructed in their cities. Building codes have mainly been possible due to vigilant observation on earthquake sites, taking notes on the different reasons for some buildings collapsing while other have come through unscathed. John Milne was one of the first to recognize the importance of gathering information, for further study. 6.1 John Milne (1850 - 1913) Born in Liverpool, England, and educated at kings college in London, he was appointed as professor of geology and mining in the imperial college of engineering in Tokyo in 1875. He became known as `Earthquake Milne` in Tokyo, after developing an interest in seismology. He , and two other British geologist founded the Seismological society of Japan in 1880. Milne found it very important to register and document every earthquake to hit the country, and even asked the postal authorities in every town in Japan to register and send weekly updates on the amount of earthquakes felt during the week. He also set up 900 monitoring stations around the country, and invented a seismograph, to assist in monitoring the sizes of the earthquakes39. In 1894 Milne returned to England, where he set up his home in Shide, on the Isle of Wight. This location became the center for the international system of gathering and distributing seismological data. 6.2 The 1919 urban building law The 1919 urban building law was Japans first attempt to create common laws for constructing earthquake safe buildings. It was created to regulate building construction in six of the major cities of Japan40. Law enforcement order of 1920:  

39 40

Height limit for buildings of 30.5 meters. Structural design for masonry, timber, reinforced concrete, brick and steel structures

http://www.answers.com/topic/milne-john Historical development of building codes in Japan, Shunsuke Otani Chiba University.

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Law enforcement regulations of 1920:     

Specifications for structural design Allowable stress design Quality of the materials Live and dead loads No seismic requirements

1924 Revision of law enforcement regulations: There came an introduction of seismic design forces in the revision.   

Maximum ground acceleration at the University of Tokyo = 0.3G Safety factor in allowable stress design = 3.0 Seismic coefficient = 0.3/3.0 = 0.1

41

Figur 17: Seismic coefficient

41

Historical development of building codes in Japan, Shunsuke Otani Chiba University. Figue 17: Historical development of building codes in Japan, Shunsuke Otani Chiba University

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6.3 Building codes following the rebuilding of Japan after WW2 In the wake of the second world war there was a need for an orderly and efficient rebuilding of the country. New laws were implied to build safer housing for the population of Japan42. 1. Building standard law (1950) - This law was implemented to safeguard the life, property and health of people by providing minimum standards for the site, equipment, structure, and use of the buildings. 2. Architect law (1950) - This law was made to define the qualification of engineers who design buildings and supervise construction work. 3. Construction trade law (1949) - This law was implemented to improve the quality of those engaged in the construction trade, and to promote fair construction contracts. There are three types of qualified architects (Kenchiku -shi): 1. 1st class Kenchiku-shi - Can design and superintend work on all buildings. 2. 2nd class Kenchiku-shi - Can design and superintend work mainly only on small buildings. 3. Mukuzo Kenchiku-shi - Can design and superintend work on only small wooden buildings.

There was an emergency revision of the Building standard law in 1971, following concerns with reinforced concrete columns. It asked for a narrower spacing of column ties, after many concrete columns had completely fallen apart from within during an earthquake in 1968 . This is one example of how important it is to continue to observe and report damage from earthquakes, and to also continue to study the effects in laboratories to continually apply findings to the building codes. Japanese building codes are different than the ones that you might find in places like the America and Canada, where earthquakes are also common. In the America building codes are not enforced by law, unlike Japan where it is the central government that has put up the building codes as an enforced administrative law, meaning that it is illegal not to construct following them. Japan today uses the Building Standard law (BSL) that was first put in effect in 1950, with revisions and amendments that have been added following findings from major earthquakes over the decades.

42

Historical development of building codes in Japan, Shunsuke Otani Chiba University.

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6.4 Conclusion In this chapter I investigated the building codes used in Japan. What I found out was that it was an English man who first created a seismological society in Japan, following his own interest in the subject. I also found out that they already started creating laws on buildings as early as 1919, and fully mastered it after the war in 1950.

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7. Conclusion In this dissertation about earthquakes and their effects on buildings, it is clear how important it is to understand not only the causes and effects that earthquakes have on buildings, but also how to avoid damage and loss of life. In the beginning of the report I asked myself questions that I thought were fundamental in understanding the topic fully. My main question was "how do you build a multistory building to avoid damage, and prevent loss of life?". In this question I found a lot of theories and methods for such problems. I focused my research on Japan, and found an abundance of techniques, such as counter weights, dampeners and base isolators. The field of earthquake proofing technologies is forever evolving and improving, and however tragic it sounds, future devastating earthquakes help us make the future a little more safe, as scientists and researchers pour through gathered information, which they then apply to new buildings. Also I wanted to understand what happens to a building when it is shaken by the earth, and I found out that it is basically down to physics. Inertia is what makes the building sway, and the trick to keeping a building safe is to cancel out this back and forth movement as much as possible. The most dangerous phenomenon to occur to a building while the ground is moving is when the ground makes the building sway in its own natural frequency. This is what brought down the bridge, that became infamous for this very thing. Japan are really the front runners when it comes down to this field, and they seem to understand the importance of mastering each step of construction, down to the design itself. They have three classes of architects, each specializing in one specific field, which is really a very intelligent method of design. As I stated in the report, the design of the building is incredibly important, as it must be designed to handle violent movement without collapsing. The other questions I asked myself in the beginning, were questions such as "how does Japan cope with earthquakes in Tokyo?" and questions regarding building codes and height limits. I found out that when an earthquake happens in the area of Tokyo there is not much anyone can do but run for cover. I was surprised to find out that the amount of time you have from the quake to the actual warning is just mere seconds. That makes me understand how important it is that the population is not only fully briefed on what actions to take, but also to have a secure home or building to shelter in. Japan have a very excellent building code, which is mandatory by law for all to follow, that has been improved since it was first published in the 1950´s. The last question that I wanted to find

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out was if there were any specific build heights you were not allowed to exceed, and according to the building codes in Japan this is 30.5 meters. Honestly, looking at the skyline of Tokyo, there must be some way to get around this limit, as there are many buildings clearly exceeding the limit. I suspect that there are permits you can apply for, if you can document that your building is safe from the maximum earthquakes. Now that I have completed this dissertation I feel that all the question I previously had before I started writing have been answered, and I know more about this subject than I ever thought that I would.

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8. Literature list

Books: Earthquake Resistant Design of Structures, by Pankaj Agarwal, Manish Shrikhande Japan: large-scale floods and earthquakes, By Organisation for Economic Co-operation and Development The Independent: Tokyo faces catastrophic earthquake risk, Richard Lloyd Parry, 1996 Risk assessment models, RMS Ingredients of high rise design Taipei 101, Leonard M. Joseph, Dennis Poon & Shaw-song Shieh, 2006 Simplified building design for wind and earthquakes, by James Ambrose, Dimitry Vergun Sheer walls, Timothy P. McCormick, P.E Steel moment frames, Scott M. Adan, Ph.D., S.E., SECB and Ronald O. Hamburger, S.E Seismic performance of RC frames with concentric internal steel bracing, M.A Youssef Historical development of building codes in Japan, Shunsuke Otani Chiba University Articles: Earthquake early warning, Kinkyu Jishin Sokuhou, 1 April 2009

Earthquake early warning, Administration Division, Seismological and Volcanological Department Japan Meteorological Agency, 10 August 2007

Info from Japanese flyer of do´s and don´ts

Self righting buildings, Louise Bergeron

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Base Isolation http://articles.architectjaved.com/earthquake_resistant_structures/seismic-base-isolationtechnique-for-building-earthquake-resistance/

Web pages: Earthquakes http://www.wisegeek.com/what-are-earthquakes.htm

Predicting earthquakes http://www.geography-site.co.uk/pages/physical/earth/pred.html

Earthquake early warning http://www.jma.go.jp/jma/en/Activities/EEWLeaflet.pdf Discovery Channel http://dsc.discovery.com/guides/planetearth/earthquake/interactive/interactive.html

Building structure http://www.nd.edu/~tkijewsk/Instruction/solution.html

Fundamental rules for earthquake design http://www.samco.org/download/reports/rules.pdf

NASA homepage http://www.nasa.gov/worldbook/earthquake_worldbook.html

Requirements and Verification of Seismic Resistant Structures http://www.fgg.uni-lj.si/kmk/ESDEP/master/wg17/l0500.htm Soft story http://www.wisegeek.com/what-is-a-soft-story-building.htm

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Understanding physics of inertia forces http://www.suite101.com/content/understanding-physics-of-inertial-forces-a129313

How buildings respond to inertia forces http://mceer.buffalo.edu/infoservice/reference_services/buildingRespondEQ.asp Earthquake effects http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/earthquake_effe cts.html

The physics of resonance http://www.intuitor.com/resonance/swings.html

Natural frequency of a building http://www.ideers.bris.ac.uk/resistant/vibrating_build_natfreq.html

Tacoma bridge http://www.vibrationdata.com/Tacoma.htm

Government webpage http://www.abag.ca.gov/bayarea/eqmaps/fixit/manual/PT07-Ch-3A.PDF

What is a moment frame http://www.wisegeek.com/what-is-a-moment-frame.htm

John Milne http://www.answers.com/topic/milne-john

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