Darren Alphonse and Winifred LaoStevens Institute of Technology

Mentor: Frank XuCo-Mentor: Cooper Hu

Civil Engineering

Basics of Earthquakes Goal of Research Technology and Designs of Earthquake

Engineering Acoustic band gap Theory: Seismic Waves vs. Sound Waves

An earthquake is the shaking of the ground caused by sudden breaking and movement in large sections of plate tectonics.

Most earthquakes happen along fault lines when the plates tectonic slide past each other or collide against each other. This area is called the hypocenter (or focus)

The magnitude of the earthquake depends on displacement of the plate tectonics

The feeling of earthquakes can be explained by the elastic theory.

Elastic Theory-energy is spread during earthquakes.

When the plate tectonics move, they absorb energy, but as they break, they release energy. This energy is how we feel shaking.

The energy that travels from the hypocenter is also known as seismic waves.

◦ Collapse buildings and bridges◦ Destruction of vehicles and railroads◦ Broken power and gas Lines◦ Landslides◦ Snow Avalanches ◦ Tsunamis

All of these events will cause many deaths…

Rank Death Toll   Event   Location   Date  

1 830,000 Shaanxi earthquake China 1556

2 255,000 Tangshan earthquake China 1976

3 240,000 Haiyuan earthquake China 1920

4 230,000 Aleppo earthquake Syria 1138

5 229,866 Indian Ocean earthquake Indonesia, Sri Lanka, India, Thailand 2004

6 200,000 Damghan earthquake Iran 856

7 150,000 Ardabil earthquake Iran 893

8 137,000 Hokkaidō earthquake Japan 1730

9 110,000 Ashgabat earthquake Turkmenistan 1948

10 105,000 Great Kanto earthquake Japan 1923

11 100,000 Messina earthquake Italy 1908

12 100,000 Lisbon earthquake Portugal 1755

13 100,000 Chihli earthquake China 1290

14 86,000 Kashmir earthquake Pakistan 2005

15 85,000 Great Ansei Nankai

earthquakes Japan 1854

16 80,000 Shamakhi Azerbaijan 1667

17 77,000 Tabriz Earthquake Iran 1727

18 70,000 Changma, Gansu earthquake China 1932

19 69,197 Sichuan earthquake China 2008

20 66,000 Ancash earthquake Peru 1970

List of Death Caused by Earthquakes

Seismic waves are the energy released from the movement of the faults.

There are two types of seismic waves: body waves and surface waves

Body waves travels within the earth’s crust and consists of ◦ P waves: also known as primary or compressional waves◦ S Waves: also known as secondary or shear or transverse

waves Surface waves travels along the earth’s surface and consists of:

◦ L waves: also known as Love waves◦ R waves: also known as Rayleigh waves

Body vs. Surface waves

◦ P waves cause the ground to move up and down and is parallel to the direction of the wave

◦ S Waves cause the ground to move back and forth and is perpendicular to the direction of the wave

◦ L waves cause the ground to move sideways and up and down.

◦ R waves cause the ground to move in a rippling up and down motion.

Resonance is the vibration frequency the object receives from sudden movement

Example:

A push will increase the motion of the swing, meaning the swing moves faster for a longer period of time.

How it applies to earthquakes:◦ P waves come first and moves the ground, causing

preliminary damage. ◦ S waves come and moves the ground at the same

frequency as the P waves did, thus creating resonance: increase of movement and greater damage.

◦ R waves and L waves arrive, creating damage in the same manner as the S wave.

Idea: To prevent resonance on a building from occurring.

To find better technology from the effects of earthquakes, specifically movement of buildings.

Mr. Frank Xu’s research is to design technology to absorb energy released by earthquakes to prevent movement of buildings. He is still in preliminary research.

Our goal of this summer is to assist in his preliminary research to help find more methods to prevent earthquake damages.

Diaphragms are horizontal resistance elements (ex. floor or roof)

Shear walls are vertical resistance elements (ex. walls) Brace frames are diagonal resistance elements, can be

connected in many different ways. It is very important that the connection between

diaphragms and shear walls are strong.

Different types of brace

Moment Resistant Frames are the skeletal structure of a building consisting of columns and beams

They must be strongly bolted together

Example of bolted connection Example of Moment Resistant Frames

Base Isolation is a popular choice of design It is when there are structures placed between the building

and foundation. Two known base isolation designs are:

◦ Lead-Rubber Bearing◦ Sliding Isolation System

The building is connected to lead-rubber bearings, which are also attached to the foundation

When an earthquake occurs, the building itself should not be affected, but the lead-rubber bearings are.

The lead absorbs the kinetic energy of the movement of the ground and releases it as heat. The rubber is deformed.

Before and during an earthquake, snapshot of lead-rubber bearings

There is a half spherical bearing, which supports the building and has low friction.

When the ground is in motion because of earthquake, the building moves on the bearing in a pendulum motion.

Different size bearings results in different pendulum period length.

Example of Sliding Isolation System

The idea of damping is to dissipate the energy that is concentrated on one area.

The base isolation designs considered damping the energy from earthquakes because:◦ Lead-Rubber Bearings Design: the energy is converted to

heat◦ Sliding Isolation System: the movement of the building in

the pendulum motion cancels out with the energy causing the movement of the building

P waves and sound waves are similar because they are both mechanical waves (meaning the wave requires a medium to transport their energy)

P waves and sound waves also travel similarly:

One particle vibrates and hits the next one and continues pattern

How a sound is created (using tuning fork)

Acoustic Band gap- is the acoustic wave equivalent of an electronic or photonic band gap. Where a wide range of frequencies are forbidden to exist in

a structured material. If acoustic bandgap is used, then the amount of sound is

control.

Since P-waves and Sound waves are similar in movement we can apply the same idea of controlling sound wave frequencies to controlling seismic wave frequencies.

Sound can be controlled by acoustic bandgap. Theory: Seismic waves can be controlled by a technology

similar to acoustic bandgap.

Earthquakes are caused by breakage of plate tectonics. The energy released from breakage of plate tectonics is

seismic waves and that is how we feel earthquakes. There are four types of seismic waves: P waves, S waves, L

waves, R waves. Resonance is damaging to buildings. Base isolation is used to dissipate energy from being

concentrated in one area There are two types of base isolation: lead-rubber and

sliding isolation system Sound waves and P waves are very similar

To test theory Comparing different types of earthquake designs.

Ahmadizade, Mehdi. Structural Properties. 25 July 2006. <http://mceer.buffalo.edu/connected_teaching/lessons/aboutEQengineering.pdf>.

Bertero, V. V. Earthquake Engineering. October 1997. <http://nisee.berkeley.edu/bertero/index.html>.

Henderson, Tom. The Nature of Sound. 2009. <http://www.physicsclassroom.com/Class/sound/u11l1a.cfm>.

Leung-Wai, Jason and Ganesh Nana. "Economic Impact of Seismic Isolation Technology." Report to: Ministry of Research Science and Technology. June 2004.

Mork, Peter. Earthquake Resisting Systems. 29 June 1999. <http://www.atcouncil.org/pdfs/bp1c.pdf>.

Naderzadch, Ahmad. "Application of Seismic Base Isolation Technology in Iran." Feb 2009.

Taylor, Andrew W. and Takeru Igusa. Primer on seismic isolation. ASCE Publications, 2004.

Mentor Frank Xu Co Mentor Cooper Hu Stevens Institute of Technology Rockefeller University Harlem Children Society Dr Sat Staff