Earthquake Engineering

Earthquake Engineering Darren Alphonse and Winifred Lao Stevens Institute of Technology Mentor: Frank Xu Co-Mentor: Cooper Hu Civil Engineering

Table of Contents/ Overview • Basics of Earthquakes • Goal of Research • Technology and Designs of Earthquake Engineering • Acoustic band gap • Theory: Seismic Waves vs. Sound Waves

What is an Earthquake? • 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

How do we feel Earthquakes? • 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.

Earthquake Results Include • 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…

Statistics about Earthquakes List of Death Caused by Earthquakes

Seismic Waves: Energy Released • 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

Seismic Waves: Diagram • 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: Damaging Buildings • 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.

Resonance: Damaging Building (cont’d) • 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.

Goal of Research • 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.

Existing Designs: Basic • 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

Existing Designs: Moment Resistant Frames • 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

Existing Designs: Base Isolation • 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

Base Isolation: Lead-Rubber Bearing • 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

Base Isolation: Sliding Isolation System • 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

Importance of Damping • 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

Seismic Waves vs. Sound Waves • 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 Bandgap • 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.

Our Theory • 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.

Summary • 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

Future Works • To test theory • Comparing different types of earthquake designs.

Bibliography • 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.

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

Thank You!! 

Earthquake Engineering