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Darren Alphonse and Winifred Lao Stevens Institute of Technology Mentor: Frank Xu Co-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… List of Death Caused by Earthquakes 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 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 Kashmir earthquake 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 leadrubber 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/aboutEQen gineering.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