LEC1_Introduction to Earthquake Engineering.pdf

1 EARTHQUAKE ENGINEERING Image referen...

1 EARTHQUAKE ENGINEERING Image reference: https://banner2.cleanpng.com/20180919/ugh/kisspng-earthquake- engineering-building-seismic-retrofit-5ba2b836dc8716.2567771215373906469033.jpg  2 An earthquake is a phenomenon resulting from the sudden release of stored energy in the Earth’s crust which creates seismic waves.  3 A broad-banded vibratory ground motions, resulting from several causes including tectonic ground motions, volcanism, and man- made explosions Image reference: https://i.gifer.com/OCWu.gif  4 Image reference: https://thumbs.gfycat.com/DirtyBogusBaiji-size_restricted.gif  5 Image reference: https://thumbs.gfycat.com/YoungRichAzurevase-size_restricted.gif  6 Damaging effect of earthquakes In general, an earthquake can damage a structure in three different ways: 1. By causing a ground failure 2. By producing other effects that may indirectly affect the structure, e.g., ground cracking, landslides or tsunami 3. By shaking the ground on which the structure rests.  7 1. GROUND FAILURE TYPE: SURFACE FAULTING It is the displacement that reaches the earth's surface during slip along a fault. Image reference: https://media.springernature.com/lw785/springer-static/image/chp%3A10.1007%2F978-94-017-8026-1_20/MediaObjects/305484_1_En_20_Fig7_HTML.gif 1. GROUND FAILURE 8 TYPE: GROUND CRACKING  when the soil at the HORST HORST surface loses its support GRABEN and sinks, or when it is GRABEN transported to a different location  when displaced, a soil layer breaks causing fissures, scarps, horsts and grabens on the ground surface. Image reference: https://lh3.googleusercontent.com/proxy/v6d43YvyK2JpRZoThW0UuW5sbyiSeo9PPVVVZYZAqNNEwTOP9eN3SFawMYH0M-zKp0PZ_-pfeEDRD0XEAeWvUvIldV2xr7m_lN67UC1Qw_c- x9efvuYEZkFeWIMZO3nQdg  9 1. GROUND FAILURE TYPE: GROUND SUBSIDENCE  A phenomenon in which the ground surface of a site settles or depresses as a result of compaction induced by an earthquake’s vibrations  Sites with loose or compressible soils are susceptible  Damage: cracks and/or tilting of building  Pipelines, channels and road embarkments may damage Image reference: https://scx1.b-cdn.net/csz/news/800/2018/1-animationbas.gif  10 1. GROUND FAILURE TYPE: LANDSLIDES  represent the failure of slopes that are marginally stable before the earthquake and become unstable as a result of the violent shaking generated by the earthquake Image reference: https://i.gifer.com/origin/37/376e550dba30cfb106f8c7897d0aae17.gif  11 1. GROUND FAILURE TYPE: SOIL LIQUEFACTION 1906 San Francisco Earthquake  a phenomenon by which fine saturated granular soils temporarily change from a solid to a liquid state and as a result lose their ability to carry loads or remain stable  when a loose soil is vigorously shaken or vibrated Image reference: https://media1.giphy.com/media/fjy5rSzFQVctVlCoxf/giphy.gif  12 2. INDIRECT EFFECTS TO STRUCTURE : TSUNAMIS It is a large sea wave generated mostly by an undersea earthquake. Image reference: https://cdn4.vectorstock.com/i/1000x1000/69/58/earthquake- tsunami-and-volcano-tsunami-vector-19596958.jpg  13 2. INDIRECT EFFECTS TO STRUCTURE: SEICHES  long-period oscillating waves generated by distant earthquakes in enclosed bodies of water such as bays, lakes, reservoirs, and even swimming pools  Occurs when the natural frequency of a water body matches the frequency of the incoming earthquake waves 2015 Nepal Earthquake Image reference: https://thumbs.gfycat.com/UnnaturalGratefulDunnart-size_restricted.gif  14 3. GROUND SHAKING a structure lying on the shaking ground oscillate back and forth and up and down and makes the structure experience large stresses and deformations in the process https://thumbs.gfycat.com/CandidIdioticCockatiel-size_restricted.gif  15 EARTHQUAKE FORCES Depends on magnitude, duration of the earthquake, location, type of foundation soil and type of structure.  16 BRIEF HISTORY OF EARTHQUAKE Robert Mallet  an Irish civil engineer  first earthquake engineer  his report on the 1857 Naples earthquake is the first scientific investigation that included observations of the seismological, geological, and engineering aspects of an earthquake.  17 BRIEF HISTORY OF EARTHQUAKE Modern research on earthquake-resistant structures  began in Japan in 1881  the year of the 1890 Nobi Earthquake  first proposed the use of a lateral force equal to the fraction of the total weight of a building to account for the forces exerted on buildings  18 BRIEF HISTORY OF EARTHQUAKE  study the earthquake and the formulation of practical recommendations for the seismic design of buildings  recommended buildings were to be designed for horizontal forces equal to fractions of the building weight based on different story levels  19 BRIEF HISTORY OF EARTHQUAKE The 20th Century can be divided into three very distinct periods:  First period (until 1950): is characterized by very timid attempts to develop a consistent explanation of the nature of earthquake by recording, 1940 El Centro earthquake.  Second period (1950-1980): coherent theory development: limited information concerning the characteristics of ground motions and damage done by these earthquakes.  Third period: A dense network of instrumental seismic stations characterizes the last period of 20th Century with large number of records and developing of anti-seismic concepts.  20 End. 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