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Design Steps for Earthquake Resistant Structures


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This Presentation details the formation of Earthquake with the design steps used for Earthquake Resistant Structures.

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Design Steps for Earthquake Resistant Structures

  2. 2. CONTENTS • Introduction • What is an Earthquake? • Causes • Epicenter • Earth’s Interior • Plate Tectonics • Safety Drills • Intensity of Earthquake • Earthquake Wave • Indian Earthquake Zones • Role of RCC Framed Structure
  3. 3. • Base Isolation • How Earth is formed? • Faults • Plate Movement • Design Steps for Earthquake Resistant Buildings • Earthquake Resistant Structures • Shape of Building • Strengthening of Foundation and Wall • Methods of making Flexible Design • Earthquake Hazards
  4. 4. INTRODUCTION • An earthquake is a series of vibrations on the earth's surface caused by the generation of elastic (seismic) waves due to sudden rupture within the earth during release of accumulated strain energy. • The earth’s different layers are in constant motion, their movement is due to many different aspects like underground volcanic activity or oceanic movements etc. • Due this constant motion, small intensity earthquakes occur continuously on all faults around the world. • Science has yet to discover a sound method of predicting these seismic cataclysms. • It is always beneficial to be prepared for any situation even if there are no chances of earth quakes.
  5. 5. What is an earthquake? • An earthquake is a shaking of the ground caused by the sudden breaking and movement of large sections (tectonic plates) of the earth's rocky outermost crust. The edges of the tectonic plates are marked by faults (or fractures). Most earthquakes occur along the fault lines when the plates slide past each other or collide against each other. • The shifting masses send out shock waves that may be powerful enough to alter the surface of the Earth, thrusting up cliffs and opening great cracks in the ground and cause great damage ... collapse of buildings and other man-made structures, broken power and gas lines (and the consequent fire), landslides, snow avalanches, tsunamis (giant sea waves) and volcanic eruptions
  6. 6. CAUSES OF EARTHQUAKE The primary cause of an earthquake is faults on the crust of the earth. “A Fault is a break or fracture b/w two blocks of rocks in response to stress.” This movement may occur rapidly, in the form of an earthquake or may occur slowly, in the form of creep. Earth scientists use the angle of the fault with respect to the surface (known as the dip) and the direction of slip along the fault to classify faults.
  7. 7. • Thrust (reverse)fault: • Classification Of Faults Normal fault: a dip-slip fault in which the block above the fault has moved downward relative to the block below. • Thrust (reverse)fault: a dip-slip fault in which the upper block, above the fault plane, moves up and over the lower block. • Strike-slip fault: A left-lateral strike-slip fault : It is one on which the displacement of the far block is to the left when viewed from either side. A right-lateral strike-slip fault: It is one on which the displacement of the far block is to the right when viewed from either side.
  8. 8. • Some major causes of earthquakes on basic of its causes are: • Surface causes Volcanic causes Tectonic causes Surface cause: Great explosions, landslides, slips on steep coasts, dashing of sea waves , avalanches , railway trains, heavy trucks, some large engineering projects cause minor tremors. some of them are man made, other are natural. • Volcanic cause: Volcanic eruptions produce earthquakes. Earthquakes may precede, accompany and frequently follow volcanic eruptions. They are caused by sudden displacements of lava within or beneath the earth crust.
  9. 9. • There are two general categories of earthquakes that can occur at a volcano: volcano-tectonic earthquakes long period earthquakes. • Tectonic cause: Structural disturbances resulting in the parts of the lithosphere is the main cause of this type of earthquake. Most of the disastrous earthquakes belong to this category and occur in areas of great faults and fractures. Sudden yielding to strain produced on the rocks of accumulating stress causes displacements especially along old fault zones known as great transform faults.
  10. 10. What is an Epicenter? • The epicenter, epicentre or epicentrum is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates.
  11. 11. • In the case of earthquakes, the epicenter is directly above the point where the fault begins to rupture, and in most cases, it is the area of greatest damage. However, in larger events, the length of the fault rupture is much longer, and damage can be spread across the rupture zone.
  12. 12. Epicentral distance • During an earthquake seismic waves propagate spherically out from the hypocenter. Seismic shadowing occurs on the opposite side of the Earth from the earthquake epicenter because the liquid outer core refracts the longitudinal or compressional (P-waves) while it absorbs the transverse or shear waves (S-waves). Outside of the seismic shadow zone both types of wave can be detected but, due to their different velocities and paths through the Earth, they arrive at different times. By measuring the time difference on any seismograph as well as the distance on a travel- time graph at which the P-wave and S-wave have the same separation, geologists can calculate the distance to the earthquake's epicenter. This distance is called the epicentral distance, commonly measured in ° (degrees) and denoted as Δ (delta) in seismology. • Once epicentral distances have been calculated from at least three seismographic measuring stations, it is a simple matter to find out where the epicenter was located using trilateration. • Epicentral distance is also used in calculating seismic magnitudes developed by Richter and Gutenberg.[8][9]
  13. 13. EARTH’S INTERIOR • Five billion years ago the Earth was formed in a massive conglomeration and bombardment of meteorites and comets. • The immense amount of heat energy released by the high-velocity bombardment melted the entire planet, and it is still cooling off today. • Denser materials like iron (Fe) from the meteorites sank into the core of the Earth, while lighter silicates (Si), other oxygen (O) compounds, and water from comets rose near the surface. • The earth is divided into four main layers: • Inner core • Outer core • Mantle • Crust
  14. 14. PLATE TECTONICS • The Earth releases its internal heat by convection, or boiling much like a pot of pudding on the stove. • Hot mantle rises to the surface and spreads laterally, transporting oceans and continents as on a slow conveyor belt. • The speed of this motion is a few centimeters per year, about as fast as your fingernails grow. • The new crust cools as it ages and eventually becomes dense enough to sink back into the mantle. • The subducted crust releases water to form volcanic island chains above, and after a few hundred million years will be heated and recycled back to the spreading centers.
  15. 15. • The boundary formation at the different faults is categorized according to the type of motion of the plates at the boundary. The types are: • Divergent Plate Boundary, in which the motion of the adjacent plates is opposite each other. • Mid-Ocean Ridges are created when plates collide on ocean floors.
  16. 16. • Convergent plate boundaries, in which adjacent plates collide head-on with each other. • In Transform plate boundaries, the adjacent plates slide against each other. • Complex boundaries, comprise of more than one type of movements of the plates.
  17. 17. FORESHOCKS, MAINSHOCK AND AFTERSHOCKS • A major earthquake never occurs alone. • The mainshock, which is the earthquake with the highest magnitude, is accompanied by foreshocks and aftershocks. • The smaller intensity shocks, which occur before the mainshock is called the foreshock. • The fault that moves in the mainshock experiences massive redistribution of stress and this disrupted surface causes most of the aftershocks. • The higher the magnitude of the mainshock, the larger the radius in which the aftershocks will be felt. For example, the aftershock zone of magnitude 5 earthquake will be around 5 miles while that of a magnitude 8 will be more than 200 miles. • The quantity of aftershocks also depends on the magnitude of the mainshock. For example, a magnitude 5 aftershock will produce in a sequence 10 magnitude 4 aftershocks, 100 magnitude 3 aftershocks and 1000 magnitude 2 aftershocks and so on.
  18. 18. FAMILY EARTHQUAKE DRILLS • This will help you and your family plan and react; remembering where to seek shelter and how to protect yourselves. • Identify safe spots and places in each room • Under a doorway, sturdy table, desk, or kitchen counter. • Against an inside corner or wall; cover head with hands. • Know and reinforce these locations by practice. • Beware of danger zones and stay clear of • Windows that may shatter, including mirrors and picture frames. Heating units, fireplace, stove, and area around chimneys. • Cabinets, refrigerators, and bookcases that may topple. • Practice safe quake actions Conduct drills, check reactions and choices.
  19. 19. FAMILY EARTHQUAKE DRILLS (contd.) • Earthquake occurs with no warning; therefore, life protecting actions must be taken at the first indication of ground shaking. • Before the Earthquake • Identify potential dangers in the home using common sense, fore-sight, and your imagination to reduce risk in the event of an • earthquake. • Take active security measures, surveying the home for possible • hazards. • Take steps to correct and secure these hazards, reducing risk. • Tall heavy furniture which could fall; fix it to a wall. • Hot water heaters that can fall away from pipes need to be • anchored to a wall. • Be sure heavy mirrors or picture frames are placed away from beds and
  20. 20. • During the Earthquake • If inside the house • Take cover under a table or other sturdy furniture, keeping close to the floor. Be ready to move if the cover becomes unstable or shaky. • If there is no sturdy cover available, then stay close to a structurally sound interior wall keeping hands on the floor for balance. • Do not stand in doorways and move away from windows, mirrors and other heavy objects which are unsecured. • If in bed, cover yourself with pillows and blankets. • Do not try to run outside and never use a lift/elevator. But if the house construction is not sturdy then move outside cautiously.
  21. 21. • If outdoors • Move out in the open and stay there until the shocks die off. Keep • away from buildings, streetlights, wires and other structures. • If the house is badly damaged, try to collect essential items, • important documents and leave. • Do not reenter and stay away from damaged buildings.
  22. 22. • After the Earthquake • After the main shock, be prepared for aftershocks. They are less in intensity but can cause further damage to structures which are weakened by the main shock. • Use flashlights instead of candles and lanterns to avoid fire hazards. • If a building is safe then remain inside but if the structural damage is questionable then evacuate cautiously. • Provide help to trapped or injured people. Give first-aid if possible. • Keep abreast of the latest emergency news if possible. • Stay out of damaged buildings. • Return home only when the authorities declare it safe. • Check for electrical damages, gas leakages and other damages.
  24. 24. EARTHQUAKESEARTHQUAKES • Caused by plate tectonic stresses sudden movement or shaking of the Earthsudden movement or shaking of the Earth • Located at plate boundaries • Resulting in breakage of the Earth’s brittle crust
  25. 25. EARTHQUAKE DAMAGEEARTHQUAKE DAMAGE • LandsidesLandsides • Building damageBuilding damage • LiquefactionLiquefaction
  26. 26. LIQUEFACTIONLIQUEFACTION • Results in a loss of soil strength & the ability of the soil to support weight when a solid (sand and soil) becomes saturatedwhen a solid (sand and soil) becomes saturated with water and actswith water and acts like a heavy liquidlike a heavy liquid
  27. 27. EARTHQUAKE INTENSITYEARTHQUAKE INTENSITY Modified Mercalli scaleModified Mercalli scale= measurement of damage to structures= measurement of damage to structures • From I to XIIFrom I to XII (Roman numerals)(Roman numerals) • Descriptive, changes withDescriptive, changes with distance from epicenterdistance from epicenter • Can change from locationCan change from location toto locationlocation What you need:What you need: • Your senses!Your senses! measures damage to man-made structures at certain locationmeasures damage to man-made structures at certain location
  28. 28. ISOSEISMIC MAPSISOSEISMIC MAPS Loma Prieta EarthquakeLoma Prieta Earthquake 19891989 • Connects areas of with theConnects areas of with the same Modified Mercallisame Modified Mercalli numbernumber • Areas are coloredAreas are colored according to Modifiedaccording to Modified Mercalli numberMercalli number show the distribution of intensitiesshow the distribution of intensities
  29. 29. EARTHQUAKE WAVESEARTHQUAKE WAVES • FOCUSFOCUS = place deep within the Earth and along the fault where= place deep within the Earth and along the fault where rupture occursrupture occurs • EPICENTEREPICENTER = geographic point= geographic point on surface directly above focuson surface directly above focus • SEISMIC WAVESSEISMIC WAVES produced by the release of energy – move out in circles from the point of rupture (focus)move out in circles from the point of rupture (focus) – 2 types: surface &2 types: surface & bodybody (travel inside & through earth’s layers)(travel inside & through earth’s layers) • P waves: back and forth movement of rock; travel thru solid, liquid, gas • S waves: sideways movement of rock; travel thru solids only
  30. 30. EARTHQUAKE WAVESEARTHQUAKE WAVES SeismographsSeismographs record earthquake wavesrecord earthquake waves SeismogramsSeismograms show:show: • Amplitude of seismic waves (how much rockAmplitude of seismic waves (how much rock moves or vibrates)moves or vibrates) • Distance to the epicenterDistance to the epicenter • Earthquake directionEarthquake direction
  31. 31. EARTHQUAKE WAVESEARTHQUAKE WAVES • 3 types of seismic waves show up on seismogram3 types of seismic waves show up on seismogram – P waves: shake earth in same direction as wave; travel thru solid, liquid, gas – S waves: Shake earth sideways to wave direction; travel thru solids only – Surface waves: circular movement of rock; travel on surface – cause most damage!!
  32. 32. EARTHQUAKE WAVESEARTHQUAKE WAVES Body P waves S waves waves AKA Moves through Movement of rock Primary (1st to arrive) Longitudinal, Compression all states of matter (solid, liquid, gas) back and forth movement of rock • push/pull or compression/stretch out • Like slinky down stairs Vibration is same as the direction of travel Secondary (2nd to arrive - larger) Transverse, Shear Can go through solids only Move sideways • perpendicular to direction of wave travel • Like snake
  33. 33. EARTHQUAKE WAVESEARTHQUAKE WAVES Lets test your understanding!! Is this a P or an S wave? P wave! S Wave
  34. 34. EARTHQUAKE WAVESEARTHQUAKE WAVES P waves move through solids & liquids S waves move through solids only!!!
  35. 35. EARTHQUAKEEARTHQUAKE MAGNITUDEMAGNITUDE measures the size of seismic wavesmeasures the size of seismic waves  the energy released by the earthquakethe energy released by the earthquake Richter scaleRichter scale=measurement of energy released=measurement of energy released based upon wave amplitude (size of vibration)based upon wave amplitude (size of vibration) • <2 to ~10<2 to ~10 • Amplitude of wave goes upAmplitude of wave goes up by 10 (Logarithmic scale)by 10 (Logarithmic scale) What you need:What you need: • Amplitude (size of vibration = wave height)Amplitude (size of vibration = wave height) • Time between arrival of 1Time between arrival of 1stst P and 1P and 1stst S wavesS waves
  38. 38. ZONING IN INDIA • ZONE 1 • ZONE 2 • ZONE 3 • ZONE 4 • ZONE 5
  39. 39. EARTHQUAKES IN INDIA The major earthquakes in India are 2004 Sumatra Earthquake (9.1) 1934 Bihar Earthquake (8.7) 1950 Assam (Shillong Plateau) Earthquake (8.7) 1897 Assam (Tibetian Plateau) Earthquake (8.5) 2005 Kashmir Earthquake (7.6) 2001 Gujarat(Kutch) Earthquake (7.1)
  40. 40. EARTHQUAKE ZONES IN INDIA There are five seismic zones named as I to V based on Modified Mercalli Scale (MM Scale) as details given below: Zone V: Covers the areas liable to seismic intensity IX and above on MM Scale. This is the most severe seismic zone and is referred here as Very High Damage Risk Zone. Zone IV: Gives the area liable to MM VIII. This, zone is second in severity to zone V. This is referred here as High Damage Risk Zone. Zone III: The associated intensity is MM VII. This is termed here as Moderate Damage Risk Zone. Zone II: The probable intensity is MM VI. This zone is referred to as Low Damage Risk Zone. Zone I: Here the maximum intensity is estimated as MM V or less. This zone is termed here as Very Low Damage Risk Zone.
  41. 41. EARTHQUAKE ZONES IN INDIA Zone V: Kashmir, Punjab, the western and Central Himalayas, the North- East Indian region and the Rann of Kutch fall in this zone. Zone IV: Indo-Gangetic basin and the capital of the country(Delhi, Jammu) and Bihar fall in Zone 4. Zone III: The Andaman and Nicobar Islands, parts of Kashmir, Western Himalayas, Western Ghats fall under this zone Zone II: Other parts of India namely Hyderabad, Lakshadweep, Orissa etc. Zone I : No
  42. 42. EARTHQUAKE ZONES IN INDIA Cities and Zones • Zone III :- Ahemdabad, Vadodara, Rajkot, Bhavnagar, Surat,Mumbai, Agra, Bhiwandi, Nashik, Kanpur Pune, Bhubneshwar, Cuttack, Asansol, Kochi, Kolkata, Varanasi, Bareilly, Lucknow, Indore, Jabalpur, Vijaywada, Dhanwad, Chennai, Coimbatore, Manglore, Kozhikode ,Trivandrum. • Zone IV :- Dehradun, New Delhi, Jamunanagar, Patna, Meerut, Jammu, Amristar,Jalandhar. • Zone V:- Guwahati and Srinagar.
  45. 45. Click to add text Plan of building -Symmetry -Regularity -Simplicity -Separation of Blocks -Enclosed area -Separate Buildings for Different Functions Choice of site GENERAL PLANNING AND DESIGN ASPECTS
  46. 46. TECHNIQUES TO RESIST EARTHQUAKE • Shear walls • Bracing • Dampers • Rollers • Isolation • Light weight material • Bands • Others
  47. 47. SHEAR WALLS Resist; • Gravity Loads • Lateral Loads
  49. 49. BRACING Diagonal Cross Chevron Eccentric Link Beams
  50. 50. DAMPERS
  51. 51. LIQUID TUNED MASS DAMPER One Rincon Hill, San Francisco
  52. 52. ROLLERS
  53. 53. ISOLATION
  55. 55. BANDS
  57. 57. MATERIALS AND BASIC UNDERSTANDING • Shape (configuration) of building: – Square or rectangular usually perform better than L, T, U, H, +, O, or a combination of these. • Construction material: steel, concrete, wood, brick. – Concrete is the most widely used construction material in the world. – Ductile materials perform better than brittle ones. Ductile materials include steel and aluminum. Brittle materials include brick, stone and unstrengthened concrete.
  58. 58. BASE ISOLATION  Base isolation is a passive vibration control system.  The goal of base isolation is to reduce the energy that is transferred from the ground motion to the structure. (a) Conventional structure (b) base isolated structure.
  59. 59. THE PURPOSE OF BASE ISOLATION  As for all the load cases encountered in the design process, such as gravity and wind, should work to meet a single basic equation: CAPACITY > DEMAND. This can be achieved by,  Ductility EFFECTS OF DUCTILITY  Leads to higher floor accelerations.  Damage to structural components, which may not be repairable.
  60. 60. TYPES OF ISOLATOR  Lead rubber bearing (LRB)  Flat sliding bearing (PTFE) COMPONENTS OF LRB
  61. 61. Effects of Base Isolation System
  62. 62. Application of Base-isolated Structure • 1) Government and Municipal Office, • Fire Station, Police Station, • Broadcasting Station • 2) Hospital, Social welfare facilities • 3) Laboratory • 4) Computer Center • 5) Museum, Gallery, Library • 6) Apartment House • 7) Cultural Asset, Historic Structure
  63. 63. 4.6 Billion Years Ago4.6 Billion Years Ago  With the rise of the sun, the remaining material began to clump up. Small particles drew together, bound by the force of gravity, into larger particles. The solar wind swept away lighter elements, such as hydrogen and helium, from the closer regions, leaving only heavy, rocky materials to create smaller terrestrial worlds like Earth. But farther away, the solar winds had less impact on lighter elements, allowing them to coalesce into gas giants. In this way, asteroids ,comets, planets, and moons were created.
  64. 64. ..  Earth's rocky core formed first, with heavy elements colliding and binding together. Dense material sank to the center, while the lighter pieces created the crust. The planet's magnetic field probably formed around this time. Gravity captured some of the lighter elements that make up the planet's early atmosphere.  Early in its evolution, Earth suffered an impact by a large body that catapulted pieces of the young planet's mantle into space. Gravity caused many of these pieces to draw together and form the moon, which took up orbit around its creator.
  65. 65. ..  Although the population of comets and asteroids passing through the inner solar system is sparse today, they were more abundant when the planets and sun were young. Collisions from these icy bodies likely deposited much of the Earth's water on its surface. Because the planet is in the Goldilocks zone, the region where liquid water neither freezes nor evaporates bur can remain as a liquid, the water remained at the surface, which many feel plays a key role in the development of life.
  66. 66. .. 400 Million Years Ago  Life begins developing in the form of trees and plants. These produce more oxygen. Earth has a cooler temperature, with changeable weather. This weather (rain, snow, wind, frost) causes the tops of the ancient volcanoes to wear away, creating lower ground. Dinosaurs eventually develop, ruling the planet. Flowers are later formed, along with insects. 65 Million Years Ago  Life was wiped off the face of the planet! It is believed that a huge meteorite or comet hit the Earth's surface, causing clouds of dust which suffocated the dinosaurs and other creatures on the planet. Conditions on the planet were suffocating as poisonous chemicals were unable to leave the planet's atmosphere, and life-giving energy from the Sun could not enter. After settling again, the Earth was suitable for life, an the ancestors of human beings developed.
  67. 67. TodayToday  Earth is still developing. Volcanoes still erupt, the earth still shakes, weather still forms landscapes. Creatures evolve. Some go extinct, others adapt to the changing planet. Nobody knows what the future holds. The air is becoming more polluted, and the temperature on the planet is gradually rising. Earth remains a target for meteors, comets and asteroids travelling through space.
  68. 68. Naturally occurring earthquakesNaturally occurring earthquakes
  69. 69. Different types of FaultsDifferent types of Faults A close look at faults helps geologists to understand how the tectonic plates have moved relative to one another. Types of movement of crustal blocks that can occur along faults during an earthquake:
  70. 70. The Awatere FaultThe Awatere Fault cuts a clear linecuts a clear line across the hills. Itacross the hills. It last ruptured in thelast ruptured in the 1848 Marlborough1848 Marlborough EarthquakeEarthquake
  71. 71. Plate TectonicsPlate Tectonics  The Earth’s crust is divided into 12 major plates which are moved in various directions.  This plate motion causes them to collide, pull apart, or scrape against each other.  Each type of interaction causes a characteristic set of Earth structures or “tectonic” features.  The word, tectonic, refers to the deformation of the crust as a consequence of plate interaction.
  72. 72. Plate MovementPlate Movement “Plates” of lithosphere are moved around by the underlying hot mantle convection cells.
  73. 73. Divergent Convergent Transform Three types of plate boundary
  74. 74. Spreading ridges ◦ As plates move apart new material is erupted to fill the gap Divergent Boundaries Convergent Boundaries There are three styles of convergent plate boundaries --Continent-continent collision --Continent-oceanic crust collision --Ocean-ocean collision
  75. 75. Continent-Continent- ContinentContinent CollisionCollision Forms mountains, e.g. European Alps, Himalayas Ocean-Ocean Plate Collision When two oceanic plates collide, one runs over the other which causes it to sink into the mantle forming a subduction zone. The subducting plate is bent downward to form a very deep depression in the ocean floor called a trench. The worlds deepest parts of the ocean are found along trenches. E.g. The Mariana Trench is 11 km deep!
  76. 76. Where plates slide past each other Transform Boundaries Above: View of the San Andreas transform fault
  77. 77. Where do earthquakes form?Where do earthquakes form? Figure showing the tectonic setting of earthquakes
  78. 78. Plate Tectonics SummaryPlate Tectonics Summary The Earth is made up of 3 main layers (core, mantle, crust) On the surface of the Earth are tectonic plates that slowly move around the globe Plates are made of crust and upper mantle (lithosphere) There are 3 types of plate boundaries Volcanoes and Earthquakes are closely linked to the margins of the tectonic plates.
  79. 79. Liquefaction : Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. Liquefaction and related phenomena have been responsible for tremendous amounts of damage in historical earthquakes around the world.
  80. 80. Landslide: A landslide, also known as a landslip, is a geological phenomenon that includes a wide range of ground movements, such as rockfalls, deep failure ofslopes and shallow debris flows
  82. 82. GEOMETRYGEOMETRY::  Building need to be proportioned reasonably to avoid unduly long, tall or wide dimensions which are known to result in poor seismic performance during an earthquake. Thus urban by-laws tend to control the overall geometry of the buildings with respect to the plot size. These are helpful in controlling problems like blockade of roads or collapsing on adjacent buildings in an unfortunate situation of a building collapse during an earthquake.  Height/plot width <1.3 as per clause 6.6 NBC(1983) (part III) for plot size and clause 9.4.1 for height. Ex: plot area 10.0x18.0m-Max.permissible height= 1.3x10=13.0m  Length to width ratio<1.66 Clause 6.6 NBC & 8.2.1 for side open space.  Ex: helps in ensuring rigid diaphragm action.
  83. 83.  Plot area 12mx20m -deduct standard setbacks. -Remaining maximum coverage area:6.0mx15.5m. -Maximum possible plan size: 6mx9.6m. LENGTH OF BUILDING:  Shall not be more than 150m.  Clear height of 6m at every 30m intervals at ground level for a passage of 7.5m width. 30m 150m (max) 6m 7.5m
  84. 84.  Thermal consideration requires expansion joints after every 45m. These joints become seismic joints in buildings locates in seismic zones. In such situations, the 150m specified is not relevant. OTHER CONSIDERATIONS: IS 1893 Provisions. -Improve shape and subsequently behavior of building during earthquake shaking. Design provisions may not exist to explicitly limit the height of buildings. But, it is desirable to ensure that - Buildings are not made too long. - Building height gives a regular (desired) slenderness ratio.
  85. 85. 6. For cantilevers it is designed for gravity and other loads as usual for the top bars and thickness but designed in addition to that as per the is code 1893-2002 clause which states: All horizontal projections like corniced and balconies shall be designed and checked for stability for five times the design coefficient specified in 6.4.5(that is =10/3 Ah). HOW TO INCREASE THE DUCTILITY : Ductility; is defined as the ability of a structure to undergo inelastic deformations beyond the initial yield deformation with no decrease in the load. RESISTANCE CAN BE INCREASED IN A SECTION BY: 1. Decrease the percentage of tension steel (pt). 2. Increase the percentage compression steel (pc). 3. Decrease in the tensile strength of steel. (Fy=415N/mm^2). 4. Increase in the compressive strength of concrete.-Min M20 to M30 and above. 5. Increase in the compression flange area in flanged beams (T and L beams) and 6. Increase in the transverse (Shear) reinforcement.
  86. 86. Earthquake-resistant StructuresEarthquake-resistant Structures
  87. 87. While it is not possible to accurately predict earthquakes, measures can beWhile it is not possible to accurately predict earthquakes, measures can be taken to reduce the devastation by constructing earthquake-resistanttaken to reduce the devastation by constructing earthquake-resistant structures. Earthquakes have the ability to level entire office buildingsstructures. Earthquakes have the ability to level entire office buildings and homes, destroy bridges and overpasses, roads, and breakand homes, destroy bridges and overpasses, roads, and break underground water lines. In some cases, building practices are not up tounderground water lines. In some cases, building practices are not up to code, and in the event of an earthquake, the loss of life is catastrophic.code, and in the event of an earthquake, the loss of life is catastrophic. In earthquake-prone areas, buildings are now being constructed withIn earthquake-prone areas, buildings are now being constructed with moorings filled with alternating layers of rubber and steel. These aremoorings filled with alternating layers of rubber and steel. These are called base isolators. The rubber acts as an “earthquake absorber.”called base isolators. The rubber acts as an “earthquake absorber.” Buildings with these types of moorings are designed to withstand aBuildings with these types of moorings are designed to withstand a magnitude 8.3 earthquake.magnitude 8.3 earthquake. In attempts to reduce damage to structures, engineers try toIn attempts to reduce damage to structures, engineers try to Increase the natural period of the structure through “base isolation.”Increase the natural period of the structure through “base isolation.” Install “energy dissipating devices” to dampen the system.Install “energy dissipating devices” to dampen the system.
  88. 88. Simple reinforcement methods used by engineers include usingSimple reinforcement methods used by engineers include using large bolts to secure buildings to their foundations, as well aslarge bolts to secure buildings to their foundations, as well as providing supporting walls, or shear walls, made of reinforcedproviding supporting walls, or shear walls, made of reinforced concrete. This can help to reduce the rocking effect of a buildingconcrete. This can help to reduce the rocking effect of a building during and after a seismic event.during and after a seismic event. Shear walls at the center of the building (around an elevator shaft)Shear walls at the center of the building (around an elevator shaft) can form a shear core.can form a shear core. Employing cross-braces, where walls are built with diagonal steelEmploying cross-braces, where walls are built with diagonal steel beams, adds extra support.beams, adds extra support. World Book illustration by Dan Swanson, Van Garde Imagery
  90. 90. The behaviour of a building during earthquakes depends critically on its overall shape,The behaviour of a building during earthquakes depends critically on its overall shape, size and geometry, in addition to how the earthquake forces are carried to the ground.size and geometry, in addition to how the earthquake forces are carried to the ground. Sometimes the shape of the building catches the eye of the visitor, sometimes theSometimes the shape of the building catches the eye of the visitor, sometimes the structural system appeals, and in other occasions both shape and structural systemstructural system appeals, and in other occasions both shape and structural system work together to make the structure a together to make the structure a marvel. Size of Buildings:Size of Buildings: In tall buildings with large height-to-base size ratio (Figure 1a),In tall buildings with large height-to-base size ratio (Figure 1a), the horizontal movement of the floors during ground shaking is large. In short but very longthe horizontal movement of the floors during ground shaking is large. In short but very long buildings (Figure 1b), the damaging effects during earthquake shaking are many. And, in buildingsbuildings (Figure 1b), the damaging effects during earthquake shaking are many. And, in buildings with large plan area like warehouses (Figure 1c), the horizontal seismic forceswith large plan area like warehouses (Figure 1c), the horizontal seismic forces can be excessive to be carried by columns and walls.can be excessive to be carried by columns and walls.
  91. 91. Horizontal Layout of Buildings: In general,buildings with simple geometry in plan (Figure 2a) have performed well during strong earthquakes. Buildings with re-entrant corners, like those U, V, H and + shaped in plan (Figure 2b), have sustained significant damage. Many times, the bad effects of these interior corners in the plan of buildings are avoided by making the buildings in two parts. For example, an L-shaped plan can be broken up into two rectangular plan shapes using a separation joint at the junction (Figure 2c). Often, the plan is simple, but the columns/walls are not equally distributed in plan. Buildings with such features tend to twist during earthquake shaking. When irregular features are included in buildings, a considerably higher level of engineering effort is required in the structural design and yet the building may not be as good as one with simple architectural features.
  92. 92. STENGTHENING OF FOUNDATION AND WALLS Strengthening of structural system are very necessary because if foundation isnt strong enough to with stand the load, the whole building will collapse. • If the soil is loose, we choose pile foundation for the building till the pile reach the hard strata of earth at that region. If the hard strata isnt reachable, the pile is made with some friction component so that it creats a frition with soil so that it binds with the loose soil. • Dampers are also used to soak the vibration occure due to earthquake. Rough surface for creating friction with the soil
  93. 93. • Strengthning of wall: 1. Walls can be strengthened by making a good bonding in the brick work. 2. Framed structure is advisable so that walls are just used as in filling. So that loads are transffered by beam and columns , wall should not bear any load 3. Shear can be used to make structure stable . 4. Diagonal braces can also be used to make walls more strong.
  94. 94. METHODS FOR MAKING FLEXIBLE DESIGN Flexible design for making earthquake resistant building is to make building in a grid form and as well as framed structure. Framed structure is advisable so that all the all load are directed towards the foundation of the that infilling of walls can be made flexible as per the requirement.
  95. 95. EARTHQUAKE HAZARD • Ground Shaking: Shakes structures constructed on ground causing them to collapse. • Liquefaction: Conversion of formally stable cohesion-less soils to a fluid mass, causing damage to the structures. • Landslides: Triggered by the vibrations • Retaining structure failure: Damage of anchored wall, sheet pile, other retaining walls and sea walls. • Fire: Indirect result of earthquakes triggered by broken gas and power lines. • Tsunamis: large waves created by the instantaneous displacement of the sea floor during submarine faulting
  96. 96. THANK YOU