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Slides Earthquake Resistant Design part2

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Dr.Subramanian Narayanan
Dr.Subramanian Narayanan

This document discusses various earthquake design considerations for buildings. It notes that buildings with unequal mass distribution, soft ground floors, or uneven structural elements can twist during shaking. Different buildings respond differently to ground vibrations depending on the period of earthquake waves. Indian design codes like IS 13920 and IS 1893 provide guidelines for ductile reinforcement details. Proper detailing of beams, columns, joints, walls and foundations is necessary to resist seismic forces. Base isolation and damping devices can also help reduce earthquake shaking and damage.

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Earthquake Design Considerations By Dr. N. Subramanian 3rd Nov. 2012 Dr. N. Subramanian
Pounding between adjoining buildings due to horizontal vibrations Dr. N. Subramanian
More mass on one side causes the floors to twist Dr. N. Subramanian
One-side open ground storey building twists during earthquake shaking Dr. N. Subramanian
Unequal vertical members cause building to twist about a vertical axis Dr. N. Subramanian
Waves of different periods If the ground is shaken by earthquake waves that have short periods, then short period buildings will have large response. Similarly, if the earthquake ground motion has long period waves, then long period buildings will have larger response. Dr. N. Subramanian
Soil condition at site may influence damage Different Buildings Respond Differently to Same Ground Vibration Dr. N. Subramanian
Design Codes  IS 13920, 1993, Indian Standard Code of Practice for Ductile Detailing of Reinforced Concrete Structures Subjected to Seismic Forces  IS 1893 (Part I), 2002, Indian Standard Criteria for Earthquake Resistant Design of Structures (5th Revision)  IS 4326, 1993, Indian Standard Code of Practice for Earthquake Resistant Design and Construction of Buildings (2nd Revision) Dr. N. Subramanian
Longitudinal steel in Beams Dr. N. Subramanian
Stirrups as per IS 13920 Dr. N. Subramanian
Stirrups with 135 degree hooks at the end are required Dr. N. Subramanian
Lapping of Longitudinal bars Dr. N. Subramanian
Soft storey created by open GF car park Dr. N. Subramanian
Earthquakes do not kill people; man in his role as a builder, kills people. Total Horz. EQ Force increases downwards along its height Collapse of partially open GF building in Bhuj EQ, with vertical split at the middle! Dr. N. Subramanian
Possible plastic collapse mechanisms Dr. N. Subramanian
Strong-Column Weak –beam Principle Dr. N. Subramanian
Circular spiral columns Vs Rect. Columns in the same building during 1971 SFO EQ Dr. N. Subramanian
Column reinforcement Dr. N. Subramanian
Detailing of columns in seismic zones 180 links are necessary to prevent the 135 tie from bulging outwards Dr. N. Subramanian
Shear failure of column Large spacing of ties and lack of 135 hook ends caused brittle failure of columns during 2001 Bhuj earthquake Dr. N. Subramanian
Buckling of column bars Dr. N. Subramanian
Confinement steel in columns Dr. N. Subramanian
Correct location for column splices Dr. N. Subramanian
Short Column effect Short columns are stiffer and attract larger forces during earthquakes – this must be accounted for in design Dr. N. Subramanian
Short column effect Dr. N. Subramanian
Short column effect Dr. N. Subramanian
Detailing of short columns Dr. N. Subramanian
Beam-Column joints should be designed and detailed properly Dr. N. Subramanian
Detailing of beam-column joints Ties with 135 degree hooks resists the ill effects of distortion of joints Dr. N. Subramanian
Pull-Push forces cause two problems Dr. N. Subramanian
Three stage procedure to provide horizontal ties in joints Dr. N. Subramanian
Anchorage of beam bars in interior joints Dr. N. Subramanian
Anchorage of beam bars in exterior joints Dr. N. Subramanian
Shear walls are to be placed symmetrically to avoid twist Dr. N. Subramanian
Detailing of shear walls as per IS 13920 Dr. N. Subramanian
Collapse of nominally connected water tank IS 1893 – Connections designed for five times the design horizontal acceleration coefficient Dr. N. Subramanian
Bare Vs infilled frame Predominant frame action Predominant shear action Dr. N. Subramanian
Effect of infill walls Dr. N. Subramanian
Collapse of intermediate storey in 6 storey building, Bhuj, 2001 Dr. N. Subramanian
Improper Anchorage into stiff RC elevator core walls in Ghandhidham Dr. N. Subramanian
Effect of Staircases Diagonal slabs or beams in staircases attract large seismic forces-sliding supports limits the seismic forces Dr. N. Subramanian
Brick Buildings- Horz. Bands Dr. N. Subramanian
Base isolation of buildings to reduce shaking Dr. N. Subramanian
Base Isolation Technology  One of the most significant developments in earthquake engineering in the past 35 years.  It provides the design profession the ability to design a building that is “operational” after a major earthquake Base isolated structure Conventional structure Dr.N.Subramanian 44
BASE ISOLATOR Base isolators may be either coiled springs or laminated rubber- bearing pads, made of alternate layers of steel and rubber, and have a low lateral stiffness. Dr.N.Subramanian 45
Examples of Base Isolated Systems Base Isolated LA City Hall Base isolator being installed. during a seismic event. Every isolator will extend in any direction 21 inches. San Francisco Airport International Terminal is the World’s Largest Base Isolated Building Dr.N.Subramanian 46
Energy Absorbing Devices • “Passive energy dissipation is an emerging technology that enhances the performance of buildings by adding damping to buildings.” • (ASCE/SEI 41-06, pg 280) Dr.N.Subramanian 47
Commonly used dampers  Viscous dampers (They consist of a piston-cylinder arrangement filled with a viscous silicon based fluid, which absorbs the energy)  Friction dampers (energy is absorbed by the friction between two layers, which are made to rub against each other).  Hysteretic dampers (energy is absorbed by yielding metallic parts)  Visco-elastic dampers (containing visco-elastic material, sandwiched between two steel plates, which undergoes shear deformation, thus dissipating energy. Dr.N.Subramanian 48
Other Types Of Dampers  Tuned mass dampers (TMD)- They are extra masses attached to the structure by a spring- dashpot system and designed to vibrate out of phase with the structure.  Tuned liquid dampers (TLD) – They are essentially water tanks mounted on structures and dissipate energy by the splashing of the water.  Hydraulic activators- They are active vibration control devices and have a sensor to sense the vibration and activate the activator to counter it. - Require external energy source and are expensive. Dr.N.Subramanian 49
Why Use Dampers? Dampers dramatically decrease earthquake induced motion .  Less displacement : over 50% reduction in drift in many cases  Decreased base shear and inter-story shear, up to 40%  Much lower “g” forces in the structure. Equipment keeps working and people are not injured  Reduced displacements and forces can mean less steel. This offsets the damper cost and can sometimes even reduce overall cost. Dr.N.Subramanian 50
Viscous Damper Dr.N.Subramanian 51
Example- Viscous damper Dr. N. Subramanian
Tuned Mass Damper (TMD) Taipei 101, the world's second tallest skyscraper is equipped with a tuned mass damper. This 18 feet dia.,730-ton TMD acts like a giant pendulum to counteract the building's movement--reducing sway due to wind by 30 to 40 %. Cost: $4 million Dr.N.Subramanian 53
Dr.N.Subramanian 54

More Related Content

Slides Earthquake Resistant Design part2

  • 1. Earthquake Design Considerations By Dr. N. Subramanian 3rd Nov. 2012 Dr. N. Subramanian
  • 2. Pounding between adjoining buildings due to horizontal vibrations Dr. N. Subramanian
  • 3. More mass on one side causes the floors to twist Dr. N. Subramanian
  • 4. One-side open ground storey building twists during earthquake shaking Dr. N. Subramanian
  • 5. Unequal vertical members cause building to twist about a vertical axis Dr. N. Subramanian
  • 6. Waves of different periods If the ground is shaken by earthquake waves that have short periods, then short period buildings will have large response. Similarly, if the earthquake ground motion has long period waves, then long period buildings will have larger response. Dr. N. Subramanian
  • 7. Soil condition at site may influence damage Different Buildings Respond Differently to Same Ground Vibration Dr. N. Subramanian
  • 8. Design Codes  IS 13920, 1993, Indian Standard Code of Practice for Ductile Detailing of Reinforced Concrete Structures Subjected to Seismic Forces  IS 1893 (Part I), 2002, Indian Standard Criteria for Earthquake Resistant Design of Structures (5th Revision)  IS 4326, 1993, Indian Standard Code of Practice for Earthquake Resistant Design and Construction of Buildings (2nd Revision) Dr. N. Subramanian
  • 9. Longitudinal steel in Beams Dr. N. Subramanian
  • 10. Stirrups as per IS 13920 Dr. N. Subramanian
  • 11. Stirrups with 135 degree hooks at the end are required Dr. N. Subramanian
  • 12. Lapping of Longitudinal bars Dr. N. Subramanian
  • 13. Soft storey created by open GF car park Dr. N. Subramanian
  • 14. Earthquakes do not kill people; man in his role as a builder, kills people. Total Horz. EQ Force increases downwards along its height Collapse of partially open GF building in Bhuj EQ, with vertical split at the middle! Dr. N. Subramanian
  • 15. Possible plastic collapse mechanisms Dr. N. Subramanian
  • 16. Strong-Column Weak –beam Principle Dr. N. Subramanian
  • 17. Circular spiral columns Vs Rect. Columns in the same building during 1971 SFO EQ Dr. N. Subramanian
  • 18. Column reinforcement Dr. N. Subramanian
  • 19. Detailing of columns in seismic zones 180 links are necessary to prevent the 135 tie from bulging outwards Dr. N. Subramanian
  • 20. Shear failure of column Large spacing of ties and lack of 135 hook ends caused brittle failure of columns during 2001 Bhuj earthquake Dr. N. Subramanian
  • 21. Buckling of column bars Dr. N. Subramanian
  • 22. Confinement steel in columns Dr. N. Subramanian
  • 23. Correct location for column splices Dr. N. Subramanian
  • 24. Short Column effect Short columns are stiffer and attract larger forces during earthquakes – this must be accounted for in design Dr. N. Subramanian
  • 25. Short column effect Dr. N. Subramanian
  • 26. Short column effect Dr. N. Subramanian
  • 27. Detailing of short columns Dr. N. Subramanian
  • 28. Beam-Column joints should be designed and detailed properly Dr. N. Subramanian
  • 29. Detailing of beam-column joints Ties with 135 degree hooks resists the ill effects of distortion of joints Dr. N. Subramanian
  • 30. Pull-Push forces cause two problems Dr. N. Subramanian
  • 31. Three stage procedure to provide horizontal ties in joints Dr. N. Subramanian
  • 32. Anchorage of beam bars in interior joints Dr. N. Subramanian
  • 33. Anchorage of beam bars in exterior joints Dr. N. Subramanian
  • 34. Shear walls are to be placed symmetrically to avoid twist Dr. N. Subramanian
  • 35. Detailing of shear walls as per IS 13920 Dr. N. Subramanian
  • 36. Collapse of nominally connected water tank IS 1893 – Connections designed for five times the design horizontal acceleration coefficient Dr. N. Subramanian
  • 37. Bare Vs infilled frame Predominant frame action Predominant shear action Dr. N. Subramanian
  • 38. Effect of infill walls Dr. N. Subramanian
  • 39. Collapse of intermediate storey in 6 storey building, Bhuj, 2001 Dr. N. Subramanian
  • 40. Improper Anchorage into stiff RC elevator core walls in Ghandhidham Dr. N. Subramanian
  • 41. Effect of Staircases Diagonal slabs or beams in staircases attract large seismic forces-sliding supports limits the seismic forces Dr. N. Subramanian
  • 42. Brick Buildings- Horz. Bands Dr. N. Subramanian
  • 43. Base isolation of buildings to reduce shaking Dr. N. Subramanian
  • 44. Base Isolation Technology  One of the most significant developments in earthquake engineering in the past 35 years.  It provides the design profession the ability to design a building that is “operational” after a major earthquake Base isolated structure Conventional structure Dr.N.Subramanian 44
  • 45. BASE ISOLATOR Base isolators may be either coiled springs or laminated rubber- bearing pads, made of alternate layers of steel and rubber, and have a low lateral stiffness. Dr.N.Subramanian 45
  • 46. Examples of Base Isolated Systems Base Isolated LA City Hall Base isolator being installed. during a seismic event. Every isolator will extend in any direction 21 inches. San Francisco Airport International Terminal is the World’s Largest Base Isolated Building Dr.N.Subramanian 46
  • 47. Energy Absorbing Devices • “Passive energy dissipation is an emerging technology that enhances the performance of buildings by adding damping to buildings.” • (ASCE/SEI 41-06, pg 280) Dr.N.Subramanian 47
  • 48. Commonly used dampers  Viscous dampers (They consist of a piston-cylinder arrangement filled with a viscous silicon based fluid, which absorbs the energy)  Friction dampers (energy is absorbed by the friction between two layers, which are made to rub against each other).  Hysteretic dampers (energy is absorbed by yielding metallic parts)  Visco-elastic dampers (containing visco-elastic material, sandwiched between two steel plates, which undergoes shear deformation, thus dissipating energy. Dr.N.Subramanian 48
  • 49. Other Types Of Dampers  Tuned mass dampers (TMD)- They are extra masses attached to the structure by a spring- dashpot system and designed to vibrate out of phase with the structure.  Tuned liquid dampers (TLD) – They are essentially water tanks mounted on structures and dissipate energy by the splashing of the water.  Hydraulic activators- They are active vibration control devices and have a sensor to sense the vibration and activate the activator to counter it. - Require external energy source and are expensive. Dr.N.Subramanian 49
  • 50. Why Use Dampers? Dampers dramatically decrease earthquake induced motion .  Less displacement : over 50% reduction in drift in many cases  Decreased base shear and inter-story shear, up to 40%  Much lower “g” forces in the structure. Equipment keeps working and people are not injured  Reduced displacements and forces can mean less steel. This offsets the damper cost and can sometimes even reduce overall cost. Dr.N.Subramanian 50
  • 51. Viscous Damper Dr.N.Subramanian 51
  • 52. Example- Viscous damper Dr. N. Subramanian
  • 53. Tuned Mass Damper (TMD) Taipei 101, the world's second tallest skyscraper is equipped with a tuned mass damper. This 18 feet dia.,730-ton TMD acts like a giant pendulum to counteract the building's movement--reducing sway due to wind by 30 to 40 %. Cost: $4 million Dr.N.Subramanian 53