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23576671 presentation


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23576671 presentation

  1. 1. Lateral Load Resisting Systems.  Presented By : Chirag Shah
  2. 2. 1 Frame Action Of Column and Two-Way Slab Systems Concrete floors in tall buildings often consist of a two-way floor system such as a flat slab, or a waffle system.  Advantages 1. Optimum use of floor space 2. Relatively simple construction process  Disadvantages 1. Generally flexible structure and lateral deflection govern the design process.
  3. 3. Effective Width of flat Slab.  The effective width of flat slab can be used to determine the equivalent width of slab.  The effective width depends on 1. Column aspect ratios 2. Distance between columns 3. Thickness of flat slab.
  4. 4. 2 Rigid Frame  Cast in Place Concrete Building has inherent advantages of continuity at joints.  Beams framing directly into columns, can be considered rigid with the columns.  Beams carry shear and bending moments due to lateral loads often require additional construction depth.  The design and detailing of joints where beams and columns meet the special attention is required.
  5. 5. Behaviour of Rigid Frame
  6. 6.  Advantages 1. Rigid Frame systems for resisting lateral and vertical loads have long been accepted as a standard means of designing buildings. because they make use of the stiffness in the beams and columns that are required in any case to carry the gravity loads.  Limitation 1. Rigid Frames are not Stiff as compared to shear wall. 2. Excessive depth of girder required to make the rigid frame economical.
  7. 7.  Disadvantages
  8. 8. 3 Rigid Frame with Haunch Girder
  9. 9. Uses  When the Structure is of tube type and the adjacent distance between two columns are 40ft then the beam depth required is much more and this beam is called haunch beams.  If the depth of haunch beam is more then 3 ft then the posttensioning is used.  A haunch girder with more depth give the required stiffness for lateral loads without having to increase the floor to floor height.  This is achieved by making the mid section of the girder flush with the floor system.
  10. 10. 4 Shear Walls  The elevator shafts, stairwells necessary for access in a high rise must be protected by fire walls, as demanded by fire safety regulation.  It makes sense to exploit them in improving the building rigidity.  With their highly resistance to shear stress, are highly suitable for assuming the shear forces that arise through lateral loads.
  11. 11. Classification of Shear Walls  Classification of Shear wall should be based on following criteria. 1. Based On Shape 2. Based on dimension 3. Based on Opening
  12. 12. Based On Shape 1. Rectangular 2. Dumbled 3. Intersection of Two Shear Walls
  13. 13. Based on Dimension  h/ l < 1 Square shear wall  H / l > = 1 Slender Shear Wall l h
  14. 14. Based on Opening  Solid  With Opening  Coupled Shear Walls
  15. 15. Failures in Shear Walls
  16. 16. Coupled Shear Walls  When two or more shear walls are interconnected by a system of beams or slabs, the total stiffness of the system exceeds the summation of the individual wall stiffnesses because, the connecting slab or beam restrains the individual cantilever action by forcing the system to work as composite unit.  used economically to resist lateral loads in building upto about 40 stories.  However planer shear walls are only efficient lateral carieers only in that planes hence it is necessary to provide wals in two orthogonal directions.
  17. 17. Behaviour Of Couple shear wall.
  18. 18. 5 Shear Wall Frame Interaction  Most Popular System  Broad Range of Application and has been used for 10 – stories to as high as 50 stories or even taller building.
  19. 19. Rigid Frame Shear Wall Interaction.  Using only shear walls to respond to lateral loads is impractival above about 500ft.  The lateral rigidity is gratly improved by using not only the shear wall system but also the rigid frame to resist lateral forces.  The total deflection of the interacting shear wall and rigid frame systems is obtained by superimposing the individual models of deformation as shown in fig.
  20. 20. Thank You