2. A VERY SIMPLE UNDERSTANDING
By
Yasaswini Laxmi.V

3. Why should we know about
TALL BUILDINGS???

8. TYPES OF TALL BUILDINGS

9. WHY EARTHQUAKE
RESISTANCE?

10. CASE STUDY: BHUJ EARTHQUAKE GUJARAT
Date- Time : 26th January 2001 03:16:40
Location 23.41N70.23E : Magnitude : 7.7 Depth : 16 Kms : Source : USGS NEIC
Death toll : 19,727 Injured 166,000 Homeless :600,000 Economic Losses : $1.3 billion

11. The earthquake design philosophy may be summarized
as follows.
• Under minor but frequent shaking, the main members
of the building that carry vertical and
•horizontal forces should not be damaged
• Under moderate but occasional shaking, the main
members may sustain repairable damage.
•Under strong but rare shaking, the main members may
sustain severe (even irreparable) damage, but the
building should not collapse.

12. STEPS IN SEISMIC DESIGN:
A.PLANNING STAGE:
1. Plan the building and structures in a symmetrical way
both in plan (horizontal axis) and elevation. (vertical
axis).
2. Avoid open ground (Soft storey) which is used for car
parking.
3. Avoid weak storey and provide strong diaphragm. That
is thinner slabs and flat slabs are to be avoided.
4. Provide openings for doors and windows at a distance of
min 0.6 m from the column edges. Follow the IS code
4326 –page 11-for more details for masonry structures.
5. Follow the codal provisions for location of water tanks
and swimming pools etc which will create a vast
difference of Centre of mass.

13. 6. Conduct soil test and investigate the soil nature
to avoid soil liquefactions.
7. Follow the IS codal and NBC provisions while in Planning stage
which will aid more safer structures.
8. Select good materials-concrete ingredients, brick, steel etc.
Specially steel having an elongation of above 14% and yield strength
of 415N/mm^2.
9. The yield stress shall not be greater than 415N/mm^2. Steel
having an yield strength 500 N/mm^2 may be used provided the %
of elongation is above 14%. Make sure before approving it by means
of lab. test results.
10. Provide plinth beam at ground level , lintel and roof band
(masonry structures).
11. Do not lower the beams in RCC frames at lintel level to have
financial savings since the load path will not be there.

14. 1) Building Plan
Efficient Bearing of
Earthquake Forces
2) Heavy mass at top should be avoided NO YES
Smaller water tank at top is preferred

15. 3) Large projections not allowed
4) Floating column not allowed
5) Soft Storey at
Ground Floor

16. 6) Foundation (Isolated footings)
Tie Beams
Similarly can have RAFT, STRIP , STRAP foundations

17. KEY CONCEPT TO EARTHQUAKE
RESISTANT STRUCTURES
 Ductility
 Divertingthe forces of an
earthquake safely

18. HOW TO INCREASE DUCTILTY?
 Ductility of a section can be increased by :
 Decrease the % of the tension steel.
 Increase the % of compression steel.
 Else provide as per steel beam theory.
 Increase in compressive strength of
concrete.
 Increase in transverse shear
reinforcement.
 For ductile detailng –IS 13920- 1993.

19. How to divert the forces safely?
 Dissipation of forces through reliable
load paths:
Primary load paths
Horizontal vertical

20. Horizontal load path
 Tuned liquid dampeners (TLD)
 Self righting buildings
 Tuned mass dampeners (TMD)
 Base isolation

21. Tuned liquid dampeners (TLD)

22. Self righting buildings

23. Tuned mass dampeners (TMD)

24. Base isolation

25. Vertical load path:
Sesimic resistance of building can be
enhanced mainly by:
 Providing shear walls .
 Tubular designs(tube in tube/tube in tubes).
 Providing bracing in walls.

26. BRACED STRUCTURES
DIAGONAL BRACING X- BRACING V- BRACING
INVERTED V- BRACING K- BRACING

27. TUBED
 STRUCTURE
• WILLIS TOWER
(CHICAGO)

28. SHEAR WALL CONSTRUCTION
AND DESIGN

29. What is a Shear Wall?
Buildings often have vertical plate-like RC
walls
called Shear Walls in addition to slabs,
beams
and columns.

31. PURPOSE OF A SHEAR WALL
Shear walls provide large strength and
stiffness to buildings in the direction of
their orientation, which significantly
reduces lateral sway of the building and
there by enhances the earthquake
resistance of the structure.

32. How shear forces work?

33. Architectural Aspects of Shear
Walls
 Shear walls should be provided along
preferably both length and width.
 If they are provided along only one
direction, a proper grid of beams and
columns in the vertical plane (called a
moment-resistant frame) must be
provided along the other direction to
resist strong earthquake effects.

34.  Door or window openings can be provided in
shear walls, but their size must be small to
ensure least interruption to force flow
through walls.
 Shear walls in buildings must be
symmetrically
located in plan to reduce ill-effects of twist in
buildings.
 Shear walls are more effective when located
along exterior perimeter of the building.

36. GEOMETRY OF SHEAR WALLS
 Shear walls are oblong in cross-section,
i.e., one dimension of the cross-section
is much larger than the other.
 While rectangular cross-section is
common, L- and U-shaped sections are
also used.

38. REINFORCEMENT DETAILS
 The minimum area of reinforcing steel to
be provided is 0.0025 times the cross-
sectional area, along each of the
horizontal and
vertical directions.
 This reinforcement should be distributed
uniformly across the wall cross-section
as vertical and horizontal grids.

39.  The vertical and horizontal reinforcement in
the wall can be placed in one or two parallel
layers called curtains.
 Horizontal reinforcement needs to be
anchored at the ends of walls.

41.  Under the large overturning effects caused
by horizontal earthquake forces, edges of
shear walls experience high compressive
and tensile stresses.
 To ensure that shear walls behave in a
ductile way, concrete in the wall end regions
must be reinforced in a special manner to
sustain these load reversals without loosing
strength.

43. ADVANTAGES OF SHEAR WALLS
 Shear walls are easy to construct,
because reinforcement detailing of walls
is relatively straight-forward and
therefore easily implemented at site.
 Shear walls are efficient, both in terms
of construction cost and effectiveness in
minimizing earthquake damage in
structural and non-structural elements
(like glass windows and building
contents).

45. TUBED STRUCTURES

46. What are TUBED STRUCTURES?
 A three dimensional space structure
composed of three, four, or possibly more
frames, braced frames, or shear walls,
joined at or near their edges to form a
vertical tube-like structural system capable
of resisting lateral forces in any direction by
cantilevering from the foundation.

47. The tube system concept is based on the idea
that a building can be designed to resist lateral
loads by designing it as a hollow cantilever
perpendicular to the ground.

48. Where do we use tubed
structures?
skyscraper design and
construction

49. •In the simplest incarnation of the tube, the
perimeter of the exterior consists of closely
spaced columns that are tied together with deep
spandrel beams through moment connections.

50. ADVANTAGES
 Framed tubes allow fewer interior
columns, and so create more usable
floor space.
 It can take a variety of floor plan shapes
from square and rectangular, circular,
and freeform giving scope for
architecture.

51. TYPES OF TUBED STRUCTURES
 Bundled Tube
 Framed Tube
 Braced Tube
 Tube in Tube

52. BUNDLED TUBE

53. FRAMED TUBE

54. BRACED TUBE

55. TUBE IN TUBE

56. References :
•IS 1893 (2002) – Criteria for earthquake resistant
design of structures
•IS 13920 (1993) – Ductile detailing of reinforced
concrete structures subjected to seismic forces
•IS 4326 (1993) – Earthquake resistant design and
construction of buildings
•Tall Buildings by Mark Fintel

57. Web pages:
•Building structure
http://www.nd.edu/~tkijewsk/Instruction/solution.h
tml
•Fundamental rules for earthquake design
http://www.samco.org/download/reports/rules.pdf
•IITK, BMTPC Earthquake Tips by
Prof.C.V.R.Murthy IIT Kanpur.
•http://www.bstn.co.nr