position of oppening in shear wall

1. Definition of shear wall
Position
Design provisions
Behavior
Case studies
PRESENTATION OUTLINE
1

2. 2
Fig. 1 A reinforced concrete wall

3. Known as shear walls
Designed to resist lateral forces
Excellent structural system to resist earthquake
Provided throughout the entire height of wall
Practicing from 1960s for medium and high rise
buildings (4 to 35 stories high)
RC STRUCTURAL WALLS
3

4. Provide large strength and stiffness in the
direction of orientation
Significantly reduces lateral sway
Easy construction and implementation
Efficient in terms of construction cost and
effectiveness in minimizing earthquake damage
ADVANTAGES OF SHEAR WALLS
4

5. PLACEMENT OF SHEAR WALLS
5

6. Located symmetrically to reduce ill effects of twist
Symmetry can be along one or both the directions
Can be located at exterior or interior
More effective when located along exterior
perimeter of building
PLACEMENT OF SHEAR WALLS
6

7. 7
Fig. 2 Reinforced concrete shear wall (Murthy C.V.R.
,2005)

8. Located symmetrically to avoid ill effects of
twisting
Symmetry can be along one or both the directions
Can be located at exterior or interior
More effective when located along exterior
perimeter of building
PLACEMENT OF SHEAR WALLS
6

9. Widely used design approaches for shear walls
ACI method (ACI 318-1995)
IS 13920:1993 - Indian Standard Ductile
Detailing of RC members
Code provides a ductile design to give
adequate toughness and ductility to resist
severe earthquakes
CODES FOR DESIGN OF SHEAR
WALLS
8

10. Thickness 150 – 400 mm
Minimum reinforcement 0.25% of gross area in
each direction
Diameter shall not exceed 1/10 th thickness of
section
Reinforcement provided in two curtains when:
Factored shear stress exceeds or
Wall thickness exceeds 200 mm
DESIGN CONSIDERATIONS
9
0.25 ckf

11. Nominal shear stress,
SHEAR STRENGTH OF WALLS
10
v
u
v
w w
V
t d
 

Factored shear
force
Thickness of wall
section
Effective depth of wall
section = for
rectangular sections
0.8 wl

12. Design shear stress, from table 19 of IS
456:2000
If < minimum shear reinforcement
If > shear reinforcement is designed
for excess shear force of
SHEAR STRENGTH OF WALLS CONTD…
11
v
v c
c
c
usV

13. 0.87 y h w
us
v
f A d
V
S

SHEAR STRENGTH OF WALLS CONTD…
12
c w wVu t d
= characteristic strength of steel
= effective depth of wall section
yf
wd
Area of horizontal shear
reinforcement
Vertical
spacing

14. For
where,
FLEXURAL STRENGTH
13
u u
w w
x x
l l


2
2
2
1
1 0.416 0.168
2 3
uv u u
ck w w w w
M x x
f t l l l
 


       
           
        
2 0.36
u
w
x
l
 

 
   
0.0035
0.87
0.0035
u
yw
x
fl
Es



0.87 y
ck
f
f

 
u
ck w w
P
f t l
  0.87
0.0035
y
s
f
E
  st
w w
A
t l
 

15. FLEXURAL STRENGTH CONTD…
14
For 1u u
w w
x x
l l

 
2
1 2 32
2
uv u u
ck w w w w
M x x
f t l l l

  
   
      
   
1
0.36 1
2 2



  
    
  
2
1
0.15 1
2 2 3
 


  
     
  
 
1
3
6 /u wx l


 
 
 
ux  depth of NA from extreme compression fibre
*
ux  balanced depth of NA

16. Portions along edges of shear wall strengthened
by longitudinal and transverse reinforcement
Can have same or greater thickness compared
to wall
Develop good flexural strength
Should have adequate axial load carrying
capacity
BOUNDARY ELEMENTS
16

17. Factors governing seismic behavior of shear
walls:
Ductility
Stiffness
Soil structure interaction effects
Period of structure
SEISMIC BEHAVIOUR OF WALLS
15

18. Ductility
Ratio of displacement at maximum load to
that at yield
Highly desirable property for shear walls
Stiffness
Property of element to resist displacement
More stiffer wall need more force to deflect it
SEISMIC BEHAVIOUR CONTD…
16

19. Soil- structure interaction
Structural damage directly related to depth
of soil overlying the rock and period of
vibration of soil
Understanding relationship between period
of vibrations of soil and structure is
important
SEISMIC BEHAVIOUR CONTD…
18

20. Period of a building
Important index that identifies vulnerability to
excessive drift
A simple approximation to period of building:
(Mete a Sozen,
2004)
SEISMIC BEHAVIOUR CONTD…
19
4
2
3.5
w
c w
w
T
E I
mh



21. Some important conclusions from extensive
experimental studies on seismic behaviour of
shear walls:
High axial load ratio is undesirable for structures
[7]
Damage always initiate from top of splices. So
splice impacts seismic performance [1]
SEISMIC BEHAVIOUR CONTD…
20

22. For accurate evaluation of seismic
demands soil structure interaction must
also be considered [8]
Shear walls with staggered openings
produce better results in earthquakes [4]
SEISMIC BEHAVIOUR CONTD…
22

23. CASE STUDY 1
22

24. Three specimens
W1, W2, W3
Represent slender shear walls
Aspect ratio 4
Axial load ratios (ALR) 0.25,0.5,0.5 resp.
BEHAVIOUR OF SHEAR WALLS UNDER
HIGH AXIAL LOAD RATIO
[R.K.L. Su and S.M. Wong]
23

25. 24
wh
wl
Fig. 3 A shear wall
w
w
h
l
1
1 2
2
Squat
Intermediate
Slender
  
  
 
   
Aspect ratio =

26. Three specimens
W1, W2, W3
Represent tall slender shear walls
Aspect ratio 4
Axial load ratios (ALR) 0.25,0.5,0.5 resp.
BEHAVIOUR OF SHEAR WALLS
UNDER HIGH AXIAL LOAD RATIO
[R.K.L. Su and S.M. Wong]
23

27. applied axial load
axial load capacity at a section
AXIAL LOAD RATIO
25
Axial load ratio =
'
u
c g
P
ALR
f A

compressive strength of concrete
gross cross section of the wall
'
cf 
gA 

28. TESTING METHODOLOGY
26
Fig.4 Testing rig (R.K.L. Su and S.M. Wong,

29. Specimens placed in a steel loading frame
Compressive axial force applied from bottom
simulated gravity load
Push and pull forces to the flange beam
represented lateral seismic loads
TESTING METHODOLOGY CONTD…
27

30. 28
Fig. 5 Testing rig and load application (Su and Wong,
2006)

31. Specimens placed in a steel loading frame
Compressive axial force applied from bottom
simulated gravity load
Push and pull forces to the flange beam
represented lateral seismic loads
TESTING METHODOLOGY CONTD…
27

32. 28
Testing rig and load application (Su and Wong,
2006)

33. W1 exhibited flexural
ductile failure
Cracks developed at
early stage
Propagated inwards
to the core of the
section
OBSERVATIONS
29
Fig. 6 Failure pattern of specimen
W1
(Su and Wong, 2006)

34. W2 and W3 exhibited brittle compression failure
Spalling of concrete observed due to high ALR
OBSERVATIONS CONTD…
30
Fig.7 Failure pattern of specimens W2 and W3
(Su and Wong, 2006)

35. ALR affect failure
High ALR has a suppressive effect on ductility
As ALR increases energy dissipation decreases
Axial stiffness reduces with increasing lateral
deformation
Leads to reduction in applied axial load
With high ALR faster and greater reduction
SUMMARY
31

36. 32
Fig. 8 Energy dissipation of specimens (Su and Wong, 2006)

37. High ALR affect failure
High ALR has a suppressive effect on ductility
As ALR increases energy dissipation decreases
Axial stiffness reduces with increasing lateral
deformation
Leads to reduction in applied axial load
With high ALR faster and greater reduction
SUMMARY
31

38. 33
Fig. 9 Reduction in ALR (Su and Wong, 2006)

39. CASE STUDY 2
34

40.  To study effect of staggered openings
 5 specimens with same amount of reinforcement
 Represented 4 storey rectangular walls
 Specimen W1 without opening
 W2,W3,W4 with staggered openings
 W5 with regular openings
SEISMIC PERFORMANCE OF SHEAR
WALLS
(MOSOARCA MARIUS, 2013)
35

41. 36
Wall without opening

42.  To study effect of staggered openings
 5 specimens with same amount of reinforcement
 Represented 5 storey rectangular walls
 Specimen W1 without opening
 W2,W3,W4 with staggered openings
 W5 with regular openings
SEISMIC PERFORMANCE OF SHEAR
WALLS
(MOSOARCA MARIUS, 2013)
35

43. 36
Wall without opening Staggered openings

44.  To study effect of staggered openings
 5 specimens with same amount of reinforcement
 Represented 5 storey rectangular walls
 Specimen W1 without opening
 W2,W3,W4 with staggered openings
 W5 with regular openings
SEISMIC PERFORMANCE OF SHEAR
WALLS
(MOSOARCA MARIUS, 2013)
35

45. 36
Wall without opening Staggered openings Regular
openings

46. TESTING METHODOLOGY
37
Fig. 10 The test bench (Mosoarca Marius, 2013)

47. Reversed cyclic lateral loads
A constant vertical force
Seismic behaviour studied for different
horizontal displacements
Behaviour of specimens monitored by
transducers, strain gauges etc.
TESTING METHODOLOGY CONTD…
38

48. OBSERVATIONS
39
Model
Initial
cracking
Plasticized
concrete
Crushed
concrete
P (kN) P (kN) P (kN)
W1 29.33 113.63 114.43
W2 25.12 100.12 103.72
W3 25.13 88.63 92.03
W4 25.15 88.40 95.90
W5 17.7 69.70 73.80

49. Walls with staggered openings were more rigid
With same amount of reinforcement ductile failure
observed for staggered opening walls and brittle
failure for regular opening walls
Staggered opening walls failed at higher seismic
forces and horizontal displacements
SUMMARY
40

50.  Shear walls are efficient in resisting earthquakes
 More efficient with increased ductility
 Soil structure interaction studies are important
 ALR ratio has adverse influence on seismic
performance of shear walls
 Shear walls with staggered openings are more
effective than walls with regular openings
CONCLUSIONS
41

51. 1. Anna Birely and Dawn Lehman (2008).
“Investigation of the seismic behavior and
analysis of reinforced concrete structural walls”.
The 14th World Conference on Earthquake
Engineering, Beijing, China.
2. Lepage, A (1994). “Seismic Drift Estimates for
RC Structures”. Eleventh World Conference on
Earthquake Engineering, Acapulco, Mexico.
REFERENCES
42

52. 3. Murty, C.V.R.(2005). “Earthquake Tips. Learning
Earthquake design and Construction”. IIT Kanpur
4. Mosoarca Marius (2013). “Seismic behavior of
reinforced concrete shear walls with regular and
staggered openings after the strong earthquakes
between 2009 and 2011”. Journal of Engineering
Failure Analysis.
REFERENCES CONTD…
43

53. 5. Mete A. Sozen, (2004) “Earthquake Engineering
from engineering seismology to Performance
based Engineering”. Second Edition, CRC Press.
6. Shimazaki and Sozen, M.A., (1984).”Seismic
drift of reinforced conctrete structures”. Technical
Research Report of Hazana- Gumi, Tokyo. Vol. 5,
ISSN 0385- 7123.
REFERENCES CONTD…
44

54. 7. Su, R.K.L. Wong, S.M. (2006). “Seismic behavior
of slender reinforced concrete shears walls under
high axial load ratio”. Journal of Engineering
Structures, 29 (2007) 1957-1965.
8. Yuchuan Tang and Jian Zhang (2010).
“Probabilistic seismic demand analysis of a slender
RC shear wall considering soil- structure interaction
effects”. Journal of Engineering Structures, 33
(2011) 218-229.
REFERENCES CONTD…
45

55. THANK YOU…