1. Short Course on Seismic Design of Reinforced and Confined Masonry Buildings
February 17-21, 2014, IIT Gandhinagar, India

2. Acknowledgments
Kiran Rangwani, IIT Gandhinagar, India
EERI Confined Masonry Network – authors
of the confined masonry guide: Roberto
Meli and others

3. Topics
Part 1: Simplified Method (Svetlana Brzev)
Part 2: Wide Column Model (J.J. Perez
Gavilan)

4. The Simplified Method (SM)
Based on an idealized distribution of lateral
seismic forces in regular shear wall structures
with rigid diaphragms.
Shear strength of all walls at any floor level is
required to exceed the seismic demand
(applied shear force due to earthquake ground
shaking)

5. Assumptions
1.It is assumed that all walls at each floor
level fail simultaneously.
2.The walls have shear-dominant behaviour
(the effect of bending is ignored).
3.The method assumes rigid diaphragm
behaviour.
4.The method ignores torsional effects.

6. Theoretical Background
The goal:
Shear strength of all walls at any floor level (VR )
should exceed the seismic shear force demand
(Vx) at the same level

7. Seismic Shear Force Demand
Interstorey shear force Vx
 ix QV

8. Seismic Force Distribution to Individual Walls
Wall shear demand Vjx

9. Seismic Force Distribution to Individual Walls
xN
j
jx
jx
xjxjx V
k
k
DkV


1
j
jAEj
jx
H
AFG
k




 N
j
jAEj
jAE
xjx
AF
AF
VV j
1

10. Wall resistance VRj
Storey Shear Resistance
Seismic load
Ap
Aw
Wall cross-section Aj

11. Storey Shear Resistance
1AEF when 33.1
L
H
2
33.1 






H
L
FAE when 33.1
L
H
AEjsRj FAfV 

12. Wall Density Index (d)
One of the key indicators of seismic resistance
p
w
A
A
d 
Seismic load
Ap
Aw

13. Wall Density Index Derivations
Goal: resistance
greater than demand ws
N
j
jsR AfAfV  1
ThB WAV  pT nwAW 
s
h
f
wnA
d


BR VV 

14. Wall Density Index – India
Allowable shear stress
(N/mm2)
Floor weight
(kN/m2)
Number of storeys Seismic Zone
III IV V
0.3
6.0
1 1.6 2.4 3.6
2 3.2 4.8 7.2
3 4.8 7.2 10.8
0.4
1 1.2 1.8 2.7
2 2.4 3.6 5.4
3 3.6 5.4 8.1
0.5
1 1.0 1.5 2.2
2 2.0 2.9 4.4
3 2.9 4.4 6.5
0.3
8.0
1 2.2 3.2 4.8
2 4.3 6.4 9.6
3 6.5 9.6 14.4
0.4
1 1.6 2.4 3.6
2 3.2 4.8 7.2
3 4.8 7.2 10.8
0.5
1 1.3 2.0 2.9
2 2.6 3.9 5.8
3 3.9 5.8 8.7

15. Assumptions
1. 𝑅=2.5 for confined masonry (currently not addressed by IS
1893)
2.
𝑆𝑎
𝑔
= 2.5 assuming the fundamental period range from 0.1
to 0.4 sec
3. Importance factor 𝐼=1 assuming regular importance
4. Allowable masonry shear stress (fs): from 0.3 to 0.5 N/mm2
5. Floor weight (w) – two values: 6.0 kN/m2 (light-weight floor
structure) and 8.0 kN/m2 (heavy-weight floor structure e.g.
RC slab).

16. Further Reading
 Attached writeup
(document) on the
Simplified Method
 Seismic Design Guide
for Low-Rise Confined
Masonry Buildings,
EERI, 2011
www.confinedmasonry.org