Page 31 - EQTips_Eng

IITK-BMTPC Earthquake Tip 15

Why is Vertical Reinforcement required in Masonry Buildings? page 2
How Vertical Reinforcement Helps
Embedding vertical reinforcement bars in the Earthquake-induced inertia force
edges of the wall piers and anchoring them in the
foundation at the bottom and in the roof band at the Cracking
top (Figure 4), forces the slender masonry piers to
undergo bending instead of rocking. In wider wall piers,
the vertical bars enhance their capability to resist
horizontal earthquake forces and delay the X-cracking.
Adequate cross-sectional area of these vertical bars
prevents the bar from yielding in tension. Further, the
vertical bars also help protect the wall from sliding as
well as from collapsing in the weak direction. (a) Cracking in building with no corner reinforcement

Bending
of Pier Lintel Band Reinforcement
Bars
Sill Band
(Similar to
Lintel Band,
but discontinued
at door openings)

Vertical steel bars anchored in
foundation and roof band (b) No cracks in building with vertical reinforcement
(a) Vertical reinforcement causes bending of

masonry piers in place of rocking (See Figure 2). Figure 5: Cracks at corners of openings in a
masonry building – reinforcement around them
helps.

Related - Earthquake Tip
Tip 5: What are the seismic effects on structures?
Tip12: How brick masonry houses behave during earthquakes?
Tip13: Why masonry buildings should have simple structural
configuration?
Tip14: Why horizontal bands are required in masonry buildings?

(b) Vertical reinforcement prevents sliding in walls Reading Material

(See Figure 3). Amrose,J., (1991), Simplified Design of Masonry Structures, John Wiley
& Sons, Inc., USA
Figure 4: Vertical reinforcement in masonry walls BMTPC, (2000), Guidelines: Improving Earthquake Resistance of
– wall behaviour is modified. Housing, Building Materials and Technology Promotion Council,
New Delhi
Protection of Openings in Walls IS 4326, (1993), Indian Standard Code of Practice for Earthquake Resistant
Design and Construction of Buildings, Bureau of Indian Standards,
Sliding failure mentioned above is rare, even in New Delhi
unconfined masonry buildings. However, the most IS 13828, (1993), Indian Standard Guidelines for Improving Earthquake
common damage, observed after an earthquake, is Resistance of Low-strength Masonry Buildings, Bureau of Indian
diagonal X-cracking of wall piers, and also inclined Standards, New Delhi
cracks at the corners of door and window openings.
When a wall with an opening deforms during Authored by:
earthquake shaking, the shape of the opening distorts C.V.R.Murty
and becomes more like a rhombus - two opposite Indian Institute of Technology Kanpur
corners move away and the other two come closer. Kanpur, India
Under this type of deformation, the corners that come Sponsored by:
closer develop cracks (Figure 5a). The cracks are bigger Building Materials and Technology Promotion
when the opening sizes are larger. Steel bars provided Council, New Delhi, India
in the wall masonry all around the openings restrict
these cracks at the corners (Figure 5b). In summary, This release is a property of IIT Kanpur and BMTPC New
lintel and sill bands above and below openings, and Delhi. It may be reproduced without changing its contents
vertical reinforcement adjacent to vertical edges, and with due acknowledgement. Suggestions/comments
may be sent to: nicee@iitk.ac.in. Visit www.nicee.org or
provide protection against this type of damage. www.bmtpc.org, to see previous IITK-BMTPC Earthquake Tips.
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