Page 45 - EQTips_Eng

IITK-BMTPC Earthquake Tip 22

Why are Short Columns more damaged during Earthquakes? page 2

Length depends

on diameter of

longitudinal bar

Regular floor

Mezzanine
floor
Closely spaced special transverse confining ties throughout the height and into column above Closely spaced special transverse confining ties,
only at ends
Short column Source:
between lintel
Wakabayashi,M.,
and sill of Design of Earthquake-Resistant Buildings,
McGraw Hill Book Company, New York,
window
Figure 4: Effective height of column over which it
can bend is restricted by adjacent walls –this Short Column Regular Column
short-column effect is most severe when
opening height is small. Figure 5: Details of reinforcement in a building

with short column effect in some columns –
The Solution additional special requirements are given in
In new buildings, short column effect should be IS:13920-1993 for the short columns.
avoided to the extent possible during architectural
design stage itself. When it is not possible to avoid Related - Earthquake Tip
short columns, this effect must be addressed in Tip 6: How Architectural Features Affect Buildings During
structural design. The Indian Standard IS:13920-1993 Earthquakes?
for ductile detailing of RC structures requires special Tip 17: How do Earthquakes Affect Reinforced Concrete Buildings?
confining reinforcement to be provided over the full Tip 19: How do Columns in RC Buildings Resist Earthquakes?
height of columns that are likely to sustain short Reading Material
column effect. The special confining reinforcement (i.e., IS 13920, (1993), “Indian Standard Code of Practice for Ductile Detailing
closely spaced closed ties) must extend beyond the of Reinforced Concrete Structures Subjected to Seismic Forces,” Bureau
short column into the columns vertically above and of Indian Standards, New Delhi

below by a certain distance as shown in Figure 5. See
IITK-BMTPC Earthquake Tip 19 for details of the special Authored by:
confinement reinforcement. C.V.R.Murty
In existing buildings with short columns, different Indian Institute of Technology Kanpur
retrofit solutions can be employed to avoid damage in Kanpur, India
future earthquakes. Where walls of partial height are Sponsored by:
present, the simplest solution is to close the openings Building Materials and Technology Promotion
by building a wall of full height – this will eliminate Council, New Delhi, India
the short column effect. If that is not possible, short
columns need to be strengthened using one of the well This release is a property of IIT Kanpur and BMTPC New
established retrofit techniques. The retrofit solution Delhi. It may be reproduced without changing its contents
should be designed by a qualified structural engineer and with due acknowledgement. Suggestions/comments
may be sent to: nicee@iitk.ac.in Visit www.nicee.org or
with requisite background. www.bmtpc.org, to see previous IITK-BMTPC Earthquake Tips.

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