COMMONLY
ASKED
QUESTIONS
|
by
Muthiah Kasi, PE, S. E, C.V.S.
Alfred Benesch & Co.
Chicago, IL |
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CONCRETE REINFORCING
STEEL INSTITUTE
REINFORCED CONCRETE COLUMNS
MAJOR ELEMENTS FOR OPTIMAL BUILDING DESIGN
Columns are structural elements that
have a major impact on the owner's needs. The architect/engineer should be able to modify
all the various factors involved in the design of reinforced concrete columns to satisfy
the various project requirements.
What considerations should the
architect/engineer be aware of when evaluating and designing columns?
There are four main factors the
architect/engineer should consider when designing reinforced concrete columns: size,
shape, strength, and time.
These four factors need to be thoroughly evaluated to obtain the
optimum design for the owner.
What are the major advantages
of reinforced concrete columns?
Reinforced concrete columns allow a great deal of
flexibility in the design. Column size and shape, and material strengths can all be varied
even after construction has started.
Most of the time, the "as-built" concrete compressive
strength exceeds the specified strength. In addition, as columns age, concrete strengths
can increase as much as 30%.
What are the advantages of a
round-tied column over a square or rectangular column?
Round columns require fewer numbers of
ties, are easier to form, and faster to build. In the recent design of a high-rise
building in Chicago, a value engineering study showed a significant savings by
substituting round for rectangular columns.
Another issue is public safety. Focus groups have reported that
circular-shaped columns offer a psychological edge for security. In isolated public areas
such as parking garages and public transit terminals, circular-shaped columns provide
better visibility which leads to better security.
How difficult is it to connect
attachments to existing reinforced concrete columns?
Expansion anchors can be drilled into existing
columns to provide connections for attachments. The capacity of these anchors in tension
and shear are much more than what is needed in most cases. All connections to columns
provide additional loading, and need to be analyzed by the architect/engineer. If future
connections are anticipated, anchors can be cast into the columns during construction to
facilitate future attachments. Threaded rods can be inserted into couplers to continue
column reinforcement at the roof.
Furring costs are generally the same for round and square columns |
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ENGINEERING
INFORMATION PROGRAM-DECEMBER 1997 |
