Small increase in reinforcing steel can
result in large increase in load capacity.
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What
other advantages do these two systems have?
There are two other major advantages:
1) Flexibility of column locations.
2) Adaptability for future use.
The columns need not be in a grid system and can be offset to suit
various needs. By a slight increase in reinforcement, the live load capacity can be
doubled. Thus, one can design a flat slab system for any reasonable type of occupancy
change and still meet the live load requirement of the code. For example, an increase in
reinforcement from 3.20 psf to 3.79 psf will cost approximately $0.20/sq. ft. However, the
live load capacity will be increased from 40 psf to 100 psf for a 30-foot span.Are there any other added advantages
to the user by utilizing a reinforced concrete system?
Concrete systems have the advantage of providing redundancy, plus
vibration and sound control.
Cast-in-place concrete, because of its monolithic nature, is inherently
redundant. Redundancy safeguards structural integrity. Concrete frames can be designed and
detailed to provide redundancy that will delay or minimize progressive collapse under
unusual and extreme loading conditions. Other structural systems, to possess the same
redundancy, require special details or framing.
Building types such as hospitals, hotels, laboratories, libraries and
courthouses are extremely sensitive to vibration and sound transmission. For buildings
like these, the inherent sound insulating barrier of a concrete frame is superior to other
systems. Building owners often like the sense of greater solidity of concrete frames
because of the noise and vibration dissipation.
Vibrations can cause both movement and noise irritations. Concrete as a
building material has more stiffness and inertia than other framing types.
Why should a contractor
prefer flat plate and flat slab systems?
The contractor has better control of schedule, construction methods and
design changes. This is possible because of the use of local labor and material, no
prefabricated shop elements, and no need for lead time from the shop.
This is a brief discussion of commonly asked questions by
the building team when they are evaluating various structural systems, especially in the
early conceptual phase. For more detailed information on conceptual design or about how to
evaluate concrete building systems, see CRSI’s Guide to Structural System
Selection, and Workbook for Evaluating Concrete Building Designs.
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|
Guide to Structural
System Selection |
Workbook for Evaluating
Concrete Building Designs |
Muthiah Kasi, PE.,
S.E., C.V.S.
Alfred Benesch & Company
ENGINEERING
INFORMATION PROGRAM-JUNE 1997 |
