750
Cost and Time Analysis: First Cost
To check the cost break assumption, three general structural types were
carried through detailed design on the basis of a single bay of 22'6" with a
span of 58'6" plus an 18' cantilever. Appropriate items were added to
each to make final figures comparable, e.g., cost of hangers added to
beams and fireproofing added to steel. The conclusion was that concrete
beams are much lower in cost than steel trusses at these spans, and steel
beams are slightly less than trusses. The following figures include 10%
contingency and 10% contractor's overhead and profit, but cost savings
attributable to speed of construction were not estimated.
Structure-Ceiling Solution
$/OGSF
Cast-in-place concrete beams and
ceiling
8.00
Steel beams and suspended ceiling
10.25
Steel truss and directly attached
ceiling
10.50
The functional advantages of the beam-and-hanger solution are:
1. Service zone more efficiently utilized by ductwork, etc.
2. Less obstruction to movement of workmen and equipment.
3. Independence of structural depth and service zone depth.
Trusses also have some advantages:
1. Less deflection.
2. Less weight.
3 - 200
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