Bridge Construction Details

THERE is a wide variation in the complexity of bridge
construction details that satisfactorily perform identical
functions. These details have a profound effect on the cost of
short span bridges and should be afforded more attention than
is usually given to them.
One study has shown a range in cost from $0.22/lb to
$0.16/lb for the same structure with different framing and
details. This has more significance than the 38 percent spread
in these prices. Assuming the material cost to be $0.08/lb and
deducting this cost from the total, the amount required for
fabrication and erection (the remaining portion of the cost) is
$0.08/lb for one and $0.14/lb for the other. This is a 75
percent variation in the cost of fabrication and erection due to
differences in the design of the framing and details.
To achieve the minimum cost, bridge details should be
examined in the light of their intended functions. The least
sophisticated device that will satisfy the need will generally
be the least costly. For all details used in the construction of
bridges, the AASHO and AREA specifications provide a
latitude of choice, with restrictions imposed by individual
states or railroads due to geographical differences and special
preferences. However, it is not uncommon to disregard this
latitude of choice and select standard details, instead of
applying objective consideration to the specific need for the
detail. This can be costly.
AISC has studied a large number of details contained in
the standards submitted by 32 state highway departments. A
selection was made of typical details which
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