Figure 1-6.—Nomenclature of a fixed
the center line. A space of approximately one-quarter
inch should be provided between the planks to allow for
swelling, to provide water drainage, and to permit air
circulation. The minimum thickness of decking is 3
inches in all cases; however, when the required
thickness of plank decking exceeds 6 inches, then a
laminated type of decking should be used.
FOUNDATIONS AND PILES
That part of a building or structure located below
the surface of the ground is called the foundation. Its
purpose is to distribute the weight of the building or
structure and all live loads over an area of subgrade large
enough to prevent settlement and collapse.
A pile is a slender structural unit driven into the
ground to transmit loads to the underground strata. It
transfers loads to the surrounding underground strata by
friction along its surface or by direct bearing on the
highway bridge superstructure.
compressed soil at or near the bottom. A bearing pile
sustains a downward load and may be driven vertically
or otherwise; however, when a bearing pile is driven
other than vertically, it is known as a batter pile.
Another type of pile is the sheet pile. It is used to resist
lateral soil pressure.
The following discussion is intended to introduce
and familiarize you with some of the common types of
foundations and piles that you may be required to
include in your construction drawings.
FOUNDATIONS
In general, all foundations consist of three essential
parts: the foundation bed, which consists of the soil or
rock upon which the building or structure rests; the
footing, which is normally widened and rests on the
foundation bed; and the foundation wall, which rises
from the foundation to a location somewhere above the
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