Heavy construction includes structures made of
steel, timber, concrete, or a combination of these ma-
terials. Examples include trestles, timber piers, and
waterfront structures. The requirement for heavy con-
struction today is not as important as in earlier years;
however, the need to understand this type of construc-
tion still remains.
In this chapter, well examine the materials used
in building heavy structures. Well also discuss the
methods and techniques of heavy construction, in-
cluding shoring and excavation. In addition, well
look at the procedures used in maintaining the struc-
LEARNING OBJECTIVE: Upon completing
this section, you should be able to identify the
parts of a trestle, and describe the procedures
for erecting bents and superstructures.
A trestle is a braced framework of timbers, piles,
or steel members, It is typically built to carry a road-
way across a depression, such as a gully, a canyon, or
the valley of a stream. The two main parts of a trestle
Figure 10-1.-Abutment sill and footing and abutment
are the substructure, consisting of the supporting
members, and the superstructure, consisting of the
decking and the stringers on which the decking is laid.
The substructure of a timber trestle is a series of
transverse frameworks called bents. Trestle bents are
used on solid, dry ground, or in shallow water with a
solid bottom. Pile bents are used in soft or marshy
ground, or where the water is so deep or the current so
swift that the use of trestle bents is impossible. The
posts of a pile bent are bearing piles or vertical mem-
bers driven into the ground.
The following terms are common to timber trestle
Abutment The ground support at each of the
extreme ends of a trestle superstructure. Examples
are shown in figures 10-1 and 10-2.
Bracing The timbers used to brace a trestle bent,
called transverse bracing, or the timbers used to
brace bents to each other, called longitudinal
Figure 10-2.-Placing and leveling abutment footings and