TM 5-850-1
CHAPTER 8
STRUCTURAL DESIGN
8-1.
Structural types.
(3) Wheel loads through fill. These loads
a. Open piers and wharves. These piers and
should be distributed in accordance with AASHTO
specifications for truck wheels and the AREA
wharves have open water flowing underneath them and
specifications for railroad locomotive wheels.
consist of platform structures supported on various types
b. Timber deck requirements (figure 8-16).
of piles.
Open-type construction falls into two
(1) Caps. Two types of caps are in general
classifications:
use: (a) single piece timbers across the tops of the piles
(1) Relieving platform in which fill is
(b) a pair of clamps dapped into the tops of piles at the
superimposed, topped off by the finished deck.
sides. The single-piece cap is preferred. Caps will be
(2) High-level superstructure in which the
strapped to piles.
deck system is supported directly on the piles. The
(2) Anchorages for deck fittings. Bollards,
principal types of open pier and wharf construction are
shown in figures 8-1 through 8-10. These types should
bitts, and cleats should be anchored to decks and piling
be used where piers extend out board of legal bulkhead
by using spiral-drive drift bolts and metal straps.
(3) Deck planks and treads. In addition to
lines. Open construction is also used where tidal and
stream prism restrictions should be minimized; where
planks, timber decks designed for truck loadings should
flows in which piers are built carry heavy silt loads; and
be provided with treads. Treads should be 3 inches
where bottoms are soft. For pier widths up to 125 feet,
minimum. Do not consider treads as load-carrying
open structures are usually more economical. Open pile
members.
(4) Bridging. Place solid bridging between
structures are not advisable where heavy accumulations
of sheet or drift ice occur. Open-type piers are suitable
stringers over all pile caps. One intermediate line of
in any water depth.
solid bridging will be placed at the midpoints of all spans
b. Solid piers and wharves. The deck of a solid
between 21 and 40 feet, and two lines at the third points
pier or wharf is supported in full, whereas the perimeter
of spans 41 to 60 feet.
(5) Stringers. These stringers will bear on full
structure is essentially a continuous bulkhead or quay
wall. The principal types of solid piers and wharves are
widths of caps and should lap adjacent stringers.
shown in figures 8-11 through 8-15.
Solid piers
Lapped ends of untreated stringers should be separated
generally require less maintenance than open types.
0.5 inch and blocked.
c. Concrete deck requirements. General design
For pier widths greater than 125 feet, and where good
foundation material exists at or above dredge levels,
requirements will conform to the current American
solid or combination piers are usually more economical.
Concrete Institute (ACI), AASHTO, and AREA
c. Combination piers. These piers combine open
specifications. Special reinforcement may be provided
and solid types with a filled center and open perimeter.
to distribute loads from deck fittings.
d. Composite deck requirements.
For timber-
8-2.
Deck structure design.
concrete decks, concrete slab and timber caps shall
conform to timber and concrete deck requirements
a. Concentrated load distribution to decks.
specified above. For timber-steel and steel-concrete
(1) Truck loads. Concentrated wheel loads
decks, concrete and timber slabs and caps should
conform to timber and concrete deck requirements.
(including impact) will be distributed to deck slab,
e. Solid
and
combination
pier
decks.
stringers, and pile caps in conformity with distribution of
wheel loads to deck slabs, stringers, and floor beams of
Requirements for these types of decks are indicated
highway bridges specified in AASHTO specification.
below.
(2) Railroad loads. Concentrated wheel loads
(1) Interior columns for pier shed. These
(including impact) will be distributed to supporting slabs,
columns should be carried on isolated pile caps or piers
stringers, and pile caps of steel frame structures in
supported at or below the dredge line. Some loss of fill
accordance with AREA specifications. For concrete
is inevitable. Therefore, this loading requirement is
structures, the live loads (including impact) should be
necessary to prevent undermining shallow supports.
distributed over widths of tracks.
8-1
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