28 July 2005
determining lateral earth pressures due to seismic forces are discussed in UFC 3-
Consider pressures due to water level differentials, resulting from tidal fluctuations
and/or groundwater accumulations, in the design of sheet pile bulkheads, cells, and
curtain walls, and in stability investigations for embankments and fills. Consider
additional loading due to hydrodynamic pressure for retaining structures as
addressed in UFC 3-220-01N in seismic areas.
The effect of thermal forces that build up in the structure due to fluctuations in
temperature will vary from those measured at the time of construction. For piers and
wharves, the large body of adjacent water has a substantial moderating effect on the
structure. Consequently, the structure may not attain an overall temperature 10 deg.
F to 20 deg. F higher or lower than the water temperature. The effect will be even
less for ballasted deck construction. However, unballasted decks may see a large
temperature differential through depth. Solid-type piers and wharves and floating
structures are less likely to be affected by temperature variations.
Typically, decks of pile-supported structures will be subjected to temperature
differential. However, since the axial stiffness of the deck elements will be much
higher than the flexural stiffness of piles, the deck will expand or contract without any
restraint from piles (for narrow marginal wharves, the short inboard piles may offer
some restraint, and hence need to be analyzed) and will subject the piles to bending
moments and shear forces. Locate batter piles so as not to restrain thermal motion
(usually in the middle portion of a long structure).
In addition to the weight of accumulated ice on the structure, consider the forces
exerted by floating ice. The principal modes of action of floating ice are shown in
Figure 3-6 and discussed below.
Follow the criteria in the AASHTO standard to the extent feasible. For lightly loaded
structures and for open pile platforms, these criteria may result in structures of
unreasonable proportions. In such cases, consider reducing the AASHTO criteria in
accordance with the Canadian code. See Dynamic Ice Forces on Piers and Piles.
The values of effective pressure are