Book 1 - City of St. Petersburg

BASIS OF DESIGN BOOK 1
3 GENERAL PLANNING CRITERIA
ENGINEERING CRITERIA
(continued)
Foundation Selection and Design
The piles that will support the new Pier must be engineered to
withstand not only the dead and live loads of the Pier, but also
the loads from hurricane winds, breaking waves, and lateral
currents. There are several pile type options that can be used to
form the foundation of the Pier. Although not recommended,
reuse of existing piles is a possibility after a thorough inspection
of their current condition is completed. Driving new piles is
another option as well. Additional information related to the
existing piles and other engineering concerns that was discussed
in a meeting concerning general site conditions can be found in
Appendix D: General Site Conditions Meeting Minutes, June 27,
2012 (McLaren Engineering Group).
New piles can be made of steel, timber, or prestressed concrete.
Each material option has its advantages and an analysis weighing
function with cost is necessary to determine the optimal material
for final design. A preliminary analysis of foundation types
follows:
Existing Piles
Reusing the existing piles is not recommended. The existing
piles are approximately 90 years old and, in many cases, have
been condemned, driving the decision to demolish the existing
Pier. The location and orientation of the existing piles in relation
to the intersecting new Pier would also be a limitation. However,
the existing caissons under the Inverted Pyramid building have
potential for reuse to support the offshore components of the
new Pier.
New Steel Piles
Steel piles are generally either pipe piles or rolled steel
H-section piles. Using steel as a pile material has the advantage
of being easy to handle with respect to cutoff and extension to
the desired length during installation. They have a high loadcarrying
capacity and can penetrate hard layers such as dense
gravel and soft rock. However, they are relatively costly and are
subject to corrosion. Due to the corrosive nature of a coastal
environment, epoxy coatings must be applied to resist the
effects of salt water.
Prestressed Concrete Piles
Concrete piles are reinforced to resist the bending moment
developed during pickup and transportation, the vertical load
and the bending moment caused by a lateral load. They can be
subject to hard driving, can be easily combined with a concrete
superstructure and are corrosion resistant. However, they can
be difficult to transport in some locations and achieving proper
cutoff during installation may be difficult. Despite this, concrete
piles may be the best option as concrete is resilient in coastal
environments and is not affected by marine borers.
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THE NEW ST. PETERSBURG PIER