Section 3.10: Site Plans and Technical Data - Rick Neufeld Comments

Northern Gateway Pipelines Inc.
Section 3.10: Site Plans and Technical Data
Table of Contents
Vertical loading is taken directly from the deck down into the bedrock through the vertical legs of the
jackets. For horizontal loads in either direction, the fully-braced jackets act as cantilevered trusses taking
the loads down to the bedrock as axial forces in the legs and bracing.
Method of Installation
The jackets will be prefabricated in a shop environment, shipped to site via barge, floated or lifted into
position, and seated on rock benches. Underwater benches will be blasted into the bedrock to provide a
level and stable surface which the jackets can be seated. The seated jackets in turn provide a stable
platform from which drilling operations can be conducted. The legs of the jackets are hollow and act as a
template guide for drilling accurately-aligned holes into the bedrock. After the holes in the bedrock have
been drilled, anchors (rock dowels or sockets) will be installed into the holes and grouted.
A rock dowel is a steel pile which extends through its respective jacket leg and into the drilled hole in the
bedrock. The pile is fully grouted within the jacket leg as well as the hole in the bedrock, thereby
providing full anchorage. A rock socket is similar to a rock dowel, but in lieu of a steel pile, it uses a castin-place
reinforced concrete core which extends through the hollow jacket leg and into the hole drilled
into the bedrock.
After pile installation, the deck framing can be assembled on a barge and lifted as complete or partial
assemblies onto the jackets via a barge crane. The deck structures are field welded to the jackets to
complete the erection of the primary structural members.
2.3.2.2 Pile and Deck Option
Proposed Type of Construction
The pile and deck option for the loading platforms consists of individual steel pipe piles connected with
concrete pile caps as shown in Drawing No. 007. The deck will likely be comprised concrete box-girders
with a composite concrete deck slab, although the deck could also be comprised of steel beams and
decking. The individual piles will likely be vertical and may be either partially or entirely filled with
concrete. To account for the larger construction tolerances for individual piles, the pile caps will consist
of cast-in-place concrete. The precast concrete box girders span perpendicular to the pile caps and bear on
ledges formed on either side of the pile cap. A space is provided between the ends of the box girders to
allow steel reinforcement extending from the box girder ends and the lower half of the pile cap to be cast
in a second pour which forms the top portion of concrete pile cap. Once cured, the deck and pile caps will
behave monolithically. A top deck slab can be cast either simultaneously with or after the second pile cap
pour. The cast-in-place deck slab ties the entire deck structure together as a diaphragm and also can allow
for composite bending action between the deck slab and the precast concrete box girders to help resist
vertical loads.
The vertical loads are resisted via bending in the deck girders and deck slab which in turn transfer the
loads to the pile caps and then directly into the piles. Horizontal loads acting parallel to the berthing line
are resisted by frame action resulting from the continuity among the deck, pile cap, and piles. Horizontal
loads acting perpendicular to the berthing line can be directly transferred through the deck diaphragm to
the abutments on land.
January 20, 2010 FINAL - Rev. 0 Page 2-11