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Harbor
Loss of Transverse Negative Moment Capacity over the Outboard
Crane Rail
Upon removal of the old crane rails, extensive corrosion was discovered
in the top layer of steel reinforcement adjacent to the outboard
rails (Figure 15). This condition compromises the flexural and shear
capacity of the adjacent slab to support loads between the outside
rail and curb. The structural analysis showed that the deck needs
a flexural capacity of 1,150 in-kip/ft (130 kN?m) to support outriggers.
This will be provided in the upgrade area with carbon reinforcing
rods. While there is no proof of the cause of deterioration, standing
water in the rail slot that has migrated through cracks to the reinforcing
was a major contributing factor.
This obviously has been occurring over decades and in some areas
the rebar had not been replaced when previous repairs were made.
Corrosion and damage was discovered when the rails were removed.
The techniques for detecting corrosion and delamination did not
detect the damage beforehand. The rails have excessive corrosion,
which has contaminated the grout bed (up to 2 inches (5 cm) thick)
below the rail (Figure 16). The extensive repair project finished
in 1996 either did not detect these damaged areas or repairs were
made to the concrete without replacing the corroded steel. Since
the corrosion exists along the 200-foot (60 m) length of the upgrade
project site there is an excellent chance damage is extensive along
the entire length (3,200 feet (980 m)) of all the Bravo wharves
(22 through 26). Since the outboard rail area is badly corroded,
the interior rails may also be corroded. Given that the repair project
of 1996 missed the damage on Bravo 25, future repair projects could
just as easily result in the same oversight.
Figure 15. Detail of corroded Number 3 and Number 6 bars adjacent
to outboard crane rail slot.
Figure 16. Exposed rebar near rail slot on the east end of Bravo
25. Rail plate and grout bed are still in place. Area had been previously
repaired without replacing steel.
Figure 17. Crane operators attempt to achieve as much reach as possible
by placing outriggers close to curb.
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