THE LPG PIER
Work on the LPG (Liquefied Petroleum Gas) pier (also known as
export terminal) was started in August 1983, by the Contractor
Toyo Engineering Corporation, who engaged CNP (Christiani and
Nielsen, and Pilecon) to build the LPG Jetty, designed by SSP.
Design (click here for plan)
The jetty is planned to accommodate LPG tankers between
1000 and 40,000 DWT, but the jetty breasting dolphins are
designed to accommodate bigger ships for possible future
development. It consists of 2 Nos. big breasting dolphins, 2
smaller ones for smaller ships and for protecting the central
platform, four mooring dolphins and a central platform which is
accessed by a 300m long approach bridge.
The main points regarding design are as follows:
The piles were high tensile (Grade 50 B) tubular steel piles.
Steel piles are selected for the very strong driving required for
good penetration into the black hard somewhat decomposed silt
stone, or shale; and also to resist the waves, and in the
breasting dolphins the impact of ships. The durability is
achieved by shot-blasting the steel to grade SA. 2.5 of the
Swedish Standard, and painted with zinc primer and 2 layers of
coal tar epoxy. The piles are for structural reasons firmly
embedded in the R.C. cap. From about 75 mm into the pile cap and
to 1 m below low tide the steel pile has a steel sleeve around
(painted the same way) with an annular space of 150 mm. This is
filled with concrete after the bottom is sealed and water pumped
out. Below the steel sleeve, the piles are catholically protected
by sacrificial anodes.
Features
The breasting dolphins and the central platform ( see plan ) are connected by two steel
piles, cast well into the structures, and well latticed outside
the structures by smaller steel pipes. This is in order to
strengthen the single structures against longitudinal forces, and
against twisting. It also increases the resistance against
transverse forces. The transverse impact results in tension in
the seaward piles, which tension is taken by ground anchors. In
order to reduce the uplift the breasting dolphins are designed as
truncated A-frames. The voids in the piles of the big and small
breasting dolphins are emptied of earth, etc down to RL -20 m ACD
and filled with concrete.
The 300m long approach bridge has only one joint over that
length; all pile caps, beams, and slabs are cast together. There
is a moveable joint between the bridge and the central platform.
This could of course not be done in a climate with cold winters
and warm summers; but in the topics with the small temperature
differences many joints can be saved, and thereby the strength of
the structure increased.
Construction
The tubular piles of diameter (dia) 1000 x 16mm and dia 900 x
12mm, dia 700 x 12mm and dia 600 x 12mm were driven by diesel
hammers Kobe K 45 and KB 60 to the required ultimate driving
resistance of twice the working load as per the Hiley formula.
Penetrations ranged between 10 and 25m, and the pile lengths
between 24 to 40m.
Apart from some lower precast elements and pile caps, and the
prestressed concrete bridge beams, the rest of the concrete was
designed to be cast in-situ. The contractor was able to change a
great part of in-situ work to precast concrete work, which
expedited the work and improved the quality of the concrete.
The ground anchors of 100 and 120 ton working load, which was 40%
of ultimate strength of tendons, with 13 and 15 Nos. seven wire
strands of 12.7 mm. A 200 mm dia 24m long steel casing was placed
centrally in the pile after dewatering, and the annular space was
concreted. A 165 mm dia hole was drilled beyond the toe of the
casing to give a 10m bonding length in bed rock. The deepest
drilling was done down to 61m below pile cap. The tendon was now
inserted in the empty drill hole and primary grouting was carried
out in two stages using ordinary Portland cement with 0.5
water/cement ratio and under pressure of 30 kg/cm2. After setting
of the grout in the drill hole the tendon was stressed to working
load, and thereafter secondary grouting of casing was carried
out.
Pile tests: one compression test to 450 tonnes (1.5 times W.L.)
and two tension tests on one 100 ton and one 150 tonnes anchors
were tested to 1.2 x working load. All tests were satisfactory.
The construction period was short, 15 months from August 1983. It
was necessary for the contractor to drive all piles before the
monsoon (local tropical storm). With the good penetration of the
piles the contractor chose not to brace the piles but leave them
standing singly during the monsoon. The piles did not move
significantly.
The rest of the wharf was completed in November 1984, during the
monsoon. This was a feat as the sea swell was considerable at the
unprotected site location.
The cost of the project was Ringgit 18 million (or approx. US $7
million).
Photograph of LPG Pier (on completion in 1984)
Photo of LPG Pier & South Breakwater (in 1989)
