Model twin-hull semi-submersible 
platform. 
Figure 4. 
Fabrication of Pipe Sections 
All pipe elements were centrifugally cast by 
Ameron Pipe Products at South Gate, California. A 
minimum concrete cylinder strength of 5,000 psi was 
specified. The actual strength was nominally 6,300 
psi at 7 days. Standard 7-sack concrete mix and 
curing procedures were used to produce the pipe. 
All pipe ends were square and plain. 
The 664-inch OD cylinder of a hull was made up 
of four 8-foot long pipeswith a 4-inch wall. Eight 
longitudinal l-inch ducts were provided through the 
center of the wall and at equal circumferential 
spacing to accommodate prestressing strands. The 
wall was reinforced with two circular cages, one on 
each side of the ducts. A cage consisted of 5% 
coils of 3/8-inch bars per foot and nominal 
longitudinals. 
The 444-inch OD pipe for the colums was 7 
feet long with a 3-inch wall. Eight longitudinal 
3/4-inch ducts at equal spacing were provided in 
the wall center for prestressing. The wall was 
reinforced with 5% coils of 3/8-inch bars per foot 
on the outside of the ducts. 
Since joints in the hull cylinder were 
vertical, it was convenient to use non-slumping and 
fast-curing joining material that would stick to 
vertical concrete surfaces and flow into joint 
irregularities when compressed. Nukem No. 109 
epoxy filler compound manufactured by Ameron's 
Corrosion Control Division was selected. The cured 
epoxy joint was reported to be stronger than the 
concrete of the pipe. 
x a 
As reported by A. B. Szulc, Project Engineer, 
Ameron Corporate Research and Development 
Department. 
C8 
Prior to joining the hull sections, all joint 
surfaces were sandblasted and sealed with primer. 
The four pipe sections were then aligned ina 
horizontal position; about a 3/4-inch thick layer 
of filler compound was applied to one surface of 
each joint; and the pipe sections were then post- 
tensioned together. Excess compound which squeezed 
Out was removed, and paper tape was bonded over the 
joints to confine the material during cure. 
Steel end rings, 3/4-inch thick, were also 
bonded with the epoxy compound to the ends of the 
32-foot long cylinder (Figure 5). The rings 
served as anchor plates for distribution of 
lontigudinal prestressing forces to the concrete, 
and provided attachment for the concrete hemi- 
spheres over the ends. 
Detail of column/hull intersection 
and hull end rings. 
Figure 5. 
The hull was prestressed with eight 4-inch, 
Grade 270 strands to 250 psi resultant concrete 
compression. The strands passed through the ducts 
in the wall and their ends were anchored with 
individual chucks against the steel end rings. 
Four symmetrically located strands were stressed 
at a time to produce uniform compression. After 
completion of prestressing, all ducts were pres- 
sure grouted with cement mortar mainly to protect 
the strands against corrosion. 
For pipe columns with square, plain ends, 
special concrete saddles, as may be noted in 
Figure 5, and anchor blocks were required to 
attach and prestress them to the hull cylinder. 
During model construction, it was more economical 
to cast concrete ring saddles directly on the hull 
than to precast or integrally cast the saddles 
with the cylinder or columms. The ring saddles 
were reinforced and tied to the cylinder wall with 
eight pipe ducts passing through holes drilled 
through the hull wall, and with %-inch bar hoops. 
