Civil Engineering Reference
In-Depth Information
The assembly and erection phases are based on the following objectives:
Increase the opportunity for access around the jacket during execution and
for ground assembly
●
Decrease the number or erection of joints in the main structural elements,
such as jacket legs, launch runners, rows and levels. Align critical areas,
such as conductor guides, pile sleeves and launch runners.
●
Sub-assemble principal structural elements of the jacket, such as jacket legs,
rows and levels. Sub-assemble, and where possible pre-test, systems such as
grouting and ballasting. Include the maximum quantity of secondary items,
such as anodes, risers, J-tubes and caissons. Coat or paint required areas
prior to erection.
●
Where possible, reduce the use of temporary structures, such as scaffolding,
walkways and lifting aids that require subsequent removal, and pre-install
such aids where they are necessary.
●
Usually, the assembly of a jacket frame, often having a base spread of 50 m
or more, places severe demands on field layout and survey and on temporary
support and adjustment bracing (see
Figure 5.17
). Such large dimensions
mean that thermal changes can be significant. Temperature differences may
be as great as 30
C between
various parts of the structure, resulting in several centimeters of distortion.
º
C between dawn and afternoon and as much as 15
º
FIGURE 5.17
Frame jacket located horizontally.
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