Structural Repair

Grouted steel repair clamps

Foundocean has exaltensive experience in the installation and grouting of structural strengthening schemes with over 100 projects completed worldwide. Contracts have included more than 300 grouted clamps to strengthen, connect and repair tubulars and node joints as well as member infilling and resin repairs to concrete structures.

For this type of work Foundocean can provide mixing and pumping equipment specially designed for use on live production platforms. To monitor grout quality, offshore laboratories may be provided.

All offshore equipment is suitable for working in hazardous Zone 2 areas.

Repairs to offshore structures may be required for a number of reasons:

• Fatigue. The design of early jackets was heavily dependent on experience in the Gulf of Mexico. Fatigue damage typically takes the form of cracks at the end of horizontal members where they frame into the main structure.
• Increased code requirements. As environmental data has improved, the wave load requirements have increased. It has been found necessary to upgrade the structural performance of jackets to meet new requirements, or to meet other requirements subsequently introduced by jacket operators.
• Ship impact. Damage caused by ship impact typically takes the form of bent or buckled members.
• Impact by debris. Objects dropped overboard can cause damage to the jacket.

There are three types of structural repair:

• Grouted Clamp. A clamp in which the outer sleeve is formed in segments which are placed around an existing joint. The splits are closed by pre-tightened bolts prior to the injection of a cement grout into the annulus between the clamp and the existing tubulars
• Stressed Grouted Clamp. This is similar to a grouted clamp. Grout is placed into the annular space between the clamp and the existing tubular joint. The grout is allowed to reach a predefined strength prior to the application of an external stressing force
• Grout filled tubular. A structural member which has been filled with grout

Repairs to offshore structures may be required for a number of reasons:

• As an installation aid to enable the connection of two parts of a member together to form a continuous structural element
• To strengthen understrength members, such as legs, to increase their axial strength and stability characteristics
• To strengthen damaged members by offering a parallel load path across defective areas.(defects such as dents, punctures, corrosion holes, etc. may be repaired in this manner)
• To offer a means of connecting a new member into a structure
• Filling a member with grout offers the advantage of not increasing member diameter (as an outer sleeve would) or wave loading.

Grouting a tubular member may be carried out the following reasons:

• To increase axial compressive strength of the member
• To improve overall member strength and stability
• To improve strength at a tubular joint

Recognised advantages of grouted repair techniques are as follows:

• Normal fabrication imperfections are easily accommodated by grout
• Geometrical damage is easily accommodated
• Full strength of damaged sections can easily be restored
• Increased strength can readily be provided
• Uses known and proven technology
• Repairs can be carried out at any depth within the range of the structure

Foundocean can also provide advice and assistance with the analysis and design of structural repair solutions.