Table 530 Figure 4 Timber scab detail

Table 5-31 Planning and Estimating Data for Timber Pile Repair Using Partial Replacement to or Below Mudline

Description of Task: Repair a severely deteriorated timber pile by posting to the mudline with a new pile butt connected with a pipe sleeve at the base of the replacement section. Total length of repair is 20 to 30 feet.

Size of Crew: Dive station, two laborers.

Special Training Requirements: Familiarity with underwater cutting techniques, procedures for removal of marine growth, jetting or air lifting procedures, underwater lifting procedures, and drilling procedures.

Equipment Requirements: High-pressure waterblaster, hydraulic grinder with Barnacle Buster attachment, hydraulic drill with bits, hydraulic power unit, air lift or jetting pump and hose, rigging equipment, crane or lifting equipment, float stage, oxy-acetylene torch equipment, clamping template for cutting piles, and hydraulic chain saw.

Productivity of Crew: 10 hours per pile. Materials:

Replacement Pile Section - The replacement pile section should be long enough to span the measured distance between the bottom cut and the top cut on the damaged pile. If replacement is to be performed to the bottom of the concrete deck, allowance must be made for "swinging" room in bringing the pile under the deck and a shim installed to fill the gap.

Pipe Sleeve - The pipe sleeve is required to provide a moment resisting connection at the base of the repair. The diameter of the pipe sleeve must be sufficientiy large to accept both the existing pipe and the replacement section. The minimum length of the pipe sleeve should be 3 feet.

Fish Plate - Fish plates are used in pairs, one on each side of the repair, and are made of 4- by 10-inch treated timber. The minimum length of each fish plate is about 3 feet.

Connection Hardware - Connection hardware will depend on the details of the repair. Allow for losses due to dropping.

Potential Problems: All load must be removed from the existing pile before it is cut to avoid jamming the saw. Creosote will ruin a wet suit and may cause skin irritation.

Another method of posting uses a pipe sleeve at the bottom joint to develop a moment connection, as illustrated in Figure 2 of Table 5-30. A pipe or split sleeve compatible in diameter with the remaining pile is selected, and the new pile butt post is shaped to fit into the pipe or sleeve. The pile butt and sleeve is placed over the cut off pile and maneuvered under the pile cap. If pipe is being used, one-half of its length is slipped over the pile butt and fastened with 8-inch-long by 3/8-inch-diameter boat spikes. The new pile butt is shimmed tight against the pile cap and secured with a 7/8-inch-diameter drift pin. The area around the base of the pile is then backfilled.

5.9.2.2 Bracing Posted Piles. When adjacent timber piles have been repaired using either posting or fish plating techniques, it may be necessary to provide some resistance to lateral loads imposed on the structure. This can be done by installing X-bracing between piles, as illustrated in Figure 5-22. Treated timbers are fastened high on one pile and low on the adjacent pile, forming an X pattern. Where the X-bracing crosses, a timber spacer should be bolted between the bracing pieces to shorten the unsupported length of span.

5.93 Complete Replacement

Piles subjected to severe deterioration may be more economically repaired by complete replacement of the pile. The installation of timber replacement piles is similar to that described in Section 5.5.3 for steel piles.

Timber Cap

Timber Cap

Construction Estimation Chart
Figure 5-22. Bracing posted piles.

Pile replacement techniques require heavy equipment that is not normally available to the UCTs and would usually be carried out by others. NMCBs and Construction Battalion Units (CBUs) have the heavy equipment required to carry out timber pile replacement.

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  • lavinia
    What is bracing in construction?
    3 years ago

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