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 TB 55-1900-201-45/1
advantages in saved weight and their use permits thinner sections to be used in highly stressed areas which would oth-
erwise require excessively thick sections of conventional ship steel. However, the thinner plating and sections of high
strength steel are not as forgiving of poor design as the heavier sections of mild steel. Special attention must be paid to
the possibility of buckling and detailing in the design and careful fabrication becomes a must. Also special procedures
are required for welding. These are discussed in Section V.
b. Structural renewals in areas where high strength steels have been used must be made with the same high
strength steel. In some cases, an equivalent grade may be substituted. Also, repairs to high strength steels must be
made in accordance with the specified procedures. A problem arises because high strength steels are not visually distin-
guishable from ordinary ship steel. The use of such steels should be indicated on the vessel's Certificate of Inspection
and by the entry "special material" in column (4) in the "RECORD" of the American Bureau of Shipping. Further, both
the American Bureau and the Coast Guard have requested that vessels utilizing high strength steels in their construction
shall retain onboard structural drawings identifying the special steel, indicating where it is used and specifying, in detail,
the required welding and fabrication procedures.
c. In any larger vessel built since 1964, renewal or repair in way of the main hull girder should not be undertaken
without first examining the vessel's approved structural plans to confirm if high strength steels were used. If so, every
care must be exercised to use the correct steel for renewals and to adhere to the specified procedures for both renewals
and repairs. It is well to note that there is no such thing as a "minor" repair where high strength steels are involved.
Further information on the use of high strength steels is available from the Commandant (MMT) or field (mmt) office.
E-15. Alternatives. In some instances, owners may desire to install supplemental structural reinforcement rather than
replace deteriorated material. This may be feasible, but since it constitutes a modification of design, plans detailing the
proposed changes should be approved before the work is carried out.
E-16. Deck Plating. Deck plating comprises a highly stressed portion of the hull girder and is of critical importance to the
longitudinal strength of the vessel. Accelerated corrosion may be expected in the deck because it is subject to mechani-
cal abuse from deck cargo, hatch beams and repeated scaling. Also, it is always exposed and frequently awash. Be-
cause of this, the deck plating, especially in the midship's half length, should be carefully examined for cracks, leaks, or
signs of excessive wear. The corners of hatch or other deck openings, the corners of deck erections, pads, or other
items producing discontinuities or hard spots should be examined for evidence of cracking. Whenever practicable, the
detail concerned should be eased and made less abrupt when repairs are made. In the case of riveted
E-9
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