Section 1 Under-deck Girders

101. Arrangement

1. At places where beams need to be supported, underdeck girders or equivalent structures are to be provided in accordance with the requirements in this chapter.

2. Under-deck girders, etc. are to be provided, as necessary, under masts, derrick posts, deck machi- nery and other heavy concentrated loads.

102. Construction of Girders

Under-deck girders are to be uniform in depth throughout the part between bulkheads and to have sufficient bending rigidity.

103. Section Modulus of Girders

The section modulus of under-deck girders is not to be less than obtained from the following for- mula:

Ě Ņ Ǽ ᾎ ᾜ ᾨĪ Ncm Į Ń

where,

ᾎ : Distance between the mid-points of spaces from the girder to the adjacent girders or the inner edges of brackets (m ). (See Fig 11.1)

ᾨ : Distance between the supporting points of girders (m ). (See Fig 11.1)

ᾜ : As specified in Ch 7, 203.(kNÕmĪ ). Where, however, ᾜ is to be in accordance with the requirements in Ch 7, 203. 3, ᾜ is to be as specified in the followings

(1) Afore 0.3 Ã from the fore end : 0.13 Ã + 4.5 (kNÕmĪ)

(2) Abaft 0.3 Ã from the fore end : 0.11 Ã + 4.5 (kNÕmĪ )

Ǽ : Coefficient given below:

(1) Midship part 0.4 Ã : 4.3

(2) Elsewhere : 3.4

104. Supports and Connections at Ends

1. The ends of under-deck girders are to be supported by bulkhead stiffeners. These stiffeners are to be properly strengthened.

2. Where two adjacent under-deck girders or an underdeck girder and a longitudinal bulkhead are not in line in way of a transverse bulkhead, etc., each of them is to be extended beyond the transverse bulkhead, etc. for at least one frame space.

Fig 11.1 Measurement of ᾎ, ᾨ, Ċ, and ᾨL

105. Hat-type Construction

The scantlings of under-deck girders of hat-type construction are to be in accordance with the re- quirements in Ch 1, 305. in addition to those in this chapter.