Hull Scantling Calculation Part.1

Structural Part of Ship

1. MAIN PARTICULAR / APPENDIX INFORMATION of SHIP :
Length between Perpendicular (L) in M
Length Water Line (Lwl) in M
Breadth of ship (B) in M
Draft  (T) in M or can be obtained by T=0.66H+0.9 in M
Height  (H) in M
Block coefficient (CB) = Δ / (L.B.T)
Displacement (Δ) in Ton
Volume of Displacement ∇ in M^3
Frame spacing (a) in M
Web Frame spacing (e) in M

Material factor (k) 
Yield strength (ReH) in N/mm^2

ref. BKI vol.II sec.2, A-2

2. SCANTLING CALCULATION
2.1  Bottom Shell Plating: 
#Length co-efficient (CL)      = 1                          for L ≥ 90 m        (BKI vol.II.ref.sec-4, A.2.2) 
                                               = (L/90)^0.5           for L < 90 m

#Service coefficient (CRW)   = 1 for unlimited range service            (BKI vol.II.ref.sec-4, A.2.2)
                                                = 0,90 for service range P
                                                = 0,75 for service range L
                                                = 0,60 for service range T

#Distribution factor (CF x CD)  = 1 for midship,                               (BKI vol.II.ref.sec-4, B.1)

#Wave coefficient, (Co) , see below for detail.                     (BKI vol.II.ref.sec-4, A.3)

 #nf                                    = 1,0 for transverse framing                (BKI vol.II.ref.sec-6, A.1)
                                          = 0,83 for longitudinal framing

#Probability factor, (f)                                                                   (BKI vol.II.ref.sec-4, A.2)
                                          = 1,0 for plate panels of the outer hull (shell plating, weather decks)
                                          = 0,75 for secondary stiffening members of theouter hull (frames,
                                              deck beams), but not less than fQ according to Section 5, D.1.
                                          = 0,60 for girders and girder systems of the outer hull (web frames,
                                              stringers, grillage systems), but not less than fQ/1,25

#Basic external dynamic load (Po)
   Po (kN/m2) = 2.1(CB+0.7) x Co x CL x f

2.2  Bottom Plate Thickness
#Load at bottom (PB)
   PB (kN/m2) = 10T + Po x Cf

σ perm             = permissible design stress [N/mm2]
                        = (0.8 + L/450)x230/k [N/mm2]        for L < 90 m
                        = 230/k [N/mm2]                                for L ≥ 90 m

σLB                 = Maximum bottom design hull girder bending stress [N/mm2] according to
                            Section 5, D.1.
As a first approximation σLB and τL may be taken as follows:
σLB                 =  (12.6√L)/k [N/mm2]                      for L < 90 m
                        =  120/k [N/mm2]                               for L ≥ 90 m
τL                    = 0



Corrosion addition (tk)                                               (BKI vol.II.ref.sec-3, k)
                        = 1,5 mm                                            for t' =10 mm           
                        = 0.1xt'/√k + 0.5 mm, max.3.0mm     for t' >10mm
                      
#Ships with lengths L < 90 m
The thickness of the bottom shell plating within 0,4 L amidships is not to be less than:

tB1 = 1.9 . nf . a√PB.k + tk [mm]

Within 0,1 L forward of the aft end of the length L and within 0,05 L aft of F.P. the thickness is not to be less than tB2.

#Ships with length L ≥ 90 m
The thickness of the bottom plating is not to be less than the greater of the two following values:
tB1 = 18.3 . nf . a√PB/σpl  + tk  [mm]

tB2 = 1.21 . a√PB.k  + tk  [mm]

σ pl =  √( σperm^2-3τL^2) - 0.89.σLB  [N/mm2]

2.3 Minimum Bottom plate thicknes
At no point the thickness of the bottom shell plating shall be not less than :

tmin = (1.5 - 0.01 . L)√(L.k)   [mm]          for L < 50 m                       (BKI vol.II,ref.Sec-6, B-3)
tmin = √(L.k)                          [mm]          for L ≥ 50 m
tmax = 16.0 mm                                         in general

to be continued ... see Part 2

Hopefully helpfully 😀