1、The Korea Shipbuilders Association,Shipbuilders Experience “ preparing a bid for an FPSO to be converted from a 1996 DH VLCC In our search for candidate tankers we looked closely at your hull (1997) and found it in excellent condition. Ballast tank coatings, cargo tank under deck coatings, and tank

2、bottom coatings are still in excellent condition so there is virtually no corrosion. We looked at another shipyards tanker (1996) which was built with no coating under deck in the cargo tanks, and found general wastage around 2mm on the deck plate; there was little or no wastage on uncoated structur

3、e (longs, transverse webs) lower in the cargo tanks.”,3mm,3mm,3.5mm,4mm,4mm,3mm,4.5mm,3.5mm,3.5mm,2.5mm,2.5mm,2.5mm,3mm ,7/31,2. Technical Issues for Oil Tankers,2.2 Minimum / Maximum Draughts of Abreast Full / Empty Conditions,Note : Tsc = Scantling Draught,8/31,2. Technical Issues for Oil Tankers,

4、Min./Max. Draught Requirements (Proposed by KOSHIPA),9/31,2. Technical Issues for Oil Tankers,2.3 D/B Floor Thick. Requirement (Bottom Slamming),42mm (HT32 ) By Prescriptive Req.,42mm(HT32),tmean = 65 Mpa164 Mpa(Criteria),40% ONLY,10/31,2. Technical Issues for Oil Tankers,- Coefficient fdist must be

5、 lesser, since floor length is short.,-Effect on stiffness of bottom longitudinals is necessary.,fdist,fbtm-lg,Prescriptive Requirement,?,11/31,2. Technical Issues for Oil Tankers,2.4 Shear Force Correction i.w.o. Bulkhead Stringers,26mm (HT32 ) By Prescriptive Req.,28mm (mold ) By Prescriptive Req.

6、,28mm (mild ) By Prescriptive Req.,O.T.BHD,No.1STR.,No.2STR.,No.3STR.,12/31,2. Technical Issues for Oil Tankers,Prescriptive Requirement,FE Analysis,?,?,?,13/31,2. Technical Issues for Oil Tankers,2.5 Prescriptive Requirement for Primary Support Member (PSM) CSR specifies as follows; “The section mo

7、dulus and/or shear area of a primary support member and/or the cross sectional area of a primary support member and a cross tie may be reduced to 85% of the prescriptive requirements provided that the reduced scantlings comply with the FE cargo tank structural analysis”,14/31,2. Technical Issues for

8、 Oil Tankers,Subject requirement is based on simple formula with unclear assumptions, which can be dealt with by FEA properly and transparently.,Prescriptive Requirement,D = 0.2 lbdg-dt,D = 0.13 lbdg-dt,Z =,1000 M C yield,FE Analysis,15/31,2. Technical Issues for Oil Tankers,Subject requirement is b

9、ased on simple formula with unclear assumptions, which can be dealt with by FEA properly and transparently.,Prescriptive Requirement,D = 0.2 lbdg-dt,D = 0.13 lbdg-dt,Z =,1000 M C yield,FE Analysis,16/31,2. Technical Issues for Oil Tankers,2.6 Effect of Toe Grinding on Fatigue Strength CSR specifies

10、as follows; “The benefits of weld toe grinding should not be taken into consideration at the design stage. However, an exception may be made for the weld connection between the hopper plate and inner bottom if the required design fatigue life can not be satisfied by means of practical design options

11、 such as increasing local thickness, extending weld leg length and modifying local geometry. The calculated fatigue life is to be greater than 17 years excluding grinding effects.”,17/31,2. Technical Issues for Oil Tankers,KOSHIPA carried out fatigue experiment It utilizes high technology such as computerized calculation, introduction of dynamic loading and ultimate strength. Shipbuilders need to concentrate only one (1) set rule.,29/31,6. Concluding Remark,However, CSR contains several technical subjects, which are NOT transparent / ra