Ultimate strength performance of tankers associated with industry corrosion addition practices

Transcription

1 csnak, 2014 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~528 pissn: , eissn: Ultimate strength performance of tankers associated with industry corrosion addition practices Do Kyun Kim 1,2, Han Byul Kim 3, Xiaoming Zhang 4, Chen Guang Li 5 and Jeom Kee Paik 5 1 Civil Engineering Department, Universiti Teknologi PETRONAS, Tronoh, Malaysia 2 Graduate School of Engineering Mastership, Pohang University of Science and Technology, Pohang, Korea 3 Structure Research Department, Hyundai Maritime Research Institute, Hyundai Heavy Industries Co. Ltd., Ulsan, Korea 4 OPR Offshore Pipelines & Risers Inc., Zhejiang, China 5 The Ship and Offshore Research Institute (Lloyd s Register Foundation Research Centre of Excellence), Department of Naval Architecture and Ocean Engineering, Pusan National University, Busan, Korea ABSTRACT: In the ship and offshore structure design, age-related prolems such as corrosion damage, local denting, and fatigue damage are important factors to e considered in uilding a reliale structure as they have a significant influence on the residual structural capacity. In shipping, corrosion addition methods are widely adopted in structural design to prevent structural capacity degradation. The present study focuses on the historical trend of corrosion addition rules for ship structural design and investigates their effects on the ultimate strength performance such as hull girder and stiffened panel of doule hull oil tankers. Three types of rules ased on corrosion addition models, namely historic corrosion rules (pre-csr), Common Structural Rules (CSR), and harmonised Common Structural Rules (CSR- H) are considered and compared with two other corrosion models namely model, suggested y the Union of Greek Shipowners (), and Time-Dependent Corrosion Wastage Model (). To identify the general trend in the effects of corrosion damage on the ultimate longitudinal strength performance, the corrosion addition rules are applied to four representative sizes of doule hull oil tankers namely,,, and. The results are helpful in understanding the trend of corrosion additions for tanker structures. KEY WORDS: Corrosion addition; Doule hull oil tankers; Age-related degradation; Corrosion maintenance; ; Common structural rules (CSR); Harmonised common structural rules (CSR-H); Time-dependent corrosion wastage model (); Union of greek shipowners (). ABBREVIATIONS & NOMENCLATURES CSR Common structural rule D s Ship depth CSR-H Harmonised common structural rule h w We height of stiffener Structural rule applied efore CSR I Moment of inertia Corresponding author: Jeom Kee Paik, jeompaik@pusan.ac.kr This is an Open-Access article distriuted under the terms of the Creative Commons Attriution Non-Commercial License ( which permits unrestricted non-commercial use, distriution, and reproduction in any medium, provided the original work is properly cited /ijnaoe

2 508 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~528 Time-dependent corrosion wastage L s Ship length model proposed y Paik et al. (2003a) M u Ultimate hull girder ending moment Union of greek shipowners a Length of stiffened panel M u_net Ultimate hull girder ending moment B Breadth of stiffened panel at net scantling t Plate thickness B s Ship readth t f Flange thickness Breadth etween longitudinal stiffeners t w We thickness f Breadth of flange σ Y Yield strength Block coefficient C INTRODUCTION Corrosion is an important age-related degradation prolem that has a great impact on the service life of marine structures. Since the 1950s, the construction time of ships and offshore structures has een significantly reduced y the development of welding and maintenance technology. With maintenance technology advancing at a fast growing rate, the structural failure due to in-service damage is decreasing. These advances, along with other technical developments, have extended the lifespan of ships and offshore structures y two or three times. Historically, various technologies for preventing corrosion have een suggested, such as corrosion addition, coating, cathodic protection, allast water deoxygenation, and chemical inhiition (Paik and Melchers, 2008). Of these technologies, coating and corrosion addition are the two most widely adopted technologies y ship designers and uilders to protect structural memers from corrosion degradation ecause of their cost effectiveness, simple practicaility, and relevance. Before the introduction of CSR, corrosion addition rules were developed and maintained y individual classification odies, a period known as pre-csr. To achieve roust and safer ships, the IACS adopted CSR for oil tankers and ulk carriers on 1 st April 2006, at which the corrosion additions for oil tankers and ulk carriers were specified (IACS, 2006a; 2006). However, the CSR for oil tankers and ulk carriers were developed independently y different teams using different technical approaches. During the review of the CSR, industry stakeholders urged the IACS to harmonise the key technologies used to derive the rules. The IACS agreed and was committed to develop a harmonised version of the rules (IMO, 2012). The new structural rules are known as CSR-H (IMO, 2012), as shown in Fig. 1. The outcome of the verification will e effective soon. The CSR-H is made up of common general hull requirements for oth ship types, and separate parts for ship-type specific requirements applicale to oil tankers and ulk carriers, respectively (Kim and Cheng, 2012). The rules on the corrosion additions for each ship type are expected to e located in the ship type specific parts, and corrosion additions can e defined for a range of cargo hold circumstances for each ship type. April 2006 Under evaluation CSR CSR-H Past Future July st CSR-H Draft Fig. 1 Overview of corrosion addition rules (DNV, 2005; IACS, 2006a; 2006; IMO, 2012). This study investigates the historical trend of corrosion additions for doule hull oil tankers and their effect on the ultimate strength performance of hull girders. For comparison, two other corrosion models namely model, a new corrosion model /ijnaoe

3 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~ suggested y the and the time-dependent corrosion wastage model are also examined. Many Greek shipowners have called for larger corrosion additions. However, no action has hitherto een taken to change the current corrosion addition rules. This matter has led to the developing an increased corrosion addition model (Gratsos et al., 2009; 2010). Four representtative classes of doule hull oil tanker structures, namely,,, and, are used to trace the general trend in corrosion addition effects. In addition, ulk carriers have een considered to draw the general tendency using similar procedure as present study y Kim et al. (2014). The insights otained in this study will help in understanding the trend in corrosion additions for doule hull oil tankers and their effect on the ultimate strength performance. GENERAL CORROSION ADDITIONS FOR TANKERS Trend in corrosion addition rules for ship design The CSR for corrosion additions were specified for doule hull oil tanker and ulk carrier structures in early 2006 for several reasons (IACS, 2006a; 2006) as follows: To reflect the experience and resources of all the classification societies (IACS memers) in a set of unified rules. To remove the confusion surrounding the corrosion additions of different classification societies. To achieve a 25-year design life. To apply the net thickness approach to ultimate strength analysis for stiffened panels and the half corrosion addition approach for hull girders. The historical trend in corrosion additions for each structural memer for doule hull oil tankers is presented in Fig. 2. The figure shows that there is no difference etween the CSR and CSR-H, ut the CSR corrosion additions are much greater than the pre-csr corrosion additions. It seems that the specified CSR corrosion additions are sufficient, and thus the same additions have een included in the CSR-H. Of course, the approach etween pre-csr and CSR is originally differing from each other. The pre-csr has adopted the net-scantling approach for ultimate strength analysis of stiffened panels and half corrosion addition deduced scantling approach for ultimate strength analysis of hull girders. However, the structural scantlings have een changed due to the different strength capacity requirements when the CSR was originally introduced in 2006, as shown in Fig. 3. CSR CSR-H Unit: mm Internals in upper portion of WBT 3.0 / 4.0 / 4.0 Deck longi. stiff. 2.0 / 4.0 / 4.0 Longi. BHD 2.0 / 4.0 / 4.0 Longi. BHD stiff. 2.0 / 4.0 / 4.0 Deck trans. we 2.0 / 4.0 / 4.0 Face plate 2.0 / 4.0 / 4.0 Deck 1.0 / 4.0 / 4.0 Plate sheer strake 2.0 / 3.5 / 3.5 Sheer strake longi. 2.5 / 4.0 / 4.0 To 3m elow top of tank Inner skin 1.0 / 3.5 / 3.5 Longi. stiff. 1.5 / 3.5 / 3.5 Longi. BHD stiff. / 2.5 / 2.5 Longi. BHD / 2.5 / 2.5 Horizontal Face plate 1.0 / 3.5 / 3.5 We 1.0 / 2.5 / 2.5 Inner skin 2.5 / 4.5 / 4.5 Inner skin longi. stiff. 2.0 / 4.5 / 4.5 Stringer 1.5 / 3.0 / 3.0 Side shell 1.0 / 3.0 / 3.0 We plate 1.5 / 3.0 / 3.0 Hopper longi. 1.0 / 3.5 / 3.5 Face plate 1.5 / 3.5 / 3.5 Inner ottom 1.5 / 4.5 / 4.5 Longi. stiff. 1.5 / 3.5 / 3.5 Longi. stiff. 1.5 / 3.0 / 3.0 Longi. girders 1.5 / 3.0 / 3.0 Bottom & ilge 1.0 / 3.0 / 3.0 Fig. 2 Changes in corrosion addition rules for doule hull oil tanker structures (DNV, 2005; IACS, 2006a; 2006; IMO, 2012) /ijnaoe

4 510 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~528 Deck: 23 AH32 [19] 400x12[8] AH X15[11] AH32 T Deck: 20 AH32 [19] 283x90x13[11] AH32 /17[15] AH32 Angle Frame spacing at deck and ottom = 4800 Inner Bottom: 19.3 AH32 [14.8] 500x11.5[8] AH X24[20.5] AH36 T Inner Bottom: 16.6 AH32 [15.1] 560x11.5[10] AH X18[16.5] AH32 T Outer Bottom: 22.5 AH32 [19.5] 500x11.5[8.5] AH X24[21] AH32 T Outer Bottom: 20 AH32 [19] 470x11.5[10] AH X28[26.5] AH32 T CSR Fig. 3 Comparison of structural scantlings of a class doule hull oil tanker s mid-ship section in pre-csr and CSR designs (racket indicate the net thickness) (Paik et al., 2009). Corrosion addition for CSR Gross (As-uilt) scantling of CSR design scantling of CSR design (Reference point) Target scantlings for Applied corrosion present study (Ref.+ α) additions (α) Fig. 4 Applied corrosion additions with structural reference scantlings (net scantlings) (Note: gross scantling = net scantling + full corrosion addition, half corrosion addition deducted scantling = net scantling + half corrosion addition). Four types of doule hull oil tankers designed using the IACS CSR method are employed to avoid complex structural design selection prolems. The net scantlings in the CSR design are taken as the reference scantlings in the present study, as shown in Fig. 4. Other corrosion addition models The for ships and offshore structures (Paik et al., 2003a; 2003; 2004; Guedes Soares et al., 2008) was deducted from the results of statistical analyses using real corrosion measurement data. As mentioned previously, two types of corrosion models (CSR and CSR-H) were also proposed ased on real measured time-variant corrosion wastage. But, other types of TD- CWM have een developed y researchers. Recently, more refined time-dependent corrosion wastage model techniques have een proposed y Paik and Kim (2012) and applied to the various structures such as susea well tue (Mohd Hairil and Paik, 2013) and susea gas pipeline (Mohd Hairil et al., 2014). For the condition assessment of corrosion damaged structures, Paik et al. (2003a) developed two types of for tankers that cover average and severe cases. Kim et al. (2012a; 2012) performed an ultimate strength comparison study of hull girders and stiffened panels using the CSR corrosion addition and the average. Their results showed that the difference in ultimate hull girder strength etween the two corrosion models at the 25 years (net) scantling was around 10-20%. Recently, Kim et al. (2014a) investigated an ultimate hull girder strength of corroded class oil tanker under grounding damage. In the comparison in this study, a representative severe for a doule hull oil tanker (Paik et al., 2003a) is applied, as shown in Fig. 5 see Tale A.1 for areviation used /ijnaoe

5 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~ A/B-H : 323 A/O-H : C DLC(W) : DLC(F) : DLB(W) : 244 A/B-V : B/S-V : O/B-V : O/O-V : B/B-H : 586 B/B-H : 586 Plating Longi. Stiffeners Coating life = 7.5years, Unit = mm/year Severe corrosion model LBLC(W) : 942 LBLC(F) : 921 BSLB(W) : 461 BSLB(F) : 343 LBLB(W) : LBLB(F) : LBLB(W) : LBLB(F) : SSLB(W) : 595 SSLB(F) : BLGB : B/S-H : BSLB(W) : 461, BSLB(F) : 343 (a) Time-dependent corrosion wastage model (). A/B-H : 4.0mm A/O-H : 3.0mm C DLC(W) : 2.0mm DLC(F) : 2.0mm DLB(W) : 7.5mm A/B-V : 3.5mm B/S-V : 3.0mm O/B-V : 3.5mm O/O-V : 3.0mm B/B-H : 4.5mm B/B-H : 4.5mm Plating Longi. Stiffeners Unit = mm/year LBLC(W) : 1.5mm LBLC(F) : 1.5mm BSLB(W) : 4.5mm BSLB(F) : 4.0mm LBLB(W) : 7.0mm LBLB(F) : 6.0mm LBLB(W) : 7.0mm LBLB(F) : 6.0mm SSLB(W) : 4.5mm SSLB(F) : 3.0mm BLGB : 3.0mm B/S-H : 3.0mm BSLB(W) : 4.5mm, BSLB(F) : 4.0mm () Corrosion addition model determined from. Fig. 5 Corrosion addition model determined from for doule hull oil tanker (Paik et al., 2003a). CSR Unit: mm Internals in upper portion of WBT 3.0 / 4.0 / 4.5 Deck longi. stiff. 2.0 / 4.0 / 5.0 Longi. BHD 2.0 / 4.0 / 4.5 Longi. BHD stiff. 2.0 / 4.0 / 4.5 Deck trans. we 2.0 / 4.0 / 4.5 Face plate 2.0 / 4.0 / 5.0 Deck 1.0 / 4.0 / 4.5 Plate sheer strake 2.0 / 3.5 / 4.0 Sheer strake longi. 2.5 / 4.0 / 4.0 To 3m elow top of tank Inner skin 1.0 / 3.5 / 3.7 Longi. stiff. 1.5 / 3.5 / 3.7 Longi. BHD stiff. / 2.5 / 3.5 Longi. BHD / 2.5 / 3.5 Horizontal Face plate 1.0 / 3.5 / 4.5 We 1.0 / 2.5 / 3.5 Inner skin 2.5 / 4.5 / 4.0 Inner skin longi. stiff. 2.0 / 4.5 / 4.5 Stringer 1.5 / 3.0 / 4.0 Side shell 1.0 / 3.0 / 4.0 We plate 1.5 / 3.0 / 4.0 Hopper longi. 1.0 / 3.5 / 3.7 Face plate 1.5 / 3.5 / 4.0 Inner ottom 1.5 / 4.5 / 4.0 Longi. stiff. 1.5 / 3.5 / 4.0 Longi. stiff. 1.5 / 3.0 / 4.0 Longi. girders 1.5 / 3.0 / 4.0 Bottom & ilge 1.0 / 3.0 / 4.0 Fig. 6 corrosion addition model for doule hull oil tanker with previous rules including pre-csr and CSR (DNV, 2005; IACS, 2006a; 2006; Gratos et al., 2010) /ijnaoe

6 512 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~528 Moreover, the suggested a new corrosion addition model (Gratos et al., 2009; 2010), as shown in Fig. 6, that reflects their experience of doule hull oil tanker structures to reduce maintenance costs. The model meets with opposition from other shipowners who have confidence in the current maintenance of their ship. Fig. 6 presents the corrosion addition models for each structural memer against other pre-csr and CSR corrosion addition rules. The corrosion additions are around mm to 1.0 mm greater than the CSR corrosion additions. The corrosion model is also considered here in investigating the effect of corrosion additions on the ultimate strength performance of doule hull oil tanker structures. ULTIMATE STRENGTH ANALYSIS Hull girders In the structural analysis of ships, gloal scantling check (hull girder) and local scantling check (stiffened panel) are performed sequentially. Applied examples for hull girders Four sizes of doule hull oil tankers (Paik et al., 2012) are selected as representative vessels to investigate the general trend in corrosion addition effects. The principal dimensions of each ship are illustrated in Tale 1. The ALPS/HULL (2013) progressive hull collapse analysis program is used for the hull girder ultimate strength analysis. The details of ALPS/HULL program are descried in Hughes and Paik (2010) and enchmark studies have een performed to verify its accuracy and efficiency (Paik et al., 2012a). Tale 1 General mid-ship section information with principal dimensions of the target structures with net scantlings (reference point as illustrated in Fig. 4). Tanker type L s (m) B s (m) D s (m) C 4 I ( m ) N.A.(m) Vertical ending moments including hogging and sagging, which are the dominant loads for ships during operation period, are considered in the ultimate strength analysis for the gross scantlings, half addition scantling, and net scantlings of the ship. Only the average levels of initial distortions, which are performed y plate initial deflection and stiffener distortion, are considered. The weld-induced residual strength is not considered for hull girder strength analysis according to the CSR (IACS, 2006a). Analysis results of hull girders The ultimate hull girder strength analysis results for the four sizes of doule hull oil tanker structures and the five types of corrosion addition models are compared in Figs. A.1 to A.4, respectively. Empirical formulas ased on the analysis results are otained y the curve-fitting approach presented in Fig. 7 and Tale 2. It is apparent that the effect of corrosion additions on the ultimate hull girder (longitudinal) strength tends to decrease as the vessel length increases. This effect is ecause the same corrosion additions per each structural memer are applied to all types of doule hull oil tanker structures. In terms of the loading conditions, sagging ending moments affect the ultimate hull girder strength more significantly than hogging. The mean value and Coefficient of Variation (COV) are presented in Tale A.2(a) and A.2(). The empirical formulas can e defined as follows: /ijnaoe

7 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~ L L Mu / Mu net = ξ + ψ + ζ (1) The coefficients are as summarised in Tale Gross Half CSR&CSR-H Gross Half CSR&CSR-H M u /M u-net 1.4 M u /M u-net L (m) L (m) (a). (). Fig. 7 Summary of the ultimate hull girder strength analysis results. Tale 2 Coefficients of the empirical formulas under vertical ending moments. Coefficients CSR & CSR-H ξ ψ ζ 2 R Gross Half Gross Half Gross Half Gross Half Note: 2 R = coefficient of determination. In a sagging condition, these empirical formulas cannot e applied to evaluate the residual strength performance when the vessel length is larger than m (a class doule hull oil tanker). In this case, a constant value that can e calculated from the average value from the results for and class doule hull oil tankers is applied /ijnaoe

8 514 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~528 The differences in the mean values are presented in Figs. 8(a) and (), and more details of the statistical analysis results are given in Tale A.2(a) and A.2(). From the mean values shown in Figs. 9(a) and (), it is apparent that the ultimate strength capacity of the hull girders can e specified y the following order. For a hogging condition Pre - CSR < < (2.a) For a sagging condition Pre - CSR < < < (2.) M u-others (GNm) Hog Sag CSR&CSR-H Mean C.O.V CSR&CSR-H M u-net (GNm) M u-others (GNm) Hog Sag CSR&CSR-H Mean C.O.V CSR&CSR-H M u-net (GNm) (a). (). Fig. 8 Deviation in the ultimate strength of hull girders etween net scantlings and the five corrosion addition models. M u / M u-net deducted scantlings M u / M u-net deducted scantlings CSR&CSR-H CSR&CSR-H (a). (). Fig. 9 Mean values for the ultimate strength of hull girders for doule hull oil tankers /ijnaoe

9 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~ Stiffened panels The local scantlings are also investigated y applying the ALPS/ULSAP ultimate strength analysis program for stiffened panel. The details of ALPS/ULSAP program have een descried in Hughes and Paik (2010) and enchmark studies for stiffened panels have een performed to verify the accuracy and efficiency aout the ALPS/ULSAP program (Paik et al., 2012a). Applied examples for stiffened panels It is well known that maximum axial compression or tension are applied to the deck, inner ottom, and outer ottom stiffened panel structures, which are located far away from the neutral axis of the ship, as presented in Fig. 10 (Paik et al., 2013). The details of the selected three stiffened panels are presented in Tale 3(a) to (d). Schematic diagram of stiffened panel is presented in Fig. 11 and the nomenclatures of the stiffener dimensions are illustrated in Fig. 12. Fig. 10 Longitudinal stress distriution of tanker mid hull at the ultimate limit state (Paik et al., 2013). Transverse frames a a B a a L Longitudinals Fig. 11 Schematic diagram of general shape of stiffened panel structure (Hughes and Paik, 2010) /ijnaoe

10 516 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~528 p-gross p-gross p-gross t p-gross t p-gross t p-gross t w-gross h w-gross t w-gross h w-gross t f-gross t w-gross t f-gross h w-gross f-gross f-gross Fig.12 Nomenclature of the stiffener dimensions. Analysis results for stiffened panels Fig. A.5 to A.8 show the ultimate strength analysis results of stiffened panels for four types of doule hull oil tanker structures sujected to axial or iaxial compression. In case of stiffened panels, the empirical formulas are not presented ecause the structural scantlings of stiffened panels of each doule hull oil tanker show the dissimilar trend. In this regard, only mean values and COV calculations are performed. 2 2 The capacity for iaxial compressive action ( σc = σxu + σ ) is compared and the otained results are plotted in Figs. 13(a) yu and () with mean and COV values. The corresponding figures present the trend of the deviation in ultimate limit state of stiffened panels etween net scantlings and the five corrosion addition models. The details of statistical analysis results (i.e., mean, standard deviation, and coefficient of variation) are as summarised in Tale A.3(a) and A.3() Deck I.B O.B Deck I.B O.B σ c-others / σ Yeq σ c-others / σ Yeq Green Blue Red Purple CSR&CSR-H Mean C.O.V Green Blue Red Purple CSR&CSR-H Mean C.O.V σ c-net / σ Yeq σ c-net / σ Yeq (a). (). Fig. 13 Deviation in the ultimate strength of stiffened panels etween net scantlings and the five corrosion addition models. From the mean values shown in Figs. 13(a)-(), it is apparent that the ultimate strength capacity of the stiffened panels can e specified in the following order and the order of ultimate strength capacity would e linked with Figs. 14(a)-(c). For deck stiffened panels Pre - CSR < < < (3.a) /ijnaoe

11 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~ For inner ottom stiffened panels Pre - CSR < < < (3.) For outer ottom stiffened panels Pre - CSR < < (3.c) Deck Inner ottom Mean of (σ c /σ c-net ) Mean of (σ c /σ c-net ) CSR&CSR-H CSR&CSR-H (a) Deck stiffened panel. () Inner ottom stiffened panel Outer ottom Mean of (σ c /σ c-net ) CSR&CSR-H (c) Outer ottom stiffened panel. Fig. 14 Mean values for ultimate strength of stiffened panels for doule hull oil tankers. Tale 3(a) Properties of the stiffened panels of panamax class tanker with net scantlings ased on Figs. 11 and 12. class tanker a B t Stiff. type No. of stiff. h w t w f t f σ Y (MPa) Plate Stiff. Deck Angle Inner ottom (I.B.) Tee Outer ottom (O.B.) Tee /ijnaoe

12 518 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~528 Tale 3() Properties of the stiffened panels of aframax class tanker with net scantlings ased on Figs. 11 and 12. class tanker a B t Stiff. type No. of stiff. h w t w f t f σ Y (MPa) Plate Stiff. Deck Angle Inner ottom (I.B.) Tee Outer ottom (O.B.) Tee Tale 3(c) Properties of the stiffened panels of suezmax class tanker with net scantlings ased on Figs. 11 and 12. class tanker a B t Stiff. type No. of stiff. h w t w f t f σ Y (MPa) Plate Stiff. Deck Tee Inner ottom (I.B.) Tee Outer ottom (O.B.) Tee Tale 3(d) Properties of the stiffened panels of tanker with net scantlings ased on Figs. 11 and 12. class tanker a B t Stiff. type No. of stiff. h w t w f t f σ Y (MPa) Plate Stiff. Deck Tee Inner ottom (I.B.) Tee Outer ottom (O.B.) Tee CONCLUDING REMARKS This study investigates the trend in corrosion additions in the structural design of ships and the effect of corrosion additions on the ultimate strength performance of four doule hull oil tanker structures, namely,,, and. Five types of corrosion addition models, namely, CSR, CSR-H,, and, are applied to investigate the general trend in corrosion additions. The ultimate strength performance of hull girders and stiffened panels are investigated in terms of the gross, half corrosion addition deducted, and net scantlings. The net scantlings in CSR design are set as the reference scantlings from which the minimum required strength thickness is otained and to which the additional corrosion additions (margins) of each corrosion models are added, as shown in Fig. 4. Based on these assumptions, empirical formulas are proposed for the ultimate hull girder strength performance of doule hull oil tankers for the different corrosion addition rules. But, additional case studies for doule hull oil tankers should e performed and considered to develop reliale empirical formulas. The results are expected to e helpful in evaluating the effect of corrosion additions on the ultimate strength performance of doule hull oil tanker structures and to help understand the history of structural design rules on corrosion. Future studies could investigate the effect of corrosion addition models on economics in terms of the consumption of steel and fuel ratio, and the effect of corrosion additions in ulk carriers. ACKNOWLEDGEMENTS This study was supported y Basic Science Research Program through the National Research Foundation of Korea (NRF) funded y the Ministry of Education, Science and Technology (Grant Numer: 2013R1A6A3A ). This study was also /ijnaoe

13 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~ supported y Leading Foreign Research Institute Recruitment Program through the National Research Foundation of Korea (NRF) funded y the Ministry of Science, Ict & future Planning (MSIP) (Grant Numer: ). Some part of this paper has een presented at the 12 th International Symposium on Practical Design of Ships and Other Floating Structures (PRADS 2013), Octoer, 2013, Changwon, Korea. REFERENCES ALPS/HULL, A computer program for progressive collapse analysis of ship hulls. [computer program] DRS Defense Solutions Avaliale at: < [Accessed 10 January 2014] DNV, Rules for classification of ships-hull structural design ship with length 100 meters and aove. Oslo: Det Norske Veritas. Gratsos, G.A., Psaraftis, H.N. and Zachariadis, P., The Life cycle cost of maintaining the effectiveness of a ship s structure and environmental impact of ship design parameters. Royal Institution of Naval Architect (RINA) Conference on the Design and Operation of Bulk Carriers, Athens, Greece, Octoer 2009, pp Gratsos, G.A., Psaraftis, H.N. and Zachariadis P., Life-cycle CO2 emissions of ulk carriers: A comparative study. International Journal of Maritime Engineering, 152(A3), pp Guedes Soares, C., Garatov, Y., Zayed, A. and Wang, G., Corrosion wastage model for ship crude oil tanks. Corrosion Science, 50(11), pp Hughes, O.F. and Paik, J.K., Ship structural analysis and design. New Jersey: The Society of Naval Architects and Marine Engineers. IACS, 2006a. Common structural rules for doule hull oil tankers. London: International Association of Classification Societies. IACS, Common structural rules for ulk carriers. London: International Association of Classification Societies. IMO, Harmonised common structural rules (CSR-H) for oil tankers and ulk carriers. London: International Association of Classification Societies (IACS) - MSC 87/5/6. Kim, D.K., Kim, B.J., Seo, J.K., Kim, H.B., Zhang, X.M. and Paik, J.K., 2014a. Time-dependent residual ultimate longitudinal strength - grounding damage index (R-D) diagram. Ocean Engineering, 76, pp Kim, D.K., Kim, S.J., Kim, H.B., Zhang, X.M., Li, C.G. and Paik, J.K., Ultimate strength performance of ulk carriers with various corrosion additions. Ships and Offshore Structures. [online] Availale at: < / > [Accessed 10 January 2014]. Kim, D.K., Park, D.K., Kim, J.H., Kim, S.J., Kim, B.J., Seo, J.K. and Paik, J.K., 2012a. Effect of corrosion on the ultimate strength of doule hull oil tankers - Part I: stiffened panels. Structural Engineering and Mechanics, 42(4), pp Kim, D.K., Park, D.K., Park, D.H., Kim, H.B., Kim, B.J., Seo, J.K. and Paik, J.K., Effect of corrosion on the ultimate strength of doule hull oil tankers - Part II: hull girders. Structural Engineering and Mechanics, 42(4), pp Kim, M.S. and Cheng, Y.F., Limit states rules: Past experiences and future scenarios. The 11 th International Marine Design Conference (IMDC 2012), Glasgow, UK, June 2012, pp Mohd Hairil, M., Kim, D.K., Kim, D.W. and Paik, J.K., A time-variant corrosion wastage model for susea gas pipelines. Ships and Offshore Structures, 9(2), pp Mohd Hairil, M. and Paik, J.K., Investigation of the corrosion progress characteristics of offshore susea oil well tues. Corrosion Science, 67, pp Paik, J.K., Amlashi, H., Boon, B., Branner, K., Caridis, P., Das, P., Fujikuo, M., Huang, C.H., Josefson, L., Kaeding, P., Kim, C.W., Parmentier, G., Pasqualino, I.P., Rizzo, C.M., Vhanmane, S., Wang, X. and Yang, P., 2012a. Ultimate strength - final report of ISSC III.1. Germany: International Ship and Offshore Structures Congress (ISSC 2012). Paik, J.K. and Kim, D.K., Advanced method for the development of an empirical model to predict time-dependent corrosion wastage. Corrosion Science, 63, pp Paik, J.K., Kim, D.K. and Kim, M.S., Ultimate strength performance of suezmax tanker structures: pre-csr versus CSR designs. International Journal of Maritime Engineering, 151(A2), pp /ijnaoe

14 520 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~528 Paik, J.K., Kim, D.K., Park, D.H., Kim, H.B. and Kim, M.S., A new method for assessing the safety of ships damaged y grounding. International Journal of Maritime Engineering, 154(A1), pp Paik, J.K., Kim, D.K., Park, D.H., Kim, H.B., Mansour, A.E. and Caldwell, J.B., Modified Paik-Mansour formula for ultimate strength calculations of ship hulls. Ships and Offshore Structures, 8(3-4), pp Paik, J.K., Lee, J.M., Hwang, J.S. and Park, Y.I., 2003a. A time-dependent corrosion wastage model for the structures of single/doule hull tankers and FSOs/FPSOs. Marine Technology, 40(3), pp Paik, J.K. and Melchers, R.E., Condition assessment of aged structures. New York: CRC Press. Paik, J.K., Thayamalli, A.K., Park, Y.I. and Hwang, J.S., A time-dependent corrosion wastage model for ulk carrier structures. International Journal of Maritime Engineering, 145(A2), pp Paik, J.K., Thayamalli, A.K., Park, Y.I. and Hwang, J.S., A time-dependent corrosion wastage model for seawater allast tanks of ships. Corrosion Science, 46(2), pp APPENDIX Vertical ending moment (GNm) Curvature (1/km) (a) Curvature (1/km) () Half addition scantlings. Fig. A.1. Ultimate hull girder strength analysis results of panamax class tanker. Vertical ending moment (GNm) Vertical ending moment (GNm) Curvature (1/km) (a) Curvature (1/km) () Half addition scantlings. Fig. A.2 Ultimate hull girder strength analysis results of aframax class tanker. Vertical ending moment (GNm) /ijnaoe

15 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~ Vertical ending moment (GNm) Curvature (1/km) (a) Curvature (1/km) () Half addition scantlings. Fig. A.3 Ultimate hull girder strength analysis results of suezmax class tanker. Vertical ending moment (GNm) Vertical ending moment (GNm) Vertical ending moment (GNm) Curvature (1/km) (a). () Half addition scantlings. Fig. A.4 Ultimate hull girder strength analysis results of tanker Curvature (1/km) /ijnaoe

16 522 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~528 deck deck (a) Deck-gross scantlings. () Deck-half corrosion addition. I.B. I.B. 1.0 (c) I.B.-gross scantlings. 1.0 (d) I.B.-half corrosion addition. O.B. O.B (e) O.B.-gross scantlings. (f) O.B.-half corrosion addition. Fig. A.5 Ultimate stiffened panel strength analysis results of panamax class tanker /ijnaoe

17 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~ deck deck 1.0 (a) Deck-gross scantlings. 1.0 () Deck-half corrosion addition. I.B. I.B. 1.0 (c) I.B.-gross scantlings. 1.0 (d) I.B.-half corrosion addition. O.B. O.B (e) O.B.-gross scantlings. (f) O.B.-half corrosion addition. Fig. A.6 Ultimate stiffened panel strength analysis results of aframax class tanker /ijnaoe

18 524 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~528 deck deck 1.0 (a) Deck-gross scantlings. 1.0 () Deck-half corrosion addition. I.B. I.B. 1.0 (c) I.B.-gross scantlings. 1.0 (d) I.B.-half corrosion addition. O.B. O.B (e) O.B.-gross scantlings. (f) O.B.-half corrosion addition. Fig. A.7 Ultimate stiffened panel strength analysis results of suezmax class tanker /ijnaoe

19 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~ deck deck 1.0 (a) Deck-gross scantlings. 1.0 () Deck-half corrosion addition. I.B. I.B. 1.0 (c) I.B.-gross scantlings. 1.0 (d) I.B.-half corrosion addition. O.B. O.B (e) O.B.-gross scantlings. (f) O.B.-half corrosion addition. Fig. A.8 Ultimate stiffened panel strength analysis results of tanker /ijnaoe

20 526 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~528 Tale A.1 Areviation of midship memer presented in Fig. 5 (Paik et al. 2003a). B/S-H Bottom shell plating (segregated allast tank) SSLB(W) Side shell longitudinals in allast tank, we A/B-H Deck plating (segregated allast tank) SSLB(F) Side shell longitudinals in allast tank, flange A/B-V B/S-V Side shell plating aove draft line (segregated allast tank) Side shell plating elow draft line (segregated allast tank) LBLB(W) LBLB(F) Longitudinal ulkhead longitudinals in allast tank, we Longitudinal ulkhead longitudinals in allast tank, flange BLGB Bilge plating (segregated allast tank) BSLC(W) Bottom shell longitudinals in cargo oil tank, we O/B-V Longitudinal ulkhead plating (segregated allast tank) BSLC(F) Bottom shell longitudinals in cargo oil tank, flange B/B-H Stringer plating (segregated allast tank) DLC(W) Deck longitudinals in cargo oil tank, we O/S-H Bottom shell plating (cargo oil tank) DLC(F) Deck longitudinals in cargo oil tank, flange A/O-H Deck plating (cargo oil tank) SSLC(W) Side shell longitudinals in cargo oil tank, we A/O-V Side shell plating aove draft line (cargo oil tank) SSLC(F) Side shell longitudinals in cargo oil tank, flange O/S-V Side shell plating elow draft line (cargo oil tank) LBLC(W) BLGC Bilge plating (cargo oil tank) LBLC(F) Longitudinal ulkhead longitudinals in cargo oil tank, we Longitudinal ulkhead longitudinals in cargo oil tank, flange O/O-V Longitudinal ulkhead plating (cargo oil tank) BGLC(W) Bottom girder longitudinals in cargo oil tank, we O/O-H Stringer plating (cargo oil tank) BGLC(F) Bottom girder longitudinals in cargo oil tank, flange BSLB(W) Bottom shell longitudinals in allast tank, we DGLC(W) Deck girder longitudinals in cargo oil tank, we BSLB(F) Bottom shell longitudinals in allast tank, flange DLB(W) Deck longitudinals in allast tank, we DGLC(F) Deck girder longitudinals in cargo oil tank, flange SSTLC(W) Side stringer longitudinals in cargo oil tank, we Tale A.2(a). Statistical analysis results of hull girder with gross scantlings. Mu (Gross) / CSR / / / CSR / / / /CSR /CSR / D/H oil tankers Mean C.O.V Mean C.O.V Tale A.2(). Statistical analysis results of hull girder with half corroded scantlings. Mu (Half) / CSR / / / CSR / / / /CSR /CSR / D/H oil tankers Mean C.O.V Mean C.O.V /ijnaoe

21 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~ Tale A.3(a) Statistical analysis results of stiffened panel with gross scantlings. σ c (Gross) / CSR / / / CSR / / / /CSR /CSR / Deck Mean C.O.V I.B. Mean C.O.V O.B. Mean C.O.V Deck Mean C.O.V I.B. Mean C.O.V O.B. Mean C.O.V Deck Mean C.O.V I.B. Mean C.O.V O.B. Mean C.O.V Deck Mean C.O.V I.B. Mean C.O.V O.B. Mean C.O.V /ijnaoe

22 528 Int. J. Nav. Archit. Ocean Eng. (2014) 6:507~528 Tale A.3(). Statistical analysis results of stiffened panel with half corroded scantlings. σ c (Half) / CSR / / / CSR / / / /CSR /CSR / Deck Mean C.O.V I.B. Mean C.O.V O.B. Mean C.O.V Deck Mean C.O.V I.B. Mean C.O.V O.B. Mean C.O.V Deck Mean C.O.V I.B. Mean C.O.V O.B. Mean C.O.V Deck Mean C.O.V I.B. Mean C.O.V O.B. Mean C.O.V /ijnaoe