4153.1.kokrakis dejong

8/12/2019 4153.1.Kokrakis Dejong

1/15

A PRACTICAL ASSESSMENT OF EXISTING BULK CARRIER LOCAL STRUCTURAL

STRENGTH IN RELATION TO THE ALLOWABLE HOLD MASS CURVES

K Chatzitolios, Bureau Veritas, GreeceG de Jong, Bureau Veritas, France

Dr JE Kokarakis, Bureau Veritas, Greece

SUMMARY

The allowable hold mass curves for vessels built after 1998 are mandatory in the loading manual & the loadinginstrument as per IACS Unified Requirements S1A. The majority of the bulk carriers in service have been constructedbefore 1998 and generally do not have allowable hold mass curves.

Pre-1998 bulk carriers engaged in multi-port operations need to have allowable hold mass curves to control the localstrength of the cargo hold structure for the envisaged loading conditions. The curves are produced according to theloading conditions of the approved loading manual as a function of the draught. For the case of an individual hold theyare determined by examining bending and shear stresses in floors and girders, as well as buckling stresses in theassociated plating. For the case of two adjacent holds the strength of the transverse bulkhead and cross deck isconsidered as well. The curves can be checked with finite element analysis or other methods to obtain the applicable

safety margin. The paper presents a theoretical derivation of the hold mass curves as function of the draught andprovides some comparisons with formulations by other class societies and IACS requirements. A practical methodologyto determine the hold mass curves when not available is proposed.

An interesting application, presented in a case study in the paper, is the determination of the maximum draught as afunction of the static still water bending moment at the empty holds. The combination of a hogging hull girder bending

moment and hydrostatic pressure at 60 to 70% of the scantling draught may cause severe buckling of the bottom platingand exceed its ultimate strength. A methodology on how to assess this loading condition for holds which are not usuallyempty is proposed.

1. INTRODUCTIONIn 1998 IACS adopted Unified Requirement (UR) S1A,

effectively introducing additional requirements forloading conditions, loading manuals and loadinginstruments of both new and existing bulk carriers

1.

UR S1A requires existing bulk carriers (that is, bulkcarriers contracted for construction before 1 July 1998)

with a length of 150 m and above to be provided with aclass approved loading instrument in order to enable theships master to check the envisaged loading conditions(whether at sea or in port) against permissiblelongitudinal strength criteria (hull girder bendingmoments and shear forces). In this context a loading

instrument is considered as an effective means topreventing overstressing of the hull girder, which couldpotentially result in global structural collapse. In addition,UR S1A requires single side skin bulk carriers of 150 mlength and above to be provided with a class approvedloading manual with typical loading sequences where the

vessel is loaded from commencement of cargo loading toreaching the full deadweight capacity, and vice versa.The reasoning behind this requirement is to ensure that

1UR S1A was introduced as an addition to UR S1, whichprovides more general requirements for loadingconditions, loading manuals and loading instruments. UR

S1 is considered to be an implementation of therequirements of Regulation 10(1) of the InternationalConvention on Load Lines, 1966.

the vessel is not overstressed during loading anddischarging in port, which can happen due to faultyloading sequences or (de)ballasting operations. The

sequence of loading the cargo holds, as well as theamount of cargo which is loaded in each hold in one timegreatly influences the induced hull girder loads. Thisissue is still very actual, in particular due to high speedcargo loading at iron ore terminals (up to 16,000 tonnesper hour) [1].

For new bulk carriers (contracted for construction on orafter 1 July 1998) of 150 m length and above, UR S1Arequires the class approved loading manual toadditionally include the following data:

Maximum allowable and minimum required mass ofcargo and double bottom contents of each hold as afunction of the draught at mid-hold position;

Maximum allowable and minimum required mass ofcargo and double bottom contents of any twoadjacent holds each hold as a function of meandraught in way of these holds.

The values of maximum allowable and minimumrequired mass of cargo can be plotted as a function of the

draught and are generally referred to as hold masscurves. The loading instrument is required to displaywhether the cargo hold mass is within permissible limitsand therefore needs to incorporate the hold mass curves.

This requirement for new ships effectively regulatesthat, for any given loading condition, the local strengthcapacity of the hull structure (strength of double bottom,


2/15

transverse bulkheads, etc.) is not exceeded and thereforeis to be considered as a complementary safety criterion tothe longitudinal strength criteria applicable to both newand existing bulk carriers.

As pre 1998 bulk carriers are not required to have hold

mass curves, from an operational viewpoint they areinherently less flexible than there newer counterparts, asin practice they can only sail in the loading conditionswhich have been approved in the loading manual. Thisbecomes a handicap if they are engaged in multi-port

operations, where the vessel will experience a widevariety of loading conditions which may not be included

in the loading manual. Therefore, pre 1998 bulk carrierseffectively need hold mass curves in order to operatesafely on multi-port trades. As about 60% of theapproximately 7,000 bulk carriers in service today have

been built before 2000 (assuming a time delay of 18months between contract signing and ship delivery), this

is by no means an academic issue [2].

For an individual hold the hold mass curves aredetermined by examining shear stresses in floors and

double bottom girders, while for adjacent holds thestrength of cross deck and transverse bulkheads are of

main concern. The adjacent holds model is furtherstudied by evaluation of cross deck stresses stemmingfrom bending of the transverse bulkhead and hull girdertorsion. The curves can be checked with Finite Element

Analysis (FEA) or other methods to obtain the safetymargin.

This paper presents a comparison between variousformulations of hold mass curves amongst classificationsocieties and proposes ways to determine the curves forexisting ships when not available (pre 1998 bulk carriers),as such creating a safe and easy way to expand the

trading flexibility of older bulk carriers.

In section 2 the technical background of the hold masscurves is presented, considering formulations by differentclass societies as well as IACS. Section 3 explains theimportance of hold mass curves for bulk carriers engaged

in multi-port operations; the focus is on the maximumpermissible draught in way of the empty holds as a

function of the hogging SWBM (Still Water BendingMoment). Section 4 proposes a methodology for derivingthe hold mass curves on the basis of the theoreticalconsiderations presented in the previous sections and

presents an interesting application of hold mass curves:the determination of the maximum draught as a functionof the static bending moment at the empty holds. Thecombination of a hogging hull girder bending momentand hydrostatic pressure at 60 to 70% of the scantlingdraft is considered, which may cause severe buckling ofthe bottom plating and exceed its ultimate strength

capacity. A methodology on how to assess this loadingcondition for holds which are not usually empty is

proposed. Finally, in section 5 the main conclusions aredrawn and further recommendations are made.

2. TECHNICAL BACKGROUND2.1 HOLD MASS CURVES FOR SEAGOING

CONDITIONS

As explained above, the hold mass curves are a means

for the master to decide obtain the maximum allowableor minimum required cargo mass for an envisagedloading condition which is not included in the loadingmanual. The goal is to prevent overloading of the localstructure, such as the double bottom structure (plating,

floors and girders), the transverse bulkheads and thecross deck structures. For example, if for an individual

cargo hold a cargo mass P has been approved for aloading condition with a draught T1at mid-length of theconsidered hold, the double bottom structure mightexperience excessive flexural deformation if the same

cargo mass is loaded for a loading condition with acorresponding draught less than T1 (e.g. 0.5T1), as

depicted in Figure 1.

Figure 1: Excessive flexural deformation of doublebottom structure [3]

The basic idea behind the derivation of the hold masscurves is to use the approved loading conditions from the

loading manual as a starting point for an inverse analysisin order to obtain acceptable new conditions. As the netresultant load on the double bottom is the governingparameter for the variation in the local structuralresponse, the objective of the exercise is to control thisload, which is defined as the difference between the

downward force exerted by the mass of the cargo in thehold & ballast water in the double bottom tanks and the

upward force resulting from the sea pressure. Both forcesare composed of a static and a dynamic component. Thedownward force consists of the own weight of the massof the cargo and ballast water (static part) plus the inertia

loads caused by the ship motion induced accelerationsacting on this mass (dynamic part)

2. The upward force

consists of the hydrostatic load (static part) plus thehydrodynamic loads caused by ship motions in waves(dynamic part). In linear rigid body dynamics thehydrodynamic load is considered to be the sum of thehydromechanical (reaction) loads caused by the ship

moving (oscillating) in the undisturbed fluid surface and

2The own mass of the ship structure is neglected as it is

small compared to the mass of the cargo.


3/15

the forces exerted by the waves on the restrained body(wave exciting loads). An example of the net resultantload on the double bottom is presented in Figure 1, inwhich only the static parts are considered.

For the purpose of structural analysis it is sufficiently

accurate to approximate the hydrodynamic load by aFroude-Krylov type of wave load using the ship relativemotion as wave amplitude (as opposed to the waveelevation relative to the undisturbed free surface) [4]. Asthe variation of the net resultant load on the double

bottom is the highest for the upright ship condition(usually the head sea condition is considered) the

analysis focuses on this condition, see Figure 2.

Figure 2: Wave load distribution on the basis of the

relative ship motion hUin upright ship condition [4]

In a generic form, the net resultant load on the doublebottom of a single cargo hold, in terms of the average

pressure DBp , can be expressed as follows:

+

++=

L

T2

U1

H

ZUDBCDB

1

ehTgB

)ag)(MM(p

(1)

whereMCis the mass of the cargo, MDBthe mass of the

ballast water in the double bottom tanks, g the gravityacceleration, aZU the vertical acceleration at mid-length

of the cargo hold, Hthe length of the considered hold,Bthe moulded breadth, the density of seawater, T1 thedraught at mid-length of the considered hold, hU therelative motion at mid-length of the considered holdcorresponding to the vertical acceleration aZU and L the

ship length (as defined in the Rules)3. The factor L

T2 1

e

is

a correction on the relative wave motion (or elevation),

taking into account the rapid decrease in orbital motionand velocity of the fluid particles with increasingdistance from the free surface, effectively reducing the

hydrodynamic pressure on the bottom with increasingdraught and vice versa. The corrected wave elevation isusually called the effective wave elevation [5]. Inhydrodynamic literature this effect is sometimes referredto as the Smith Effect. It is to be noted that for reasonsof simplicity the presence of the hopper tanks and lower

stool of the (corrugated) transverse bulkheads is ignored;

3It is assumed that the ship is moving in deep water with

wavelength equal to the ship length.

an issue which needs to be accounted for later on in theanalysis

4.

The vertical acceleration aZUand relative motion hUneedto be evaluated simultaneously (at the same time instant)to satisfy Newtons Second Law. This can be done on the

basis of ship motion calculations (2D or 3D radiation-

diffraction analysis) and or by applying reference valuesof the load cases defined in the Rules (which have beenobtained from a statistical analysis of a large amount ofship motion calculations) [6].

The goal is to obtain the maximum values of the netresulting upward and downward loads, which can then be

compared to the net loads of the corresponding approvedloading conditions. By plotting the known approvedcombinations of cargo mass and draught in a graph, thehold mass curves are obtained, as schematically shown in

Figure 3. Curve (a) connects the approved loadingconditions 1 (maximum cargo mass P at scantling

draught T) and 2 (part load condition), denoting themaximum permissible cargo mass. Curve (b) connectsthe approved loading conditions 3 (loading condition atthe maximum permissible draught Tmax at which the

considered hold may be empty) and 4 (minimumrequired cargo mass at scantling draught). The enclosed

(shaded) area is considered to be the safe loading area inwhich the net resulting load on the double bottom iswithin acceptable limits.

Figure 3: Example of hold mass curves

It is to be noted that the approach is rather conservative,as curve (a) suggests that the maximum permissible

cargo mass which can be taken in the hold can only beloaded when sailing at the scantling draught. Mostdesigns, however, have sufficient margin to sail with themaximum cargo mass at a draught less than the scantling

draught. In that case curve (a) is replaced by the twosegmented curve (c), thus enlarging the loadingflexibility of the ship5. It is also to be noted that the holdmass curves are not necessarily straight lines.

4 It is also assumed that the cargo upper surface ishorizontal, but this assumption is also made in the base

case (loading condition in the approved loading manual).5This is explicitly taken into account by UR S25 and the

CSR.


4/15

The hold mass curves can be computed by demandingthat the net resultant double bottom pressure in theenvisaged loading condition is to be equal to the netresultant pressure in the approved reference loadingcondition. Considering that the variation in vertical

acceleration and relative motion is small over the range

of operational draughts [7], the maximum permissiblecargo mass Pmax at draught TT1< , where there is noballast water in the double bottom tanks, can be written

as follows (curve (a) in Figure 3):

+

+

=L

T2

L

T2

U1

ZU

Hmax

1

eeh)TT(ag

BgPP

(2)

where Pis the maximum cargo mass at scantling draughtT (see above).

The worst load case for the downward net resultingdouble bottom pressure, which is relevant for themaximum permissible cargo mass, is the case where thevertical downward acceleration aZU reaches the

maximum value. In BV Rules this is represented in loadcase b, for which the relative wave motion is half of the

maximum value. The maximum value is attained in loadcase a, which is essentially a Froude-Krylov case as thevertical acceleration for this load case is zero (ship fixedin the undisturbed wave) [6].

Expression (2) can be simplified by considering that, for

practical loading conditions, the absolute value of the

term

L

T2

L

T2

U

1

eeh is much smaller than )TT( 1

and also has a negative value which increases Pmax.

Therefore, if this term is neglected for reasons ofsimplicity this is on the safe side. Applying this

simplification, expression (2) reduces to:

)TT(ag

gBPP 1

ZU

Hmax += (3)

which is still dependent on the vertical acceleration aZU.

Computation of the value of aZU utilising the formulaefrom the Rules is straightforward and can today easily beincorporated in the on-board loading computer. For olderships with less modern on-board tools, however, this may

be more difficult. In order to achieve fast and practicalresults, suitable for on-board calculation, the term

ZUag

g

+may be set to unity (essentially neglecting aZU).

This is again a simplification on the safe side, as inreality the term is always less than unity

6. Applying this

second simplification, expression (2) further reduces to:

)TT(BPP 1Hmax = (4)

6 For a capesize bulk carrier the term typically varies

between 0.7 (midship region) and 0.85 (hold no 1),where the accelerations are calculated for a probabilitylevel of 10

-5.

which is very easy to apply. On the basis of equation (4),the slope of curve (a) in Figure 3, dPmax/dT, is constant

and equal to BH , which is in essence the hold water-plane area multiplied by the water density.

Following the same reasoning as above, the minimum

required cargo mass Pminat draught max1 TT > , where theamount of ballast water in the double bottom tanks is thesame for both loading conditions (may be empty or full),can be written as follows (curve (b) in Figure 3):

+

+

=

L

T2

L

T2

Umax1

ZU

Hmin

max1

eeh)TT(ag

BgP

(5)

The worst load case for the upward net resulting double

bottom pressure, which is relevant for the minimumrequired cargo mass, is the case where the positiverelative motion hU reaches the maximum value. In BV

Rules this is represented in load case a, for which thevertical acceleration is zero (see above). Applicationreduces (5) to:

+=

L

T2

L

T2

Umax1Hmin

max1

eeh)TT(BP (6)

Expression (6) can be simplified by considering that, for

practical loading conditions, the absolute value of theterm

L

T2

L

T2

U

max1

eeh is much smaller than )TT( max1

and also has a negative value which decreases Pmin.Therefore, if this term is neglected for reasons of

simplicity, this is on the safe side. Applying thissimplification, expression (6) reduces to:

)TT(BP max1Hmin = (7)which is independent of the relative motion hU and thevertical acceleration aZUand therefore very easy to apply.Similarly to the development above, the slope of curve(b) is equal to the one of curve (a). Consequently curves(a) and (b) are parallel.

Further analysis of expressions (4) and (7) learns that,due to the simplifications, the imposed conservation ofload (net resulting double bottom pressure) has in factbeen reduced to imposed conservation of mass, which iseasier to compute. For the case of the maximum cargomass the reduced hold displacement due to the reductionin draught equals the reduction in permissible cargo mass,

while for the case of the minimum cargo mass theincreased hold displacement due to the increase indraught equals the increase in required cargo mass.

As mentioned above the presence of the hopper tanks andtransverse bulkhead lower stool have been ignored. The

consequences of these simplifications are depending onthe height of the rated upper surface of the bulk cargoabove the tank top hm, see Figure 4.


5/15

Figure 4: Effect of cargo filling level on double bottomcargo pressure

For the maximum permissible cargo mass we consider

case a, denoted by hm,a, where the rated upper surface isabove the hopper tank and can be considered as the

maximum filling level corresponding to the maximumcargo mass Pat the scantling draught T. If a new loadingcondition with less draught is envisaged, application of

(4) yields a reduction in cargo mass of )TT(B 1H .

This is achieved by reducing hm by )TT( 1B

, where

Bis the bulk cargo density. This expression is valid onlyif the new rated upper surface cargo level is above the

top of the hopper tank; in other words: DBHTm hhh . Ifthe rated upper surface would be less (case b), the

amount of cargo mass reduction to keep constant the netresultant pressure on the double bottom (flat part) would

be less due to the presence of the hopper tank andtransverse bulkhead lower stool volumes. This meansthat the results are slightly conservative but on the safeside.

For the minimum required cargo mass the draught isincreased above the maximum Tmaxdraught for which thecargo hold has may be empty in accordance with theapproved loading manual. So the hold is filled from zeroto a certain value to compensate for the increase in sea

pressure exerted on the double bottom. Application of (7)yields an increase in cargo mass (from zero) of

)TT(B max1H . However, due to the presence of thehopper tanks and transverse bulkhead lower stool lesscargo mass is required to achieve the necessary cargopressure increase on the double bottom (flat part) than iscomputed by expression (7), where the full displacementaddition (acting on the total width of the ships bottom)is compensated as cargo mass increase (gradually

increasing its influence from the width of the flat part ofthe double bottom to the total ship breadth). Therefore,the minimum required cargo mass is overestimated byexpression (7) and can be corrected for the presence ofthe non cargo carrying volumes. For a rated uppersurface cargo level above the top of the hopper tank

( DBHTm hhh ), the correction includes the completevolume of the hopper tanks, which gives:

[ ]LSDBHTHTHBmax1Hmin V)hh(b)TT(BP = (8)where, bHTis the width of the hopper tank, hHTthe heightof the hopper tank and hDB the height of the double

bottom.

For a rated upper surface cargo level below the top of the

hopper tank ( DBHTm hhh < ), the correction isdependent on the value of hm, which is not known a priori

but can be estimated by )TT(h max1B

m

= . As the

hopper tanks are neglected, this is a conservativeapproach (hm is overestimated). The minimum cargomass can than easily be calculated by considering thecargo volume up to filling level hm and the associated

bulk cargo density. As the transverse bulkhead lowerstool is low compared to the height of the cargo hold, hmwill usually be higher than the height of the lower stool.This justifies a correction on Pminby subtracting the term

LSBV . Defining bmas follows, see Figure 5:

)TT(hh

bb max1

DBHT

HT

B

m

= (9)

we can write for the minimum required cargo mass:

+= LSDBHT

HT

mHTmHBmin V)hh(

b

b)b2Bb(P (10)

Figure 5: Definition of bm

The verification of the maximum permissible andminimum required cargo mass is to be performed for thecase of individual cargo holds, as described above, andfor the case of two adjacent cargo holds. In fact, the caseof individual cargo holds addresses the maximumbending moment and shear force in the floors, the

maximum bending moment in the double bottom girders

at mid-length of the cargo hold and the maximum shearforce in the double bottom girders at the ends of thecargo hold when considering alternate loading conditions(angular deformation at hold ends due to asymmetricalloading produces the maximum bending moment in the

double bottom girders at mid-length of hold). The case oftwo adjacent cargo holds considers the maximumbending moment and shear force in the double bottomgirders acting simultaneously at the transverse bulkhead(the condition of zero angular deformation at the holdends due to symmetric loading produces the maximum

bending moment in the double bottom girders at the holdends) and the shear strength of the (corrugated)

transverse bulkhead.


6/15

Based on the derivations and considerations above, it iseasy to see that a straightforward application of theconservation of mass principle provides quick andconservative estimates of the maximum permissible andminimum required cargo mass. The maximum

permissible cargo mass for two adjacent holds

max21 )PP( + at a draught TT1< can be written asfollows:

)TT(B)(PP)PP( 12H1H21max21 ++=+ (11)

where 21 PP + is the maximum mass of cargo in two

adjacent holds at the scantling draught, while H1and H2denote the length of the two adjacent cargo holds,respectively.

Following the same reasoning, the minimum required

cargo mass for two adjacent holds min21 )PP( + at a

draught max1 TT > can be written as follows:

)TT(B)()PP(max12H1Hmin21

+=+ (12)

2.2 HOLD MASS CURVES FOR HARBOURCONDITIONS

During loading and unloading in port the maximumallowable cargo mass is higher than at sea due to the

absence of waves generating large vertical accelerationsand relative motions. In a similar fashion the minimumrequired cargo mass is less than at sea. Due to thisreduction of dynamic loads, the ship has more flexibilityin loading conditions during port operations, which isregulated by providing specific hold mass curves for the

harbour conditions in addition to the seagoing conditions.

In the ideal port situation of no accelerations and norelative motions expression (1) reduces to:

1

H

DBCDB gT

B

g)MM(p

+=

(13)

The maximum permissible cargo mass for a single holdin harbour condition Pmax is derived on the basis of the

known maximum permissible cargo mass from seagoingcondition at the scantling draught. Equating expression

(1) for seagoing condition with PMC= , 0MDB = and

TT1= to expression (14), after some algebra, gives:

DB1L

T2

UHZU

max MTehTBg

agPP

+=

(14)

This expression requires computation of aZU and hU.Simply ignoring them would yield extremelyconservative results, as expression (15) would beeffectively reduced to expression (4) for seagoingconditions, with the exception of the double bottomballast water mass which is very small compared to the

maximum cargo mass. In other words, the loadingflexibility of the ship would be too much restricted.

Therefore, any attempt for simplification of (15) must

still include one of the two dynamic parameters.Rewriting (14) into a static and a dynamic part gives:

( ) DB1Hstaticmax, MTTBPP = (15)

L

T2

UHZU

dynamicmax, eBhg

aPP

= (16)

The key point for simplification is to evaluate the two

terms of (17) against each other. Making use of practicaldata on typical bulk carriers and considering the worstload case for the downward net resulting double bottomload (maximum downward vertical acceleration), it can

be shown that approximately LT2

UHZU eBh3g

aP

.

Therefore, (17) can be approximated by:

L

T2

UHdynamicmax, eBh2P

(17)

It can further be shown that the L/T ratio for typical bulkcarriers from 10k DWT is between 12.5 and 19.

Therefore, the term LT2

e

will be between 0.60 and 0.70.

By setting LT2

e

to a conservative value of 0.5 (the

corresponding L/T ratio is 9), expression (18) can beconservatively further reduced to:

UHdynamicmax, BhP (18)

This is conservative, as the value of the dynamic part,giving a positive contribution to the maximum

permissible cargo mass, is underestimated. As such,

expression (14) can be safely simplified as follows:( ) DB1UHmax MThTBPP = (19)

where hUcorresponds to the relative motion for the loadcase where the vertical acceleration is maximum, whichis easy to calculate (BV Rules load case b).

The minimum required cargo mass for a single hold inharbour condition Pmin is derived on the basis of the

known minimum required permissible cargo mass fromseagoing condition at the scantling draught. Equatingexpression (1) for seagoing condition with

0MC= , 0MDB = and max1 TT = to expression (14)

results in the following expression

DBmaxL

T2

U1Hmin MTehTBPmax

=

(20)

which is independent of the vertical acceleration aZU.

Following the reasoning above, LT2

e

can be taken as 0.5.

This underestimation is on the safe, side as it increasesthe minimum required cargo mass. In doing so,

expression (21) can be reduced to:

DBmaxU1Hmin M)Th5.0T(BP = (21)where hUcorresponds to the relative motion for the load

case where the relative motion is maximum, which iseasy to calculate (BV Rules load case a).


7/15

In a similar fashion as above, applying the conservationof mass principle, expressions for the maximumpermissible and minimum required cargo mass for twoadjacent holds can be derived. The maximum permissible

cargo mass for two adjacent holds max21 )PP( + at a

draught TT1< can be written as follows:

2DB1DB1U2H1H

21max21

MM)ThT(B)(

PP)PP(

+

+=+

(22)

where 21 PP + is the maximum mass of cargo in two

adjacent holds at the scantling draught, H1 and H2denote the length of the two adjacent cargo holds,

respectively, hU corresponds to the relative motion forthe load case where the vertical acceleration is maximum

(BV Rules load case b), whileMDB1andMDB1representthe mass of the double bottom ballast water of the twoadjacent cargo holds, respectively.

Applying the same reasoning, the minimum required

cargo mass for two adjacent holds min21 )PP( + at a

draught max1 TT > can be written as follows:

2DB1DB

maxU12H1Hmin21

MM

)ThT(B)()PP(

+=+ (23)

where hUcorresponds to the relative motion for the loadcase where the relative motion is maximum (BV Rulesload case a).

2.3 CONSIDERATIONS FOR IMPROVEMENTIn order to make the process of evaluating hold mass

curves as practical and efficient as possible, the formulaederived in this section have been simplified as far aspossible. This enables easy calculation on-board whichdoes not require complicated mathematics. In order to

stay on the safe side, the simplifications give a ratherconservative result, which inherently means that there isroom for optimisation of loading flexibility when themore complex formulae are used instead of thesimplified ones. The obvious conservative assumption inall formulations for the generation of the mass hold

curves is that it is assumed that the shear strength at fulldraft is marginal and it is necessary to preserve shearforce at different drafts.

With the availability of good on-board computation tools,in particular the loading instrument, this has become

relatively easy to implement. In fact, improvements inthe Rules after the introduction of UR S1A aremandating the implementation of the hold mass curves inthe loading instrument, as will be described in thefollowing section.

2.4 DEVELOPMENTS OF IACS UNIFIEDREQUIREMENTS FOR HOLDS MASSCURVES FOR NEW RULES AFTER UR S1A

As described in the introduction, UR S1A makes theinclusion of the hold mass curves in the approved loading

instrument mandatory for new ships7

. UR S20 hasintroduced the development of the hold mass curves havetaking into account cargo hold flooding, UR S20 isapplicable to new single and double side skin bulkcarriers of 150 m length and over with cargo density

equal to or higher than 1.0 m3(applicable for single side

skin bulk carriers contracted for construction on or after1 July 1998 and double side skin bulk carrier contractedfor construction on or after 1 July 1999 or 1 January2000, depending on the width of the double side skin)and considers the allowable hold loading in the case of

flooding of any (individual) cargo hold on the basis ofthe cargo carried (volume, density and permeability),

effectively increasing bulk carrier safety. Due to thechange in the maximum permissible cargo mass at themaximum draft, the hold mass curves for the maximumpermissible cargo mass for a reduced draught are

changed as well. In a similar fashion UR S22 haschanged the allowable hold loading of the foremost cargo

hold of bulk carriers bulk carriers contracted forconstruction before 1 July 1998, with length of 150 m ormore and cargo density of equal to or higher than 1.78t/m3.

With the introduction of UR S25 the hold mass curves

have been further developed. UR S25 is applicable tobulk carriers of 150 m in length and over, which arecontracted for construction on or after 1 July 2003. WithUR S25, harmonised notations and associated design

loading conditions have been introduced. This hascreated a uniform way to assess bulk carrier designs with

regard to their cargo carrying capacity and loading

flexibility. This in turn has generated a high degree oftransparency for ship owners and operators, as well as atechnical level playing field for designers and classsocieties, and as such further enhanced bulk carrier safety.The three basic notations are as follows [8]:

BC-A: for bulk carriers designed to carry dry bulkcargoes of cargo density 1.0 t/m

3 and above

with specific holds empty at maximum draughtin addition to BC-B conditions

BC-B: for bulk carriers designed to carry dry bulkcargoes of cargo density 1.0 t/m3 and above

with all cargo holds loaded in addition to BC-Cconditions

BC-C: for bulk carriers designed to carry dry bulkcargoes of cargo density less than 1.0 t/m3

For each of the three notations UR S25 provides a list of

design loading conditions to be checked. These loadingconditions are chosen in such a way that the designincorporates multi-port operations which affect the localstrength and therefore directly define the hold masscurves.

7In the context of UR S1A new ships are ships

contracted for construction on or after 1 July 1998.


8/15

Key seagoing loading conditions in this respect are thefollowing [8]:

Any cargo hold is to be able to of carrying full cargomass with fuel oil tanks in double bottom in way ofthe cargo hold, if any, being 100% full and ballastwater tanks in the double bottom in way of the cargo

hold being empty, at 67% of the maximum draught8

; Any cargo hold is to be capable of being empty with

all double bottom tanks in the way of the cargo holdbeing empty, at 83% of the maximum draught;

Similar conditions apply for the case of two adjacentcargo holds, with the empty cargo holds condition at

75% of the maximum draught. In addition, loadingconditions while in harbour are addressed.

In applying these seagoing conditions, the loadingconditions 5 and 3 presented in Figure 3 are fixed. In fact,curve (a) is replaced by curve (c), as shown in Figure 6.

Only if the ship is assigned the additional notation {noMP} these conditions can be waived.

Figure 6: Hold mass curves based on UR S25, includingmulti-port operations

For BC-A bulk carriers, which are capable of sailing inalternate conditions, specific additional loadingconditions are specified, including a margin in cargoloading for the carriage of high density cargo (equal to10% of full cargo mass).

UR S25 specifically addresses the issue of the hold masscurves as based on the design loading conditions. For

other draughts than those specified in the design loadingconditions, the maximum allowable and minimumrequired mass is to be adjusted for the change inbuoyancy acting on the bottom (to be calculated usingthe water plan area at each draught). This is, in fact, an

implementation of the principle of the conservation ofmass as derived and justified in section 2.1.

8The full cargo mass is defined as the cargo mass in a

hold corresponding to cargo with a virtual density(homogeneous mass/hold cubic capacity, minimum 1.0t/m3) filled to the top of the hatch coaming and is not to

be less than the actual cargo mass in a cargo holdcorresponding to a homogeneously loaded condition atmaximum draught [8].

2.5 OTHER CLASS SOCIETIESSimilarly to the developments described above, otherclass societies apply the same basic concept in order toestimate the mass hold curves. Examples of other pre-

CSR methods utilised by other classes are depicted on

Figure 7 for the seagoing case only.

The upper curve in essence preserves the net load, i.e.the difference between the cargo weight and thebuoyancy of the cargo hold on the basis of purely static

considerations. The maximum cargo is deduced addingthe net load to the buoyancy force. Of course the

maximum cargo has been determined beforehand foreach hold by structural analysis. The minimum cargo atdesign draft is determined by subtracting the net loadfrom the buoyancy. The abscissa for the minimum cargo

curve is determined from similar triangles, being parallelto the maximum cargo curve.

Figure 7: Hold mass hold curves, pre-CSR, seagoing

The lower curve is based on the same philosophy, but itaccounts for dynamic effects as shown in the derivation

above. Parameter k ranges from 0.67 to 1 depending onthe load cases studied at the design stage. It is known thatIACS UR S25 dictates that the case of 67% of full draftwith the maximum cargo hold load be studied in thedesign stage, with respect to local and global strength.The minimum cargo curve, although not shown in thelower part of Figure 6, is determined by the following

relationship:

= 4T

T5P11.0P

max

maxmin (24)


9/15

Equation (24) provides the interesting relation betweenthe minimum and the maximum cargo in the hold. Thisrelation is based on statistical evaluation of many bulkcarriers instead of computations. According to (24), theminimum cargo load is 11% of the maximum one.

2.6 DEVELOPMENT OF HOLDS MASSCURVES FOR THE COMMONSTRUCTURAL RULES

Hold mass curves generation is necessary for all bulk

carriers above 90 meters according to the CSR. Theapproach follows the logic introduced in UR S25, see

section 2.4. According to the formulation, the maximumcargo mass for a draught less than 67% of the maximumis given by:

( )h

TT67.0V025.1M1.0M)T(P maxHHHDmax

+= (25)

where his the vertical distance from the top of the inner

bottom to the main deck at centre-line, VHis the volumeof the hold excluding the volume enclosed by the hatchcoaming,MHis the actual cargo mass corresponding to a

homogeneously loaded condition at maximum draught,MHDis the maximum cargo mass allowed to be carried ina cargo hold according to the design loading conditionswith specified holds empty at maximum draught, Tmaxisthe maximum draught and Tis the actual draught underconsideration.

Similarly for the minimum load:

( )

h

T83.0TV025.1)T(P maxHmin

= (26)

Equation (26) is valid for a draught above 83% of themaximum as dictated by UR S25. The two relationsabove which are depicted pictorially on Figure 8, arevalid for holds designed to be always full, like the oreholds. For holds which can be empty at maximum draft,

there is no meaning for minimum cargo, whereas themaximum cargo for draught less than 67% of the

maximum is given by:

( )h

TT67.0V025.1M)T(P maxHFullmax

= (27)

where MFull is the cargo mass corresponding to cargo

with virtual density filled up to the top of hatch coaming.The density is the maximum between one andMH/VH.

Figure 8: Mass hold curves according to CSR (ore hold)

The curves are simplified greatly at the expense ofoperational flexibility when the limitation {No MP} isadded to the vessel notation (see also section 2.4), as thisnotation removes the need to evaluate additional loadingconditions dictated by UR S25, such as the carriage of

the maximum cargo at 67% of the maximum draught and

empty ore hold at a draught as high as 83% of themaximum.

3. INFLUENCE OF STILL WATERBENDING MOMENT

Bulk carriers are sometimes engaged in multi-port

loading operations, although the great majority are notdesigned for such. It is possible in such a multi-portoperation that the designated ore holds may be unloadedat one port with the vessel proceeding to another port for

further unloading. In such a case, the combination ofhogging hull girder bending moment and external

pressure corresponding to a reduced draught of the orderof 60 to 70% of the maximum one may result in bucklingof the bottom plating. Importantly, this is a case which isnot routinely checked. A simple procedure is derived

below which aims to calculate the maximum permissibledraught in way of the empty ore hold (designed to carry

heavy cargo but operating empty) as a function of thehogging SWBM (Still Water Bending Moment). Thisprocedure does not require performing a finite elementanalysis. Typically the calculations are performed for the

midship ore hold and are applicable to all ore holds whenoperating empty. In case the draught is severely limiting,

local reinforcement of the bottom may be necessary to

resolve the buckling problem. It is thus proposed todevelop a graph of the maximum permissible graph as afunction of the SWBM on the basis of satisfying thebuckling strength criterion:

0.1BF

9.1

y,crit

yRm

9.1

x,crit

xRm =

+

(28)

Where Rm, are the material and the load factors, bothequal to 1.02, BF is the buckling factor defined by

equation (28), crit,x and crit,y are the critical bucklingstresses for the panel under consideration, while x andy are the stresses exerted on the bottom panels in the

longitudinal and transverse directions, respectively.

Transverse stress y results from the hydrostatic andhydrodynamic pressures on the bottom, computed from

analysis of the elementary bottom panel. This stress isdetermined from a grillage analysis through the BVprogram STEEL described in the next section. It can alsobe estimated by simple panel response relations with the

handicap that the fixity of the plate boundaries needs tobe assumed as either fixed or clamped. Longitudinal

stress ystems from the contribution of hull girder staticand dynamic bending moments and the bottom pressure.

The former can be determined by :

wavestaticgirderhull,x 05.1 += (29)


10/15

where the factor 1.05 is a safety margin type factor dueto the higher uncertainty of the wave induced stress. Thewave induced and the static stress are computed on thebasis of simple beam theory. The wave induced stress ismultiplied by a factor equal to 0.625 which represents the

maximum in 105 wave encounters. Satisfaction of

equation (28) above needs to be ensured at allcombinations of draught and SWBM (which can becontrolled). An application of the procedure describedwill be presented in the examples section.

A limitation for the SWBM for a given draught should beobtained as well from the buckling requirements of the

upper sloping bulkhead and side shell in the upper wingtank (due to sagging bending moment). This limitationcould be critical for the bulk carriers with transverselyframed side shell in upper tank and thin sloping

bulkheads. The shear strength of the side shell betweenthe loaded and empty holds (in block loading) should

also be checked for the allowable cargo mass. Thesagging SWBM at any seagoing condition is not toexceed:

WIBMy

ISWBM critsagmax = (30)

where I is the hull girder net moment of inertia at themid-hold section, y is the distance between the hullgirder neutral axis and the structural member underconsideration (plate panel or longitudinal stiffeners), critis the critical buckling stress of the structural member

under consideration and WIBM is the Wave InducedBending Moment as prescribed in the Rules.

4. CASE STUDIES4.1 DERIVATION OF HOLD MASS CURVES

As has been described previously, the hold mass curvesmay provide the pre-1998 bulk carriers with the ability tosafely operate a variety of loading conditions apart fromthe ones checked in the design stage. It is very common,from an operational point of view, for a vessel to be

needed to load cargoes at reduced draughts and inloading patterns different from the ones shown in the

loading manual. These loading conditions, apart from thestability and longitudinal strength aspect which are

examined on-board with the aid of the loading instrument,have also to be checked from local strength point of view

in the plan approval office. The aim of this examinationis to verify the structural integrity of the plating, the

ordinary stiffeners and the primary supporting membersfor each hold under the given loading condition. Theplating and the stiffeners are checked at various sectionsof the ships length with the MARS program (a typical

section in MARS is shown in Figure 9). MARS is apanel-to-panel 2D analysis tool based on the

requirements of the BV Rules. The primary supportingmembers (girders and floors) are assessed using theSTEEL program. STEEL is a 3D beam analysisprogram which calculates all deformations, local

moments, forces and stresses in structures modelled by

beams subjected to static loads (in Figure 10 a STEELmodel is shown extending from the middle of one hold tothe middle of the next hold is depicted). Depending onthe loading condition at hand, the review may alsoinclude the examination of the transverse bulkheads and

the cross deck areas. All this process is time consuming

and is also specific for each loading condition, whichmeans that it has to be repeated every time the proposedcondition deviates from the loading manual.

In order to bypass the process described above, the hold

mass curves can be formulated based on the vesselsexisting loading manual. By the time these curves have

been created and implemented on board (as a supplementto the loading manual), the vessel gains the flexibility tobe loaded in ways, otherwise restrictive, without furtherexamination.

Figure 9: Typical MARS section for the assessment ofthe plating and ordinary stiffeners

Figure 10: Two-hold model in STEEL for the assessmentof the primary supporting members of the bottom

Application of the mathematical equations presented insection 2 on a capesize bulk carrier yields the hold masscurves for each hold and for the pairs of adjacent holds.These are depicted in Figures 11 and 12 for No 5 and No

6 cargo holds, respectively, and in Figure 13 for theadjacent No 5 and No 6 cargo holds. The main

particulars of the vessel are given in Table 1.


11/15

Table 1: Main particulars of the case study vessel

Length over all (Loa) 253.92 m

Length between perpendiculars 241.00 m

Moulded breadth 40.00 m

Moulded depth 21.00 m

Scantling draught 14.60 m

Block coefficient (CB) 0.822Deadweight (approx.) 100,000 t

Figure 11: Hold mass curves for No 5 cargo hold

Figure 12: Hold mass curves for No 6 cargo hold

The loading manual can provide directly points 3 and 5(see Figure 11), that produce the Pmaxcurve (a) and thePmincurve (b) for seagoing conditions. More specifically,point 5 corresponds to a loading condition at which thehold is fully loaded at the minimum possible draughtTactual calculated at mid length of the hold. The critical

condition for the even holds that fulfils this requirementis usually the full load homogeneous condition (inparticular the arrival condition, which has a smallerdraught than the departure condition) or the full loadalternate (arrival) condition for the ore holds. Since Tactual(as depicted by the actual full load condition) is usually

smaller than the scantling draught T, the Pmax curveobtains the flat section between points 5 and 1 by

applying TTactual= in expression (4). It is important tonote at this point that when calculating the minimum and

maximum mass for each hold from the actual loadingconditions, the mass of double bottom contents MDB (ifany) should be added to the mass of cargo in the hold, as

this weight also counteracts to the upward acting seapressure. ThisMDBshould not be confused as being onlyballast water, since it represents any liquid weight in thedouble bottom situated underneath the flat inner bottomof the cargo hold. It is common to have fuel and diesel

oil tanks underneath the aft holds of bulk carriers and this

weight is bound to be present in the full load condition,while ballast water is not.

By following the same approach as above, point 3corresponds to a loading condition at which the hold may

be empty, at the maximum possible draught Tmax(calculated at mid-length of the hold). For an (uneven)

ore hold this is typically the heavy ballast condition (andespecially the departure condition, which has a greaterdraught than the arrival condition), whereas for an evenhold this is, in most cases, the alternate condition at full

draught (departure condition). Due to these differentdraughts, the Pmincurve of the even holds (curve (b) of

Figure 12) is usually a flat line which coincides with theaxis of the draughts (horizontal axis). The relevant curvefor the ore hold (curve (b) of Figure 11) starts at Tmaxand ends at T, being at the same time parallel to the Pmax

curve.

Following the procedure described above for No 5 cargohold, with a length of 26.6 m, points 5 and 3 would bethe following for the vessel under consideration (draughtin m, cargo mass in t):

)26949,15.14()P,T(P maxactual5 ==

(associated bulk cargo density: 1.67 t/m3))0,07.10()0,T(P max3 ==

The Pmin and Pmax curves for seagoing conditions cannow be derived from expressions (4) and (7),respectively. In order to produce the relevant curves forharbour conditions, we need to calculate the relativemotion hU.. According to BV Rules, the reference value

of the relative motion, at any hull transverse section, canbe obtained from the formulas in Table 2 [9].

Table 2: Maximum relative motion h1in the upright shipcondition [9]


12/15

T1 shown in Table 2 (for a location between 0,3L and0,7L) may be taken equal to Tactual (for the Pmax curve)and Tmax (for the Pmin curve). The wave parameter iscalculated on the basis of the wave parameter C (seeTable 3) and the navigation coefficient n (see Table 4).

Based on the above, for No 5 cargo hold (mid-length

situated at x= 0.43L), the relative motion hU is equal tom291.3

2

hh 1U == for the Pmax curve (load case b), and

m582.6hh 1U == for the Pmincurve (load case a).

The relevant curves for harbour conditions (curves (c)and (d)) can now be produced by substituting the data of

points 3 and 5 and hU to expressions (19) and (21). Incase that Pmax (seagoing) is calculated from a loadingcondition with a liquid weight MDBunderneath the hold,then this weight has to be deducted in (19) and (21).

Table 3: Wave parameter C [9]

Table 4: Navigation coefficient n[9]

Figure 13: Hold mass curves for No 5 and No 6 adjacentcargo holds

The same procedure should be followed for producingthe hold mass curves for two adjacent holds. The loadingconditions in the loading manual will provide points 3

and 5 of Figure 13. Point 5 represents the loadingcondition at which the sum of the cargo mass in the twoadjacent holds and the related double bottom

contents )MM( 2DB1DB + (if any) is maximum, at the

minimum possible draught Tactual (calculated at mid-length of the holds). This could be a full loadhomogeneous condition at the maximum draught (arrival

condition). Again by applying TTactual = in (11), the

max21 )PP( + curve (a) shows the flat section betweenpoints 5 and 1.

In a similar manner, point 3 now corresponds to aloading condition at which the sum of cargo in twoadjacent holds and their relative double bottom contents

)MM( 2DB1DB + (if any) is minimum, at the maximumpossible draught Tmax (calculated at mid-length of theholds). An expected loading condition for this pointwould be the heavy ballast condition in which the

adjacent holds are empty. This condition will not applyto the heavy ballast hold and its adjacent holds becauseof the weight of ballast water in the cargo hold. For thispair of holds, the light ballast condition could be a

possible determinant for point 3. For the vessel underconsideration, points 5 and 3 are the following (draught

in m, cargo mass in t):)29407,46.14())PP(,T(P max21actual5 =+=

)0,09.10()0,T(P max3 ==

The min21 )PP( + and max21 )PP( + curves for seagoingconditions can now be derived by substituting the data ofpoints 3 and 5 to the expressions (11) and (12),respectively (with length of No 6 cargo hold 26.6 m).Similarly expressions (22) and (23) will yield the

relevant max21 )PP( + and max21 )PP( + curves for the

harbour conditions. In case that max21 )PP( + (seagoing)is calculated from a loading condition with a liquid

weight )MM( 2DB1DB + underneath the hold(s), then thisweight has to be deducted in expressions (22) and (23).

In the description given above for the creation of the holdmass curves from the actual conditions of the loadingmanual, points 5 and 3 have been correlated to typical

conditions found in all loading manuals. While this istrue most of the times, it is not always the case.Sometimes these points correspond to different loadingconditions which involve combination of slack holds and

ballasted double bottom tanks. This is due to the fact thatbulk carriers built prior to the UR S25 requirementswould include in their loading manuals each condition

pattern (i.e. slack holds) that the vessel was designed forto sail. The UR S25 solved this issue by applying genericloading conditions during the design stage depending onthe type of the vessel.

4.2 MAXIMUM DRAFT AS A FUNCTION OF

STATIC BENDING MOMENT (ORE HOLDS)

The capesize bulk carrier utilised in the previous sectionto demonstrate the derivation of the hold mass curves

will also be used to apply the method described inSection 3 to study the influence of draught and static

bending moment on the bottom strength of the ore holds


13/15


14/15

the conditions of the approved loading manual areenvisaged, the hold mass curves need to be specificallyderived to check the local strength of the cargo holdstructure. This is particularly important when the vesselwill be engaged in multi-port operations with strong

variation of cargo mass against draught for the different

cargo holds. As the majority of the in-service of bulkcarriers consists of pre-UR S1A ships, a practical methodfor establishing the hold mass curves is needed.

On the theoretical level (section 2), the basic requirement

for the derivation of the hold mass curves is theconservation of the net vertical load on the double

bottom structure. These curves have been derived in thispaper and it was shown that, by conservativelysimplifying the derived expressions, the conservation ofload requirement reduces to the conservation of mass

requirement generally adopted in UR S25. With thismethod simple expressions are obtained for calculating

the hold mass curves for individual cargo holds and twoadjacent cargo holds, in seagoing as well as harbourconditions.

With the introduction of UR S25, later followed by theCSR, the minimum envelope of the hold mass curves has

been clearly defined and the hold mass curves followdirectly from the application of the rule strengthrequirements to the prescribed loading conditions. Forpre-UR S25 bulk carriers the situation is more

complicated. Generally speaking, the set of approvedloading conditions from the loading manual serves to

define the hold mass curves on the basis of the

expressions derived in this paper, which provides theship owner with more loading flexibility. In case theenvisaged loading condition is outside the hold masscurves obtained in this manner, additional strengthchecks are to be performed in order to accept the new

loading condition. It is obvious that the loadingflexibility obtained from the hold mass curves issomewhat limited due to the conservative simplificationswhich have been made in order to ensure an easy andquick process. When the more general expressions(before application of the simplifications) are applied,

more loading flexibility can be obtained in result.

In section 3 the importance of the combination of draughtand hogging still water bending moment for the case ofempty holds in multi-port conditions was emphasised, asthere is a significant risk of buckling of the bottom

plating due to the combination of local and globalcompression stresses. This issue needs to be specificallyaddressed when deriving the hold mass curves for multi-port operations.

A practical application of the derived hold mass curves ispresented in the case studies on a 100k DWT capesize

bulk carrier. Hold mass curves have been derived for No5 cargo hold, No 6 cargo hold and the adjacent No 5 and

No 6 cargo holds. In addition, the maximum draught atwhich No 5 cargo hold can be empty, while the

maximum hogging still water bending moment is acting,has been derived from a buckling analysis of the bottomplating. Finally, a sensitivity study into the effect of thevalue of the still water bending moment and bottomplating thickness was carried out.

In conclusion, a practical methodology for the derivationof the hold mass curves has been presented, which iseasy to apply to existing bulk carrier and can be used toextend the operating profile of bulk carriers in a safe way,taking into account the relevant strength limits of the

cargo hold local structure. This is particularly relevantfor existing ships which need to engage in multi-port

operations.

6. REFERENCES1. Intercargo, Intercargo Briefing: Loading Rates,

Rev.0.1, 21 November 2008

2. Lloyds MIU, SeaWay, May 20093. IACS, Bulk Carriers - Guidance and Information onBulk Cargo Loading and Discharging to Reduce theLikelihood of Over-stressing the Hull Structure,

Rec. 46, 19974. Bureau Veritas, Rules for the Classification of Steel

Ships, Pt B, Ch 5, Sec 5, [2], April 20095. Journe JMJ, Massie WW, Offshore

Hydrodynamics, First Edition, Delft University ofTechnology, January 2001

6. Bureau Veritas, Rules for the Classification of SteelShips, Pt B, Ch 5, Sec 4, April 2009

7. Bureau Veritas, Rules for the Classification of SteelShips, Pt B, Ch 5, Sec 3, [2], April 2009

8. IACS, Harmonised Notations and CorrespondingDesign Loading Conditions for Bulk Carriers, URS25, Rev. 2, July 2004

9. Bureau Veritas, Rules for the Classification of SteelShips, Pt B, Ch 5, April 2009

7. AUTHORS BIOGRAPHIESKostantinos Chatzitolios currently works in Bureau

Veritas as a hull surveyor in the plan approval office

(HPO) of Piraeus, Greece. He joined Bureau Veritas in

2005 after obtaining a Diploma in Naval Architecture

and Marine Engineering from the National TechnicalUniversity of Athens. In the four years that he has

worked in HPO he has dealt with stability and hull

matters of bulk carriers, oil tankers and passenger ships.

In the last two years he is specialized in the hull structure

of bulk carriers (existing and CSR) and oil tankers.

Konstantinos is currently undertaking a Masters degree

in Business Administration (International MBA) in the

Athens University of Economics and Business.

Gijsbert de Jong holds the current position of product

manager at Bureau Veritas and is based in the HeadOffice in Paris. He is responsible for the international

business development in the field of container ships and


15/15

dry bulk carriers, as well as a number of specialised ship

types.

Gijsbert joined Bureau Veritas in 2001 after obtaining an

MSc in Naval Architecture & Marine Engineering from

Delft University of Technology. Before moving to Sales

& Marketing Management in 2007, he has worked ashull surveyor and department manager for the Bureau

Veritas plan approval office in Rotterdam. During this

period Gijsbert has built up extensive experience with

dry cargo & container ships, dredgers, asphalt carriers,

product tankers, reefers & tugs. In his present position he

is working closely together with BVs technical

specialists and extensive international network to

develop new products and services meeting with the

maritime industrys specific needs.

Gijsbert has published technical papers on container

ships, bulk carriers, arctic shipping and fuel cell powersystems and regularly writes articles for marine industry

magazines.

Dr John Emmanuel Kokarakis, a 1979 graduate ofNational Technical University of Athens, he holds PhD(1986) and Masters degrees in Naval Architecture (1983)and Masters in Mechanical Engineering (1984) from theUniversity of Michigan. He worked for over ten years as

a consultant undertaking technical problems worldwide.His specialization was in the area of technicalinvestigation of marine accidents. In his capacity as aforensic engineer he participated in the technical

investigation of the Exxon Valdez grounding, Sea-crestCapsize, Piper Alpha fire and explosion, Aleutian

Enterprise foundering in Alaska as well as many otheraccidents of less notoriety.

The last eleven years he works in Greece, in the area ofclassification. Having served in the plan approval officeof American Bureau of Shipping in Piraeus, he then

joined Germanischer Lloyd heading their tanker and bulkcarrier team in Greece. He is currently the Technical

Director of Bureau Veritas in the Hellenic and Black SeaRegion. In his duties Dr. Kokarakis is responsible for thesmooth technical operation in the region as well as in the

harmonic cooperation with the BV offices worldwide tothe benefit of the BV clients in Greece. He was amember of the team which developed the CommonStructural Rules.

4153.1.kokrakis dejong

Documents