Analytical method of ship motions moored to quay walls and application to port planning

Analytical Method of Ship Motions Moored t o Quay Walls and Application t o Port Planning

Siigeru Ueda* INTRUDUCTTION.

This paper describes an a n a l y t i c a l method t o c a l c u l a t e s h i p motions moored t o quay walls and application of the method i n order t o e s t a b l i s h the p o r t planning method i n t a k i n g account both s h i p motions' and safety measures of mooring ships.

There are two major subjects f o r port planning concerning ship's mooring problems. One i s a subject oh safety measures f o r moored ships i n ports during rough weather conditions such as a typhoon. Currently i n Japan, i t i s recommended' f o r those ships more than 1 ,ppOGT t o go out of a p o r t and t o anchor in'a, bay when a typhoon i s approaching t o the d i s t r i c t where t h e . p o r t i s l o c a t e d . But r e c e n t l y , , according not only t o increase of both ship size ahd the number of coming ships but also t o complex u t i l i z a t i o n of marine space, i t becomes d i f f i c u l t f o r a l l o f those ships t o f i n d enough space f o r anchoring i n a bay. T h e r e f o r e , i t must, be heeded t o take some couhtermeasiures of harbouring most of those ships; Another i s a ^subject on e f f e c t of ship motions t o port operation rate concerning loading and unloading. ' On p l a n n i n g o f p o r t f a c i l i t i e s ,such as breakwaters and quay w a l l s , one must e s t i m a t e a t f i r s t p o r t o p e r a t i o n r a t e through a year which i s p o r t a v a i l a b i l i t y f o r loading and unloading o p e r a t i o n . Up t o now,, estimation of port operation rate i s made mainly according t o the wave h e i g h t i n f r o n t o f the quay w a l l . This method I s a p p r o p r i a t e i f the p o r t i s l o c a t e d a t the heart of bay or i n l e t , where s h i p motions may not be so large t o hinder loading and unloading operationSi & i t j when the p o r t I s l o c a t e d a t rather outer p a r t of bay and sometimes I s facing t o the ocean, long period waves come i n t o the port and^ cause a ship long period o s c i l l a t i o n s such as slow d r i f t o s c i l l a t i o n s and/or subharmonic motions especially i n both surge artd sway motions when a ship i s moored to a s o f t mooring system and/or t o an asymmetry mooring system. These long p e r i o d ship motions may h i n d e r l o a d i n g and unloading o p e r a t i o n s . Therefore, i t i s not proper f o r such a p o r t t o ^estimate p o r t o p e r a t i o n r a t e according only t o the wave h e i g h t . The •estimation s h a l l be made considering not only ship motions subjected

t o the waves ahd the wind but also the allowable ship movements f o r l o a d i n g " and unloading operarions. According t o development o f computation method, ship motions can be estimated a n a l y t i c a l l y . For those .subjects above-mentioned, we can f i n d the optimum s o l u t i o n f o r planning and improving both port f a c i l i t i e s and imooring equipments by use o f the n u m e r i c a l s i m u l a t i o n method presented i n t h l s papaer. I n t h i s paper, description i s madë on the numerical simulation method of moored ship subjected to both the irregular wavesand the gusty wind * Chief of the Offshore Structures Laboratory/Structures Division^

Port and Harbour Research I h s l t u t e Ministry of Transport,Japan

'^"•ö COASTAL ZONE'87

NUMEIRCAL SIMULATIOI MEffiOD

do many eitperimental « T a . ^ ^ ^""^ ^""^ to

ship motions can be calc^ulated solving t ï ï ^ t ^ ^ ^ ^ T ' ^ ' " ' of the wave f n r r j i c ; o h t - = ^ „ ^ w... "^-^^-^"^ "^he equation of motions by use

hand, l ï ï ^ ^ n ^ 5 ] t ^ ? S d ï h ^ ^ " ? f - "^thod. on the other thre; d L e n s i o r ï l ^ f ï S ? C b c Ï Ï ; wÏÏchTs m°cJ>r:dTo'tT^'^

system i n the proceeding ^e^^! lU^

[1975] and Sawaragi [1983] i n d i v i d u a l v . i ^ ^ I t o [1972] Oortmerssen standing waves N o n - l i n e J r ^ h i y = Ï ^'^^"^'^ ^ solution i n the

incorporated " t h ^ a r ^ l ^ L ^y "^^^^^^^^^^^ was [1983] and the Authors M Q I I i c i f i ï f o- I . ^' ^91^], Sawaragi

indicated that slow 'J^^!

^'^l'^

motions are calculat J the ^^^^^^^^ ship only t o the waves but Th^ * .^^^ ^ ^^^P subjected

A c c o r d i n g l y , Tn thi^ ^oer s h f n l ^ ' ' ^ ° ^ "'"'^ incorporated, domain under the condttiSAs wh^.n ^ ^•''^ calculated i n the time

mooring system and j f s ^ - T ^ ^ ^ Lf^^ r ° ' ^ ^ ^ non-linear

wir.. by means of the .rSnfTnu^J^'^^l^^^^^ ^^^^ the - ^ t e o ' ^ ^ ^ ^ ^ ^ ^ ^ ^ O f a i l ,

d e \ ^ ^ r e f ^ . : e " r l d ^ a ^ ^ ^ ^

forces due t o w i v e f generat^ calculat^ as the hydrodynamic this forces are t o b? t S a f e d ^ . . °^ amplitude. And coefficients i n the eauatiS, f f^'^^^ '"^^^^^ ^"'^ ^^^^ damping calculated integratirS t h t ° ^ motions. The wave forces are Lewis formXprSmated^ arn. P^^^^^f^ acting on about twenty surge m o t i o n ! X ' t a v e f o r i ° 7 , ^ ^ ^ ^ ^ ^ ^ ^ ship hull Regarding t o taking accoun^t t h ^ P^se^d^^fle^nL^^^^^^^^

SHIP MOTIONS 1547 proposed by Bredschneider-Mituyasu, JGNSWAP, Ochi-Hubble and any o p t i o n a l ones can be used t o generate the i r r e g u l a r waves The d i r e c t i o n a l spreading of spectra can be a l s o considered m the c a l c u l a t i o n o f wave f o r c e s , a l t h o u g h i t t a k e s much t i m e o f computation, Ilie wind force acting on a ship h u l l i s calculated by use of Hughes's experimental formula. Tfhe drag c o e f f i c i e n t s f o r " i n d force should be appropriately determined according t o the r e s u l t s of wind t u n n e l t e s t ( T u j 1,1972}. The frequency spectra of wind proposed by Davenport and H i n o can be used t o g e n e r a t e t h e g u s t y w i n d . Furthermore, the c u r r e n t f o r c e and the wave d r i f t i n g f o r c e s can be i n c o r p o r a t e i n t h i s numerical simulation method. Generally, as load-d e f l e c t i o n c h a r a c t e r i s t i c of fenload-ders anload-d mooring ropes i s non-linear and some f e n d e r s e x h i b i t large h y s t e r i s l s , t h i s n o n - l i n e a r i t y i s incorporated i n the numerical simulation method. T^e s o l u t i o n w i l l be obtained i n the time domain by numeircally integrating the equation ot motions by use of Wilson- e method.

HYDRAURIG MODEL TESTS AND OOMPARISCN WITH OOMPI/TATIONS Hydraulic model tests were carried out i n

a wave basin w i t h 25m l o n g , 15m wide and Im deep i n t h e P o r t and Harbour Research I n s t i t u t e . Wave generators ( f i x e d ) and wind fans (movable) are set i n the wave basirii Tests were c a r r i e d out under the c o n d i t i o n s o f regular waves, i r r e g u l a r waves, steady wind and gusty wind. The model ship i s a 10,000DWT cargo s h i p , scaled i n t o 1/30 t o the s i z e o f 440cm long, 61 cm wide and 41cm deep. Draught of model s h i p i s 27.7cm i n f u l l laden, 22.6cm i n h a l f load and 14.4cm i n b a l l a s t e d c o n d i t i o n s . The model ship i s moored t o a model quay w a i l w i t h s i x mooring ropes made o f pieces o f nylon stocking by t w i s t i n g and two model fenders. Two types o f f e n d e r s were mainly used. One i s so

c a l l e d the b u c k l i n g type (Type No.l) and the ^ i o t h e r i s so c a l l e d the pneumatic type (Type No.3). The type No.l

fender e x h i b i t s t a t i o n a r y r e a c t i o n p a r t and l a r g e h y s t e r e s i s on u n l o a d i n g , but the type No.3 fender e x h i b i t the h y p e r b o l i c l o a d -d e f l e c t i o n c h a r a c t e r i s t i c anc3 small hysteresis as shown i n Figure 1. These characteristics were represented by use of c o i l springs and an-pressures. I n t h i s paper, b r i e f e x p l a n a t i o n on comparison between h y d r a u l i c model t e s t s and numerical s i m u l a t i o n s prsented m t n i s paper.

Figure 2 shows time h i s t o r i e s of sway motions of both hydraulic model t e s t s and numerical simulations. The mooring system consists of the type No.l f e n d e r s and mooring ropes. The model s h i p i s subDectea t o the i r r e g u l a r waves w i t h Hi 73= 1.67cm and T^ ^3=1.83s and a l s o t o the steady wind w i t h mean windspeed 5.48m/s or (Tm/s. Both t h e w^ves and the wind s u b j e c t t o the model s h i p f r o m the d i r e c t i o n of 90 degrees (ABQHIR and ABQHCIR30). The upper two diagrams are^ t i m e h i s t o r i e s when the wind speed i s Om/s. Large and long period o^xs-.^re sway motions occur both i n the hydraulic model tests and the numerical simulations. T^ie lower two diagrams are time h i s t o r i e s of sway motions

DEFLECTION Figure 1. Fender C h a r a c t e r i s t i c s

COASTAL ZONE '87

C c m D

10. 0 SWAY E X P A B Q H I R

•JO. 0

8.'Or SWAY COMP _{A B Q H I R}

3 2G ₁₈₀

T I M E - S E C O N D

Figure 2 , Time Histories of Sway Motions(ABQHIR,ABQAIR)

A B Q H G I R 3 0

t o r SWAY COMP _{A B Q A C J R 3 0} 0 h • ,- .

T I M E - S E C O N D

Figure 3, Time Histories of Sway Motions(ABQHGIR30,ABQACIR30)

ri^g ^ r ^ ^ ^ ^ ' S S ^ e ï w a ^ ^ S o i ! ^ ^ two diagrams,

becomes n e a r l y equal t o ' ^ t h f w ^ | p e ^ i ^ ' ^ t o ' ^ , f , ^ ^ ^ ^ ^ sway period tests and the numerical s i m u l a t i o n r P i V m . o ^ u. ^he^hydraulic model sway motions of h n f h uJLT^\^}^°!!t. ^ ^ ^ ^ ^ ^.^ows time h i s t o r i e s of when the model s h i p is"',;;;rr;d%o7hP ^ ^ ' ^ ^ numerical simulations

SHIP MOTIONS

Figure 4. Frequency Spectrums Figure 5. Frequency Spectrums,

(ABC»1IR,ABQAIR) (AB(^CIR30,ABQAGIR30) The c o n d i t i o n s o f waves and wind are as same as cases o f Figure

2. I n these diagrams, sway periods are nearly equal t o the wave period under the c o n d i t i o n s w i t h o r w i t h o u t wind. Figures 4 and 5 are frequency spectrums o f those diagrams shown i n F i g u r e s 2 and 3. I n case o f ABQHIR, i t I s c l e a r t h a t there i s long p e r i o d m o t i o n as w e l l , as s h o r t p e r i o d motions nearly equal t o the wave p e r i o d . T h i s long period motion i s so called siitdiarmonic motion caused by asymmetry of mooring system consists of the type No.l fenders and mooring ropes. Itegarding t o the mooring system consists of the Type No.3 fenders and mooring ropes, the asymmetry becomes r a t h e r week t h a t long p e r i o d motion does riot occur. This e f f e c t i s also appear everi f o r the mooring system w i t h the Type No.l fenders when the wind speed increazed and a ship i s pushed t o the fenders continuously. Above those comparison are o n l y an example t o prove r e l i a b i l i t y o f t h i s n u m e r i c a l s i m u l a t i o n methodi Most o f a l l are published i n the references [Ueda, 1983,1984]. APPLICATION TO THE SUBJECT OF HARBOURING SHIPS AGAINST TYPHOONS

As already mentioned/ i n Japan, ships moré than 1,000GT are recommended t o go out of a prot and to anchor i n a bay when a typhoon i s approaching t o the d i s t r i c t where the p o r t i s l o c a t e d . T h i s recommendation has been enforced since the K i t t y Typhoon [1950] and the Jane Typhoon [1951] attacked the Port of Yokohama and the Port of Kdbe, respectively, because a great deal of c3amage was done t o ships moored t o quay walls and anchored inside or outside a p o r t . For more than t h i r t y years, these l a r g e s i z e d ships have t o undock f o r s u r v i v i n g a s t o r m . I t i s t r u e t h a t s h i p damage has c o n s i d e r a b l y reduced according t o enforcement of t h i s recommendation. But recently, i t becomes d i f f i c u l t f o r those ships t o f i n d enough space f o r

COASTAL ZONE'87

a ^ ™ " n ^ u ^ S / / o 7 S J " ^ - ^ - ^ h i p Size marine space, i t i s e s t i m a t l j t h a t l n n h n ° u t i l i z a t i o n of

vessels i s needed both i n ï o k S FSI o ^".^ ^P^'^^ ^ ^ " t 240

Ise Bay. But the i n v e s t i g a t i o n ï a ^ r J ï f d ' n n ^ . ^ f ^ ï ^ ' vessels i n Cbnstruction Bureau, M i n i s t w of ^ a n i ^ . ? " * ' the Second D i s t r i c t anchoring space only 90

t7l2G

disr^ard of the r i , L e n d ^ ? i o n a ^ ^ l f ^ ^ Tokyo Bay. m fact, i n

xnside a port during tvohSSl' u J u ^ ""^'^'^ °^ ^^^P^ had stayed d i s t r i c t where the p^t i s ^ W e d 1 ^^^^^ ° ^ "^^^^ t ^

than 10,OOODWT i n c l S S , e s ^ a U v ^ n I t " ^ ^ ' ^ °^ ^^ips more

the Port of Yokohama a i d ?h^ Po/t of Toklo t""^ °'

damage has occur«3. I t i s said S i t h h l F o r t u n a t e l y , no serious

could be served for habourS i ^ ^ f , . ^ ' ' ^ T ^^""^^^^ " - ^ I s which the Port of Y o k o h a m a T T t ^ S n ï s n o t ' S . h ^ ^ '.IS "^"^ ° ' "^«^y^

they want t o stay i n s i d e a ^ r T i f p o r t f ^ ^ v V ^ "^^^^^^ Bay t h a t

that ships can moor d u r i m ^ t v o h o n ^ ^ l ^ ^ ^ ^ ' u ^ ^ ° """^h improved or near the d i s t r i c t whe^e the n ^ t • . f P P ^ f ^ ^ " 9 ^nd passing over nowadays, Tokyo Bay, O s a k a ^ v and I s . n i ^ " " ^ ' ^ ^ - ° " ° t h e r hand, Osaka Bay, the Kansai I n t e ^ t ^ c L l U l o ^ t ^ f ^ u t i l i z e d . I n Port Islands such as Kobe ^ k k o o " ^ ^ ^ construction,

c o r ^ t r u c t e and operating n e w ^ i t v w ^ ^ ^ Osaka Nannko are a l r e a d y

goods, t r a f f i c s f b u s i n e s s L n t p r ^ h ^"""^ transportation of h o s p i t a l s , c o m m u n l t T c L t e r s and°^^^ '"eeting h a l l s ,

established by constructing^^made t l a n d ° " ; n ^ * ' r ^ f u n c t i o n s a r e for ships become r«3uced a s ^ n S s < ^ ^ " ^ Anchoring space countenneasures are needed for h ^ , ! ? [ I ^ v , " ^ ^ . ^ " " ^ - I^^refore, some

obtain the solution how x ^ p r S v e ^ f a S i - ? ^ ' " 2 ' ? ^ ^^'^^ -""st

walls whether can be served or n ^ f f o r h i evaluate quay

the s o l u t i o n i s t o know m o t i o n r a n J ° ^'^^'^"f^"^ ships..The key foJ subjected t o the strong gusty

J^^'^^^^^^

port. This numerical s l m u l a t i ^ ^ttZr^l Y ^ ^ ^ - ^ «aves inside a

porpose. ^ simulation method s h a l l be useful for t h a t Case study was carried out

by means of t h i s numerical '

simulation method for 10,OOODWT,

5,000DWT and 3,000DWT c a r g o " . . g ^ e C r n " " T T ^

-s h i p -s . The m a j o r d i -s c u -s -s i o n ^-15.3x^.7. f50x6.52.2o i m c ? o v . ° I ï * ' ^ ^ ^ " ^ " ' " ' ^ Y i s

'''^''^''-•^^

which c o n s i s t s of f e n d e r s , ^

mooring ropes and b o l l a r d « ;

p-F i r s t of a l l , size and the ^ ^ " ' ^ ^' ^ ^ ^ " ^ - ' " - " t of number of mooring ropes was Mooring Ropes

e^rp^^^^^^^ O f mooring shown i n Figure 6. This i s a ^ f m o l i f ^ e d a r ' ^ ' ' ^ '^"^^"^ ^ ^^^P^oon as consists of bow l i n e s stern i f n ^ ^ ^ arrangement of mooring ropes saving the computation ^ . n e S n u n , . ' ^ ' ^ ^^'^^ p o r ^ S ^ ? diameter are t h e ^ a l u e s forTo,OOoSwï ca^"a^^ l'!'''^^^'^^^' Size and s p r i n g l i n e s are not taken l ^ ^ i r ^ L f ^ ^ ^ P i n s t a n c e . Here,

SHIP MOTIONS •mi

Table 1. Properties of Fenders

Type No.l Type tto.3 io,ooocwr 1 eOOrron x 2 2000niin x 2 IBOOmm x 3 5,ooocwr r250iTm X 2 leOOnm X 2 ISOOnm X 3 3,000DWT 1150nw. X 2 150Prran x 2

the wind blows from a l l o f the directions arroud a ship whenever any wind p r o t e c t i o n boards or warehouses are c o n s t r u c t e d on t h e w h a r f . Regarding t o f e n d e r s , the on-shore wind which blows f r o m the sea toward the wharf induces the maximum reaction force. Regarding to. the Type No. 1 fenders (buckling type), fender size i s determined so t h a t the d e f l e c t i o n of fenders s h a l l be less than 10% of I t s height against the wind load w i t h the mean wind speed and the t o t a l d e f l e c t i o n adding the d e f l e c t i o n caused by s h i p motions s h a l l be l e s s than 35% o f i t s h e i g h t . And r e g a r i n g t o the Type No. 3 (pnumatic t y p e ) f e n d e r s , fender s i z e i s determined so t h a t the r e a c t i o n f o r c e a g a i n s t the d e f l e c t i o n o f 50% o f i t s h e i g h t s h a l l be less than h a l f o f the r e a c t i o n f o r c e caused by the wind load w i t h mean wind speed and the t o t a i d e f l e c t i o n adding the d e f l e c t i o n caused by s h i p motions a c c o r d i n g t o t h e wave f o r c e s s h a l l be l e s s than 50% o f i t s h e i g h t . Where, the mean wind speed i s 35m/s. Table 1 l i s t s fender size area the number of fenders t o be set both two type of fenders; Case sutudy was c a r r i r e d out under the conditions that the wave heights are Hw3= 0.3> 0.5, 0.7, 1.0m, the wave periods are T i / 3 = 8, 10, 12s, the waye d i r e c t i o n s are 30, 45, 60, 90 degrees, the wind speeds are 30, 35m/s, and the wind d i r e c t i o n s are 90, 120, 150, 180, 210, 240, 270 degrees. I t must be emphasized that large sized fenders should be i n s t a l l e d a t quay walls which would be served f o r harbouring ships. Usually, fender size i s about 300 t o 500mm to buckling type fenders and 600 t o 1,000mm t o pnumatic type fenders f o r those ships i n the range f r o m 3,000 t o 10,000DWT. But, according t o the results, fender size became 1,150 t u

1,600mm t o buckling type fenders and 1,500 t o 2,000mm t o pnumatic type

fenders.The main r e s u l t s of the case study are summerized aa f o l l o w s .

(1) For 10,000DWT cargo ships j u

Harbouring ships moored t o quy w a l l s may be f e a s i b l e under t h e c o n d i t i o n s t h a t t h e wave d i r e c t i o n i s i n the range f r o m 30 t o 45 degrees, the waVe height Hwo i s less than 0.5m, the wave period T-,/3=

10s, the wind d i r e c t i o n i s i n the range f r o m 0 t o 180 degrees which means t h a t the wind blows from the sea t o the wharf and pushes a ship toward a quay w a l l , and the wind speed i s l e s s than 30m/s. For t h e c o n d i t i o n s above mentioned, the fender r e a c t i o n f o r c e s , the f e n d e r d e f l e c t i o n s and the tensions of mooring ropes do n o t exceed t h e a l l o w a b l e v a l u e s . I f the wave d i r e c t i o n i s about 30 degrees, the f e n d e r d e f l e c t i o n i s l e s s than the a l l o w a b l e v a l u e a g a i n s t the wind w i t h mean wind speed 35m/s, except surge motion which becomes 5 t o 12 m a g a i n s t the wind d i r e c t i o n f r o m 1.20 t o 180 degrees. I f the wind d i r e c t i o n s are i n the range from 180 t o 360 degrees which means t h a t the wind blows f r o m the wharf t o the sea, a moored s h i p w i l l be d r i f t e d about 15 t o 17m apart f r o m the quay l i n e and the excess t e n n s i o n over t h e a l l o w a b l e value w i l l be induced i n some mooring ropes. Tnis means that the capacity of mooring ^ i p m e n t s i n s t a l l e d on s h i p i s l e s s than the mooring f o r c e s Induced by the wind w i t h mean wind speed 30m/s. T h e r f o r e i f the r u l e s f o r s t e e l s h i p s were n o t

'^^2 COASTAL ZONE'87

S < ^ i ^ ^ ' ] ^ ' e r r S ^ n S ° r * ' ^ ' ' ' " ? ' " ' ' ^ " ^ ° " ^ ^ " ^ ^ ^he wind f o r c e s should be

Ti/3= 10 s, and the wind spLd i ^ i o ^ ^ " ^ ^ ^ P ^ ^ ^ ° ^

(2) For 5,000DWT cargo ships

35m/. But, surge m o ^ i ^ T e l ^ L s 5 ' t l T f m ' " a g f l n ^ t ' t h e ^

(3) For 3,000DWT cargo ships

tuf ^'^^ ^'^.^^^^^^^"^^^^^^

exce^as t e „ a i o „ " l v ' e ^ ^ S ^ ^ t l L ' ^ a b e" ^ I T l W d i K ^ V a ' f „ " ' 'm'^

re

"s

-t

-/4r

^?^,o-o

^s^.^-%mè^

(4) Protection against wind

presented. Whe^ t t ^Ive fei*t h ? - T f i V r t ^?2HVIR30high i s t o be

^ t ^ t - a ï S ^ m ^ o d l n ^ ^ ^ ^

Figures 8 ^ d 9 S th/^Smr."? " " " ' " ^ ' ^ ^ ^ s i m u l a t i o n s as shown i n t h l T t h e s ; J Ï Ï ? ' „ e ï n ° " ; "^Z " ^ ^ - ^ '"e conditions 90 and 270 S q r ^ i H L l ! ^ " " ^ " ^ " ^ d i r e c t i o n s Were co^aition W h « ' t h e

w l ^ ' : ^ ' i | a

2'wT'and'^n™

90 dergrees f i t s beat wl?h i-h ^ " " " ' ^ and the wind d i r e c t i o n was

Accordi'ngly, 0 * ^ ^ . ^ " S S . ü l i ï ï S » » " " r ^ ^ .

SHIP MOTIONS 1553

1.2ra

Wind S c r e e n D i s t a n c e -1.2 m Wind D i r e c t i o n 270° Might 0.4 m

Figure 7. D i s t r i b u t i o n of Wind Speed behind Wind Protection Board

C C m D

SWAY EXP FBGHVI.R30

. SWAY EXP F B Q H V I R 3 0 LOW

"J J SWAY EXP F B Q H V I R 3 I Ü H I G H

- ^ • ° 0 B O 1 2 0 1 8 0

T I M E - S E C O N D

COASTAL ZONE '87 C c m D 6 . 0 - 8 , 0 COMP 9 0 DEC 2 . 1 9 M / S COMP 2 7 0 D E G 2 . 1 9 M / S - 9 . 0 6 , 0 - 8 , 0 . SWAY COMP .0 M / S 1 2 0 1 8 8 T Ï : M E - S E C O N D

Figiire 9.Time Histories of Sway Motions(FBQHVIR30-O0MPUTATION) (5) S e l e c t i o n o f the quay w a l l s served

f o r harbouring ships

As an instance, some quay walls were s e l e c t e d f o r the quays, which may be s e r v é d f o r harbouring s h i p s . W i t h the aid of computer program t o calculate the wave height inside p o r t , quays where the wave h e i g h t l e s s t h a n 50cm were s e l e c t e d . F i g u r e 10 s h o w s t h e d i s t r i b u t i o n o f wave' h e i g h t i n s i d e of breakwaters o f the Port o f Yokohama against the f a c i l i t i e s l a y o u t I n 1980. I t may be said that there are such quays a t the heart o f s l i p o f the Honmoku W h a r f , t h e Y a m a s h i t a W h a r f , t h e Ohsanbasbi, t h e Shlnkou Wharf, the M i t s u b i s h i Dock, the Takashima Wharf, t h e P i e r o f A s i a S e k i y u , and t h e l^karamachi Wharf which may be served f o r harbouring ships. .

F i g u r e 10. D i s t r i b u t i o n o f Wave Height (Yokohama) APPLlCATiai TO THE SUBJECT OF PCHÏT OPERATION RATE

I n t h i s chapter, degree of sheltering of port s h a l l be discussed regarding t o port operation irate. Kubo 1198TJ s t a t i s t i c a l y a n a l i z e d t i m e sheets keeped i n the D Port which was f a c i n g t o the P a c i f i c Ocean and indicated that s w e l l i s the seccnd ranking reason to hinder l o a d i n g and unloading o p e r a t i o n i n p o r t . A l t h o u g h r a t e o f h i n d e r i s only 4.1%, the sea state when the long period waves cxime i n t o the port i s seems so calm w i t h s m a l l wave h e i g h t and no wind t h a t almost a l l the o p e r a t o r s judge t h a t l o a d i n g and u n l o a d i n g o p e r a t i o n s could be done. This causes the c o m p l a i n t and b r i n g s t h e p o r t i n t o d i s r e p u t e ,

The same instances have occured i n some p o r t s ^ ^ ^ ^ ^ ' l ^ ^ f

f a c i n g t o the Japan Sea. Gn the other hand, the Author and h i s

c ^ n ^ e obseved damages on fenders which seems t o be caused by ship ^ t i S ^ s a t several p o r t s i n Hokkaido on the coast f a c i n g t o the ^ a c ï ï c c ^ L WillsoS (19651, Vancni a ^ ^ r r ^ 9501, and Kxeth^nd

Murphy [19701 reported the long period of ship motions i n Po»^t ^f C a ^ S , LOS Angeles and San Nicholas Bay, respectively, and analyzed as U n u s e d by seiche, surge or asymmetry of mooring system, «egaró^ng t o ^ r t o p r e r a t i o n r a t e , Brunn (19811 gave ranges f o r a l l o w a b l e movements f o r various categories of vessels when unloading, assuming a

m a x i S period of 120s. Slinn (i;9791' showed e f f e c t of ship movement on

container handling rate.

H e r e , case s t u l e s c a r r i e d out f o r t h r e e p o r t s s h a l l be i n t r o d u c e d . The r e l a t i o n between s h i p motions and the wind and waye

c S ^ m o n s , and the allowable wave conditons f o r loading ar^ unloading,

d e r a t i o n s are discussed. The former two cases are the study has been

S e b e f o r e the c o n s t r u c t i o n o f p o r t , but the l a s t one i s the study

done f o r the porpose o f improvement of port operating rate, (1) Case study f o r the A Port

F i g u r e 11 shows t h e layout o f quay w a l l s i n the A P o r t . The b r e a k w a t e r i s c o n s t r u c t e d about 250m a t a moment, and w i l l be made 150m longer i n f u t u r e . There are three berths constructed f o r

a container ship (30,000DWT), ^ . o^^f

cargo ships (15,000 and Figure 11. Layout o f A P o r t

5 OOODWT). The quay w a l l s i s . . •

c S c U o n o f ^ t e e l sheet p i l e s . The wave diffraction coefficient i n

f r o n t o f b e r t h i s c a l c u l a t e d as 0.16 t o the waves " i ^ h p e r i c ^ 1 bs Fenders i n s t a l l e d t o the quay w a l l s are the V s ^ p e d rubber f e n d e r s

w i t h height 300, 500 and 600mm, w i t h length 3,000mm, and wich spacing 9 6 9.6 and 9.0m f o r -7.5m b e r t h , -10m b e r t h and j l l m b e r t h , r e s ^ c t i v e l y . Mooring ropes are nylon ropes w i t h diameter 42 mm, 55 mm and 65 mm,

Table 2. Ktovement of Container Ship Hi/3= 0.32an, T^/^^ -jgg Surge Sway Heave R o l l Yaw Movement 56.7cm 18.6cm 75.1cm 0.19deg 0.054deg Allowable lOOan 60cm 60cm 6deg 4deg

Table 2 l i s t s movements of ships subjected t o the waves w i t h period 16s and the allowable ship movemsnts presented by Brunn T l 9 8 1 1 . According t o comparison o f these v a l u e s , i t may oe concluded t h a t loading and unloading operation may be done when

COASTAL ZONE '87

f b r Snt^^L l^- ^^^'^^i "i^^ ^""'"^ i ^ 1^^^ than about T.5m f o r c o n t a i n e r ships and less than 2.0m f o r cargo s h i p s . I n ^2.1 7 wave height i n f r o n t o f quay w a i l s l e s s than c r i t i ^ T c S S f ^ ' ^ ^ ^ ''""^ cargo S h i p s are t h e (2) Case study f o r the B Port

12 shows the layout of quay w a l l s i n the B Port. Tiiere are two berths on planning f o r 27,000DWT container ships and hVre Sev are

^ ^ ^ ^ ^ L ^ ^ — O f c i s L ^ n

i n s i d e b r e a k w a t e r s , t h e wave

d i f f r a c t i o n c o e f f i c i e n t s i n f r o n t o f 90" 135° those berths are computed i n the rage \ I . f r o m 0.1 t o 0.2 f o r d i f f e r e n t wave ^ R2 * ^

periods. On the assumption t h a t a s h i p ^^"^^^'"^ff^Mr^e/Uffffffffy

w i l l moor head on, the wave d i r e c t i o n s w i l l be 190 degree and 270 degree f o r t h e RI b e r t h a n d t h e R2 b e r t h , r e s p e c t i v e l y . Fenders i n s t a l l e d on

berths are V shaped rubber fenders w i t h _{g RI} - 90* • i u v / u e t LKisaers w i t n hUMn U' '

height 1,000mm,with l e n g t h 2,000mm and ~ WAVF , ^ w i t h spacing 14m. Mooring ropes are not ! \ only nylon ropes w i t h diameter 60mm but 190° ion» also combination of nylon ropes ahd wire

S g l c t S e ï y . ' ° - ^^^"^^ ^2.Layout of B Port ^ "^^u^fulJ^^*^^ c o n d i t i o n s of computation cases. I n t h i s case study both the wind and the waves are taken account The wind and wave directions a ^ t e d i n numerical simulations are . ï a w i i n f ^ ^ e J h l pi ^ "^""^^^ ^ ^ ^ 1 o f d i f f e r e n c e appeared b e t w ^ n m ^ r i ^ ^ ^ " ' ^ ""^^ Reg^'^ding t o the R2 b^^rth, a T h ï p i s moored i n beam sea t h a t means the wave d i r e c t i o n i s 270 dSq^Ls b X t h ' the e x s t - , t i - % - ^ E - i a l l y i n sway m o t L ' i s a f f e c t mL?? e x s i s t e n c e o f wind and the fender c h a r a c t e r i s t i c s As S o f s ^ S > h sometimes te^me a S S ^ r

t h e ^ r ^ T i

^Ti-ir.

tteVi^'l

^ir'"^

'

° "Ii"

""^^

''^^

III "A"^ 9 o " ' i 3 f " , " . i ' ^ ^ " P ^ ^^'"/^ O-^/s. The wi,S d i r e c t i o n s aJe set 45, 90, 1 35, 270 degrees. Under the c o n d i t i o n w i t h no wind.

Table 3. Conditions of Gbmputation

Wind Wave. Direction Speed D i r e c t i o n Period Height

Rl Berth . o . r W s ,90 deg 30,40an

DO n^^.-u 45,90,135 „ , q . l ? . in , ^ ^ . ^ ^ 270deg u.ium/s 270 deg {5' -' J ^ - '

SHIP MOTIONS 555/ '35 90 135 270 270 10 10 10 TO TO 270 270 270 270 270 270 12 12 12 1:2 12 12 30 30 30 30 20 30 30 63 31 37 41 101 159 49 50 49 119 219 61 61 61 61 41 61 0.56 0.59 0.63 0.59 0.96 1 .73 0.60 0.94 0.38 0.10 1.26 2.01 Table 4. fto^/ëment of Cbntainer Ship

Wind Direction(deg) Wind Speed (m/s) Wave Direction(deg) Wave Period (s) Wave Height (an)

Surge (on)

Sway (cm) Heave (cm) Roll (deg) Yaw (deg)

subharmonic sway motions occur and a .ship moves about .2ni a ^ r t from

SSÏ^waïï. ButTwith the wind with mean speed lOm/s from the direction ^ 4 ^ . 90 arx3 135 degr^s, a ship i s drifted aE«rt from the quay wall and does not touch^he fenders. T h e r e f o r e , the amplitude of sway motion f a i r l y decreased compared with case with no Wind Table 6 l i s t s the c r i t i S wave height for loading anca unloading cperations m the B port.

(3) Case study for the C Port . At the end of t h i s case study, the Author may emphasize the

important of fender characteristics for port planning when the long

^ ï ï c ï ^ v e s e x s i s t and w i l l .present an Instance of improvement

performed at the C Port in Japan.

Figure 13. Layout of C Port

Figure 13 shows the layout of f a c i l i t i e s of the C Po'^t. Ip t h i s port, there are several berths available for o i l tankers ;n the range f?Sm 3,000DWT to T50,000DWT. The object of this f u d y the berth located at point C i n Figure 13. The berth i s construction of s t e e l n i ï ï s d o l D h i n type f o r 3,000DWT tankers, There are two i D r e a s t i n g

dolphins and t w T v shaped rubber fenders with height 400mm are i n s t a U e d f o r each dolphins with spacing 8m. These fenders were designed to absorb the berthing energy of ship. But, the keinem t enerdy of ship which moves i n waves i s possibly becomes l a r g e r than ?hat^of berthing. Accordingly, the l o a d - d e f l e c t i o n c h a r a c t e r i s t i c becomes rather asymmetry so that subharmonic motions which bi^^^^^^^^ loading and unloading operations occurs during ^^tober to March Possible improvement measure i s thought to replace. ferx38rs to ones which e x i h i b i t the load-deflection c h a r a c t e r i s t i c as Type No. 3 Tprimatlc tjpe). Several cases of numerical simulations were

carried-COASTAL ZONE *87 A TYPE No.l 400mm • TYPE No.21000mm O TYPE No.3 1200mm 30 -100 -50

Figure 14. Sway Moticjn

0 50

(cm) _{10 20 30 cm}

Figure 15. Fender Deformation out and good results was obtained f o r those cases using the pnumatic type fenders w i t h h e i g h t 1,000 t o 1,200mm. Figures 14 shows sway motions comparing r e s u l t s o f cases using present fenders ( b u c k l i n g type) and replaced fenders (pnumatic t y p e ) . There i s a c l e a r d i f f e r e n c e between results of two cases that ship motion i n case of replaced fenders (pnumatic type) are s m a l l e r than t h a t i n case o f present fenders ( b u c k l i n g t y p e ) . F u r t h e r t o say, o f f s h o r e motion which means s h i p motion a p a r t f r o m qauy w a l l i s reduced so much i n case of replaced fenders (pnumatic type). Figure 15 shows the fender deformations and the reaction forces of both cases.. I t i s noticed t o the Author that port operating rate has been improved since fendeires were replaced.

CONCLUSION

The numerical simulation method t o compute motions of ship moored t o a n o n - l i n e a r c h a r a c t e r i s t i c mooring system and s u b j e c t e d t o the i r r e g u l a r waves and the gusty wind i s evalueted w i t h comparison o f h y d r a u l i c model t e s t s . This n u m e r i c a l s i m u l a t i o n method may be e x t e n s i v e l y used f o r p o r t p l a n n i n g I n order t o demonstrate p o r t f u n c t i o n as much as p o s s i b l e . I n t h i s paper r e s u l t s o f f o u r case s t u d i e s were presented. Although, h a r b o u r i n g ships i s p r i m i t i v e f u n c t i o n of port, i t i s not coped t o requirement of ships a t a moment. Improving p o r t o p e r a t i o n r a t e i s a l s o the i m p o r t a n t s u b j e c t , and i n tuture ships' mooring problems regarding t o t h i s subjects s h a l l be the c r i t i c a l I t e m o f p o r t p l a n n i n g because the f u t u r e p o r t w i l l be constructed i n offshore or i n more h o s t i l e sea.

Followings are the conclusion of t h i s paper.

1. When a s h i p i s moored t o an asymmetry mooring system and a l s o subjected to the waves and the weak steady force, subharmoic swaying w i t h l a r g e a m l i t u d e w i l l occur. I t i s e f f e c t i v e t o d i m i n i s h t h i s iTiotion t o make mooring sysytem symmetry by replacing fenders f o r an mstidiirCSa

SHIP MOTIONS 1559

2, Harbouring ships i s an i m p o r t a n t s u b j e c t i n Japan e s p e c i a l l y i n

Tokyo Bay, Osaka Bay and Ise Bay according to increase both ship size and the number of coming ships and also copmlex u t i l i a z a t i o n of marine space. We have to make e f f e c t i v e countermeasures f o r t h a t porpose. •this numerical simulation method s h a l l be used e f f e c t i v e l y .

3. For those p o r t s or berths l o c a t e d i n r a t h e r o u t e r p a r t of a bay o r on the coast f a c i n g to the ocean, s h i p motions s h a l l be the c r i t i c a l item of port planning. This numerical simulation method w i l l be used e f f e c t i v e l y to c a l c u l a t e p o r t o p e r a t i o n rate and to determine size and arrangement of breakwaters.

PJEFEa?E!^CES

I . Brunn,P.[1981 h'^Breakwater or mooring system ?", The Dock & Harbour Authority, September! 198.r, PP.126-129.

2iHsu,FiA.[ 1970]'.''Analysis of Peak Mooring Forces by Slow Vessel D r i f t O s c i l l a t i o n s i n Random Seas", 2hd O f f s h o r e Technology Conference #1159, pp.1-135-1-146. ,

3;Ijdma,T. et alt1972];:"Scattering of Surface Waves and the Motions of

a Rectangular Body by Waves I n F i n i t e Water Depth", T r a n s a c t i o n o f Japan Society o f C i v i l Ek^gineers, No.202, PPo33-48.

4.ijima,T. et ai:.[1975]:"On the Motions of E l l i p t i c a l o r Rectangular F l o a t i n g Body i n Waves of F i n i t e Water Depth", Transacsion o f Japan Society of C i v i l Enginees, No.244,PP.91-105,

5 . I t o , Y . and C h l b a , S , ( 1972 ] :"An Approximate Theory of F l o a t i n g Breakwater", Report o f the Port and Harbour Research I n s t i t u t e , V o l . 1 1 , No.2, PP.1 41-166.

6. Kubo,M:"Fundamental Study on the S h e l t e r i n g Dgree o f the P o r t Regarding to the C r i t i c a l Conditions of Loading", 241 p.

7. Lean,G.H.[1971:]i:"Subharmonic Motions o f Moored Ships Subjected t o Wave A c t i o n " , Transaction o f Royal I n s i t u t e o f Naval A r c h i t e c t s , London, No.l 13, PP.387-399.

8.0ortmerssen,G.Von[1976]:"Tue Motions of Moor©3 Ship i n Waves", Publication No.SiO, Netherlands Ship Model Basin, 138p.

9 . P i n k s t e r , J . A . [ 1 9 8 0 ] : " L O W Frequency Second o r d e r Wave E x c i t a t i n g Forces on F l o a t i n g S t r u c t u r e s " , P u b l i c a t i o n Noi650, Netheriand Ship Model Basin, •204p.

10iRussel,R.C.H.[1958]:"A Study o f the Movement o f Moored Ships Subjected t o Wave Action"> Proceedings of I n s t i t u t i o n o f G i v i l Engineering. Vol.12j pp.379-398.

I I . Sawaragi,T. e t al[T983]:"New Mooring Systems to Reduce Ship Motion and B e r t h i n g Energy",Proceedings of 30th Japanese Conference on Coastal Engineering, PP.460-464.

1 2 . S l i n n , P . J . B : " E f f e e t of Ship Movement on Container Handling Rates", The Dock & Harbour Authority, August 1979, pp.117-120.

13.Takaishi,Y. and K u r o i , M . [ 1 9 7 7 ] : " P r a c t i c a l C a l c u l a t i o n Method o f Ship Motions i n - Waves", 2nd Symposium on Sea Keeping j pp. 109-13. T s u j i , T . e t a l [ 1,972 ]:"Model Test about Wind Forces A c t i n g on the Ships",Report 6f the Ship Research I n s t i t u t e , Vol.7, No.5, pp.13-37i 14. Ueda,S. and S . S h i r a i s h i [ 1983]::"Method and i t s E v a l u a t i o n f o r Computation o f Moored Ship's Motions'', Report o f the Port and Harbour Research I n s i t u t e , Vol.22, No.4, pp.188^218.

1 5.Ueda,S.,[1984 ] ; : " A n a l y t i c a l Method o f Ship M o t i o n s Moored to Quay Walls and the A p p l i c a t i o n s " , Note o f the P o r t and Harboiir Research • I n s t i t u t e , No.504, 371 p.