Model experiments of pusher barge transport systems on maneuvering and seakeeping qualities

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ARCH LEE

Introduction

The pusher-barge transport system has been

deve!-oped in U.S.A., Europe and U.S.S.R. and is used mainly in the river or lake with rather satisfactory

result.

In Japan, it

is now under examination as

one access to rationalization of transport system in inland sea and has already been put to practical use on a small scale. However, the technical data available to make use of this system in the coastal or inland service are not enough.

In response to the request of the concerned tech-nical committee organized within Ministry of Trans-port to promote development of the pusher-barge

transport system, a series of model tests were carried

out in still water and regular waves ort the maneu-vering and seakeeping qualities using models con-sisted of a pusher with many varieties of combina-tion of barges at Mitaka No. I Ship Experiment Tank of Ship Research Institute. The vessels were connected rather rigidly by a steel pipe and moments

around three axes were measured on this pipe to-gether with all modes of motions.

In this article, the motions and forces measured will be shown in the model scale and the results can be applied to the design of actual barge lines pro-vided the difference of the connecting method will be taken carefully into account.

By Yasufumi Yomonouchi, Taihei Yoshino and Makoto Kan

Ship Research Institute, Ministry of Transport

Models and Test Methods

Models

The pusher-barge line systems used widely today may be classified into two groups, viz, one pusher with one large barge and one pusher with many

small barges.

A 70 m large barge, six 30 m small barges and a

pusher of 1,000 B.P.S. class that are considered most

available and common in Japan in the near future

arc adopted and designed in the aforesaid committee.

In experiments, wooden models of these systems

made on a scale of

I to 12 are used. Principal dimensions of the assumed ships and models are shown in Tables i and 2, and hull forms are shown

in Fig. l.3.

The pusher model has ordinary twin

screw propellers, (MAU-4 type, diameter 15 cm,

pitch ratio 0.64, expanded area ratio 0.42, outward

turning) and ordinary streamlined twin hanging rudders.

Varieties of Pusher-Barge Line System

Model tests were carried out on many varieties of pusher-barge line system as shown in

Fig. 4 and

Photo 1.

Table i Principal Dimensions of Assumed Ships

Table 2 Principal Dimensions of Models

Lab.

_{y. Scheepsbouwkunde}

Technische Hogschooí

Deift

Length (oa)

L Length (bpp) Breadth (mid)B Depth (mid)D

Draft d Pusher Boat 24. 28m 22. 00m 7. 50m 3. 60m 2. 30m 70m Barge 70.00 70.00 12.00 5.00 4.00 30m Barge 28.40 26. 85 6.6 2. 645 2.08 Length (oa) L

Length (bpp) Breadth (mid)

B Depth (mid)D Draftd Displacement

Pusher Boat 2. 02m i. 83m 0.625m 0. 30m 0. 102m 0. 127 ton

70m Barge 5. 83 5.83 1.00 0.417 0. 333 1.670

30m Barge 2.36 2.24 0.55 0.22 0.173 0. 191

March 1969 ₅

Podo1 xee

ser- re Trns

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System A is the pusher only.

System B consists of a pusher with a 70 m large barge.

Both systems C and D consist of a pusher with

0 E 1,500 3.0Cm S.L. 200m S.L. lOOm S.L. AP. 5 8,250 300 300m 2.00m 1.0Cm 1.0Cm ...L... S.L. BL. S.L. BL. L .W.L. 6 7

Fig. i Lines of Pusher

six 30 m small barges. In system C, the pusher is connected with barges at the one side of two parallel lines of barges (one side pushing system), and in system D behind the center line (center pushing

200m 300m

BL. B.L.

Fig. 2 Lines of 10M Barge

300m W.L. 200m W.L. 6) 1.00mW.L. 5u, 4 Base Line 6.0W L. 5.0W. L. 4.OW.L. 3.0W L. 2.0W. L. I.OW.L. Base Line 359 3.0Gm Wi.. 2.0Gm W.L. 100m W.L. Base Line 3.00m BL. 200m S.L. 100m S.L. Center Lino 6.OW.L. And B.L. 5.OW.L. And BL. 4.OW.L. And S.L. 3.OW.L. And L. 2.OW.L. And BL. l.OW.L. And BL. B.L.-And-C.L,

6 Ja pan Shipbuilding & Marine Engineering

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System A _Pusher_Only) Lnp-= 183m C&D

)

920m Lpp.. 780m irr 2m 3m aL. BL. BL. _g? 8 8 -o_o o-9 o o 12.5m W.L. ---.-.0-le, e 15m WL. '-01

."

-ns. 1m W.L. )'4 _{05m W.L.} Base Line F_P. )A.P.) Fr-P. (3f) (A P.) Center 1.tne

Table 3 Principal Dimensions of Barge Line Models Barge Line

System Length (bpp)L9 Breadth (mid)B

Rudder Area Ratio A l.83m 0.625m 1/9.1 B 7.80 1.00 1/60 C 9.20 1.10 1/39 D 9.20 1.10 1/39 E 6.76 1.10 1/29 F1 4.30 1.10 1/19 F2 4.30 1.10 ' 1/19

Parallel Part Raked Part

35m BL. 3m BL. L. -i

-i i j

2m BL. a -j E o E E tO c'JE E ire OEL.

920m _{Clearance between Vessels0. 065m}

system F2 by a lunge. The length, breadtlì and rudder area ratio (projected area of a rudder x2/

) _{projected area of center line plane of system) of}

L

A

E

676m _{tite barge line systems are shown in Table 3.}

Connecting Method

lic

430m

)

Rod Connecting

As the method of connection between pusher and barge or between barges, the wire-lashing method is most generally used today, while the

auto-connect-L _{Hinge Correcting}

ing method using the specially designed mechanism

is adopted to some extent. In the experiments,

how-4 30m

Fig. 4 Pusher-Barge Line System Tested _{ever, the connecting method was simplified as follows:} The connection between pusher and barge or be-tween barges was fixed rigidly using a connecting

system). rod made of a thin steel pipe as shown in Fig. 5 a)

System E consists of a pusher with four 30 m small and Photo 2 at the junction where the forces were

barges. to be measured. At the other junctions, the

con-Both systems F1 and F2 consist of a pusher with nection was also made rigid using rectangular

two 30 m small barges. In system F1, the pusher timbers in systems B, C, D, E and F1. In system F2,

is connected with barges by a steel pipe and in however, a special type connecting hinge was used

March 1969 7 6 7 (3) (4) Fig. 3 (1KY (i) 8 (2) Lines of 30M Barge

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System S

System C

system F2

Photo i

as shown in Fig. 5 b) in order to keep the relative pitching motion between pusher and barge free. In

all cases except systems A and B, two small barges in parallel are connected with each other rigidly by some timbers and are always treated as one block of vessels. The height of the center of a con-necting rod or hinge above water surface was 292.5 mm.

Test Programs

On each of the abovementioned pusher-barge line systems, maneuvering tests in still water and sea-keeping tests in oblique regular waves were carried out, and moments around three axes or forces acting on the connecting rod or hinge were measured to-gether with all modes of motions.

Test Results

Maneuvering Qualities

Results of the maneuvering test are shown in the form of Q-6 curve, where Q is the steady turning rate equal to L/R (R is the steady turning radius), and 5 is the rudder angle. Q was taken at the posi. tion of the center of gravity not of the pusher-barge

line system but of the pusher in

all cases. Lpp

is the length between F.P. of the head barge and

A.P. of the pusher at the tail of the system

contain-ing the clearances between vessels. System A (Pusher Only)

Figs. 6 and 7 show the Q-5 curve of the pusher only going ahead and astern respectively. When

going ahead, it has sufficient steering and course-keeping qualities as shown in Fig. 6. But when

going astern, it has a very poor course-keeping

quality as shown in Fig. 7. These may be caused by the large rudder area ratio (1/9) and the large amount of trim by the stern (4%).

Photo 2 Connecting Rod

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Marc/i 1969 a Rod -0.4 0.6 0.8-I0 20 30 40 Starboard 8

Fig. 6 Turning Rate of Pusher vs. Rudder Angle F=O.33

System B (Pusher with One Large Barge)

Fig. 8 shows the 2-6 curve of system B going

ahead. This system seems to have considerably poor

course-keeping quality perhaps because it consists of a shallow draft pusher and a deep draft barge, and so can be regarded as a vessel having a large cut up at the stern as well as a rather small rudder area ratio (1/60).

Systems G and D (Pusher with Six Small Barges)

System C is the one side pushing system and sys-tem D is center pushing syssys-tem as abovementioned. Fig. 9 shows Q-6 curves of these systems.

In the

case of system C, the rudder angle of 3 or 4 degrees

was necessary to keep the system on a straight

Fig. 5 Connecting Rod between Vessels

Port o' o 'o 1 .5 LO 0.5 40 - 3O 20rn 10 10 20 30 40 0.5 1.0 1.5 Staboad 8

Fig. 7 Turning Rate of Pusher vs. Rudder Angle when

Going Astern F=O.12

course. At the rudder angle over 15-20 degrees,

however, the difference between starboard turning rate and the port turning rate is not so distinct by

the same rudder angle.

Also, the difference between system C and system D is not so large except the region Of small rudder

angle. Both systems C and D have better

course-keeping quality but poorer steering quality than system B. _{This could be interpreted as the effect of} the slape of system because systems C and D

con-sist of the pusher with rather deep draft and barges

of shallow draft, so accordingly, they can be regarded

as a vessel having some dead wood at the stern. Furthermore, the rudder area ratio of systems C and D is greater than that of system B (1/40).

9

Ahi

II

.INI.-.

12# h-300 370 b) Hinge 10

i

7o 350 200 450 60 65

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Fig. Il shows the drift angle during steady turn-ing.

lt

illustrates that this system has a larger

drift angle or side slip in comparison with ordinary ships, and that the pivoting point is located forward

the stern of the head barge.

System E (Pusher with Four Sinai! Barges) and System F1 (Pusher with Two Small Barges)

Both systems E and system F1 are the center push.

ing system. The 2- curses of them are shown in Fig.

4O 3O 2O

lo.

Port ß=30.5 Port) _x o 0.8 0.6 0.4 0.2 lo. 0.2 0.4 0.6 0.8

FIZ. Turn!nf Rate of System B vs. Rudder F, =0.12

20' 30' Starboard S 40' 8=25' çPort) x o 0.6 0.4 0.2 System C o System D

40' 30' 20' - 10'

Port 8=1 5 (Port) X

Fig. 11 Drift Aig!e of System D during Steady urn!ng

io Japan Shipbuilding & Marine Engineering

0.6 0.4 0.2 '-0.2 0.4 0.6

Fig. B Turning Rate of Systems C & D vs. Ruter

Ang!e F,, = 0.10

O L

O 10 2O 3Q 4O

Port 8

Fig. 10 Turning Rate of Systems D, E ! F vs. !uder An!e

/ / / / / / / 0;Turrring Center P;Pivotng Point Q;Center of System R;C.G. of Pusher Starboard S 10 20' 3O 40 i _-System D F.=0.10 --c' System E F,=0.1i System F, F.0.12

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.4O. 30' 20' E 6

-2

MIT Horuiontal 40' 20' lo. Port AI Ill March 1969 Rudder Angle M)-)

r-'

M(+) lo sec 25 Mut 30 s _{-__} _15,MJt 2 -2 _Torsional -MC) M (4-)

Fis. 13 Horizontal endtng Moment of System urin Steering F,, =0.12

IO in comparison with that of system D. It shows

that in

tile case of the system that consists of a deep draft pusher and some shallow draft barges connected in series, the more the number of the barges, the better turning rate it shows. However, if the draft of a pusher is shallower than the barges', it is possible to have the reverse tendency that the more barges, the poorer turning rate it shows. Horizontal Bending Moment and Torsional Moment Acting on Connecting iod during Steering

System B

Fig. 12 shows how the horizontal bending moment

and the torsional moment acting on the connecting

40' 30 20' O -n 4-2 Rudder Angle Horizontal -6 -8

Fig. 14 Horizontal endlnt Moment an Torsional Moment

at Point A cf System D durin SrInZ F,, ø.1O

10 15 sec sec sec 8- 6-4- _{Turning Rate} 10 15 20 25 30 Tors 20 25 30 ocal 30 10 15 20M,lIl25

Fig. 15 Horizontal !endfn Moment o! System O isrin Steer!ng F,,=C.1Ü

rod vary with time during the early stage of turn-ing, for example, of =35° port. Here, MI is the maximum value of tile horizontal bending moment that appears first when the rudder angle comes to

the set point, for instance, here at 350 port. MIX

is the maximum value that appears secondly-after

the turning rate grows up to the maximum value.

Mlii is the final steady value.

MIMilI are

shown against rudder angle in Fig. 13.

MI is

Il 0 5 10 15 20 sec 25 30 8 a 2 o 10 15 20 25 30 sec Turning Rate 10' o A C

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E

Fig. 16 Distribution of HorizontaT 8ending ornent Acting on

Connecting Rod of System D during Steering

¿=35° Port, F,,=0.10 M,I

2

10 20 3O 40 Starboard 8 - M, Ji Fig. 17 Torsional Moment of System 8 during

Steering F=0.12

nearly proportional to the rudder angle and there-fore can be regarded as to be caused by the rudder

force only.

MII and MIII show large value in

the region of small rudder angle. These results may be caused by the large turning resistance or

turning force even at small rudder angle as

ex-pected from the Q- curve in Fig. 8. However, in the iégion of large rudder angle, being cancelled by the large rudder force, MII and MIII become

rather small. Regarding the torsional moment, MtI, MTII and MDIII are defined similarly, and

the"-sults show the same tendency with the bending

moment as shown in Fig. 17.

It seems that the

torsiontI inoment during steering caused by the

difference of heel by the component vessel is not so

E

ta

Fig. 18 Torsional Moment of System D during Steering F =0.10

prominent in comparison with the moment caused by the saine forces that cause the horizontal bending moment.

System D

The horizontal bending moment and torsional moment at the transitional stage during steering are shown in Fig. 14, for example, of point A and

=35° port. The maximum value of horizontal

bending moment corresponding to MII in the case of system B does not appear in this case. This is

due to the small overshoot of turning rate, or in

other words, the good course-keeping quality of this system.

The final steady value Mili has the

opposite sign to Mill of system B and the same

sign with MI of system D, probably because the horizontal bending moment caused by the turning resistance or the turning force is not large enough tò cancel the moment caused by the rudder force in this case of system D. Fig. 15 shows MI and MIlI at connecting points A, B and C against the rudder angle. Fig. 16 shows the longitudinal

dis-tribution of MI and MIII. Fig. 18 shows the tor-sional moments at points A, B and C. At point A, M711 (lid not appear the same as already shown in

Fig. 14. At points B and C, however, MTl (lid not

appear but only MI1.

12 _{Japan Shipbuilding & Marine Enginecrìg}

M, (±)

Pusher 70m Barge

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a RoI)ing 8 March 1969 1'

x 90

2 3 4 2 3 4 5 A(m) À(In'

Fig. 19 Ro!!ing and Pitching Responses of Pusher On!y in Oblique Regular Waves

Rolling and Pitching Responses, and Moments at Connecting Point Caused by Ship Motions in

Regular Oblique Waves

Rolling and Pitching Responses of Pusher Only Fig. lO shows the rolling and pitching responses of the pusher only. In the head sea (x=180°), the so-called unsteady rolling appeared.

Rolling and Pitching Responses of 70M Barge Only The rolling and pitching responses of the 70m barge only are shown in Fig. 20. The peak of the

i 0 0.8 0.6 0.4 0.2 b Pitching 157.5. 3 4 5 7 8 A Cm)

Fig. 20 RoIling and Pitching Responses of 70M Barge Only in Oblique Regular Waves

X= 180rn 1 50 i12.5 X X 180. 90 i0 I 5Q i 35 1 20

pitching response in the beam sea may be the cou-pled effect of the large rolling motion. The small

peak other than the resonant peak of rolling

re-sponse may be caused perhaps by the peak of the exciting moment of waves. Also, the unsteady

rolling appeared in the head sea.

Rolling and Pitching Responses of System B The rolling and pitching responses of system B measured on the pusher are shown in Fig. 21. It shows similar tendencies to that of the 70m barge only and the effect of the pusher that has small

dis-X=90 I 20 135 -_D- i 50 180 * 1.4 1.2 1 .0 0.8 0.6 0,4 0.2 0 b) Pitching -5 6 ₁ 7-6 5 4 * SS-3 2 a) RoIIiig \,, x=90. 112.5 .5. 6 5 3 2 o

t -

t-I 35 7 8 9 10 A Cm)

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0.8 0.6 0.4 0.2 a Rolhng 2 10 8 2

Fig. 21 Ro!!ing and Pitching Responses of System B

¡n 05!ique Regu!ar Waves

a) Vertical Bending Moment

1=1575'

90'

X-9 10

b) Horizonta! Rendng Moment

X 180' 1575' -11 2.5'

o

90

placements does not seem to appear. The peak of

resonance in rolling response, however, comes (town

to a rather low value for wave direction, x=112.5°, in this system.

Amplitude of Vertical Bending Moment, Horizontal Bending Moment and Torsional Moment Acting on

Connecting Rod of System B

Fig. 22 a) shows the vertical bending moment, acting on the connecting rod of system B floating

freely in regular oblique waves, against wave length,

taking the wave directions as a parameter. The vertical bending moment has the similar tendency to the pitching reponse. Fig. 22 b) shows the hori-zontal bending moment, which seems to be caused mainly by the difference of phase an(l amplitude of

horizontal forces

acting on the pusher and the

barge during yawing or swaying motion. Besides,

the horizontal components of the heaving or

pitch-ing forces may be contained in

these horizontal

forces because the rolling was kept free. The varia-tion of the torsional moment, shown in Fig. 22 c), looks fairly similar to that of the horizontal

bend-ing moment. It might be interpreted that the tor-sional moment is caused by the same force that

causes the horizontal bending moment rather than

E

na

Fig. 22 Vertical and Horizonta! Bending

Moments and Torsional Moment o system

B in Oblitie eu!ar Waves Fm.

c) Torsional Moment 2.0.-112.5'

/'\"3

X-'35 1.0-

]/ \ì

/ x 90 1575 0.5 ° ₂ 3 4 7 8 9 10 ACm)

14 _{Japan Shipbuilding & Marine Engineering}

02

3 4 6 7 8 10 A (m) 25 20 15 no 10 5 o 3 4 6 7 A (m) 8 10

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a' RoPing Response 9-. B 7 6 3 2

Vertical Bending Moment

Horizontal Bending Moment

1.00.8 -0.6 (t 0.4 0.2 b) Pitching Response A =4m 20 40' 60' 80' X

Fig. 23 Roflin and tciin !esponses of Sys'em ! wt' rorw2rd _{Speed J, =0.12}

0 20' 40' 60' 80 100' 120 140' 160 180' X Torsional Moment 0' 20' 40' 60' 80' 100' 120' 140' 160' 180' X Rolling Response Pitching Response 0.8 0.8 -A 9m,F,-0 A-4m. ,'f \F, 0 100' 120' 140 160' 180' X 135' o 90' AK 4 5 6 7 8 A Im) o--- 157.5

1t.

Q n 10 flg. 2 oWn Itc!tIn R8 00881 of Systen D 1,, .0

the difference of _lt:1se

or :mp!irudc of

lolling

forces. Fig. 23 shows the rolling and pitching

re-sponses of system B running at the speed of F,,=O.l2

in regular oblique waves, versus wave direction, in

comparison with the values at F,, =0. Fig. 24 shows

the variation of moments of system B running in waves in various directions. These moments are

nearly symmetrical around x=90° but slightly greater

in the head seas than in tite following seas. olling and Pitching Responses of System D

The rolling and pitching responses of system D

Fig. 24 Vertca? and Horizonta! Bending Moments and Torsiona!

Moment of Systert B with Forward Speed 1,, =0.12 X March 1969 ₁₅ .*r._______ 1 57.5' Z _1.0 's. ___L._

----o .0 5 7 8 9 10 A Im) 25 2.0 93m A 0.6 3.. 0.4 (t 0.2 O

7

o 1.80V

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measured on the pusher are shown in Fig. 25. The resonant point of rolling response was À=2.24m in model scale, however, this wave was not con-tained in this test. The measured data of system D are more scattered than for tystem B because the

response

of a pusher must be,

strictly speaking,

varied according to the position of the connecting rod made of elastic steel pipe.

Amplitude of Moments Acting on Connecting Rod of System D

Figs. 26-28 show the vertical bending moment, horizontal bending moment and torsional moment acting on the connecting rod at three points A, B and C of system D. The vertical bending moment at point A is similar to the pitching response shown in Fig. 25 b), but the one at point C is not. This

is perhaps because the pitching response of the head barges may differ from that of the pusher. The similarity between the horizontal bending moment and the torsional moment seems to be weaker

ex-cept for point A in system D than in system B. This

is probably due to the fact that the torsional mo-ment caused by the same force that yields the

hori-zontal bending momeht becomes smaller in system D

because of the shallow draft of barges in

compari-son with system B. Figs. 29-31 show the variation of moments versus wave direction. Fig. 32 shows the longitudinal distributions of moments. As the

16 20 E E to E to 5 b) Horizontal 10'-X = 11 2 __1 35 -. 0 4 c) Torsional 2-X=1 12.5 135 157.5V 90 180 0 4 5 6 7 8 9 10 A rn 180rn 90 6 7 A (rn) X = 1 57 5 1 80 I 35 10

Fig. 26 Vertical and Horizontal Bending Moments and Torsional

Moment at Point A of System D

F=O, H/x1/85

wave length becomes shorter, the position of the maximum peak of the horizontal and vertical

bend-ing moments goes forward. However, it is not the case for the torsional moment.

Systems F1 and F2

Figs. 33 a) and b) show the pitching response and vertical bending moment acting on the connecting rod of system F1 in head sea (x= 180°). The pitch-ing response of system F1 is less than that of either one of the pusher only or two parallel barges only. Fig. 34 a) shows the pitching response in head sea measured on the pusher of system F2 keeping the relative pitching motion between pusher and barges free by a special hinge. It shows that the pitching

a Vertical E E to2 o ₄ ₅ 6 7 8 A rn 20- 15-10 / s- ...'

x

° c) Torsional 3 o

f,

1

_/ / .._

135/ ,/

'--' / ,'157.5 / / / /

Fig. 27 Vertical and Horizontal Bending Moments and Tsjona!

Moment at Point B of System D

FC, Hw/À1/5

Japan Shipbuilding & Marine Engineering

7 10 A (m) 9 10 o

04

7 8 A 10 1 80 go. 5 7 8 9 lo Am X-112.5 a) Vertical b) Horizontal 1 38' 180' 90

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20 E 10 o o a Vertical a Point C X 180 4 5 b Horizontal ___X=135 _- ___o--1575 March 1969 4 5 6 7 8 A (ml ci Torsional 1- -- ro-I 125 - 90 10 A Im I 80 90 X= 1 125 '

-Fig. 28 Vertical and Horizontal Bending Moments and Torsional

Moment at Point C of System U F=0, H/A=1/85

response of system F2 is considerably greater than

that of system F1, where the relative pitching motion was fixed by a rigid rod. Fig. 34 b) shows the

longi-tudinal and vertical forces acting on the connecting hinge of system F2 in head sea.

In Waves H/Àl/85

In Waves Hw/A=l/70

20

E

Io

Table 4 Maximum Values Experienced during Turning and in Waevs

X

Fig. 29 Vertical Bending Moment of System D vs. Heading

Angle to Wave F =0

17

B Fm=0 23 kg-m (500 ton-m) 9 kg-m (195 ton-m) 1.8 kg-m (39 ton-m)

JI F0=0. 12 25 kg-m (545 ton-m) 8.7 kg-m (190 ton-m) 2 kg-m (43.5 ton.m)

D F00

39 kg-m (850 ton-m) 23 kg-m (500 ton-m) 3.2 kg-m (70 ton-m)

F1 F5=0 10 kg-m (220 ton-m)

System Vertical Bending_{Mom en t} Horizontal Bending_{Momen t} Torsional Moment

Turning 6=35° B 6.5 kg-m (140 ton-m) 2.6 kg-m (56.5 ton-m) D 7. 5 kg-m (165 ton-m) 2 kg-m (43.5 ton-m) 80 100 120 140 160 180 b Point B X 40 t' 30 10 E na 20 IO o 80 100 120 140 160 l80 X 10 c Point A o 4 5 6 7 A Im 20 E IO O 10 E 3 E

Vertical Force Horizontal Force

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18 10 o 20 15 10 5 o E O & Point C c Point A X

Fig. 30 Horizontal Bending Moment of System O vs.

Heading Angle to Wave F, =0

Summary of Test Results

Maneuvering Qualities

I) The steering quality of system B is better than that of system D, however, the course-keeping

quality of system B is worse titan that of system D. Concerning tite maneuvering quality, the one

side pushing system (as system C) is not so differ-ent from the cdiffer-enter pushing system (as system D). Drift angle (or side slip) of system D (luring

turn-ing is very large and tite pivoting point is

forward of tite stem.

Rolling and Pitching Responses

Generally speaking, tile rolling and pitching

re-sponses of tite system connected rigidly by rod is

0 E a' Point C c B O b Pouit B 120 140 X 160 180rn

Japan Shipbuilding & Marine Engineering

80 1LI0 120 140 160 180rn

X

Fig. 31 Torsiona! Moment of System O vs. Heading

Angle to Wave I =0

smalier than that of either tite pusher only or barge

only. In case of the system connected by hinge

as system F2 making free tite relative pitching motion,

the pitching response often becomes greater titan

that of either tite pttsiter only or barge only.

Moments on Connecting Rod

i) Tite vertical bending moment by the pitching motion is very large, therefore, it is not practical to make tite connection compietely rigid art(l

restrict the relative pitching motion. If the rela-tive pitching motion is made free completely,

however, the abovemenuoned pitenontenon (Roll-ing and Pitch(Roll-ing Responses) of increased pitch(Roll-ing

niotion will appear.

2) The horizontal bending moment of system D is

also very large. Tite relative yawing motion, however, must be restricted to a certain extent in ordei- to control tite system.

80 100 120 140 160 180 X c Point A 2í-A 80 1 00 120 140 160 I 80 X 80 1 00 _.120 140 160 i 80 E2 00 o 100 80 80 100 b Point B 120 140 160 180 X

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S) When tite system is turning in waves, moments on tite connecting materials will become exceed-ingly large, as tite moment clue to turning will be added to moments due to waves.

1) _{If there are some gaps in the connecting} mechan-ism, an unexpected large impulsive force will act on it, though it was not studied in this test.

E

20

a) Vertical Bending Moment X I 80

A

Ic-cI Torsional Moment X I35

b: Horizontal Bending Moment X --135

Fig. 32 Distribution of Bending and Torsional Moments of System D March 1969 1.4 1.2 1 .0 0.8 0.6 0.4 0.2 0 1 2 4 5 A rn b Vertical Bending Moment

10- L Jc.

/

8 6 4 2 o a Pitching Response Pusher Only

/

30m Barge 2 -- Parallel / cu' F System 3 A im: 19 8 6 b Forces f.. (+) l_ -/ pl It .4 z5 2 o y_\ / 2 3 A 'n

Fig. 34 Pitching Response and Forces of System F2

F5 =0, Jhs/A_{=1/70, x=180}

5) The maximum values experienced in _this _test

during turning and in waves are shown in Table

4. _{Values in the bracket are shown in tite scale}

of actual ship. \1\Then these data are utilized to

tite design of connecting system, tite cliflerence

be-tween the connecting method of model and ac-tual ship must be carefully considered.

o ₂ 3 4

A rn

Fig. 33 _{Pitching Response and Vertical Bending Moment of} System _{F1 F=Q JJ/A=l/7O, X=18°} a Pitching Response 5 5 1 .4 1.2 1 .0 0.8 0.6 0.4 0.2