547

1 INTRODUCTION

A port operator uses tugboats with a certain number

and capacity for berthing and un-berthing vessel

based on the requirements released by the regulator.

The Indonesian Ministry of Transportation

determined the tugboats based on the ships' length.

The total number of tugboats and their bollard pull

provided by the operator depends on the maximum

number of vessels and their main dimensions handled

at the same operation time. A high-risk corporation

has considered providing tugboat capacity to

accommodate emergency conditions where two ships

should be un-berthed simultaneously at the maximum

environment disturbance forces.

Hundreds of vessels avoid voyaging and staying

in the anchorage area of Tanjung Perak Port in

extreme wind, current, and wave conditions. In the

other case, the vessel should immediately un-berth

from the jetty in an emergency. Emergencies may

occur due to a fire in the port area, a tsunami, or other

incidents and natural disasters. The Indonesian

Council of Meteorology, Climatology, and Geophysics

predicted an earthquake of 8.7 R and a tsunami of 29

m could

occur in East Java. The same disaster can

crash West Java in Sunda Strait with about the same

intensity, 8.7 R and 30 m. The impact of the disasters

can reach the North Coast of Java Island

, including

Jakarta and Surabaya.

The safety of ship handling has been widely

investigated by researchers. It is still an interesting

topic of research that relates to several issues and

regulations. A study using maneuvering simulation in

heavy weather found that the safe ship-handling limit

of the Energy Efficiency Design Index (EEDI) power

ship is one level below the conventional engine power

ship (Nishizaki et al., 2019). The criteria applied to

Simulation Study on the Influence of Tugboats Capacity

on the Safety of Simultaneous Emergency Un

-berthing

I.P.S. Asmara

, K. Abdullah

, M.A. Mustaghfirin

& C.A. Firmansyah

Shipbuilding Institute of Polytechnic Surabaya, Surabaya, Indonesia

PT Terminal Petikemas Surabaya, Surabaya, Indonesia

ABSTRACT: This paper simulated a simultaneous un-berthing of two container ships. The simulation was

intended to determine the number and capacity of tugboats considering an emergency situation in a port. A

port provides the number and capacity of tugboats based on the regulation of the Transportation Ministry. In an

emergency condition at the terminal and the maximum environmental conditions of wind, wave, and current,

the vessel should be un-berthed simultaneously. In this study, two container ships are un-berthed

simultaneously in eight scenarios. The available tugboats are simulated using the MMG model to pull the

vessels from the jetty turn them in the approaching channel and pass the main channel to achieve the anchorage

area. The trajectories of maneuvering using the existing tugs are compared to the normal passage using the

appropriate capacity of tugboats. The number and capacity of the tugboat to comply with the safety criteria and

avoid collision between the un-berthed ships is proposed.

http://www.trans

nav.eu

the

International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 18

Number 3

September 2024

DOI: 10.12716/1001.18.03.0

548

determine the limit of the Beaufort scale were the

speed course and trajectory.

Discrete distance was introduced by Inoue (Inoue

et al., 2013) to evaluate the safety of berthing

maneuvers in case the vessel should be turned before

being berthed on the dock. Considering the

correlation between the distance of the ship to the

quay and the corresponding speed at the position, the

study proposed that the threshold of the normal area

for the turning maneuver is 0.56L, where L is the ship

length. The effect of crosswind on the increasing

number of tugboat capacities considering the

potential area of water for maneuvering in the second

berthing scheme, the scheme of turning before

berthing (Inoue et al., 2013), has been found by using

the Maneuvering Mathematical Modeling Group

(MMG) (Hejun et al., 2021).

In this study, the authors evaluate the required

number and capacity of tugboats to assist in the

emergency un-berthing maneuver of container ships

in the Container Terminal of Surabaya. Firstly, the

simulation scenario involved un-berthing using the

capacity of tugboats as required by regulation.

Secondly, the simulation predicted the required

capacity of tugboats under the maximum conditions

of the environmental disturbance forces. The

outcomes of the two simulations were analyzed and

compared to determine the capacity of the tugboats if

the maneuvering of two vessels was simultaneous.

The simultaneous un-berthing consists of eight

scenarios based on the disturbance directions and

berthing positions.

2 METHODS

The un-berthing simulation developed in this study

refers to the 3-Degrees of Freedom (3-DOF)

Mathematical Maneuvering Group (MMG) model

(Yasukawa and Yoshimura, 2015) and the

hydrodynamic force database for maneuvering

prediction of vessels with the block coefficient (CB) of

between 0.51 and 0.65 (Yoshimura and Masumoto,

2011). The coefficient block of container ships is 0.57

to 0.66 (Charchalis, 2018). The model expressed in

Equations 1 to 3 consists of environmental

disturbances and tugboat assistance.

( )

x ym G H P R A T

mmummvrmxrXXXXX+ −+ − = ++++



(1)

( )

(

)

ym x G H R A T

mmv mmurmxrY Y Y Y+ ++ + = +++



(2)

( )

zz zz G G m H R A T

I J mx r mx v ur N N N N

++ + += +++



(3)

In the equations, m is the ship’s mass and I

zz is the

moment of inertia for yawing motion. The added

mass for surge and sway and added moment of

inertia is represented by m

x, my, and Jzz, respectively. u,

m, and r represent surging velocity, swaying velocity

at the mid-ship, and yawing rate, respectively. The x

is the longitudinal center of gravity of the ship from

mid-ship. X, Y, and N denote surging force, swaying

force, and the yawing moment around mid-ship,

respectively. Subscript H, P, R, A, and T denote the

ship’s hull, propeller, rudder, wind, and tugs,

respectively. β, δ, and ψ denote the drift angle, rudder

angle, and the ship’s true heading, respectively.

The hull forces and moments are calculated using

Equations 4 to 6. This study adopts the approximation

of the hydrodynamic derivatives based on the ship’s

main dimension published by Taimura (Taimuri et al.,

2020), adopting the rapid estimation from several

publications, including (Norrbin, 1970), (Kijima et al.,

1990), (Brix, 1993) and (Yoshimura and Masumoto,

2011).

( )

' ' 2 ' ' ' '2 ' '4 2

H vv vr m rr vvvv m

X R X v X v r X r X v LdU

′

= −+ + + +

(4)

( )

' ' ' ' '3 ' '2 ' ' '2 ' '3 2

H v m r vvv m vvr m vrr m rrr

Y Yv YrYv YvrYvr Yr LdU

= ++

′

(5)

( )

' ' ' ' '3 ' '2 ' ' '2 ' '3 2 2

H v m r vvv m vvr m vrr m rrr

N Nv NrNv NvrNvr Nr LdU

= ++ +

′

(6)

In equations 4 to 6, ρ denotes the water density,

and L, d, and U denote the ship’s length between

perpendiculars, ship draft, and resultant speed,

respectively.

LdU

and

L dU

are non-

dimensional force and non-dimensional moment,

respectively.

The wind forces and moments acting on the ship

and affecting the ship’s maneuvering are calculated

based on a constant and uniform wind (Yasukawa

and Sakuno, 2020). This simulation used non-

dimensional time-averaged wave-induced steady

forces and a yaw moment. Forces and moments due

to tugboats and currents are referred to in another

paper (Putu Sindhu Asmara and Husodo, 2022).

3 RESULTS AND DISCUSSIONS

3.1 Subject Ship

The subject ship trained in the simulation is a

container ship with a capacity of 4300 TEUs, as seen in

Table 1. The vessel is the maximum capacity of the

vessel berthed in the Surabaya Container Terminal

derived from Automatic Identification System (AIS)

data. The same dimension of the vessel is assumed to

be un-berthed at the same time in the Jetty called Jetty

1 and Jetty 2.

Table 1. Ship Dimensions

________________________________________________

LOA DWT Capacity Beam Draught Block

(m) (t) (TEUs) (m) (m) Coefficient

________________________________________________

262.08 51693 4300 32.25 12 0.65

________________________________________________

3.2 Environmental Disturbances and Scenarios

The water depth is 15 m, and according to data from

the Meteorology, Climatology, and Geophysics

Council in Tanjung Perak Station, the high current

speed is up to 0.87 m/s, the low tide is -1.2 m, and the

high tide is 0.6 m. Accordingly, the water depth at

high tide is 15.6 m, and at low tide is 13.8 m. The

549

maximum wind conditions for the un-berthing

maneuver is 30 knots with a maximum wave height of

1.5 m for a period of 6 seconds, as seen in Table 2. The

water depth of the turning basin is 15 m. The vessels

were berthed in eight scenarios by the starboard side

or port side and environmental condition 1 or

condition 2, as seen in Table 3.

Table 2. Environmental Conditions

________________________________________________

Environmental Condition Condition 1 Condition 2

________________________________________________

Maximum wind speed (knots) 30 (NW to SE) 30 (NW to SE)

Maximum wave Hs: 1.5 m T: 6s Hs: 1.5 m T: 6s

Maximum current velocity (m/s) 0.87 (East to 0.87 (West to

West) East)

Maximum tidal (m) 0.6 (High Tide) -1.2 (Low Tide)

Water Depth (m) 15 15

________________________________________________

Table 3. Scenarios by Environmental and Ship Condition

________________________________________________

Sce Environmental Ship and condition

nario Condition

________________________________________________

1 Wind 30 knots from Jetty 1: Starboard – 4300 TEUs – Laden

NW (315°) Jetty 2: Starboard – 4300 TEUs – Laden

2 Wave 1.5m, 6s from Jetty 1: Port Side – 4300 TEUs – Laden

NW (315°) Jetty 2: Port Side – 4300 TEUs – Laden

3 Current 0.87 m/s to Jetty 1: Port Side – 4300 TEUs – Laden

W (270°) Jetty 2: Starboard – 4300 TEUs – Laden

4 Jetty 1: Starboard – 4300 TEUs – Laden

Jetty 2: Port Side – 4300 TEUs – Laden

________________________________________________

5 Wind 30 knots from Jetty 1: Starboard – 4300 TEUs – Laden

NW (315°) Jetty 2: Starboard – 4300 TEUs – Laden

6 Wave 1.5m, 6s from Jetty 1: Port Side – 4300 TEUs – Laden

NW (315°) Jetty 2: Port Side – 4300 TEUs – Laden

7 Current 0.87 m/s to Jetty 1: Port Side – 4300 TEUs – Laden

E (95°) Jetty 2: Starboard – 4300 TEUs – Laden

8 Jetty 1: Starboard – 4300 TEUs – Laden

Jetty 2: Port Side – 4300 TEUs – Laden

________________________________________________

3.3 Acceptance Criteria

The acceptance criteria for the success of the

simulations are:

1. At the first stage of the un-berthing maneuver, the

vessel should be pulled parallel to the jetty for a

distance of at least 100 m. This is determined based

on the discussion with a port pilot.

2. The vessels should not be out of the waterway to

avoid collision in the anchorage area.

3. The distance between two vessels is not less than

0.89L, where L is the ship length (Inoue et al.,

1994).

The status of maneuvering is successful if all

criteria are fulfilled. If, in the first stage, all tugboats

use out of full power (more than 85% of the maximum

BP, Bollard Pull), the status is marginal, although all

criteria are fulfilled.

3.4 The Capacity of Tugboats

Government regulation regarding the capacity of

tugboats to serve berthing and un-berthing maneuver

of the vessels having a length of more than 250 m is

the total bollard pull of 125 t. In normal conditions,

the vessel was served by 3 tugboats with a maximum

of 45 tons of bollard pull, each.

3.5 Maneuvering Steps

The vessel should leave the port area through the

West Part of the Surabaya Waterway. The centerline

of the channel is presented as two straight lines as

seen in Figure 1. The two red spot in the figure are the

position of the red buoy as the boundary area and the

separation between the channel and the anchorage

area. In the case of berthing on the starboard side, the

first step of the un-berthing maneuvering is to pull

out the vessel parallel to the jetty. The second is to

turn the vessel, and the third is to follow the

waterway. In the case of berthing on the port side, the

second step isn’t applicable.

3.6 Maneuvering Validation

The maneuvering simulator was validated using the

trajectories of Pure Car Carrier (PCC) having a

coefficient block of 0.54 [I.P.S. Asmara, 2015]. In this

paper, the simulation program is added by the force

and moment generated by the bollard pull of

tugboats. The surging force, swaying force, and

yawing moment due to the tugboats are presented by

XT, YT, and NT, respectively in equations 1 to 3.

3.7 Simulation Outcomes

In scenario 1, the vessel berths on the starboard side.

Figure 1 shows the three tugboats with a capacity of

45 tons bollard pull succeed to pull out and turn the

vessel, and avoid entering the anchorage area. The

output of maneuvering is presented by figures

plotting the vessel every 30 seconds, showing the

position and the heading. The outcome of this

scenario using 3 tugboats is marginal due to the

capacity of all tugboats delivered to the vessel being

100% of the maximum bollard pull as presented in

Table 4.

500 1000 1500 2000 2500 3000 3500 4000

500

1000

1500

2000

2500

3000

3500

Jetty TTL

Jetty TPS

WIND: 30 knots, WAVE: Hw1.5m,6s from 315

(North West)

CURRENT: 0.87 m/s to 270

(West)

UNBERTHING - HIGH TIDE - LADEN DRAUGHT: 12 m

WATER DEPTH: 15.6 m, TUGBOATS: 3X45 (Jetty-1), 3X45 (Jetty-2) tons

Figure 1. Un-berthing Trajectory of Scenario 1 using 3

Tugboats

550

500 1000 1500 2000 2500 3000 3500 4000

500

000

500

000

500

000

500

Jetty TTL

Jetty TPS

WIND: 30 knots, WAVE: Hw1.5m,6s from 315

(North West)

CURRENT: 0.87 m/s to 270

(West)

UNBERTHING - HIGH TIDE - LADEN DRAUGHT: 12 m

WATER DEPTH: 15.6 m, TUGBOATS: 4X45 (Jetty-1), 4X45 (Jetty-2) tons

Figure 2. Un-berthing Trajectory of Scenario 1 using 4

Tugboats

500 1000 1500 2000 2500

(s)

(knots)

SPEED

0 500 1000 1500 2000 2500

(s)

-100

100

(deg)

HEADING

-3000 -2000 -1000 0 1000

(m)

500

1000

(m)

TRAJECTORY

Figure 3. Berthing Speed, Heading, and Trajectory in

Scenario 1 using 4 Tugboats

500 1000 1500 2000 2500 3000 3500 4000

500

1000

1500

2000

2500

3000

3500

Jetty TTL

Jetty TPS

WIND: 30 knots, WAVE: Hw1.5m,6s from 315

(North West)

CURRENT: 0.87 m/s to 270

(West)

UNBERTHING - HIGH TIDE - LADEN DRAUGHT: 12 m

WATER DEPTH: 15.6 m, TUGBOATS: 3X45 (Jetty-1), 3X45 (Jetty-2) tons

Figure 4. Un-berthing Trajectory of Scenario 2 using 3

Tugboats

Figure 3 shows the speed, heading, and trajectory

of the vessel in this scenario using 4 tugboats. By

using 4 tugboats, the outcomes are successful, as seen

in Figure 2 and Table 5 which show the passage is in

the waterway and the force delivered by the tugboats

is 85%. The additional tugboat is able to result in the

improvement of the heading of the vessel at the end

stage of maneuvering.

In scenario 2, the vessel berths on the port side.

Figure 4 shows the three tugboats able to pull out the

vessel. The capacity of all tugboats delivered to the

vessel is 100% of the maximum bollard pull as

presented in Table 6. Table 6 shows the tugboat

element for un-berthing from Jetty 2. The period of

the first step is 900 s for Jetty 2 and 1200 s for Jetty 1.

The interval of 300 s is intended to keep a safe

distance between the vessels. The outcome of this

scenario using 3 tugboats is marginal.

By using 4 tugboats, the passage of the vessel is

closer to the centerline of the waterway, as seen in

Figure 5. The figure shows the vessel drifted at the

beginning of the maneuvering. The phenomenon can

be avoided by releasing the mooring line after the

tugboats are ready to pull out of the vessel. Table 7

shows the force delivered by the tugboats is 85%. The

interval period between the maneuvering in Jetty 1

and Jetty 2 in the first step is 100 s.

500 1000 1500 2000 2500 3000 3500 4000

500

1000

1500

2000

2500

3000

3500

Jetty TTL

Jetty TPS

WIND: 30 knots, WAVE: Hw1.5m,6s from 315

(North West)

CURRENT: 0.87 m/s to 270

(West)

UNBERTHING - HIGH TIDE - LADEN DRAUGHT: 12 m

WATER DEPTH: 15.6 m, TUGBOATS: 4X45 (Jetty-1), 4X45 (Jetty-2) tons

Figure 5. Un-berthing Trajectory of Scenario 2 using 4

Tugboats

In scenario 3, the vessel berths on the port side in

Jetty 1 and on the starboard side in Jetty 2. The

simultaneous un-berthing maneuver in this scenario

leads to an accident of ship-to-ship collision, as seen

in Figure 6. The tugboats should handle the un-

berthing maneuver in a sequential method.

500 1000 1500 2000 2500 3000 3500 4000

500

1000

1500

2000

2500

3000

3500

Jetty TTL

Jetty TPS

WIND: 30 knots, WAVE: Hw1.5m,6s from 315

(North West)

CURRENT: 0.87 m/s to 270

(West)

UNBERTHING - HIGH TIDE - LADEN DRAUGHT: 12 m

WATER DEPTH: 15.6 m, TUGBOATS: 4X45 (Jetty-1), 4X45 (Jetty-2) tons

Figure 6. Un-berthing Trajectory of Scenario 3 using 4

Tugboats

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Table 4. Tugboat Elements for Scenario 1 using 3 Tugboats

___________________________________________________________________________________________________

Step Time Engine Rudder Astern Tug Mid-ship Tug Forward Tug

( s ) Status Angle 45 tons Bollard Pull 45 tons Bollard Pull 45 tons Bollard Pull

Force Direction Force Direction Force Direction

___________________________________________________________________________________________________

1 0–350 Slow 0° - - - - - -

2 350–800 Slow 0° 100%×45t -85° 100%×45t -85° 100%×45t -85°

3 800–2100 Slow 0° 100%×45t 90° 100%×45t 90° 100%×45t -90°

4 2100–2400 Slow 0° 100%×45t -90° 100%×45t -90° 100%×45t 90°

___________________________________________________________________________________________________

Table 5. Tugboat Elements for Scenario 1 using 4 Tugboats

___________________________________________________________________________________________________

Step Time Engine Rudder Astern Tug Quarter Tug Shoulder Tug Forward Tug

( s ) Status Angle 45 tons Bollard Pull 45 tons Bollard Pull 45 tons Bollard Pull 45 tons Bollard Pull

Force Direction Force Direction Force Direction Force Direction

___________________________________________________________________________________________________

1 0–350 Slow 0° - - - - - - - -

2 350–800 Slow 0° 85%×45t -85° 85%×45t -85° 85%×45 t -85° 85%×45t -85°

3 800–2100 Slow 0° 85%×45t 90° 85%×45t 90° - - 85%×45t -90°

4 2100–2400 Slow 0° 85%×45t -90° 85%×45t -90° - - 85%×45t 90°

___________________________________________________________________________________________________

Table 6. Tugboat Elements for Scenario 1 using 4 Tugboats in Jetty 2

___________________________________________________________________________________________________

Step Time Engine Rudder Astern Tug Mid-ship Tug Forward Tug

( s ) Status Angle 45 tons Bollard Pull 45 tons Bollard Pull 45 tons Bollard Pull

Force Direction Force Direction Force Direction

___________________________________________________________________________________________________

1 0–900 Off 0° 100%×45t 160° 100%×45t 160° 100%×45t 160°

2 900–3000 Slow 0° 85%×45t -155° - - 85%×45t 25°

___________________________________________________________________________________________________

Table 7. Tugboat Elements for Scenario 2 using 4 Tugboats in Jetty 2

___________________________________________________________________________________________________

Step Time Engine Rudder Astern Tug Quarter Tug Shoulder Tug Forward Tug

( s ) Status Angle 45 tons Bollard Pull 45 tons Bollard Pull 45 tons Bollard Pull 45 tons Bollard Pull

Force Direction Force Direction Force Direction Force Direction

___________________________________________________________________________________________________

1 0–900 Off 0° 85%×45t 160° 85%×45t 160° 85%×45t 160° 85%×45t 160°

2 900–3000 Slow 0° 85%×45t -155° - - - - 85%×45t 25°

___________________________________________________________________________________________________

Table 8. Tugboat Elements for Scenario 5 using 3 Tugboats

___________________________________________________________________________________________________

Step Time Engine Rudder Astern Tug Mid-ship Tug Forward Tug

( s ) Status Angle 45 tons Bollard Pull 45 tons Bollard Pull 45 tons Bollard Pull

Force Direction Force Direction Force Direction

___________________________________________________________________________________________________

1 0–700 Off 0° 100%×45t -160° 100%×45t -160° 100%×45t -160°

2 700–2700 Slow 0° 100%×45t 90° 100%×45t 0° 100%×45t -90°

___________________________________________________________________________________________________

Table 9. Tugboat Elements for Scenario 6 using 3 Tugboats

___________________________________________________________________________________________________

Step Time Engine Rudder Astern Tug Mid-ship Tug Forward Tug

( s ) Status Angle 45 tons Bollard Pull 45 tons Bollard Pull 45 tons Bollard Pull

Force Direction Force Direction Force Direction

___________________________________________________________________________________________________

1 0–600 Slow 0° - - 85%×45t 90° 85%×45t 30°

2 600–1600 Slow 0° 85%×45t -160° - - 85%×45t 20°

___________________________________________________________________________________________________

Table 10. Summary of the Maneuvering Outcome

___________________________________________________________________________________________________

Scenario Tug deployment Outcome Scenario summary

___________________________________________________________________________________________________

1 Jetty 1: 3x45 tons BP Jetty 1: Marginal Un-berthing from Jetty 1: Comply with all criteria

Jetty 2: 3x45 tons BP Jetty 2: Marginal Un-berthing from Jetty 2: Comply with all criteria

2 Jetty 1: 3x45 tons BP Jetty 1: Marginal Un-berthing from Jetty 1: Comply with all criteria

Jetty 2: 3x45 tons BP Jetty 2: Marginal Un-berthing from Jetty 2: Comply with all criteria

3 Jetty 1: 3x45 tons BP Jetty 1: Failure Un-berthing from Jetty 1: Not comply with criteria 3

Jetty 2: 3x45 tons BP Jetty 2: Failure Un-berthing from Jetty 2: Not comply with criteria 3

4 Jetty 1: 3x45 tons BP Jetty 1: Marginal Un-berthing from Jetty 1: Comply with all criteria

Jetty 2: 3x45 tons BP Jetty 2: Marginal Un-berthing from Jetty 2: Comply with all criteria

5 Jetty 1: 3x45 tons BP Jetty 1: Marginal Un-berthing from Jetty 1: Comply with all criteria

Jetty 2: 3x45 tons BP Jetty 2: Marginal Un-berthing from Jetty 2: Comply with all criteria

6 Jetty 1: 3x45 tons BP Jetty 1: Successful Un-berthing from Jetty 1: Comply with all criteria

Jetty 2: 3x45 tons BP Jetty 2: Successful Un-berthing from Jetty 2: Comply with all criteria

7 Jetty 1: 3x45 tons BP Jetty 1: Marginal Un-berthing from Jetty 1: Comply with all criteria

Jetty 2: 3x45 tons BP Jetty 2: Marginal Un-berthing from Jetty 2: Comply with all criteria

8 Jetty 1: 3x45 tons BP Jetty 1: Marginal Un-berthing from Jetty 1: Comply with all criteria

Jetty 2: 3x45 tons BP Jetty 2: Marginal Un-berthing from Jetty 2: Comply with all criteria

___________________________________________________________________________________________________

552

In scenario 4, the vessel berths on the starboard

side in Jetty 1 and on the port side in Jetty 2. The

simultaneous un-berthing maneuver in this scenario

can be applied using 3 tugboats, as seen in Figure 6,

but the force delivered by the tugboats is 100% of the

maximum bollard pull.

500 1000 1500 2000 2500 3000 3500 4000

500

1000

1500

2000

2500

3000

3500

Jetty TTL

Jetty TPS

WIND: 30 knots, WAVE: Hw1.5m,6s from 315

(North West)

CURRENT: 0.87 m/s to 270

(West)

UNBERTHING - HIGH TIDE - LADEN DRAUGHT: 12 m

WATER DEPTH: 15.6 m, TUGBOATS: 3X45 (Jetty-1), 3X45 (Jetty-2) tons

Figure 7. Un-berthing Trajectory of Scenario 4 using 3

Tugboats

Figure 8 shows the 3 tugboats able to serve the

simultaneous maneuvering scenario 5. In the first

step, the vessel tends to drift and succeeds in pulling

out and turning to the West heading. The vessel is

also not out of the waterway. Table 7 shows the

tugboats delivered 100% of the maximum bollard

pull.

500

1000 1500 2000 2500 3000 3500 4000

500

1000

1500

2000

2500

3000

3500

Jetty TTL

Jetty TPS

WIND: 30 knots, WAVE: Hw1.5m,6s from 315

(North West)

CURRENT: 0.87 m/s to 95

(East)

UNBERTHING - LOW TIDE - LADEN DRAUGHT: 12 m

WATER DEPTH: 13.8 m, TUGBOATS: 3X45 (Jetty-1), 3X45 (Jetty-2)tons

Figure 8. Un-berthing Trajectory of Scenario 5 using 3

Tugboats

In scenario 6, the existing tugboat successfully un-

berth the 2 container ships simultaneously, as seen in

Figure 9, and the force delivered by the tugboat is

85%, as presented in Table 9.

Scenario 7 and scenario 8 are a combination of

scenario 5 and scenario 6. The maneuvers comply

with all the criteria, but the bollard pull delivered to

the vessel is more than 85%, so the outcomes of the

maneuvers are marginal.

500 1000 1500 2000 2500 3000 3500

4000

500

1000

1500

2000

2500

3000

3500

Jetty TTL

Jetty TPS

WIND: 30 knots,WAVE: Hw1.5m,6s from 315

(North West)

CURRENT: 0.87 m/s to 95

(East)

UNBERTHING - LOW TIDE - LADEN DRAUGHT: 12 m

WATER DEPTH: 13.8 m, TUGBOATS: 3X45(Jetty-2), 3X45 (Jetty-1) tons

Figure 9. Un-berthing Trajectory of Scenario 6 using 3

Tugboats

Table 10 shows the summary of the outcome of the

simulation for 8 scenarios. Based on the 8 scenarios,

the probability of existing tugboats successfully or

unsuccessfully performing the maneuvering

simultaneously is 12.5%. The probability of marginal

status is 75%, and this outcome can be improved by

using four tugboats for each jetty. Based on the

outcome summary, the government requirement on

the number of tugboats is not appropriate to provide

an emergency response to maritime transportation.

One additional tugboat should be provided in the

port.

4 CONCLUSIONS AND FUTURE WORKS

In this study, the authors conducted a simulation of

the un-berthing using the MMG model in heavy

weather. The number and capacity of tugboats

required based on the regulation were applied in the

simulation, and the probability of successfully un-

berthing the vessel was determined based on a case

study implemented in a container terminal using 8

scenarios. The study found that the probability of

success or failure is the same, 12.5%, and the status of

marginal is 75%. The probability of success can be

improved up to 87.5% by using additional tugboats.

The failure probability of simultaneous un-berthing is

the potential of ship-to-ship collision. In this case

study, the success status is for scenario 6 and the

failure status is for scenario 3. The hazard of scenario

3 can be mitigated by implementing sequential un-

berthing.

ACKNOWLEDGMENTS

The authors wish to deliver acknowledgments to The

Program of Domestic Applied Science Research for

Vocational Lecturers funded by RISPRO LPDP for the

encouragement and financial support with the Research

Contract No. 0765/D6/KU.04.00/2021 to accomplish and

publish this study. The authors also wish to acknowledge

the Surabaya Container Terminal for its cooperation in this

research.

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