563
1 INTRODUCTION
Indonesia is a commodity for sea transportation
where the economic sector through loading and
unloading is done chiefly at sea because it is more
efficient and cheaper as well as transportation from
one island to another island, therefore the government
has launched a program that can provide overall
welfare to its people through shipbuilding programs.
Perintis in several shipyards as a supporter of sea
transportation commodities in Indonesia.
Perintis ships are one of the sea transportations
that are highly relied upon by people living on remote
islands and borders because there are no other types
of transportation operating in these areas. Without a
Perintis ship, the economic veins in the region will be
disrupted, where this ship can carry passengers up to
500 people and can accommodate cargo for the needs
of remote communities, and also functions as a liaison
for islands that have category 3TP with larger ports
[1].
The ship used in this study is a Perintis ship with a
type of 1200 GT, which uses a transverse construction
system because the ship's structure does not have an
elongated bulkhead, which is construction braces are
installed using steel pipe pillars.
To regulate all forms of activities in the Indonesian
sea transportation sector, regulations are issued
directly by BKI (Ship Classification Bureau), where
BKI is a state-owned business in charge of issuing
rules and regulations in the sea sector in Indonesia,
including shipping, offshore buildings, and others
related to the Indonesian sea sector to ensure the
safety of Indonesian-flagged vessels and offshore
Analysis of Effect of Pillars Position on
Longitudinal Strength in Perintis Ship Structure
Type 1200 GT
H. Yudo, H.Z. Abdillah & A.F. Zakki
Diponegoro University, Semarang, Jawa, Indonesia
ABSTRACT: Perintis ships are sea transportation highly relied upon by the people in remote, frontier,
underdeveloped, and border islands, considering the absence of other types of vehicle operating in the area.
Perintis Ships can carry up to 500 people and connect islands categorized as 3TP with larger ports. This ship
will be analyzed in longitudinal strength with variations in pillar positions. The analysis results will be
compared, and whether the research results allowed the BKI regulatory standards. The maximum stress value
produced by the variation without pillars is 21.76 N/m2 in calm water conditions, 41.19 MPa in sagging
conditions, and 10.67 MPa in hogging conditions. The variation of the pillars on the side is 21.95 MPa in calm
water, 41.54 MPa in sagging conditions, and 10.76 MPa in hogging Conditions. The variation of the pillar in the
middle obtained maximum stress 21.96 MPa in calm water conditions, 41.55 MPa in sagging conditions, and
10.77 MPa in hogging conditions. Of all the variations, it has met the criteria of the BKI regulations, where the
allowable stress is not to exceed 140.14 MPa. From the analysis that has been done, it can be concluded that the
position of the pillar laying does not significantly affect the longitudinal strength of the ship.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 16
Number 3
September 2022
DOI: 10.12716/1001.16.03.19
564
structures located both domestically and
internationally [2].
So in this research, the calculation of the structure
construction on the Perintis ship 1200 GT was carried
out according to the rules and regulations that have
been regulated by the Indonesian Classification
Bureau (BKI) in Volume II Rules for Hull 2018, which
determines the ship’s maximum stress and allowable
stress when the water conditions are calm, sagging,
and hogging.
In previous studies, many analyses were carried
out, including variations in the structure of ship
construction, such as the results of stress from
changes in ship length, variations in longitudinal
construction systems, and transverse and mixed
construction. therefore is also research on changes in
the distance of the tusks on the ship to the results of
the maximum stress received by the ship. Has met the
Allowable stress from the Indonesian Classification
Bureau in Volume II Rules for Hull 2018 [3].
In this study, an analysis was made of the
variation of the influence of the position of the pillar
or reinforcement on the ship's hull to the maximum
stress that occurs when the calm water, sagging, and
hogging occurs on the 1200 GT Perintis ship.
The purpose of doing this research from the
explanation above is as follows:
1. To determine the pillars’ effect on the stresses in the
structure of the 1200 GT Perintis ship.
2. Knowing the efficient laying of pillars on the
structure of the 1200 GT Perintis ship.
3. Get the maximum response value on the stress of
hogging, sagging, and calm water from the three
variations of the ship structure.
2 METHOD
2.1 Object of Research
The object of this research is the 1200 GT Perintis ship
which has the following main sizes:
Tabel 1. Main Dimension of Ship
_______________________________________________
Data
_______________________________________________
Material Steel
Loa 62.8 m
Lpp 57.36 m
Breadth 12.0 m
Height 2.7 m
Main Deck Height 4.0 m
Coefficient Block 0.663
Speed 12 knots
Engine power 2 x 1000 HP
Frame distance 0.6 m
_______________________________________________
Figure 1. Lines plan
Figure 2. Profile Construction
Figure 3. Midship Section
2.2 Research Variable
In this study, the author will make variations of the
pillar position with a size of Ø4 inches above the main
deck and Ø5 inches above the double bottom in
565
Perintis ship construction. The variations in the
position of the pillars analyzed are:
1. Ship construction without pillars
2. Pillar construction in the middle/above the center
girder
3. Pillar construction on the side/above the side girder
and analysis of the maximum stress at the time of
the ship's condition.
4. Calm water
5. Sagging
6. Hogging
This research has a limitation: the structure of the
ship's construction has not been changed, such as the
dimension of the profile and the plate, only the laying
of the pillars.
Figure 4. Details of the pillar structure
Figure 5. Variations without pillars
Figure 6. Variations of the pillar in the middle
Figure 7. Variations of the pillar on the side
2.3 Determination of Ship Profile Dimension
The size of the profile used in the construction of the
1200 GT Perintis ship is available in the data provided
by the ship's consultant, such as the profile
construction, shell expansion, and midship section,
which will be used as a reference in this study.
2.4 Ship Load Distribution
In calculating the shear force and bending moment of
the ship, which is to first determine the distribution of
gravity along with the ship by distributing this
weight, this is part of the load that will cause bending
moment, which is the result of the sum of the weight
distribution of the empty ship (LWT) with the weight
of the cargo, supplies, crew, passengers, fuel,
lubricants, fresh water, and others (DWT) which is the
total weight when the ship is sailing [4].
After that, determine the buoyancy of the ship.
This buoyant force is a reaction from the mass of
water against the ship, which is referred to as a
displacement, where the displacement is equal to the
total mass of the ship, as well as the resultant upward
pressure must be on a vertical line with the resultant
gravity, where the displacement of the ship can be
obtained, from the integration of the longitudinal
direction of the water mass along with the ship
underwater [5].
2.5 Sagging And Hogging Waves
Sagging is a condition where the ship's load is
centered on the center of the ship so that it will cause
the pressure in the middle of the ship to be greater,
which as a result of the shape of the ship will curve
downwards while sagging can also occur because of
the two crests of the waves, namely at the front and
the back of the ship so that will cause the upward
force on the ship at the tip to be greater in value,
while at the center of the ship will experience a
greater downward compressive force [6].
566
Figure 8. Sagging and Hogging
Hogging is a condition in which the ship's cargo is
centered on the front and back of the ship, causing
greater pressure at the end of the ship as a result, the
shape of the ship will curve upwards, large in the
middle of the ship, while at the end of the ship will
experience a greater downward pressure [7].
2.6 Finite Element Method
The finite element method is a numerical method that
is suitable to be applied to calculate internal forces in
various cases in the engineering field. The analysis
process is based on the stiffness method presented in
a matrix formulation. The advantage of the finite
element method is its ability to create models from
various geometric shapes of irregular structures and
aspects of nonlinearity in geometry and materials [8].
The finite element method has also become a
commonly used method in engineering where this
method is an analytical method for predicting the
response of a structural system by dividing a
continuous form into several parts with a finite
number, these parts are called elements. Where each
element is connected to a node, then from the
mathematical equation, each element will be a
representation of the results of the model structure [9].
These elements can also be called finite elements
and are linked at several vertices.
2.7 Maximum Stress and Allowable Stress
After the ship's construction structure has been
designed, the structure’s response is analyzed with
static loading using the finite element method when
the vessel is fully loaded in calm water conditions,
sagging and hogging. For the height of the waves at
the time of sagging and hogging formula
20
Lpp
Hw m=
(1)
where :
Hw Wave Height
Lpp Ship Length from AP to FP
Based on the ship structure strength book [10],
where if calculated by Lpp along 57.36 m, then the
height of the sagging and hogging waves is 2.868 m.
The formula for Calculation of Allowed Stress for
ships with a length of fewer than 90 meters according
to BKI regulations is [11]
2
0
N/cs mm
=
(2)
where:
Ship Allowable Stress
0
18,5
L
k
for ships < 90 meters
c 1.0 for area 0,30 ≤
x
L
≤ 0,70
from the calculation formula above, the allowable
stress according to BKI regulations on the 1200 GT
Perintis ship is 140.14 MPa.
2.8 Material Definition
The material used in this research is steel with the
following specifications:
− Modulus of Elasticity: 210000 MPa
− Poisson Ratio: 0.3
− Density: 7850 kg/m
3
− Yield: 235 MPa
− Ultimate Stress: 400 Mpa
2.9 Cross-Sectional Modulus and Moment of Inertia
The modulus calculation is by the BKI Voll II Rules for
Hull 2018 regulation with the formula.
( )
26
min 0
0,7 10 3W k c L B Cb m
−
= +
(3)
where :
Wmin = Minimum Modulus
c0 =10.75-((300-L)/100)1.5
L = Ship Length
K = 1
B = ship width
Cb = coefficient block
The calculation of the moment of inertia is by the
BKI Voll II Rules for Hull 2018 regulation with the
formula.
24
3 10
L
I W m
k
−
=
(4)
where :
I = minimal moment of inertia
L = Ship Length
k = 1
W = Ship's Modulus
3 RESULTS AND DISCUSSION
3.1 Calculation of Ship Load Distribution
The load distribution on the ship is the load from the
mass distribution of the construction and the full load
of the ship, which is distributed at a predetermined
division of each station which will produce bending
moments as a result of the response to the addition of
the mass distribution of the empty ship with the cargo
mass (DWT + LWT) [12].
This calculation begins with finding the total mass
of LWT and DWT on the ship first, where the ship’s
length will be divided into 40 stations first. After that,
the value of the mass distribution at each station can
be seen from these results.
567
After obtaining the total mass on the empty ship of
834.11 tons, the total mass of the DWT of 452.52 tons,
and the mass displacement of the ship is 1286,632
tons.
The ship’s loading can be seen in the graphic chart
figure as follows.
Figure 9. Ship Load Distribution Chart
3.2 Calculation of Shear Force and Bending Moment
At this stage, the 3D model of the existing ship is
divided into 40 stations. This serves to distribute the
load of the current ship as a whole.
Figure 10. Hull in 3D model
Furthermore, the results calculating the load
distribution that have been obtained are entered into
loadcase via software Maxsurf Stability and then
input menu loadcase [13]. Then the moment analysis
is carried out by entering the value of the existing
sagging and hogging wave heights that have been
calculated in formula no 1, which is 2.868 m in each
condition of the ship.
Longitudinal Strength
Mass
Buoyancy
Net Load
Shear
Moment
-40
-30
-20
-10
0
10
20
30
40
-5
0
5
10
15
20
25
30
35
40
45
50
55
60
-100
-75
-50
-25
0
25
50
75
100
-1500
-1200
-900
-600
-300
0
300
600
900
1200
1500
Mass
Buoyancy
Net Load
Shear -99,737
Moment 1395,053
Long. Pos. m
Load t/m
Shear tonne
Moment tonne.m
Longitudinal Strength
Mass
Buoyancy
Net Load
Shear
Moment
Figure 11. Graphs of Calm Water Conditions
From the graph above, the maximum moment that
occurs in calm water conditions is 1394.55 ton.m and
converted into Nm units, namely 13,675,849.81 Nm.
Longitudinal Strength
Mass
Buoyancy
Net Load
Shear
Moment
-40
-30
-20
-10
0
10
20
30
40
-5
0
5
10
15
20
25
30
35
40
45
50
55
60
-0,2
-0,16
-0,12
-0,08
-0,04
0
0,04
0,08
0,12
0,16
0,2
-3
-2,5
-2
-1,5
-1
-0,5
0
0,5
1
1,5
2
2,5
3
Mass
Buoyancy
Net Load
Shear -0,167
Moment 2,639
Long. Pos. m
Load t/m
Shear x10^3 tonne
Moment x10^3 tonne.m
Longitudinal Strength
Mass
Buoyancy
Net Load
Shear
Moment
Figure 12. Graphs of Sagging Conditions
From the graph above, the maximum moment that
occurs in sagging conditions is 2,639 ton.m and
converted into Nm units, namely 25,879,722.96 Nm.
Longitudinal Strength
Mass
Buoyancy
Net Load
Shear
Moment
-40
-30
-20
-10
0
10
20
30
40
-5
0
5
10
15
20
25
30
35
40
45
50
55
60
-80
-60
-40
-20
0
20
40
60
80
-800
-600
-400
-200
0
200
400
600
800
Mass
Buoyancy
Net Load
Shear 63,045
Moment -683,772
Long. Pos. m
Load t/m
Shear tonne
Moment tonne.m
Longitudinal Strength
Mass
Buoyancy
Net Load
Shear
Moment
Figure 13. Graph of Hogging Conditions
From the graph above, the maximum moment that
occurs in hogging conditions is -683.77 ton.m and
converted into Nm units, namely 6,705,486.233 Nm.
3.3 Structure Modeling and Meshing
Modeling in the finite element method begins with
creating a 3D initial geometric model. Then the model
is divided into small elements through a meshing
process [14]. The division of elements is carried out
according to the laying of the profile to be made, so
that it must be in accordance with the distance of the
ship's tusks, after meshing the model is given
properties on the thickness of the plate, and the type
of material that has been determined.
Below is a Figure of the ship structure model when
it has meshed.
Figure 14. Meshing Process on Ship Model
568
3.4 Boundary Condition and Load Input On Ship
Structure
Before doing the analysis, determine the boundary
conditions on each model of the construction system.
The boundary conditions determine the object’s shape
being analyzed [15].
Table 2. Boundary Condition [16]
_______________________________________________
Location δx δy δz θx θy θz
________________________________________________
Maximum Stress Analysis
_______________________________________________
After endpoint Fix - Fix - Fix -
Front endpoint Fix - Fix - - -
_______________________________________________
The load used is the maximum moment calculated
previously for each water condition. Load Inputs are
placed at the center of gravity on the front and back
ends of the 3d model.
3.5 Stress Calculation
After determining the boundary conditions and load
on the model, an analysis can be carried out to obtain
the maximum stress in each construction system using
FEM-based software.
The results of the maximum stress analysis are in
the form of maximum stress values and also contours
or color changes in the parts of the model according to
the stresses that occur.
Samples of the contours and bending that occur
can be seen in the figure below.
Figure 15. Stress around the pillars in calm water conditions
In the post-processing figure using von Mises, it is
explained that the stress that occurs in the
construction of the ship (a) without pillars is 14.98
MPa, (b) pillar on the side is 14.56 MPa, and (c) pillar
in the middle is 15.08 MPa in calm water conditions.
Figure 16. Stress around the pillars in sagging conditions
In the post-processing figure using von Mises, it is
explained that the stress that occurs in the
construction of the ship (a) without pillars is 28.35
MPa, (b) pillar on the side is 27.55 MPa, and (c) pillar
in the middle is 28.54 MPa in sagging conditions.
Figure 17. Stress around the pillars in hogging conditions
In the post-processing figure using von Mises, it is
explained that the stress that occurs in the
construction of the ship (a) without pillars is 7.345
MPa, (b) pillar on the side is 7.138 MPa, and (c) pillar
in the middle is 7.395 MPa in hogging conditions.
Figure 18. Details of the stress around the pillar on the side
of the sagging condition
569
Figure 19. Details of the stress around the pillar in the
middle of sagging condition
From figure 18 and figure 19, it can be seen from
the stress contours that occur at the connection of the
pillar with the center deck girder where the
connection part has a high enough stress.
Figure 20. Comparison of the deflection and stress that
occurs in calm water conditions (a) without pillar (b) side
pillar (c) middle pillar
Figure 21. Comparison of the deflection and stress that
occurs in sagging conditions (a) without pillar (b) side pillar
(c) middle pillar
Figure 22. Comparison of the deflection and stress that
occurs in hogging conditions (a) without pillar (b) side pillar
(c) middle pillar
From figure 20, figure 21, and figure 22 show that
the comparison at the centerline intersection in each
construction illustrates the deflection and stress that
occurs where the comparison is not too significant.
Figure 23. Maximum stress without pillars in calm water
condition
In the post-processing image using von Mises, the
maximum stress when the ship is in a calm water
condition is 21.76 MPa.
Figure 24. Maximum stress without pillars in sagging
condition
In the post-processing image using von Mises, the
maximum stress when the ship is in a sagging
condition is 41.19 MPa.
570
Figure 25. Maximum stress without pillars in hogging
condition
In the post-processing image using von Mises, the
maximum stress when the ship is in a hogging
condition is 10.67 MPa.
Table 3. Results of Stress Analysis in the pillar area in MPa
_______________________________________________
Variation/Condition No Pillar Middle Pillar Side Pillar
_______________________________________________
Calm water 14.98 15.08 14.56
Sagging 28.35 28.54 27.55
Hogging 7.345 7.395 7.138
_______________________________________________
Table 4. Maximum Stress Analysis Results in MPa
_______________________________________________
Variation/Condition No Pillar Middle Pillar Side Pillar
_______________________________________________
Calm water 21.76 21.96 21.95
Sagging 41.19 41.55 41.54
Hogging 10.67 10.77 10.76
_______________________________________________
Based on the analysis that has been done, it can be
seen that without pillar has smaller maximum stress
in all wave conditions. At the same time, the pillar in
the middle has the greatest maximum stress in all
wave conditions.
3.6 Calculation of Allowable Stress
Calculations are carried out to determine whether the
maximum stress of each planned variation system has
met the regulation’s criteria that is the reference for
this research, namely in formula no 2 BKI Volume II
of 2018 Rules for Hull.
Table 5. Results of checking the Allowable stress
_______________________________________________
Condition Stress Allowable stress Information
(MPa) (MPa)
_______________________________________________
Without Pillar
_______________________________________________
Calm water 21.76 140.14 Allowed
Sagging 41.19 140.14 Allowed
Hogging 10.67 140.14 Allowed
_______________________________________________
Pillar in the Middle
_______________________________________________
Calm water 21.96 140.14 Allowed
Sagging 41.55 140.14 Allowed
Hogging 10.77 140.14 Allowed
_______________________________________________
Pillar on the Side
_______________________________________________
Calm water 21.95 140.14 Allowed
Sagging 41.54 140.14 Allowed
Hogging 10.76 140.14 Allowed
_______________________________________________
3.7 Calculation of the cross-sectional modulus and
moment of inertia
By using the calculation in formula number 3, the
minimum modulus of the ship is obtained, which is
0.375 m3. The analysis of the ship's modulus is 4.75
m3, on the ship's deck and 2.44 on the double bottom
of the ship, where according to regulations from BKI,
the modulus on the deck and double bottom of the
ship must be more than Wmin.
In the calculations that have been carried out, the
modulus of the construction is allowed from the
minimal modulus (Wmin).
Table 6. Results of checking the modulus
_______________________________________________
Location Modulus (m
3
) Minimum Information
modulus (m
3
)
_______________________________________________
Deck 4.75 0.375 Allowed
Double Bottom 2.44 0.375 Allowed
_______________________________________________
By using the calculation in formula number 4, the
minimum moment of inertia is obtained. It is obtained
by 0.645 m
4
, and calculating the moment of inertia on
the ship is 6.459 m
4
.
Table 7. Results of checking the moment of inertia
_______________________________________________
Moment of Minimum Moment Information
inertia (m
4
) of Inertia (m
4
)
_______________________________________________
6.65 0.645 Allowed
_______________________________________________
4 CONCLUSION
Based on the analysis of the longitudinal strength
calculation on the 1200 GT Perintis ship with
variations in pillar positions that have been carried,
the maximum stress results have met the allowable
stress criteria of the BKI regulation.
In the detailed drawing of the stress contours that
occur in variations that have pillars, there is large
stress that appears at the connection of the pillar to
the ship's deck girder. It can be concluded that the
position of the pillar slightly affects the local stresses
that occur in the ship structure, although it is not very
significant.
Comparison of the maximum stress obtained in the
three variations where the stresses that occur in ship
construction without pillars are smaller than in ship
construction with pillars in the middle with a
difference of 0.20 MPa in calm water, 0.36 MPa in
sagging conditions, and 0,10 MPa at hogging
condition.
For the calculation of the ship's cross-sectional
modulus, which is 4.75 m
3
on the deck and 2.44 m
3
on
the double bottom, the two cross-sectional modulus
have met the criteria of the BKI regulation, which is
more than 0.375 m
3
.
For the calculation of the moment of inertia of the
ship, which is 6.65 m
4
, where the moment of inertia
has met the criteria of the BKI regulation, which is
more than 0.645 m
4
.
From the results of this analysis, it can be
concluded that the position of the pillar laying does
not significantly affect the longitudinal strength of the
ship.
The longitudinal strength of the ship is more
significant by changes in longitudinal construction
variations, changes in transverse construction
variations have no significant effect on longitudinal
strength.
571
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