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BOAT LANDING AND RISER PROTECTOR DESIGN PROCEDURE

GUIDE DOC UMENT

BOAT LANDING AND RISER PROTECTOR DESIGN PROCED URE

Modifications subject of this revision concern the following pages: As marked.

Hard copies of this document are UNCONTROLL ED unless stamped otherwise.

5
4 1\7 !J. I
-~_,.
3 22.07.2012 K. Bandyapadhyay ~lachandar A. Jain \V~~ REVISED & RE-ISSUED FOR
IMPLEMENTATION

P. Gopalkrishnan REVISED & RE-ISSUED FOR

2 21 .06.2010 K. Bandyapadhyay A. Jain
IMPLEMENTATION
--
M.Pusala REVISED & RE-ISSUED FOR
1 22.06.2009 M.Balasubramanian A. Jain
IMPLEMENTATION

A. Jain/
0 31.05.2007 T. Halim A . Jain FOR IMPLEMENTATION
P. Gopalkrishnan
DATE WRITTEN BY CHECKED BY APPROVED BY STATUS
Rev
00/MM/YY (name & visa) (name & visa) (name & visa)
DOCUMENT REV ISIONS

Sections changed in last revision are Identified by a line in the right margin

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BOAT LANDING AND RISER PROTECTOR DESIGN PROCEDURE 2 / 43

Revision History

Revision Section Modification

0 All Issued for implementation.

1 1 Note included.

1 3.3 Note included

1 4 a) References for impact energy formula included.

b) Ultimate impact energy formula updated.

c) Ultimate unit elongation value included for high grade steel.

d) Shear area updated .

e) Joint Capacity formula updated .

f) Formulas added for Fixed, Pinned & Cantilever beams.

g) Energy absorption formula updated.

1 5 References section included newly.

2 3 Generally revised for analysis step and notes.

New Appendix 1.0 added for Typical boat landing SACS
2 - analysis and design example.
3 1, 2, 3 Boat landing design is generally revised .

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BOAT LANDING AND RISER PROTECTOR DESIGN PROCEDURE 3/ 43

TABLE OF CONTENTS

1. INTRODUCTION 4

2. BOAT LANDING DESIGN (WITH EAD) 5

2. 1 Overview 5
2.2 STEP-1: Ship Impact Energy calculation 5
2.3 STEP-2: EAD selection and arrangement 6
2.4 STEP-3: Boat Landing Analysis 7
2.5 STEP-4: Post Impact Scenario: Code Checking 17
3. BOAT LANDING DESIGN (WITHOUT EAD) 18

4. RISER PROTECTOR DESIGN 19

5. REFERENCES 25
APPENDIX -1 SAMPLE PROBLEM 27

APPENDIX - 2 SAMPLE DRAWINGS 35

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BOAT LANDING AND RISER PROTECTOR DESIGN PROCEDURE 4 / 43

1. INTRODUCTION

The objective of this technical guide is to provide methodology for the design of
appurtenances namely,

1) Boat landing with rub strips, connected to the jacket structure through shock
cells or compression fenders and shear mounts,
2) Boat landing with rub strips, directly connected to the jacket (without any shock
cells /compression fenders/ shear mounts)

3) Riser protector frames.

The boat landing assembly or a riser protector structure should be capable to absorb
the kinetic energy of the ship, without excessively stressing the jacket structure.

It is to be kept in mind that the boat landings are normally designed for operational
berthing of the supply boats, as the ships are supposed to approach the boat landing in
a controlled manner. However, in case of an accidental impact, should a boat loose
control or get drifted during a storm, it should be ensured that no damage is caused to
the main jacket structu re.

The energy absorbing devices (EAD's) connected to the boat landing (if any) should be
selected in such a manner that they can absorb the accidental boat impact energy
within their rated energy/reaction and deflection criteria mentioned in the vendor
catalogue.

The above mentioned criteria for boat landing design and EAD selection is purely
project specific and to be confirmed through structural design basis.

Riser protector frames are generally designed for accidental impact of the boat that gets
drifted during the storm . These frames are not meant for operational berthing of the
ships.

1) A spreadsheet under "NE-A347-052" for the design of riser guard member is

developed and provided in Structural ORB. Loca l design of the riser protector
members shall be performed using the spreadsheet.
2) However, for the design of riser protector connection to the jacket and reactions for
the global jacket design check it is suggested to use the collapse module.

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BOAT LANDING AND RISER PROTECTOR DESIGN PROCEDURE 5 1 43

2. BOAT LANDING DESIGN (WITH EAD)

2.1 Overview

The design of the boat landing can be performed by considering it as a sub-structure

along with connecting jacket legs. In case the code check is required to be performed
for the jacket members also during an impact, then full global model along with jacket
and topsides shall be used.

For boat landings connected through the shock cells and shear mounts, most of the
kinetic energy is absorbed by the deflection of these rubber fenders, besides some
energy being absorbed by the rub strips and local bending of members.
In general , the design of boat landing fitted with EADs, shall be divided in following
steps:
STEP-1: Ship Impact Energy Calculation
STEP-2: EAD selection and arrangement
STEP-3: Boat Landing Analysis, this step is further divided in
STEP-3A: Linear method-without using SACS Collapse Module
STEP-38: Non linear method-using SACS Collapse Modu le
STEP-4: Post Impact Scenario-Code checking of jacket and boat landing joints and
members as per project specification.

2.2 STEP-1: Ship Impact Energy calculation

The total kinetic energy of the impacting ship can be calculated from its mass and
velocity and is given by:

2
E = .]_(D + Ma)v
2

Where, E = Kinetic energy (kJ),

v = Velocity of ship (m/s),
D = Maximum loaded tonnage of ship (tons) ,
Ma = Added mass (tons).

Ma = p 1tT 2L
4

Where, p = Density of water (Um3 ) ,

T = Draft of the ship (m),
L = Length of the ship (m).

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6 I 43
BOAT LANDING AND RISER PROTECTOR DESIGN PROCEDURE

As per API RP 2A, C18.9.2a the impact energy of a vessel can be calculated as follows:

E = 0.5amv 2
Where, E = the kinetic energy of the vessel (kJ ),
a = added mass factor,
= 1.4 for broadside collision ,
= 1.1 for bow/stern collision,
m = vessel mass (tons),
v = velocity of vessel at impact (m/s).

It is to be noted that the approach velocity of a ship is different for the operational
berthing and for accidental impact.

2.3 STEP-2: EAD selection and arrangement

A typical design of boat landing includes energy absorbing devices like shear fenders
and compression fenders/shock cells and low friction coefficient frontal pads or rubber
strip.
The selection of number and type of shock cells/compression fenders , shear fender, rub
strips and their combinations should be such that the total energy absorbed by the
system is more than the energy to be absorbed during accidental berthing conditions or
as mentioned in the project specification. Following isometric view shows a typical
arrangement of shear fenders and shock cells to support a boat landing structure.

Boat landing system

ub Strip

Shear Mount (F

Following salient points should be noted while selecting the EADs:

• The position of EADs shall be such that the maximum amount of energy shall be
transmitted through EADs and minimum reaction is imparted on the jacket leg.

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BOAT LANDING AND RISER PROTECTOR DESIGN PROCEDURE 7 I 43

• Compression fender and shear fender(s) should deflect almost equal amount
against certain load to allow lateral motion of the boat landing.

• Reaction due to operational or accidental berthing shall not exceed the rated
reaction of the EAD (automatically this will correspond to rated deflection and
rated energy limits).

• The EADs should be capable of transferring the loads in the form of axial and/or
shear forces and the EAD assembly should have energy efficiency in lateral
directions as well.

• For efficient energy absorptions by EADs, the stubs connecting boat landing and
jacket legs (on which the EADs are placed) should not be inclined w. r.t jacket
face. Straight stub will eliminate out of plane force on compression fender during
impact. See Appendix-2 for a typical arrangement.

• EADs shall be arranged in such a manner that there should not be any sustained
tension in any EAD.

• EADs shall be light weight, maintenance free and easy to replace and smaller in
size.

Considering the eccentric (impact on left or right vertica l post of the boat landing) and
most critical impact scenario for EADs, following EAD sizing criteria may be used as "to
start with" sizes/capacity:

If, Ea= Accidental sh ip impact energy

Es= Rated capacity of each shear fender

Ec= Rated capacity of each compression fender,

Then ,

n.Es ~ 0.75Ea, where, n=number of shear fender at top of each post

n.Ec ~ 0.50Ea, where, n=number of compression fender at bottom of each post

2.4 STEP-3: Boat Landing Analysis

2.4.1 STEP-3A: Linear method-without using SACS Collapse Module

2.4.1.1 Modelling in SACS:

3-D model of the boat landing structure shall be generated and the boat landing model
shall include elements that represent proper equivalent stiffness of the rubber fenders,
thus eliminating the use of SACS coll apse module. If the code check is required to be
performed for jacket members also during an impact, then global model along-with the
jacket, topsides and piles shall be used. However, if boat landing is modelled separately,
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BOAT LANDING AND RISER PROTECTOR DESIGN PROCEDURE 8 / 43

it is recommended to model the associated jacket legs between upper and lower jacket
horizontal frame with leg ends PIN-restrained<1> to incorporate realistic support condition.
Boat landings are generally installed in offshore. The lower end stub, which is normally
below water line, is provided with a stabbing guide to facilitate the installation. Thus the
connection of the boat landing member with stabbing guide should be released for
moments in the model. The design. of the pin of stabbing guide should also be adequate
for the installation forces .
Typical technical data for Rub Strip, Shock Cell and Shear Mount (Fender) is
reproduced on the following pages. The methodology to evaluate the stiffness of shear
mounts and shock cells <2> is also described.
Note:
(1) It is observed that defining leg ends as FIXED-restrained does not majorly alter the
results and can be conservatively adopted.
(2) In case the shock cell I compression fender performance curve is of non-linear
nature, one of the following methods may be adopted and documented in the project
design specification to calculate the stiffness of the shock cell I compression fender.
• Conservatively the stiffness of the shock cell I compression fender may be
calculated based on the linear portion of the shock cells I compression fender
performance curve.
• The shock cell I compression fender stiffness may be calculated at a number of
points along the curve and an average value may be used in the analysis.
• The stiffness may be taken as average of the stiffness values ca lculated at one-third
and two-third points on the deflection axis.
• The shock cell I compression fender I shear fender stiffness may be calculated at
the rated reaction-deflection point on the curve.

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BOAT LANDING AND RISER PROTECTOR DESIGN PROCEDURE 91 43

• Rub Strip

Load-Deflection characteristics of Rub Strip

RS -~000 •nd RS-l!000-1 II!Jb Strip

without angles
RS-1000 Rub Strfpltl

RS-3000 Rub Strfpl1l

Hote : ( 1) ()p(k:nal: Tough, looN lr'.ction, wt:llr

su focts made f1om higl><;uolily

rfil
tK(tJ\.."nC

(2) ~b!xr 1<119V1 plote tenstn ~

lttickni!Ss Vatiab!( with Customet
specitk:.atb'l$
(3) Con be made solid fer high-•t>ose
cO"'difO'l5

J - - - 10"-- -J

Load Curve Energy Absorption

I 16

I
45
I i I 12
I - IJ
I
IL I '
I II
I
I I I I
I i If- I I
I
,_...I I I
I
I
15 I .1--- ..L I I !
:..,, ~--

0
/
[/.[-"
J.-.-f-
I
2 3
I
I
I
4
Deftectl()(l
7 8 0
&-F=-
I
..--+--'

2
.....

3
v

Deflection
5 6
*
7
i
I

(Inches) (Inches)
- - - - - - R5-300)
- - - - RS-1000

Notes: Test data may vary "' 10% from pub-

lished curve.
Looct Values are for 3-ft length of Rub
Strip (cNerage imP<'ct ~ea)

Conservatively energy absorbed by rub strip is not considered for the analysis.

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10 I 43
BOAT LANDING AND RISER PROTECTOR DESIGN PROCEDURE

• Shock Cell/ Compression Fender

SHOCK CELL TECHNICAL DATA

Performance results
for 3 Regal Shock Cell models.
Models SC1424, SC1830 & SC2036

SC1424
SC1830
SC2036
Design Limit •
Energy vs. Deflection Force vs. Deflection
r-:- - '''-r- r-r-r.,--,r-r-r-.--r-.-~r-r-, 2~ro~.,--,~--.-~-..-r-r--.-.,--,~~
120 H--i- t--1-i--l-+-t-t--t-1-1--+--H·- - - 240 t--+-+--t-lf-+-t--t-+--1-+--t-+-+--t-lf-+-1-l
r-+- - -+--t-+-+-+-1-t--1--1-l--t-+--t-+-l 230 t--+-t--t-lf-+-t--·1-+--1-+--t--+-tl-t--l~-t--l
110 1-+-1-+-1--1--i- i-t-t-+--1-+-+--t-l--t--H 220 H--1-+-li-+-t--+-t-t--t-1-f+ -HH--+-l
210 1-+--t-+-li-+-t--i--t-t-+-t-:..:T-.,f-+-+-t--1-i
200H--!-+-li-+-t--+-t-t-+-~~+-li-+-+-l
100 t--+-+-i-t~+-l-~+--t--+~l-t-lt--+-t--+-l
90 1-+-l--t-l--t--l-t-+-t-+--t--1:'-lr--t-l--t--1-l 1eo t--+-+--t--lt--+-t--t-+--t--+-'1-11'-+--t--lt--+-1-l
170 1-+-+-t--1-t--t-1-+--!--+>-if-J--+--t--1--t--H
801-+-l--t--lt--+-t,-++--t-+--b'>-'1---t--+-+-+-1--t
-, - -· - .. 1~ ~~~~1=~~~M+-+-t--1-t--H
1so H--1--HI-+-t--t--1--+._.":-t~-t-H-t--+-l-l
1

7oH--!--~i-+-+-+-t-t-+.1++--t-+-1i-+-+-l 140 t--+-+--1--1--t-+--t-+--,_.f-+-+-

, -t-lf-+-t---1--t-l
--' 130 1-t-l--t--lt--+-t--+-1-H--f-Lt--+-+--t--lt--+-1-l
~1-t-t--t-ll-+-t-+-1-_ ~&1 -,.- - -- - f- 120 H--+-t--1--t--1-l-.f'-1-:-+-1-t--i-t--t--i-t--l
- - - l-- l- +-t-l--l-!-:'14'-1--1-li-+-t--+-t--l 110 t--+-+-+-1--t-+--t-+t'-+- ' +-t--+-+-+-1--t--1-l
sot--+-+--HI-+-t--+-1-I,"J~'+-t-+-1-+-11--+-1--1 100 r--t-++-1-l--+-l'- .. :IL.
/ +--t---t--;r-t-++-+--+-l
.' /
001--1·-+-+-tf-+~~
~+--t-+-+--t--lf-+-t--+-1-l
40H--t--t--IH--t-t-t~-t-H-t--t--IH--H
1
r- - t-·-1-+-t--!-+-JH-t---HH--l-1-+-+-1
OOH-t---HH-~:~
~ -t-1-+--1--Hi-+-~·1-:-4~
41
1o r- . · /
301- + -+-+-1--t-+--h,=+-t-1-+--t-lt--+-l--.f--f-l 60 H-+--H.,_+-7o'+-t--t-H--!-t--IH--+-l
so _ _ -: _· __ IJ ./- I - . 1- - - 1- ·- -
~2oH--r-+-l-+~.~~~~~~q-+-t--!-+-i-+-t--~-l
s - r,.c) ~- 1-H-+-t-+-1 " 40
5 30 -
......
~10 1-l--i-·1-
~~~~~~+--t-r,_r+--!-+-i-1--1-i ~ 20 -lFr-~-+-+--+-+-t-+-1-+--t--H-+-+-l
.,
~ B IO~·~
y l-+-+-t--1-t-+-+-+--t-+-1-+-+-+-1-i
0 ,_1!.11
"-'-
" '- '--'--'--'-.1......1.-'--L-'---L-'--'--'-'--'--'
0 1 2 3 4 5 6 7 B 9 10 11 12 1314 15 16 17 18
& o ~~~~~~-L~~-L~~~~~
0 1 2 3 4 5 6 7 0 9 10 II 121314 15 16 17 10
Deflection ( inches)
From load-deflection curve:

Consider Rega l Shock Cell Model SC 1830. The shock cell characteristics are given
above.

Assume, load (P) = 50 Tons = 45 tonnes,

Correspond ing deflection (I:J.) = 3 inches = 7.62 ems.

Considering the length (l ) of shock cell is modelled as 1.5 meters in the structural mode l.

PL
- == .6.=7.62
AE

45 150
Area (A) of shock cell = * == 0.42 cm 2 ----.~G)
7.62 * 2 100

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BOAT LANDING AND RISER PROTECTOR DESIGN PROCEDURE 11 I 43

SHOCK CELL TECHNICAL DATA

Performance results
for 3 Regal Shock Cell models.
Models SC1424, SC1830 & SC2036

SC1424
SC1830
SC2036
Design Limit •

Energy Absorption vs. Rotation Torque vs. Rotation

45 ro-..,rT~~-..-ro-..-ro-.o-rT-r""~ 190
160
170 I
160
150
140 f- f-,-
130
120
, _,
.. ..·
•'
110 :,
tOO 1--
90
80
0 ..
V, ·'
....
1..
,•'

-I-
.....
0
.. .
•••••• ""' 1
:! 7.5
~ 5 H-+--HH--:-:h:~G--l-H-+-4-H-+--l-H---1--H-+-1
~~ 25. .,...1-"i"" '""'~"'" II 0 j
/' •'

•' ""'
1 ...

-- - I-

0
'l i
w 0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 25 27.5 30 0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 25 27.5 30
Rotation (degrees) Rotollon (degrees)

From Rotation-Moment curve:

L= U m
Assume, Rotation (8) = 10 degrees= 0.1745 rad .
Moment (M) = 43 T-ft = 11.89 T-M
This can be considered as a cantilever:
Load (P) = 11 .89/1.5 = 7.925 T
2
Cantilever Rotation = PL = B
2£/

Moment of Inertia (I)

2£{)

7.925* 150 2
=2*2 100*0. 1745
= 243 cm4 - - --+IJIG)

The above values of CD area and 0 moment of inertia can be used to model an
equivalent shock cell.

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BOAT LANDING AND RISER PROTECTOR DESIGN PROCEDURE 12 I 43

• Shear Mount (Fender)

Consider a Paulstra Shear Fender model SF2, the characteristics of which are shown
be low.

From load-deflection curve :

Shear Force (S) = 36 tonnes

Deflection (.6.) = 24 .5 ems.

Considering the length (L) of Shear Fender is modelled as 1.5 meters in the structural
model.

Shear fender can be considered as a fixed-fixed beam.

or,
s----+

I
3
36.0* 150 3 I L
Moment if In ertia, I = SL = = 196.8 cm
4
I
12£t. 12 *2100*24.5 I
I

Axial area (A) can be given a large value, say 1000 sq . em. to the element representing
the shear fender.

Shear fender Shear fender· SF2 .(usual tolerances"' tO%)

•
~I
without tix:ing plates with fbung plat ~s
'E
- l
i
"'
O> '•
"'r £ /
~~
w!
'I / i

/ I
25
':J:l:' ..
I- - lim, ;;:/.........,. I
.. I
eL
i
I
I
I /
/
I
J4,4
4

·~ I /
I <~;0 ! /'
/

)1>0
-- I
o..e~c i
,...-r
/

H
/ I. llljo"9\,o('..,.. .....

. ..,..""
475
~ ~'0 ....
4,4
36 36
8,8
35
11.0
36
I %I ~~e;~r ! I !
L '-f.r.outton;pu:u
0,245 ' 0 ,370 0.495 ! 0,620

~/- .-------r ....- I

I De Ill l ion (m) I

0
0 0,05 0,1 0,15 0,2 0,245

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