padeye design & concepts

7/29/2019 Padeye Design & Concepts

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5/6/2011

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Offshore Structures Offshore Lift Analysis

5/3/2011 Dr. S. NallayarasuDepartment of Ocean Engineering

Indian Institute of Technology Madras-36

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DOUBLE PADEYEMOUNTED ON

TOP



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PADEYEMOUNTED ONSIDE



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PADEYEMOUNTED ONTOP



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TRUNNION (MAIN PLATE WELDED TO SKIN)

PPvPipe

Ph

InternalRings



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TRUNNION (MAIN PLATE SLOTTED INTO TUBE)

PPvPipe

Ph

ExternalRings



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DESIGN PROCEDURE

Establish Maximum Sling Load (Fmax)

Select suitable Sling Diameter

Select Suitable Shackle

Check Suitability of Shackle and Slings

Select Suitable Main Plates and Cheek Plates

Check Suitability of Spacing, gap withselected shackle and add spacers if required



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modify either padeye, shackle or sling asnecessary


PADEYE ARRANGEMENT

Generally one main plate of thickness from 25mm to90mm can be used

Cheek lates should not be more than the thickness ofmain plates

More than one cheek plate on each face shall be avoided

Second cheek plate shall be considered as spacer plate Boring shall be done after welding the cheek plates to

main plate

A minimum clear gap (S) of 5mm shall be providedbetween shackle and the last cheek or s acer late



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Adequate space (C2)shall be provided between the top ofmain plate and the underside of shackle and shall beminimum 1.5*Sling Diameter


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CLEARANCES



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Rm

Rc

FPDLPullout shear

Plane

Main Plate(tm)

Cheek Plate(tc)

FV

Rp

P P

Structureh

Clearance for

Stiffener

FH



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B

Shackle

Q Q


Cheek Plates

FPDL/2FPDL/2Main Plate

Out-off plane

Stiffener Plate

Force of 5%FPDLCos



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bs bs


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X

Y Y

2bs



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X


The bearing stress fb shall be calculated as below:

PDLF=

Bearing Stress Calculation

fcmp Rttd 2+

WhereFPDL =Padeye Design Load

dp=Diameter of Pin

tm =Thickness of main plate



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tc =Thickness of cheek plate

Rf=Reduction Factor


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PDLF

=

PULLOUT SHEAR STRESS CALCUALTIONSPullout shear stress shall be calculated as below.

( ) ( )2 2sm p m c p c

R R t R R t +

where

FPDL=Padeye design load

Rm=Radius of main plate

Rc=Radius of cheek plate



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Rp

=Radius of pin

tm= Thickness of main plate

tc=Thickness of cheek plate


PDL

t

F Sinf

=

TENSILE STRESS AT SECTION P-P

m p m c p c

t t +

F Sin

TENSILE STRESS AT SECTION Q-Q



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[ ]4t

m s sB t b t

=+


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HORIZONTAL SHEAR STRESS AT SECTION P-P

INPLANE SHEAR STRESSES

( ) ( )2PDL

s in

m p m c p c

F Cosf

R R t R R t

= +

HORIZONTAL SHEAR STRESS AT SECTION Q-Q



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[ ]PDL

s in

m

F CosfBt

=


HORIZONTAL SHEAR STRESS AT SECTION Q-Q

OUT-OFF PLANE SHEAR STRESSES

[ ]

0.05

4PDL

s op

s s

F Cosf b t

=



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INPLANE

BENDING STRESSES AT SECTION Y-Y

23 3

xx2I

PDL

b in

F hBCosf

=



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2 412 12 2m s s s

xx s sI b t

= + +


OUT-OFF PLANE

BENDING STRESSES AT SECTION Y-Y

3 3

YY

0.05

I

PDL s

b op

F hb Cosf

=



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212 12m s s

YYI = +


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COMBINED STRESSES

2 2

b b in b of f f

= +Combined Bending Stress

2 2

s s in s opf f f

= +Combined Shear Stress



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2 2 23von t s b t bf f f f f f= + + Von Mises Stress


ALLOWABLE STRESSES

Establish stresses induced in the padeyeplates and connections and to assure they are

Bearing Stresses (0.9Fy)

Shear Stresses (0.4Fy)

Tensile Stresses (0.6Fy)

Bending Stresses (0.6Fy)



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Combined Stresses (0.75Fy)

Von Mises Stress (0.75Fy)


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0.5 FPDL0.5 FPDL

Weld Size w1WELDING BETWEEN MAIN AND

CHEEK PLATES

Main Plate : tm, Rm

Weld Size w2First Cheek Plate : tc1, Rc1

Second Cheek Plate : tc2, Rc2



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R2R2


Weld Between Main and Cheek Plates:

1

1

1 2

.PDL c

m c c

F tR

t t t=

+ +Force Transmitted betweenMain plate and First Cheek Plate

1 2

112 .0.707.c yw

R Rw

R F

+=

2

2

.PDL c

F tR

t t t=

+ +

Force Transmitted between FirstCheek plate and Second Cheek Plate

Fillet Weld Size required betweenmain plate and first cheek plate



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2

2

22 .0.707.

c yw

Rw

R F=Fillet Weld Size required between first

cheek plate and second cheek plate


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UNSYMETRIC ARRANGEMENT

Many occasions we will be using theunsymetric arrangement

The vertical load distribution across the

main plate is not uniform and itintroduces an eccentricity e whichcauses additional moment



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X

FH

FPDLF

v

UNSYMETRIC

ARRANGEMENT

YY

h



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XB

e




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CONNECTION TO THE MAIN STRUCTURE

The loads from the padeye shall betransmitted to the main structure safelywithout overstressing.

Many different methods of transmittingthe forces can be adopted.

The simple way of transferring is by either



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Methods using Bending or combination ofAxial and bending shall be avoided


FPDL

FH

Fv

h

e

PADEYE MAIN PLATE SLOTTED

TO THE DECK EXTENSION

Welding betweentube and main plate

DL



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( )

y y y

. e+D/2

4 0.4F 2 0.4F 2 0.4FPDL PDL PDL

t t t

F Sin F Sin F Cos hL

T T D T D

= +


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PADEYE MAIN PLATE SLOTTED

TO THE DECK EXTENSION


FPDL

FH

Fv

h

DL



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y y

. ( 0.5 )

4 0.4F 2 0.4F

PDL PDL

t t

F Sin F Cos h LL

T D T D

+= +


PADEYE MAIN PLATE WELDED TO

DECK LEG SKIN


FPDL

FH

Fv

h

e

DL



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y

2 0 .4 F

P D L

m

F S i nL

t

= ( Only Vertical Load

Transferred)


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MAIN PLATE WELDED TO SKIN OF TUBE

The Vertical Component of Load (FV) istransferred through the direct shear between

Horizontal component (FH) and moments shallbe decoupled between top and bottom ringplates

These forces on the rings shall be transferred ascircumferential shear



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,

these forces shall have to be transferred bybending


CALCULATION OF RING FORCES

Top Ring Plate

(0.5 ) (e+D/2)PD L P D L

T

F C os L h F SinF

L L

+=

+

Bottom Ring Plate



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.P D L PD L

TF

L L= +


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FINITE ELEMENT ANALYSIS

Finite element analysis will be carried out when

No redundancy in design failure of the.

Multiple / unclear Load path.

Manual Calculations too conservative dueto assumptions made on load path.

Manual calculation becomes toocomplicated.



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FEM analysis will give actual load path

Indicate hot spots where local stresses are high


FEA Lifting Pad-eye



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FEA - Spreader Bar



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padeye design & concepts

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