the abs safehull system -...

F OUNE)F0 7862

AMERICAN BUREAU OF SHIPPING & AFFILIATED COMPANIES

SAFEHULL SYSTEM FOR BULK CARRIERS

GUIDE ON IMPROVEMENT FOR STRUCTURAL CONNECTIONS AND SAMPLE STRUCTURAL DETAILS -SERVICE EXPERIENCE AND MODIFICATIONS FOR BULK CARRIERS

OCTOBER 1995

THE ABS SAFEHULL SYSTEM

SAFETY F SHIP STRUCTURES BY DYNAMIC BASED DESIGN AND EVALUATION

FOONDED 1862

AMERICAN BUREAU OF SHIPPING i AFFILIATED COMPANIES

Guide on Improvement for Structural Connections and Sample Structural Details — Service Experience and Modifications for Bulk Carriers

October 1995

American Bureau of Shipping Incorporated by the Legislature of the State of New York 1862

Copyright 1995 American Bureau of Shipping Two World Trade Center, 106th Floor New York, NY 10048 U.S.A.

1.0 GENERAL

This Guide identifies the influential parameters and provides guidelines on improvement of

structural connections. It also provides for reference illustrations of local structural failures

experienced in some existing bulk carriers and the corrective measures as compiled by the 1ACS

and from the American Bureau of Shipping's data files.

For structural details similar to those in tankers, reference illustrations are to be found in the

"Guide on Improvement for Structural Connections and Sample Structural Details - Service

Experience and Modifications - for Tankers".

2.0 INFLUENTIAL PARAMETERS

For design of structural details, due consideration is to be given to the following influential

parameters.

2.1 Loading Patterns and Nominal Stresses

The load distribution among the connected structural members and the corresponding

nominal stresses at the location considered should be examined for the combined load

cases specified in 513A3.5.2. It is important to consider the combined effects of all the

simultaneously imposed load components, rather than only one selected dominating load

component. The stress distribution may be obtained from a 3D structural analysis as

specified in 5/3A5.3 or by other equivalent means.

2.2 Stress Concentration

Due to load transmission and diffusion at a structural joint, it is inevitable that some form of

stress concentration is going to occur in the loaded structure. Therefore, particular

attention should be paid to structural notches, abrupt changes in structural properties and

excessive distortions and deformations; such as locations at bracket toes, cut-outs,

terminations of heavily loaded members, connection of flexible elements with much stiffer

members, ends of unbalanced structural members, just to name a few. For ship structures

designed with relatively low working stresses and high safety margins, the detrimental

effects of such stress concentrations may not readily be apparent. On the other hand, for

structures designed with high working stresses and low safety margins, damaging effects of

such stress concentrations could appear sooner than the anticipated period of time.

Appropriate stress concentration factors (SCF's) obtained from either experimental data or

structural analyses are required to evaluate the design of structural details.

2.3 Weld Effects and Fatigue Strength

Another important factor to be considered is the effects of welding on the properties of

material (heating effects) and on structural continuity (profile of the weld deposit and under-

cuts). This factor which highly depends on the welding methods, processes and

workmanship is vital for assessing fatigue strength of the joint. To date, the welding effects

on fatigue strength are primarily determined by experimental data presented in the form of

S-N curves and characteristics of the test specimens, as shown in Appendix 5/3AA of the

Rules.

3.0 CONSIDERATIONS FOR DESIGN OF STRUCTURAL DETAILS

In light of the discussions given in 5/3A5.4, it is apparent that the necessary criterion for the

design of structural details is simply to offer a well balanced joint which is "compatible' with the

anticipated working stresses. To this end, the solution is to be tailored to a specific location of a

specific design. In addition, there is no unique solution to the problem. Many alternatives may

exist. The designers/builder would have to exercise their judgment based on their fabrication

facilities, techniques and experience. The information offered below is provided for reference.

3.1 Hold Frames and End Brackets

When selecting and sizing brackets connecting hold frames, due consideration should be

given to the load transmission and relative stiffness of the members to be connected. A

9

pattern of smooth load transmission is essential. The connecting bracket is to be of

sufficient size to withstand the highly concentrated loads and to relocate the critical spots

(bracket toes) to lower stressed regions. Sample illustrations are shown in Figures 1, 1a

and lb for damages experienced in existing bulk carriers with some recorded repairs.

3.2 Connection of Transverse Bulkhead Structures

To prevent local fractures and to minimize the magnifying effects of structural notches, and

misalignment/discontinufties consideration should be given to local reinforcements at the

critical areas. Sample illustrations are shown in Figures 2a thru 2f for local damages and

some recorded repairs.

3.3 Connection of Double Bottom Structures

Sample damaged structural details and connections are illustrated in Figures 3a thru 3h for

double bottom structures. Attention should be paid to the weld connections of the slope

longitudinal bulkhead and the inner bottom plating.

3.4 Connections of Lower Wing Tank Structures

Sample damages experienced in the existing bulk carriers are shown in Figures 4a and 4b.

3.6 Structures and Connections Within the Upper Wing Tanks

Sample fractures and buckling of the transverse webs and brackets are shown in Figures

5a thru 5d.

3.6 Deck Structures

Illustrations are given for cracks at hatch corners, buckling of the cross deck structures and

hatch coaming in Figures 6a thru 6d.

3.7 Forepeak Structures

Some structural damages are shown in Figures 7a and 7b for the supporting structures in

the forepeak region.

3.8 Transition Region in the Foremost Cargo Hold

Sample structural damages and repairs are shown in Figures 8a thru 8d for connections of

the panting stringers and hold frames.

Side Frame Structure

Typical Damages to Hold Frames

Side she

Separate Bracket

upside tank

S shei

id -

Integral

1r

--.

Side frame

Fractures

Bracket

Topside tank

Fracture

Side frame

Fracture

Hopper tank

Configuration

(b)

1

.

Hopper

(a)

t2f11<_,,--

\

Configuration

The type of bracket configuration used will to a large extent dictate the location and extend of fracture. Where separate brackets are employed, the fracture location is normally at the bracket toe position on the frames, whereas with integral brackets the fracture location is at the toe position on the hopper and topside tank.

Figure 1

4


Detail of damage Fractures at bracket's toe position on the frame

Sketch of damage Sketch of repair

Topside tank

Side shell

Topside tank„,./

S, i / IL X

I 1 1 S ...

I i I

0.3x

Fractures Side

Modified brackets

shell M 0.3y A

A X

Y

N %

A AA A

A

A

1

AA

ti

R A 1 1.

A

S I' Hopper tank

S = Snaped end

X

1

1 1

HOP per \

tank

Separate Bracket Configuration

Figure lal

r

Sketch of damage

Detail of damage Fractures on brackets at termination of frame

Side shell

Separate Bracket Configuration

Sketch of repair

Side shell

S = Snaped end


Figure 1a2


Detail of damage Fractures and the Toe Position on the Side Tank Sloping Plating


--.1 Topside tank Main

frame webs

Fracture

race plate

Fracturing of Detail As modified" Side Framing --...

View ")0(" i‘, i Hopper

plating

f I

1 in 3 min_ taper

Side frame 70 mmmin.

1.4t 0

+

Modified line of bracket 1_4t mm

1 in 3 ex "X"

Original Line 10 rnm

Hopper of bracket

Integral Bracket Configuration Weld throat . 0.44 x 1.4t

Figure 9b

Fractures on web of corrugation initiating at intersection of adjacent shedder plates Fractures initiating at

the comers of the shedder plate connections to the shelf plate and corrugations

Fractures initiating at connections to side shell

Shedder plate

Shelf plate

Fractures initiating at the weld of corrugations to shelf plate and /or stool sloping plating to shelf plate

Fractures initiating at the connections of the stool sloping plating to the inner bottom

Fractures initiating at connections of stool/hopper sloping plating

(Similar d ages may occur at the upper connections of the bulkhead to the deck structure)

Figure 2 Typical Fracturing at the Connection of Transverse Bulkhead Structure

8

Detail of damage Fractures at weld connections to stool shelf plate

Sketch of damage

Bulkhead corruption

Fracture Fillet weld

Sheff plate

Weld fracture

in weld

S te pla hedder

Stool sloped Fractures es plating

Shelf plate

Sketch of repair

Welded plate collar

New sloped plate insert of increased thickness

Vertical stiffener added where there is indication of buckling

Edges prepared and full penetration welded,

o/ New shelf plate insert

of increased thickness 11111•111•11111M11111111111.11.111.11111111

X = extent of collar depending on cracking direction

Transverse Bulkhead Structure

Figure 2a

Fractures at weld connections of stool plating and corrugation flange to the shelf plate

Detail of damage

Sketch of damage

Fillet weld

Bulkhead corrugation

Frac tur in weld

Fillet weld Fracture in

Shelf plate weld

Misalignment

Stool sloped Fractures es plating

Sketch of repair

Edges prepared and full penetration welded, using low hydrogen electrodes or equivalent

Structure to be released and misalignment rectified


Figure 2b

10


Detail of damage Fractures at the upper boundaries to topside tanks

Sketch Of damage Sketch of repair

Continuous or intercostal reinforcement in line with flanges or diaphragms where not already fitted

Adjacent to the topside tank either a diaphragm or a bulb plate stiffener may be incorporated

Fracture

Topside tank

I

I I

I

1111

. il

PIE'. i

1 i

Bulb plate

stiffener

I 1 1

I I

Diaphragm (similar diaphragms on the opposite side shown dotted)

Figure 2c

Fractures on the web of corrugation initiating at intersection of adjacent shedder plates

Detail of damage

Sketch of damage

Transverse bulkhead

Tank top/ inner bottom

Sketch of repair

Flat bar extension piece fitted at -----

corrugations with overlap connections

at ends Section NA-A"


Figure 2d

12

kee Doubt bottom

Double bottom

Fractures at welded connection of lower stool plating to tank top in way of duct keel

Detail of damage

Sketch of repair It may be necessary to crop and insert

k-Jr the tank topftnner bottom plating

Sketch of damage

Bulkhead stool

Insert plate of increased thickness and/or enhanced grade

Fracture Fractures Bulkhead stool Increased depth

of stiffener, to suit arrangement of

pipes in duct keel

ha. 111111111111111111111111111111•1111111111

Full penetration welds

Fillet weld of DB OT/WT girder to be made full

penetration over length of stool space

Section "B-B"

Figure 2e

13

Section -A-A"



Detail of damage Indentation and buckling of vertical corrugations

Sketch of damage

I

I

1

Shear

buckling

Bending

compressive

buckling

ter' 0..

Sketch of repair

-... ‘.77. e":\ -..—, ..,1"'

+- ... , , - i ..,..,.:,

Rating part renewed

I

or

I

r-L.;..:.(!-i--.-%

•

4.7'

,

1

IShedder

plate

t J

Shedder

plate

1

Shelf plate

Lower stool

Tank topfinner bottom

Shelf plate

Lower stool

Tank top/inner bottom

Figure 2f

1.4

Figure 3 Typical Fractures in the Connection of Hopper Plating and Tanktopiinner bottom

15

Double Bottom Structure

Detail of damage Fracture at weld connection of floors in way of hopper/ tank top interface

Sketch of damage

Fractures

A

Sketch of repair

Full penetration weld connection to the Hopper tanktop/ inner bottom 1 transve plating I web

Dc:ubbofloorttol4m r________"---

2 j 3

Collar

am1M111100. MOM=

VI

Double bottom floor ....

Hopper transverse

web Cutout enlarged to avoid plate area of high stress

1,2,3 represents sequence of welding Tank top/inner Side girder

View 'A-A'

Transverse fractures in hopper web plating and possibly extending into

the hopper sloping plating

oi■iimemile bottom plating Floor or

transverse web plating

Reinforcement

Edge chamfered for full penetration weld

Collar plate

a Insert plate

Tank top/inner • • • m .... .......".:.:,

Additional stiffener

B

Floor or


Fractures in the floor/web of hopper transverse ring

Insert plate pr AW" . 771e I /

Additional ri, • stiffeners 4

i'l— st, gi

Section "B -B' -.

Figure 3a

16


Detail of damage Fracturing at weld connection of floors in way of hopper tank and tanktop/inner bottom interface

Sketch of damage A 44: / A

Fractures

Sketch of repair A

t

Double IN. bottom

floor

Collar

Section A -A weld inner

•

1%,

plate with full penetration connection to tanktop/ bottom, hopper plating,

/41 mi

Double bottom

floor

View Transverse fractures hopper web possibly extending

the hopper sloping

Hopper Transverse

web

"A-A' in

plating and into

plating

Floor for full penetration weld

Alternatively,

and bottom girder

Edge chamfered

Aeinforcernent A

Intermediate may stop at mat longttudinals -111 brackets fle where fitted between floors)

Floor or"


Fractures in the floor/web of hopper transverse ring

Reinforoemen B

4. inner

View 'B - B'

bottom

Faceplate of transverse

Scarfing web brackets 3270n5

Figure 3b

17


Detail of damage Fractures at Weld Connections of Floors in Way of Tank Top/inner bottom and side girder in Way of Stool plates


Sequence of welding is important

/

Staoi plate Stool plate 1

'A' View —.0.----

, 2 and 3 represent

CL. side

or girder

Collar plates CL

side

order of welding

or girder

Floor

View 'A'

Edge chamfered for full penetration weld

Side elevation

Figure 3c


Detail of damage Fracturing of bottom shell and tanktop/inner bottom longitudinals in way of tank top/in.ner bottom and bulkhead stool boundaries

Sketch of damage

Tank top/inner I bottom longitudinal A

Sketch of repair

"

\‘‘

amorror' ii...ir imealatursommor /11

1111111111111111111•11111111111111

Additional brackets with soft toes

—1 Fractures

41111111111111111111111111111

.-.

Figure 3d

19


Detail of damage Fracturing of Longitudinals in Way of Bilge Well

Sketch of damage

lic_

Tank top/Inner bottom

Sketch of repair

Alici Tank top/inner bottom

ic.-e=o-L. 1 '__..--.

e • .11 I 01 li: - iPSe, , ..,-.4.. ..,,* vIr

Tl 1 r Vir Additional brackets with

spoliL. soft toes

Fracture 1

1 visissa. 327.3, =dal

Fracture

Figure 3e

20


Detail of damage Fractures at welded boundaries of the floor stiffener (heel) to both bottom shell and tank top longitudinals

Sketch of damage

"1" to

Sketch of repair

Stiffener

Longitudinal

Bracket with soft toes fitted

(fillet welded)

Floor '

UM• itudinal

Stiffener

ngl.

It is recommended for the purpose in the stiffener

Bottom shell

that of fabrication is designed

-------.. ...---.

Stiffener

the cutout (rathole)

as shown

Fracture r ----Floor

Bottom shell

Note : same damage may occur at similar connections on tank top

Cutout

Figure 3f

21

Sketch of repair Sketch of damage

Detail of damage Fractures at welded boundaries (toe) of the floor stiffener to both bottom shell and inner bottom longitudinals

Fracture

Longl.

Stiffener

Lon• itudinal

Fracture ---- . Bottom shell

----Floor

Note : same damage may occur at similar connections to inner bottom

Repair (a)

Additional bracket with soft toes fitted (fillet welded)

Bottom shell Longl.

.....................----- ..... ,.x." Where required the longitudinal to be cropped

and part renewed

Notes on repairs

Repair (b), where the stiffeners are unconnected to the longitudinals and offset from theme is to be incorporated after approval by the classification Society concerned. Lugs and/or collars may be necessary at the cutouts in the floor for passage of longitudinals.


Figure 3g

22


Detail of damage Fractures and buckling in way of a cutout for the passage of a longitudinal through a transverse primary member

Sketch of damage

ft rl il

Floor

o

Sketch of repair

Repair

New floorplating of enhanced thickness

A

, x• i't.V.„,.•1-•?,:•'‘,.

**..,.

Lug introduced •,,.....wkri,4z

- • ."...m. ,, ra.,:.•:,-... , , " -.• ...„icz,... •,,

:•,.:77,-... .g Kr.44:44,--

'--:.• '''.--

t.:4‘,:7 :*,.. . Laic

-‘`.= •..... , • - , , -.1.4•=•1: lt - • 4 '..,

, .k.„ 1 V.% , ,

--',-r, -e-.--,' .

•-•*.' ,lar.

,-• ,zoa'--06i* •••,-.

Buckling and/or fracturing

\

•••,\

Long]. • "''''t g . -?°:. . ... -vs,

Repair B

..--

Full collar plate

1 t

t.".■ ....

Fracture

Note : same damage may occur at Similar connections on tank top

Figure 3h

23

Detail of damage Fracturing of hopper longitudinal at boundary with transverse web


Bracket partly renewed to incorporate soft toe

/ Flange removed and stiffener added

Additional bracket

Hopper Tank Structure

Figure 4a

24

Hopper Tank Structure

Detail of damage Fractures at weld connection of the transverse brackets


Fractures transverse

in the brackets Larger brackets

thickness inserted, for longitudinals closed or collar plates and

stiffening added

of increased

additional

cutouts by lugs

Note :

If the damage is caused by misalignment with the frame bracket above, the misalignment is to be rectified and the replacement by a bigger bracket incorporated only if felt necessary

Figure 4b

25

Structure Within Topside Tanks

Detail of damage Fractures around unstiffened L/H and M/H in wash bulkhead

Sketch of damage

Upper deck

Sketch of repair Repair (a)

it

thickness

(b)

Plate cropped and renewed with plating of enhanced and horizontal stiffeners

Repair

added

Fractures LJH and

around M/H

Topside

, r

(I)

tank sloping plating longitudinal

Deck longitudinal

Stiffener to longitudinals

Plate cropped out and renewed with plating of enhanced tiHand M/H may be replaced cut-out as shown and incorporating plate to form a transverse in accordance with the relevant Society Rules

thickness.

web

by a

with scantlings Classification

a face

Figure 5a

26


Detail of damage Thinning and subsequent buckling of opening

of web plating in the vicinity of radii


goi A It . Ili

4100#

111111* ilAreasIPP:40f excessive corrosion and probable subsequent buckling

min Imillit iarrmtusrsmr& I

o4tixtt

1.A441Pw

,ikt-V't

Additional stiffening added, both vertical and horizontal

NE IIIIII

lin 11111

0\

pris- w IIII

Okillit...... 11,

Figure Sb

27


Detail of damage Fractures at slots in way of transverse webs

Sketch of damage

Upper deck plating

Sketch of repair

A

Lug to be fitted Upper deck 1

kb,..

1

) Fracture

Transverse web

----

■

Deck longitudinal (flat bar)

..--.., Fracture

\ Fracture

Stiffener

d

1 Stiff4ner

b...., \ NO

Web: partly renewed

A

View 'AA'

Stiffeners to be renewed

Lug or collar plate

Upper deck 1r

Stiffener renewed

Deck bngitudi .B.)

/ Face plate of transverse web

•"1/ Full collar plate where bottom of cutout 5 0.4d and in areas of high shear stress

Figure 5c

Larger brackets inserted, cutouts for longitudinals closed by

lugs or collar plates and additional stiffening added

Fractures in the transverse brackets

Sketch of repair Sketch of damage


Figure 5d

29

Deck Structure

Detail of damage Fractures at the hatch corners


insert plate of enhanced steel thickness

...p.-74:7- •:?...,;,..,..---,,,Kk Alb.

,......„ t

IRO Fracture at hatch corner

r 3 1 5r

I

I

11M14.

I

1 I

- I1

1111111 I 111111 1

I

Figure 6a

30

Deck Structure

Detail of damage Fracture of welded seam and probable plate buckling at cross deck


_ 26mm

suitable thickness 18 -20 mm

case

AMA

Fracture at welded seam

!!.. \\.

Additional transverse stiffening if

is also evident

,

Buckling of the cross

deck

: . ,,•: - - :......, ..vm

:',-•-:-..--- ", -. ..- -....,„:m. ...,,..,=.:,:sirk .., .. .. ..... "1.4q-- &.:‘ .4/1 ....,244;:i:P

-I-- I -1- - -4-- I I I 12kun i 1

—1-

-1– 1 1 1 l 1 I I

Plate of intermediate

is inserted i.e. for this particular

buckling

12mm

Figure 6b

31

Deck Structure

Detail of damage Budding of the hatch coaming structure and the hatch end beam

Sketch of damage

C

Sketch of repair

Additional transverse stiffening

C

Additional Ii ....milegiummomornsime.

111111111111111N111111111

stiffener

Mai

Ha ch ,----- en

coam ngi Main 11111=11111111111111 111111111111111ErikiEW

. =vat

Modified hatch end beam

with face plate

deck (I-

Buckling =MI

Figure 6c

32

Deck Structure

Detn it of damage

,

Fractures in the web or at the toes of the longitudinal hatch coaming termination brackets

Sketch of damage Sketch of repair Symmetrical face bar

integral athwartship

Side CO= IN -Ilk\ k

gusset beacet

Repair

\„...---------------,,,,_,,,..

A stiffener normal

Additional

150

X Section X-X

upper deck if clear of the

stiffening member

MIL Deck plating 4,11por

Topside tank or Fractures hatch side girder

30

701,

15,4

4- , -- ;

--------

View AA

35

-.4....

Repair B

Figure 6d

33

Forepeak Structure

Detail of damage Fracture and buckle of bow transverse web in way of longitudinal cut-outs

Sketch of damage

top Peak

Sketch of repair

tank

II

--- --- ---

-

Fracture 415,.. 10.

Side shel

Localised buckling

,--- ,,v4v ‘,1 -4,,,,. ,,,„..

ISTVNt> WV, ̀k ,,,,- <„,..e......N,,.

N9VV;i■ 1,4 . \,. *

insert plate with additional

stiffening --

Transverse web frame

Figure 7a

14

Forepeak Structure

Detail of damage Fracture at toe of web frame bracket connection to stringer platform bracket

Sketch of damage

Fracture

Sketch of repair

taper of face to a

of 1:3

1s2°,

,..„,,d •-__.. 1111L1k

Modify ‘ fiat ending \ minimum

-,..

Shell insert insert plate of increased thickness

plating -

Web frame

Figure 7b

35

Transition Regions in Cargo Spaces, Fore and Aft

Detail of damage Fractures at the supporting brackets in way of the collision bulkhead, where side shell panting stringers fitted

Sketch

No

Stiffener

of damage

intapostai &tigers

Hold

1 Hold

panting

►

Frxtres

S

of stiffen

Fore peak tank

sPace

Sketch

---, S

of repair

S Mal-Tried bracket

\ \

oder

\ S

WA

ill Fcre

or space

•,11 f ...1

\ \ c --,,, ,

No

if Stever,-

1 Hold

C = Plate S = Snaped

frame

Fractre

end

\

I-10

Col5sicn bulkhead

-

Collision lxilkhead

Figure 8a


Detail of damage Fractures at the supporting brackets in way of the collision bulkhead, with no side shell panting stringers in hold

Sketch

Hold frame

No1

of damage

Hold

Stiffeners

S = Snaped

std

Fractue

exl

r.

Frxtures

:i ' .1 ....., ' \

\ '‘

Collision totikhead

of stiffener

ir

Sketch

Extension *toe

No

of repair

1 Hoid

Slifferer

S \ \ \ \

C = Plate

Modified brxket

\` \

S \

Colision bulkhead

cellar

.

Fore Peak tank

sPaPe

ra ril

IR NI tank

ril or

111 1 sPace

Figure 8b

37


Detail of damage Fractures at the supporting brackets in way of the collision bulkhead with no side shell panting stringers in hold.

Sketch of damage

Side Shellracture fracture

Topside tank

Hold frame

stringer in

Sketch of repair

UV

i 11 Vi ‘‘

Detail 'A' lk llik X li Hold

Ilk reinforced

■ ■ ■

X % ■ '■ ■ •

A

Ihill'i1/411110#400„"k'l 12.5Y

Fore Peak tank

Frame

Fore Peak tank

Stringer in

ur, mosKr Hold frames

Fore Peak Collision tank bulkhead

Hopper 50

_IL Hopper er 50 ank

View 'X - r

Figure 8c

38

Transition Regions In Cargo Spaces, Fore and Aft

Detail of damage Fractures in way of horizontal diaphragms in the connecting trunk between topside tank and hopper double bottom tank on after side of collision bulkhead in No I Hold.

Sketch

Diaphragms

of damage

Fractures

Collision Cc necting bulkhead trunk

i Side I shell

1 I

....1 ,

I

--... .... ..—.., . . .....0........, ".... ,

Topside tank Sketch of repair

I

Connecting Fractures trunk

in shell \X'

Cropped and part renewed or veed and ..xi welded as necessary

Horizontal diaphragms ■./

to be removed

Collisions bulkhead

ii...."

- - Collision

bulkhead

stringers/flats

pr Brackets with

Trunk

Of trunk

\X"

to align inboard side

\--."

41■46. 110' Hopper

tank

Fore

// Fractures

Trunk

Plan view of diaphragm

Pea tank

Figure 8d

39

the abs safehull system -...

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