SHIP & OFFSHORE STRUCTURES - Old Dominion Universityaverma/nsf/Ship_Structure IM 2/Final... ·...

MarineTech

2009 - 2011

STEM Preparation through Marine Engineering, Science and Technology Experiences

Alok Verma Lean Institute - ODU

SHIP & OFFSHORE STRUCTURES

1

MarineTech

2009 - 2011


Alok Verma Lean Institute - ODU 2

Module Description and Goals

The Engineering module offers students an opportunity to:

Examine the fundamental principles of engineering behind

structure design of ships and offshore structures.

Describe and analyze the forces that act upon structures.

Explore compression, tension, deflection, and stability of

structures.

MarineTech

2009 - 2011



Contents

Evolution of Ship Structures & Terminology 10 min

Beams 05 min

Hands-on Activity 1: Square Beam 15 min

Truss Structure 15 min

Hands-on Activity 2: Frame Stability 10 min

Uniqueness of Ship Structure 05 min

Structural Load 05 min

Hands-on Activity 3: Deflection in Structure 30 min

Offshore Structures 15 min

Hands-on Activity 4: Off-shore structure 40min

Total 2 hrs 30 min3

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Alok Verma Lean Institute - ODU 4http://www.doe.virginia.gov/vdoe/Superintendent/Sols/home.shtml

Ship Structure

Aircraft Carrier Container Ship

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Ships can carry anything………!!!

5

How ships carry heavy load??

What makes them to acquire

high strength ???

Ship Structure

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Evolution of Ship Structure

Structurally, a ship is a hollow

beam subjected to severe

bending and twisting as it

moves through waves and as its

own load changes.

Early Structures:

The strength is given by

walls only.

Use: Light weight

transportation in river

6

Early Boat Structure

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Keel

Example of Wooden Keel Construction

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Evolution of Ship StructureKeelboat

Use:

Transportation of

goods in the river

and sea.

Material used:

Wood

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A ship structure usually consists of a

network of frames and plates.

Frames consist of large members

running both longitudinally and

transversely.

Plating is attached to the frame

providing transverse and longitudinal

strength.

Material used : Steel

9


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Transverse and Longitudinal Frames of a Ship with Metal Structure

Transverse

Frame

Outer

Plates


Longitudinal

Frame

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The ship is given its shape by a

series of symmetrically curved

frames that run transversely and

that are fastened to the keel at the

center.

11


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Example of Construction Using Rivets

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General Frame Structure of a Ship

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Material Used For Ship Structure Building

At present the material used for large ship structure is – STEEL

Smaller boats and vessels are made of - ALUMINUM

How to build a ship structure??

- Use basic material shapes available in the market

14

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Structural Members

15

Beams

Channels (V Channel, C Channel)

Plates

Rods (Cylindrical, Square)

I- Beam

Square Beam

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I-Beam

16

Beams with I cross section.

The Vertical element is

called “Web”

Horizontal elements are

known as “Flanges”

Bending Load

Twisting load

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I-Beam under Bending Load

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I-Beam with Twisting Load

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Square Beam

19

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Application of Beams

20

Building Construction

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Application of Beams

21

Roller Coaster

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Bending and Twisting loads

cause deflection in structure

Deflection is critical ----can

lead to fracture or failure

Excessive deflection should

be avoided

The stress causes deflection

in structure

22

Deflection Due to Load

Tower of

Pisa

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Stress

23

Load Load

Stress

Beam

It is a load acting on unit area.

Stress = Load /Area = P/A

Stress creates “Tension” or “Compression” in

member.

PP

AA

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Hands on Activity-1

Square Beam (Loads and Deflection)

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Frame Structure :Truss

A truss is a structure comprising one or more triangular units.

25

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Truss Structure

Truss of a

Bridge

http://en.wikipedia.org/wiki/Truss_bridge

26

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Truss Structure

The basic building block of a

truss is a triangle.

Large trusses are constructed

by attaching several triangles

together.

A new triangle can be added to

truss by adding two members

and a joint.

Triangle- Building block of

truss structure

A truss structure formed by attaching

two triangles27

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Truss StructureApplication of truss structures in cranes.

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Truss StructureApplication

Golden Gate Bridge, San Francisco

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The Bridge without a Truss that Failed

30

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Link: A member of a truss structure.

Node: Junction of two members.

Loads are applied at nodes only.

A member can take tensile or compressive force, which means it can resist “pull” or “push”.

Truss Terminology

Node

Link

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Stability of Simple Trusses

A stable triangular truss

http://www.ce.ufl.edu/~mih/activities/cdrom/civil/stable.html

32

An unstable square truss

Fixed Nodes

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GROUND SUPPORT

Load Distribution

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Hands-on activity-2Frame Stability

34

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1) Which frame is showing more resistance to the pressure applied by

hand?

– Frame 3

2) Which frame contains more triangular shape elements?

– Frame 3

3) Conclusion??

- Triangular shape elements provide more stability to the structure.

Hands-on activity-2Frame Stability

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5 minutes

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Class Exercise-1Truss Structure & Stability

37

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Let n = number of nodes

b = number of links

If 2 x n = b + 3, then we can say that the truss structure is stable.

38

Stability Equation

Here n=3 and b=3

Is this structure stable?

-YES

2 x 3 = 3 + 3

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Here n=4 and b=4

Stability Equation

The structure shown here is

not stable as 2 x n ≠ b + 3

What can be done to make this

structure stable?

As, 2 x 4 ≠ 4 + 3

2 x 4 = 5 + 3

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Rules about loads (forces):

Vertically upward load (+Y direction)

Vertically downward load (-Y direction

Horizontal right hand load (+X direction)

Horizontal left hand load (-X direction)

Loads on Truss

-ve

-ve

+ve

+ve

X

Y

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Rules about loads:

For stable structure-

The sum of all the loads acting in

the horizontal direction is zero.

The sum of all the loads acting in

the vertical direction is zero.

15

5 5

15

10

Loads on Truss

X

Y

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Truss Analysis

Truss is made up of links, which are either

in compression, in tension or no-load.

The equilibrium equations at a joint is used

for solving forces inside of the truss.

How to calculate force inside a link ??

“Break the Truss !”- Draw Free Body Diagram

Compression Bar

Tension Bar

42

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Free Body Diagram of Truss

43

Load

A B

C

Link A- Push

(Compression )

Link C- Pull

(Tension)

Forces

Link B- Push

(Compression )

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Free Body Diagram of Truss

44

A B

C

Load

Link A- Pull

Under

Tension

Link B- Pull

Under

Tension

Link C- Push

Under Compression

Load

Forces

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Class Exercise-2

45

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Hands-on Activities-3Deflection in Structures

46

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Bridge Structure Ship Structure

180 deg

Analogy

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Inside Frame structure of a Ship

Analogy

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Bridge Structure Ship Structure

180 deg

Analogy

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Frame

structure of a

ship

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Uniqueness of Ship Structure

Ship structures are unique for a variety of reasons.

For example:

Ships are

www.usna.edu/Users/naome/phmiller/EN200

51

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Ships carry a variety of dynamic and random loads.

52

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Ships operate in a wide

variety of environments and

climatic conditions.

53

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Ship Structural Load The force due to water (Buoyancy).

It is uniformly distributed.

54

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Ship Structural Load

Loading may be distributed non-uniformly.

55

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Buoyancy is greater at wave crests.

If the wave crest is at the bow and stern, the vessel is said to

be sagging.

The net effect is that the middle has less support.

Sagging

Trough Amidships

56

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If sagging loads get too

57

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If the wave crest is at the middle, the vessel is said to be

hogging.

Buoyancy force is greater in the middle

The net effect is that the bow and the stem have less support.

58

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If hogging loads get too

59

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60

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Sagging and Hogging also depend on the length of the ship.

Long ship is subject to more Sagging/Hogging than small ship.

61


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Class Exercise-3

62

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10 minutes

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Offshore Structures

64Typical Oil Rig

Oil Rig Platform:

The structure used for oil well

drilling and oil extraction from

the sea bed.

Depending on conditions, this

platform may be fixed to the

sea floor or may float on the

water. Platform

Base

Platform

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Types of Oil Rigs:

1) Fixed Platform

2) Semi-submersible Platform

3) Floating Platform

4) Drill Ships

65

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Fixed Platform Oil Rig

66

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Semi - Submersible Platform Oil Rig

67

Water Level Mark

This movable structure

has hulls which causes it

to float.

The weight of the

structure keep it upright

on the water.

It can drill in deep

water up to depths of

12,000 feet.

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Floating Platform Oil

Rig

68

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Drill Ship

69

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Parts of Oil Rig

70

Drilling

Module

1) Piles

2) Drilling Module

3) Flare stack

4) Heliport

5) Production

module

6) Drilling Derrick

7) Power generation

Utilities

1

654

32

7

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Oil Drilling

71

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Oil Rig Part: Piles

72

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Flare Stack

It is an vertical elevated stack or chimney used to burn unwanted over-pressured gas.

73

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Drilling DerrickThe part built over the oil well for lifting and positioning of piping

74

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Hands on Activity 4

Offshore Structure

75

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Sample Model

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Platform Base

Examples of platform base that you can build during hands-on activity

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Review of Topics

Different ship frame structures and terminologies

Beam loads and deflection in Beams

Truss Structure, its stability and analysis

Uniqueness of ship structure

Structural loads on ship

Offshore structure: Types and part details

78

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For more information on this module

Please contact:

Dr. Alok K. Verma, P.E., CmfgE

Ray Ferrari Professor

Director-Lean Institute

Old Dominion University.

Phone (757) 683-3766

Fax (757) 683-3990

Email: [email protected]

mailto:[email protected]

SHIP & OFFSHORE STRUCTURES - Old Dominion Universityaverma/nsf/Ship_Structure IM 2/Final... ·...

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