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Page 1: Bending of Structural Hollow Sections Structural Hollow Sections can bend in either hot or cold condition. During this process folds may occur in the inner.

Bending of Structural Hollow Sections

• Structural Hollow Sections can bend in either hot or cold condition.

• During this process folds may occur in the inner zone and decrease of

thickness takes place at outer zone.

Hot Bending

1. To avoid folds fill the section with sand and heat up to 850 Degree Celsius.

2. By Induction heating locally.

Page 2: Bending of Structural Hollow Sections Structural Hollow Sections can bend in either hot or cold condition. During this process folds may occur in the inner.

Hot Bending by Induction heating Locally

Page 3: Bending of Structural Hollow Sections Structural Hollow Sections can bend in either hot or cold condition. During this process folds may occur in the inner.

Different Methods of Cold Bending

1. By Pressing

2. Using a winding system

3. By means of forming box

4. Roller Bending

5. By means of Mitre Cuts and “V” notches.

Cold Bending of Hollow Sections

Page 4: Bending of Structural Hollow Sections Structural Hollow Sections can bend in either hot or cold condition. During this process folds may occur in the inner.

1. By Pressing

In this process Hollow Section will be

set between two fixed rollers and

bending them by displacement of a

central former.

Usually this central former is

connected to a hydraulic actuator

Cold Bending of Hollow Sections

Page 5: Bending of Structural Hollow Sections Structural Hollow Sections can bend in either hot or cold condition. During this process folds may occur in the inner.

2. Winding System

The Hollow Section is held by a shoe or

clamp, firmly connected to a circular former

“b” . A corresponding fixed gliding shoe “c”

is then rotated and force the tube in to the

recess of the former “b”

Cold Bending of Hollow Sections

Page 6: Bending of Structural Hollow Sections Structural Hollow Sections can bend in either hot or cold condition. During this process folds may occur in the inner.

3. Forming Box

In this process Hollow Section will be

forced in to a pre-shaped forming box.

This method is economical if many

bends of the same size are required.

Cold Bending of Hollow Sections

Page 7: Bending of Structural Hollow Sections Structural Hollow Sections can bend in either hot or cold condition. During this process folds may occur in the inner.

4. Roller Bender

• Bending is obtained by pressing the

hollow section through three rollers.

• All three may be driven , but the

central one which determines the

radius of the bend, can be idle.

• This process is generally preferred by

the steel constructors.

Cold Bending of Hollow Sections

Page 8: Bending of Structural Hollow Sections Structural Hollow Sections can bend in either hot or cold condition. During this process folds may occur in the inner.

5. Mitre cuts or “V” Notches

• An approximate curve is obtained by

joining the straight sections end to end

by welding.

• By making “V” notches in the webs

and bottom flange and bend the top

flange to the required bend.

Cold Bending of Hollow Sections

Page 9: Bending of Structural Hollow Sections Structural Hollow Sections can bend in either hot or cold condition. During this process folds may occur in the inner.

Commonly used Methods.

Cold Bending using Three Roller Machine

Hot Bending using Induction heating with a radial arm controlling

the radius

Mitre Cutting and welding.

Bending of RHS/SHS

Page 10: Bending of Structural Hollow Sections Structural Hollow Sections can bend in either hot or cold condition. During this process folds may occur in the inner.

Bending of RHS/SHS

• In general when bending a RHS the inside face will compress, the outside wall will

stretch and the side wall will exhibit both.

• If bending is severe on a section of high width to wall thickness ratio, convexity in

the two side walls and concavity in the inner face may develop.

Page 11: Bending of Structural Hollow Sections Structural Hollow Sections can bend in either hot or cold condition. During this process folds may occur in the inner.

Problems facing for bending of 180x180x6

• Side Wall buckling

• Concavity in inner face

Page 12: Bending of Structural Hollow Sections Structural Hollow Sections can bend in either hot or cold condition. During this process folds may occur in the inner.

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