How to increase allowable bending moment

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• How to increase allowable bending moment ?
• Increase truss dimensions most effective
• Increase diameter main chords
• Increase wall thickness main chord

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• Bending moment caused by Wind force

Loading force
Wind force
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Wind loading on a canopy or projection screen
Fh 1,3 x wind Pressure Wind surfaceFmembrane
tension Fh / 0,8
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Transversal force ( Also known as shear force )
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• Examples of situations when transversal forces
  will be determine the maximum loading
• A heavy load on a short span.
• A heavy load near to the suspension point.
• Truss constructions underneath a stage floor.

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• How to increase allowable transversal force ?
• Increase the diameter of the brace
• Increase the wall thickness of the brace
• Increase wall thickness of the main chord

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• NORMAL FORCE

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• Examples of situations when a normal force
  occurs
• Towers
• Columns
• Rafter trusses in a MPT or ST roof

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• How to increase the normal force?
• Increase tube diameter
• Increase wall thickness of tubes

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• TORSION FORCE

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• Examples of situations when torsion will occur
• Equipment on a boom arm
• Equipment which are all positioned on one tube of
  a truss

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• How to increase the normal force?
• Increase the amount of cross braces inside the
  truss.
• Use a bigger truss.

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• Deflection
• The elastic movement of a structure under load
• Deformation by self weight and pay load gt the
  truss starts to bend/deflect

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• How to minimise deflection ?
• Increase truss dimensions most effective
• Use stiffer material e.g. steel
• PRE-camber the truss

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• Example of PRE-camber the truss

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• When is deflection important ?
• When rigging a fixed LED screen.
• Personal feeling gt a floor which deflects a lot
  feels unsafe

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• Suspending load from a truss system.
• Heavy loading should always be attached near or
  to or at the nodepoints
• Small loadings up to 100 Kg can be attached
  anywhere on the truss.

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• Possible mistakes of a Truss.
• Parallel running braces
• Miss nodding

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Miss Nodding
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• Analising loading of truss structures.
• The type of structure determines the allowable
  loading.
• Loading tables are only valid for simply
  supported spans.
• Other types of constructions or structures have
  to be calculated in a structural report.

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• Simply supported span
• Truss on two hoists,
• truss on two towers

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• Continious span
• Truss on three or more hoists,
• truss on three or more towers

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• Span
• Free span is the total length between 2
  suspension points
• Loading capacity
• The ability of the truss to withstand a load
  within its tolerances

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Reaction force on suspension points
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Situation 1Spann of 20m loaded with 2000 Kg UDL
( including selfweight of the truss.) The spann
is suspended on 2 chainhoist. Eache suspention
point will be loaded by 1000 Kg, a 1 ton motor
can be used.
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Situation 2Spann of 20m loaded with 2000 Kg UDL
( including selfweight of the truss.)the spann
is suspended on 3 chainhoist. The 2 outer
suspension poins will be loaded with 380 Kg, and
the middle suspention point will be loaded with
1240 Kg, the middle motor now needs to be a 2 ton
chain hoist.
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• Know your load
• Know the suspended loads from your Truss
• Know the reaction forces on the suspension points
• Make upfront a rigging plot of the loading setup

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• Know your load
• Know the suspended loads from your Truss
• Know the reaction forces on the suspension points
• Make upfront a rigging plot of the loading setup

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Text underneath the loading table
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TRUSS STANDARDS

• Design standards
• DIN 4113 German standard
• VPLT SR 1.0 German Code of practice
• BS 8118 British standard
• BS 7906-1 / BS 7905-2 British standard for
  design, manufacture and use
• Euro-code 9 European standard (not enforced yet)

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TRUSS STANDARDS

• Standards for temporary structures
• Design standards
• DIN 4112 German standard
• BS Temporary Demountable structures British code
  of practice
• EN 13814 European standard for temporary
  demountable structures

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TECHNICAL TRAINING

• Questions?