Technical TrainingBasics: What is truss

Goal of this workshop

• Share knowledge

• Actively promote safe working practices

• Provide product expertise for users

Topics

• What is truss

• Different forces on Truss

• Analising loading of truss structures

• Truss standards

• Questions

What is truss ?

• Lattice structure

• Made of (mainly) aluminium tubes• Low self weight (easy to handle )

• Modular (easy to transport)

• Flexible (lego system)

What is a lattice structure?

1. A lattice structure is an open triangular structure.

2. Triangular shapes are stable in hinged connections

3. Triangulation is essential for strength and stability

Similarity between a lattice structure and a Truss?

The Truss

Main tube

Cross bracing bracing

End bracing

Coupling system Node point

Advantages of aluminium• +/- 1/3 of the weight of steel• Non corrosive• Available in large quantities• Easy to machine• Allowable stress for tension and

compression is the same

Why is Truss made of (mainly) aluminium?

Disadvantages of aluminium• Strength decreases after welding with

+/- 50%• Less stiff as steel• More difficult to weld• More expensive

Why is Truss made of (mainly) aluminium?

Main advantage of a Truss structure :

Low self weight in relation to a high load bearing capacity.

Achieved by..

Bringing the material to the position where you need it !!!!!

Example.

Different type’s of coupling systems

• Tube coupler• Gusset / Endplate• Hinge connection Male / Female• Conical coupler

1: Tube connection-Very high bearing stress in the

main chord-Open space between main

chord.

2: Gusset / Endplate-Bending force in gusset Plate

-Open space between main chord

3: Hinge connection Male / Female-Fixed Male/Female sides wear

given extra deflexion

4: Conical coupler-Wear is compensated bij spigot

shape

Mounting different brands of truss together.

• Although the truss looks the same each type of truss has different technical specifications

• Calculation of the system with different specifications.

• Responsibility

Different forces on Truss

•Loading Forces

•Internal reaction Forces

Different type’s of loading

• Point load• Multiple point load• Concentrated load• Uniformly distributed load• Cantilever load• Normal force

Point load

Multiple point load

Concentrated load

Distributed load

Cantilever load

Normal Force

Internal reaction forces in the Truss

•Bending moment•Transversal forces ( also known as shear force )•Normal forces•Torsion force

The reaction of these forces is

•Deflection

This figure indicates where the internal forces are active in the truss.

Shear force

Bending moment

Normal force

Normal force

Normal force

Bending momentTo strain under tension, causing a straight

line structure to turn into a curve-shape

Examples of situations when a bending moment occurs:

• Self weight caused by the Force of gravity• Live loading such as lightning fixture or Sound

equipment• Curtains, back drapes• Wind force.

COMPRESSION

TENSION

MO

ME

NT

MO

ME

NT