BCM 544 - Topic 4 Trusses System

CONSTRUCTION TECHNOLOGY IV
BCM 544
TOPIC 4: TRUSSES SYSTEM
BY DR JULIANA BRAHIM
PHD IN CONSTRUCTION MANAGEMENT
MSC. IN CONSTRUCTION CONTRACT
BSC. IN CONSTRUCTION MANAGEMENT
TRUSSES SYSTEM
A truss is essentially a triangulated system of
(usually) straight interconnected structural
elements; it is sometimes also referred to as an
open web girder.
The individual elements are connected at nodes;

the connections are often assumed to be nominally
pinned. The external forces applied to the system
and the reactions at the supports are generally
applied at the nodes.
When all the members and applied forces are in a

same plane, the system is a plane or 2D truss.
• Assemblies of ties (acting in tension) and struts
(acting in compression) arranged in pin-connected
triangles.
• Timber, hot rolled, cold rolled or tubular steel

sections are used as the materials.
• The use of steel has allowed even longer spans. The

span can as long as 75 metres.
• Connections can be welded, bolted or riveted•
• The trussed system is commonly used for the roofs

of community halls, gymnasiums and factories.
• Types of Trussed System:

• Trussed Rafters
• Trussed Girders
1. TRUSSES RAFTERS
• This is a triangular shaped ‘beam’ that span between two supports.
• Within the triangular structure are diagonal braces that help distribute the transfer of the loads
to the supports.
• A pair of columns supports the roof structure.
• A row of these trussed rafters will create a long hall with a wide span and a sloping roof.
• Trussed rafters can be designed for very long spans, ranging from 15-45 m.
• They are usually fabricated from timber or steel, and are spaced at suitable centers to carry purlins.
• They typically have a low pitch to give acceptable rainwater run off and can give reasonable daylight spread from roof
lights.
• While they have the advantage of reducing roof volume, the depth, and hence volume, increases with the span.
Trussed rafter roofs, also known as roof trusses, provide a structural framework to support the roof fabric,
ceilings or floors of buildings in both domestic and commercial structures.
There are many different types of roof trusses. Robust and reliable, they can be used on a wide range of
building types including timber frame, masonry and steel frame.
2. TRUSSED GIRDER
• This consists of a long pair of parallel sections or

chords.
• • In between the pair are diagonal braces that

help distribute the transfer of the loads to the
supports.
• • A row of these trussed girders will create a

long hall with a wide span and a flat roof.
• Girder is a type of roof truss or beam that is built
stronger than a standard truss to support in
construction. It can bear the load extra loads imposed
on it.
• The girder trusses usually are specially made with heavier

chords and plates and can consist of a number of trusses
laminated with nails or bolts.
CONSTRUCTION METHOD: STEEL TRUSSES
• Steel truss fabrication is a complex process that takes special skills, tools, and techniques to form specific
structures and products.
• Metal fabricators create steel structures in three main stages:
cutting forming assembly

• Fabricators use several tools to cut the steel

of a truss, including high-tech equipment
such as plasma cutters, lasers, and water
jets.
• Saws create straight cuts, while lasers and

plasmas are reserved for more complex
shapes and curves.
• The metal fabricator punches holes using

high-pressure notches.
• To form trusses, fabricators use both

press baking and rolling. These
techniques allow for an enormous range
of metal thicknesses, sizes, and shapes
for versatile applications.
• Standard trusses use a series of

triangles. During the forming process,
fabricators create the correct truss type
for its purpose. Most roof trusses, for
example, use C-shaped metal studs.
• The manufacturer will need to know the truss type, location, wind exposure, span, desired roof
slope, and more to correctly assemble and join the steel.
• This process includes welding pieces together, bringing the final product together to serve its
intended purpose as a truss. There is specialized software the fabricator will use throughout the
design and construction process, to meet the builder’s needs.
• An experienced truss fabricator can create optimal trusses – those that are as lightweight as
possible without compromising structural stability. They must also meet stringent building
compliance codes.
• Connection between members may be bolted or welded complete in fabricating shop or, if too
large for transport, are made in two halves with the necessary connecting plates and provisions
for attaching connecting members.
• Trussed roof structures are usually assembled at ground level and then lifted by one or a pair of
mobile cranes to final positions at the column supports.
• However, the installation of the purlins, roof covering, roof bracing and the mechanical service
lines require the installation of scaffoldings.
• During the installation of the series of trussed roof structures, temporary supports (scaffold
towers or tie cables) are needed to the trussed structure from being destabilized by wind.
• Purlins are laid over the trussed roof structure to support the metal sheet roof covering.
Insulation blankets are laid under the roof coverings to provide heat sound insulation.
• The electricity lines, lights, catwalks and ventilation ducts are fixed below and within the
trussed roof structure configuration. Wind loads to the building are countered by bracing
between the trussed roof elements and their column supports.
The beams used would be purlins to support the
center of the rafters, and binders to support the
ties, generally at their third points.
STEP 1: INSTALLATION ON THE GROUND
STEP 2: ATTACH THE TRUSSESS
STEP 3: BRACE WEB
STEP 4: HOIST THE TRUSSESS
STEP 5: HOIST THE NEXT TRUSSESS
STEP 6: INSTALL SHEATHING
STEP 7: HOIST THE 7TH TRUSS
STEP 8: REPEAT THE STEPS
INSTALLATION CONSIDERATION
• Inspect before installation:
• Maintain truss straightness during

hoisting:
THANK YOU FOR YOUR KIND ATTENTION!!!!

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CONSTRUCTION TECHNOLOGY IV

The individual elements are connected at nodes;

When all the members and applied forces are in a

• Timber, hot rolled, cold rolled or tubular steel

• The use of steel has allowed even longer spans. The

• Connections can be welded, bolted or riveted•

• The trussed system is commonly used for the roofs

• Types of Trussed System:

• A pair of columns supports the roof structure.

• This consists of a long pair of parallel sections or

• • In between the pair are diagonal braces that

• • A row of these trussed girders will create a

• The girder trusses usually are specially made with heavier

• Metal fabricators create steel structures in three main stages:

cutting forming assembly

• Fabricators use several tools to cut the steel

• Saws create straight cuts, while lasers and

• The metal fabricator punches holes using

• To form trusses, fabricators use both

• Standard trusses use a series of

• Maintain truss straightness during

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