Types of Various Trusses | Wooden Trusses (2023)

The various types of trusses in use are

The principal rafters support the purlins.
The purlins support the nearly-spaced common rafters which own the same slope as the principal rafters.
The common rafters support that roof covering as usual.
The spacing from the kingpost truss is limited to 4 m from middle to middle.
The truss is suitable for spans varying from 5 to 8 metres.
The principal rafter is jointed to the tie-beam with a single abutment and ‘tenon joint’ or by a ‘bridle joint’.
The collective is further strengthened by a wrought iron heel strap, which would round the joint.
The king-post is provided among splayed shoulders and feet and is tenoned toward the upper edge of the tie beam for a sufficient distance.

A queen-post truss differs from a king-post truss in having two vertical posts, rather than one.
The vertical posts are known as queen posts, the tops of which are correlated by a horizontal piece, known as a straining beam.
Two struts are provided to join the feet of any queen-post to the principal rafter, The queen-posts are the tension members.
The straining beams receive the thrust from the principal rafters and keep the junction in a stable position.
A straining beam is introduced on the tie beam within the queen posts to counteract each thrust from inclined struts which happens in compression.
In the absence of the straining sill, the thrust from the strut would serve to force the foot of the queen-post inwards.
These trusses are suitable for spans between 8 to 12 metres.
The joint at the head of the queen-post -is formed due upon the junction of pair compression members (principal timber plus straining beam) and each tension member(queen-post).

King-post and Queen-post trusses are suitable for spans up to 12 meters.
For greater spans, the queen-post truss can strengthen by one more upright member, called a princess-post to each side.
Fig. displays the resulting combination of king-post also queen-post trusses, which are becoming up to 18 m spans.

This roof truss called given to its designer Francois Mansard, a French planner.
A mansard roof truss does a combination of king-post and queen-post trusses.
It is a two-storey truss, with the upper division consisting of a king-post truss and the lower portion of a queen-post truss.
The entire truss has two pitches. The upper pitch (king-post truss) varies from 30° to 40° while the two lower pitch (queen-truss) varies from 60° to 70°.
The use of these trusses results in an economy in space.

A truncated truss is comparable to a Mansard truss, except that its head is formed flat, with some gentle slope to one side.
This type of truss is used when it is required to provide a room in the roof, between the two queen posts of the truss, as shown in Fig.

This truss, in the form of a bow, consists of thin sections of timber, with its best chord curved.
If this roof covering is light, the roof truss can be managed up to 30 m.

Roof trusses made of two materials, such because timber also steel, are known as composite rooftop trusses.
In a composite truss, the tension members are made of steel, while compression members are made of timber.
If tension members are made of timber, their section becomes very heavy because of the reduction of a section at the joints.
Special fittings mean required for the junction of steel and timber members.