Subject: Simple Trusses

Lecture No. 23

Subject: Simple Trusses

Objectives of Lecture:

· To explain the concepts of the simple trusses

23-1 Simple Trusses

(a) Definition

A truss is defined as a structure composed of slender members made of wooden struts or metal bars joined together at their end points, as shown in Fig. 23-1

(b) Planar Trusses

· Lie in a single plane (i.e. 2-D)

· Support roofs and bridges

(i) Roof truss (Fig. 23.2)

Fig. 23.2

(ii) Bridge truss (Fig. 23.3)

Fig. 23.2

(i) All loadings are applied at the joint

Note: Distribute the weight of a truss member equally on each of its ends.

(ii) The members are joined together by smooth pins

(i.e., Mabout a joint = 0)

(d) Nature of Force in a Member

(i) If the force elongates the member it is tensile (Fig. 23.4 a)

(ii) If the force shortens the member it is compressive (Fig. 23.4 b)

(e) Simple Truss

Fig. 23.5

Fig. 23.6