Planar Trusses

Question 1

Explain the difference between a simple truss and a compounded truss.

Answer 1

A simple truss is a particular triangular truss constructed as follows: the basic structure begins with a stable triangle denoted , i.e., three bars and three nodes joined two by two. The second step consists in joining to the two nodes of this triangle (say, and ) two bars connected themselves by a common node (say, and ). The next step consists in joining to the nodes of the entire structure (say, and ) two bars connected themselves by a common node (say, and ). This step is repeated as many times as desired. The final structure constitutes a simple truss.

A compound truss is a category of triangular trusses consisting of many simple trusses connected between themselves. Each pair of simple trusses involved in a compound truss may be connected in two ways.

Question 2

What is a truss?

Answer 2

A truss is said to be triangular when the joint bars form between themselves a multitude of interconnected triangles.

Question 3

Explain the two zero-force member conditions.

Answer 3

1. When only two bars intersect at a given node and this node is free from any external force (either active or reactive), the two bars are zero-force members.
2. When three bars intersect at a given node, two of them are collinear and the node is free from any external force (either active or reactive), the non-collinear bar is a zero-force member.

Question 4

Explain The Principle of Virtual Work.

Answer 4

The theorem of virtual work was initially established to determine the displacements and the slopes developed at any point of a deformable body under any external loading.