ANALYSIS OF STRUCTURE
A structure is made up of several bars (members) riveted or welded together to form frame. There are two types of frames. A frame which is composed of members that are just sufficient to keep the frame in equilibrium under the action of external load is known as perfect frame. Triangle is a simplest perfect frame. The perfect frame follows the equation.
N = 2j -3
Where n = number of members
J = number of joints
On the other hand, a frame in which number of members are less or more than (2j- 3) is called imperfect frame. If it is less than 2j- 3, it is known as deficient imperfect frame, and if it is more than 2j- 3, it is known as redundant imperfect frame. Here we will discuss only perfect frame of pin-joined which carries load at joints.
There are three methods to analyses a frame
(i) Method of joints ;
(ii) Method of sections ;
(iii) Graphical method.
For details of (i) And (ii) refer solved examples 4.13 and 4.14 respectively.