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Analysis of Structure


4.7.1 Introduction

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.