Equilibrium of Strings

INTRODUCTION

A string (or rope), in its theoretical sense, is absolutely flexible, light (i.e. its weight is neglected) and inextensible. It is capable of offering only tensile resistance. The slope of a loaded string depends upon its length and the loads supported by it. It will be interesting to know that if the loads carried by the string are changed (in magnitude or position) its shape will also change.

SHAPE OF A LOADED STRING

Consider a string or cable suspended at two points A and B at the same level, and carrying a uniformly distributed load over its horizontal span as shown in Fig 15.1.

TENSION IN A STRING

The determination of tension in the string or cable is one of the important criterion for its design. As a matter of fact, the tension in a string depends upon the magnitude and type of loading as well as levels of the two supports. Though there are many types of strings and loadings, yet the following are important from the subject point of veiw :

1. String carrying point loads.

2. String carrying uniformly distributed load.

3. String supported at different levels.

TENSION IN A STRING CARRYING POINT LOADS

TENSION IN A STRING CARRYING UNIFORMLY DISTRIBUTED LOAD

Consider a string or cable suspended at two points A and B at the same level and carrying a uniformly distributed load over the horizontal span of the cable as shown in Fig. 15.5.