TABLE OF CONTENTS The purpose of a structure is to support the loads for which it has been designed. To accomplish this it must be able to transmit a load from one point to another, i.e. from the loading point to the supports. In Fig. 2.21, for example, the beam transmits the effects of the loads at B and C to the built-in end A. It achieves this by developing an internal force system and it is the distribution of these internal forces which must be determined before corresponding stress distributions and displacements can be found.
A knowledge of stress is essential instructural design where th ecross-sectional area of a member must be such that stresses do not exceed values that would cause breakdown in the crystalline structure of the material of the member; in other words, a structural failure. In addition to stresses, strains, and thereby displacements, must be calculated to ensure that as well as strength a structural member possesses sufficient stiffness to prevent excessive distortions damaging surrounding portions of the complete structure.
In this chapter we shall examine the different types of load to which a structural member may be subjected and then determine corresponding internal force distributions.
Structural members may be subjected to complex loading systems apparently comprised of several different types of load. However, no matter how complex such systems appear to be, they consist of a maximum of four basic load types: axial loads, shear loads, bending moments and torsion.
