TABLE OF CONTENTS It is now clear from the discussion in Chapter 7 that the structural designer requires a knowledge of the behaviour of materials under different types of load before he/she can be reasonably sure of designing a safe and, at the same time, economic structure.
One of the most important properties of a material is its strength, by which we mean the value of stress at which it fractures. Equally important in many instances, particularly in elastic design, is the stress at which yielding begins. In addition, the designer must have a knowledge of the stiffness of a material so that he/she can prevent excessive deflections occurring that could cause damage to adjacent structural members. Other factors that must be taken into consideration in design include the character of the different loads. For example, it is common experience that a material, such as cast iron fractures readily under a sharp blow whereas mild steel merely bends.
In Chapter 1 we reviewed the materials that are in common use in structural engineering; we shall now examine their properties in detail.
Engineering materials may be grouped into two distinct categories, ductile materials and brittle materials, which exhibit very different properties under load. We shall define the properties of ductility and brittleness and also some additional properties which may depend upon the applied load or which are basic characteristics of the material.
A material is said to be ductile if it is capable of withstanding large...
