Design of structural elements

3.1. Introduction

 Reinforced concrete is one of the principal materials
 used in structural design. It is a composite material,
 consisting of steel reinforcing bars embedded in
 concrete. These two materials have complementary
 properties. Concrete, on the one hand, has high
 compressive strength but low tensile strength. Steel
 bars, on the other, can resist high tensile stresses
 but will buckle when subjected to comparatively
 low compressive stresses. Steel is much more
 expensive than concrete. By providing steel bars
 predominantly in those zones within a concrete
 member which will be subjected to tensile stresses,
 an economical structural material can be produced
 which is both strong in compression and strong
 in tension. In addition, the concrete provides cor
rosion protection and fire resistance to the more
 vulnerable embedded steel reinforcing bars.
 Reinforced concrete is used in many civil
 engineering applications such as the construction
 of structural frames, foundations, retaining walls,
 water retaining structures, highways and bridges.
 They are normally designed in accordance withthe recommendations given in various documents
 including BS 5400: Part 4: Code of practice for
 design of concrete bridges, BS 8007: Code of prac
tice for the design of concrete structures for retaining
 aqueous liquids and BS 8110: Structural use of con
crete. Since the primary aim of this book is to give
 guidance on the design of structural elements, this
 is best illustrated by considering the contents of
 BS 8110.
 BS 8110 is divided into the following three parts:
 Part 1: Code of practice for design and construction.
 Part 2: Code of practice for special circumstances.
 Part 3: Design charts for singly reinforced beams, doubly
 reinforced beams and rectangular columns.
 3.1 Introduction
 Reinforced concrete is one of the principal materials
 used in structural design. It is a composite material,
 consisting of steel reinforcing bars embedded in
 concrete. These two materials have complementary
 properties. Concrete, on the one hand, has high
 compressive strength but low tensile strength. Steel
 bars, on the other, can resist high tensile stresses
 but will buckle when subjected to comparatively
 low compressive stresses. Steel is much more
 expensive than concrete. By providing steel bars
 predominantly in those zones within a concrete
 member which will be subjected to tensile stresses,
 an economical structural material can be produced
 which is both strong in compression and strong
 in tension. In addition, the concrete provides cor
rosion protection and fire resistance to the more
 vulnerable embedded steel reinforcing bars.
 Reinforced concrete is used in many civil
 engineering applications such as the construction
 of structural frames, foundations, retaining walls,
 water retaining structures, highways and bridges.
 They are normally designed in accordance with
 Part 1 covers most of the material required for
 everyday design. Since most of this chapter is
 concerned with the contents of Part 1, it should
 be assumed that all references to BS 8110 refer to
 Part 1 exclusively. Part 2 covers subjects such as
 torsional resistance, calculation of deflections and
 estimation of crack widths. These aspects of design
 are beyond the scope of this book and Part 2, there
fore, is not discussed here. Part 3 of BS 8110 con
tains charts for use in the design of singly reinforced
 beams, doubly reinforced beams and rectangular
 columns. A number of design examples illustrating
 the use of these charts are included in the relevant
 sections of this chapter