# 4.1 Introduction

Provided that we know all of the boundary conditions (including both reaction supports and external loads as described in Section 1.5, then we can analyse the structure to determine all of the reaction forces and internal forces. These internal forces include the axial force, shear force and bending moment at every point along the structural members.

Once we have 'solved' the structure, we can use the information about the internal forces to actually design the structural members. This design step differs depending on what the members are made out of, whether they are steel, concrete, wood, or something else. The design step is outside the scope of this book, but it is good to keep in mind that this is the ultimate goal and purpose for the structural analysis.

This chapter will focus on the analysis of determinate structures, that is, structures which may be fully analysed using only the equations of equilibrium. Analysis of indeterminate structures will be covered in later chapters and will require both the equations of equilibrium coupled with extra information which is provided by the compatibility of the structure as described previously in Section 1.3.