The first thing we need to look at are how the members react under different applied forces. We need to therefore look at the internal forces in members:
Knowing this, we can look at analysing structures. We will need to use our previous knowledge of how to resolve forces into their component parts, and the conditions of equilibrium: vertical forces, horizontal forces and moments.
Stages for Nodal Analysis:
- Work out any unknown external forces using moments (where possible)
- Mark on your freebody diagram the directions of all the internal forces
- Take the nodes in turn - start with the node you know the most information for.
- Redraw the node. Redraw and resolve any forces at an angle.
- Draw an up/down, right/left diagram
- Find out your unknowns and state whether the member is a strut or a tie.
- Move on to the next node
- Remember that there may be a hinge reaction at a node, in which case you need to make sure that you work out the horizontal and vertical components of it, and then use Pythagoras to find the magnitude and trig to work out the angle.
Now here is the worked example on page 2. Take some time to make sure you understand the different stages of the nodal analysis.
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