Let us consider the following truss structure:

In calculation we assume that P1 = P2= P3 = 10
[kN] and L=1[m].

Now let’s assume that the forces changes in the
5% i.e

*P*1*= P*1 ± 2.5%

*P*2*= P*2 ± 2.5%

*P*3*= P*3 ± 2.5%

If we calculate
the relative error of axial forces

then we
will get the following results:

We can see that in some cases
the relative error

of calculation is
equal to 60%.