Question 20.1: Draw influence lines for the shear force and bending moment ...

In this example we are not required to obtain the influence lines for the support reactions. However, the influence line for the reaction R_{\mathrm{A}} has been included to illustrate the difference between this influence line and the influence line for R_{\mathrm{A}} in Fig. 20.1(b); the reader should verify the R_{\mathrm{A}} influence line in Fig. 20.2(b).

Since we have established that influence lines for statically determinate structures consist of linear segments they may be constructed by placing the unit load at different positions, which will enable us to calculate the principal values.