From the overall equilibrium of the beam in Fig. S.24.1(a)
R_{\mathrm{F}}=4 \mathrm{kN} \quad R_{\mathrm{D}}=2 \mathrm{kN}
The shear load in the panel ABEF is therefore 4 kN and the shear flow q is given by

q_1=\frac{4 \times 10^3}{1000}=4 \mathrm{~N} / \mathrm{mm}

Similarly

q_2=\frac{2 \times 10^3}{1000}=2 \mathrm{~N} / \mathrm{mm}

Considering the vertical equilibrium of the length h of the stiffener BE in Fig. S.24.1(b)

P_{\mathrm{EB}}+\left(q_1+q_2\right) h=6 \times 10^3

where P_{\mathrm{EB}} is the tensile load in the stiffener at the height h, i.e.
P_{\mathrm{EB}}=6 \times 10^3-6 h (i)
Then from Eq. (i), when h = 0, P_{\mathrm{EB}} = 6000 N and when h = 1000 mm. P_{\mathrm{EB}} = 0. Therefore the stiffener load varies linearly from zero at B to 6000 N at E.

Consider now the length z of the beam in Fig. S.24.1(c). Taking moments about the bottom flange at the section z

P_{\mathrm{AB}} \times 1000+R_{\mathrm{F}} z=0
whence
P_{\mathrm{AB}} = −4z N
Thus P_{\mathrm{AB}} varies linearly from zero at A to 4000 N (compression) at B. Similarly P_{\mathrm{CB}} varies linearly from zero at C to 4000 N (compression) at B.