Using unit load method or castigliano's theorem for rigid jointed frame shown in fig.

Calculate a horizontal displacement of roller support at D.

Take $E=GPa, I=4\times 10^8mm^4$

Solution:

$\sum M_A=$

$25\times 5+30\times 4\times \frac{4}{2}-V_D\times 7=0$

$V_D= 52.14 kN$

$\sum F_y=0$

$V_A-30\times 30\times 4+52.14=0$

$V_A=67.86kN$

$\sum F_y=0(\rightarrow +ve)$

$H_A+25=0$

$H_A=-25kN$

$H_A=25kN(\leftarrow)$