1) Using 2d analysis software such as plaxis/wallap we obtain the 'strut load per mtr'.
2) Guess the capping beam and strut sizes and geometric arrangement.
3) Analyse the system using software like strand7/spacegass. use the forces obtained to design the reinforcement of the beam. We have to make sure we don't over estimate any axial forces in the beam as this often makes the beam stronger with less reo.
4) Sometimes there is some iteration to check the deflection of the beam in strand7 is in agreement with the movement in wallap/plaxis.
5) check previous designs and compare to see if 'it looks right'.
Obviously there's a bit more to it but that's the gist of it.