AutoPIPE Vessel: Moment calculation due to seismic load on bracket supported vessel

For bracket supported vessels, Autopipe vessel calculating the moment and load as follows

Earthquake Load cases (seismic loads could act in opposite direction))

Moment M = abs(Ma)+abs (Mb)

Load R = Abs(Ra) + Abs (Rb)

Where as per Hand Book "Pressure Vessel Design Manual 4th Edition by Dennis Moss and Michael Basic" Procedure 4-7: 

Moment shall be maximum of F1L3 (moment of section above the support) or F2L4 (moment of section below the support)

Shear load is Greater of F1 (shear load above the support) or F2 (shear load below the support).

What is the reference for calculating moment and shear for bracket support vessel in autopipe vessel software