ASME: Crown Bars Girder Stays design

Crown bars and girder stays for tops of combustion chambers and back connections, or wherever used, shall be proportioned to conform to the following equation: where
C = 7,000 (48) when girder is fitted with one supporting bolt
= 10,000 (69) when the girder is fitted with two or three supporting bolts
= 11,000 (76) when the girder is fitted with four or five supporting bolts
= 11,500 (79) when the girder is fitted with six or seven supporting bolts
= 12,000 (83) when the girder is fitted with eight or more supporting bolts
D1 = distance between girders from center to center
d = depth of girder
P = maximum allowable working pressure

p = pitch of supporting bolts
t = thickness of girder
W = extreme distance between supports of, in a scotch marine boiler, the distance from the fire side of the tubesheet to the fire side of the back connection plate