Page 299 - Civil Engineering Formulas

BUILDING AND STRUCTURES FORMULAS 233

For deflection determinations, that is, in computing moment of inertia to be
used in deflection calculations or in other calculations involving stiffness,

b 10,320 2,580
1 (9.84)
t f (w t) f

with f, w, and t the same as for Eq. (9.83).

Web Stresses in Light-gage Members The shear on the gross web section in
light-gage cold-formed flexural members is usually limited to two-thirds of the
basic working stress in tension and bending, or

64,000,000
Shear, psi,v (9.85)
(h/t) 2

whichever is smaller. In this expression h/t is the ratio of depth to web thick-
ness, or of stiffener spacing to web thickness, as for plate-girder construction.
Where the web consists of two sheets, as in the case of two channels fastened
back to back to form an I section, each sheet should be considered as a separate
web carrying its share of the shear.

Maximum End Reaction or Concentrated Load on End of Cantilever for
Single Unreinforced Web of Light-gage Steel
(Grade C steel, corner radii = thickness of material)
Pmax (1)

B
Overall
depth Overall
h h
H depth
H
B
Pmax (1)
t = web thickness, mm
h = clear distance between flanges, mm
B = length of bearing, mm
H = overall depth, mm
B B h h
2
Pmax(1) 100t 980 42 0.22 0.11 (9.86)
t t t t
In solving this formula, B should not be assigned any value greater than h.