9. Resistance to transverse forces tables (web bearing and buckling)

I and H and parallel flange channels

(a) The design shear resistance

The design shear resistance Vc,Rd is given by:

where:

A v is the shear area
for rolled I sections Av = A - 2 b tf + ( tw + 2 r ) tf but not less than η hw tw,
for parallel flange channels Av = A - 2 b tf + ( tw + r ) tf
f y is the yield strength
γ M0 is the partial factor for resistance of cross sections (γM0 = 1.0 , see Section 5.1)
Code Ref.
6.2.6 (1), (2)
(b) Design resistance to local buckling

The design resistance of an unstiffened web, FRd, to local buckling under transverse forces is given by:

where:

f y is the yield strength
t w is the thickness of the web
L eff is the effective length for resistance to transverse force ( χF  l y )
χ F
l y is the effective loaded length
γ M1 is the partial factor for resistance of members (γM1 = 1.0 , see Section 5.1)
F
F cr
k F
h w is the depth between flanges = h - 2tf
s s the length of stiff bearing (see Figure 6.2 of BS EN 1993-1-5)
c the distance from the end of the stiff bearing to the end of the section.

The effective loaded length l y has been calculated as the least value of the following three expressions:

l y1 eq (6.10)
l y2 eq (6.11)
l y3 eq (6.12)

where:

l e eq (6.13)
m 1
m 1
m 1

(Note that, at present, BS EN 1993-1-5, §6.5(3) erroneously refers to equations 6.11, 6.12 and 6.13. This error is due to be corrected by CEN.)

EN 1993-1-5,
6.2(1)
Figure 6.1

Values of FRd have been calculated for two values of c, where c is the distance from the end of the member to the adjacent edge of the stiff bearing length, as shown in Figure 6.1 of EN 1993-1-5

c = 0 for stiff bearing positioned at the end of the section.
c = clim for stiff bearing positioned at a distance clim from the end of the section. This position represents the minimum value of c at which the maximum resistance of the web for a given stiff bearing length, ss is attained.

where:

c lim = max (cbuckling ; cbearing )
c buckling
c bearing

For the case where the stiff bearing is positioned at an intermediate distance (i.e. c < clim  ) the resistance given for c = 0 is conservative.

EN 1993-1-5,
6.1(4)