In-plane bending of beams - The Behaviour and Design of Steel Structures to EC3 - page 187

For a stocky web with d w / t w ≤ 72 √ ( 235 / f y ) and with a non-uniform elastic
shear stress distribution (such as an unequal flanged I-section), the inequality
τ Ed ≤ f y / √ 3

(5.45)

mustbesatisfied,inwhich τ Ed isthemaximumdesignshearstressinducedinthe
web by V Ed , as determined by an elastic shear stress analysis (Section 5.4).

Webs for which d w / t w ≥ 72 √ ( 235 / f y ) have their shear resistances reduced by
localbucklingeffects,asdiscussedinSection4.7.4.Thesheardesignofthinwebs
isgovernedbyEC3-1-5[25].Workedexamplesofcheckingtheshearcapacityof
such webs are given in Sections 4.9.5 and 4.9.6.

5.6.1.6 Checking for bending and shear

High shear forces may reduce the ability of a web to resist bending moment, as
discussed in Section 4.5. To allow for this, Class 1 and Class 2 beams under
combined bending and shear, in addition to satisfying equations 5.39 and 5.43,
must also satisfy

1 −

2

2 V Ed
V pl , Rd − 1

M Ed ≤ M c , Rd

(5.46)

in which V Ed is the design shear at the cross-section being checked and V pl , Rd is
the design plastic shear resistance. This condition need only be considered when
V Ed > 0.5 V pl , Rd , as indicated in Figure 4.32. It therefore need only be checked at
cross-sections under high bending and shear, such as at the internal supports of
continuous beams. Even so, many such beams have V Ed ≤ 0.5 V pl , Rd and so this
check for combined bending and shear rarely governs.

5.6.1.7 Checking the bearing resistance

For the bearing check, the inequality

F Ed ≤ F Rd (5.47)

must be satisfied at all supports and points of concentrated load. In this equation,
F Ed is the design-concentrated load or reaction, and F Rd the bearing resistance of
the web and its load-bearing stiffeners, if any. The bearing design of webs and
load-bearingstiffenersisgovernedbyEC3-1-5[25]anddiscussedinSections4.6
and4.7.6.Stockywebsoftenhavesufficientbearingresistanceanddonotrequire
the addition of load-bearing stiffeners.
A worked example of checking the bearing resistance of a stocky unstiffened
webisgiveninSection5.12.15, whileaworkedexampleofcheckingthebearing
resistance of a slender web with load-bearing stiffeners is given in Section 4.9.9.