Tension members - The Behaviour and Design of Steel Structures to EC3 - page 40

N

w

N

Nw

Bending
moment
diagrams

(b) Transverse load and tension (a) Transverse load only

Figure 2.8 Bending of a tension member.

for failure is the linear inequality

M y , Ed

M ty , Rd + M z , Ed M rz , Rd ≤ 1,

(2.14)

where M rz , Rd is the cross-section resistance for tension and bending about the
minor principal ( z ) axis given by

M rz , Rd = M cz , Rd ( 1 − N t , Ed / N t , Rd ) (2.15)

and M ty , Rd is the lesser of the cross-section resistance M ry , Rd for tension and
bending about the major principal ( y ) axis given by

M ry , Rd = M cy , Rd ( 1 − N t , Ed / N t , Rd ) (2.16)

and the out-of-plane member buckling resistance M bt , Rd for tension and bending
about the major principal axis given by

M bt , Rd = M b , Rd ( 1 + N t , Ed / N t , Rd ) ≤ M cy , Rd (2.17)

in which M b , Rd is the lateral buckling resistance when N = 0 (see Chapter 6).
In these equations, N t , Rd is the tensile resistance in the absence of bending
(taken as the lesser of N pl and N u ) , while M cy , Rd and M cz , Rd are the cross-section
resistancesforbendingaloneaboutthe y and z axes(seeSections4.7.2and5.6.1.3).
Equation 2.14 is similar to the first yield condition of equation 2.13, but includes
a simple approximation for the possibility of lateral buckling under large values
of M y , Ed through the use of equation 2.17.

2.5 Stress concentrations
High local stress concentrations are not usually important in ductile materials
under static loading situations, because the local yielding resulting from these