Beam-columns - The Behaviour and Design of Steel Structures to EC3 - page 331

Alternative approach for cross-section resistance.
Because the section is Class 1, Clause 6.2.9.1 can be used.
No reduction in plastic moment resistance is required provided both

N Ed = 200 kN < 324.5 kN = ( 0.25 × 47.2 × 10 2 × 275 / 1.0 )/ 10 3
= 0.25 N pl , Rd and 6.2.9.1(4)
N Ed = 200 kN < 202.9 kN = 0.5 × ( 256.0 − 2 × 10.9 ) × 6.3 × 275
1.0 × 10 3

= 0.5 h w t w f y
γ M 0

6.2.9.1(4)

and so no reduction in the plastic moment resistance is required.
Thus M N , y , Rd = M pl , y , Rd = 132.8 kNm > 45.0 kNm = M y , Ed
and the cross-section resistance is adequate.
Compression member buckling resistance.
Because the member is continuously braced, beam lateral buckling and column
minor axis buckling need not be considered.

N cr , y = L cr , y

Af y 1

λ 1 =

9000
( 10.8 × 10 )

1
93.9 × 0.924 = 0.960 6.3.1.3(1)

λ y =

i y

For a rolled UB section (with h / b > 1.2 and t f ≤ 40 mm), buckling about the
y -axis, use buckling curve (a) with α = 0.21 T6.2,T6.1

Φ y = 0.5 [ 1 + 0.21 ( 0.960 − 0.2 ) + 0.960 2 ]= 1.041 6.3.1.2(1)

1.041 2 − 0.960 2 ) = 0.693 χ y = 1 /( 1.041 + 6.3.1.2(1)

N b , y , Rd = χ y Af y /γ M 1 = 0.693 × 47.2 × 10 2 × 275 / 1.0 N
= 900 kN > 200 kN = N Ed 6.3.1.1(3)

Beam-column member resistance - simplified approach (Annex B).

α h = M h / M s = 0, ψ = 0, C my = 0.90 + 0.1 α h = 0.90 TB.3

N Ed
χ y N Rk /γ M 1

C my 1 + (λ y − 0.2 ) = 0.90

200 × 10 3
0.693 × 47.2 × 10 2 × 275 / 1.0

× 1 + ( 0.960 − 0.2 ) × = 1.052