Beam-columns - The Behaviour and Design of Steel Structures to EC3 - page 334

Alternative approach for cross-section resistance.
Because the section is Class 2, Clause 6.2.9.1 can be used.

N Ed = 200 kN < 406 kN = ( 256 − 2 × 10.9 ) × 6.3 × 275 = h w t w f y

γ M 0 .
6.2.9.1(4)

1.0 × 10 3

and so no reduction in plastic moment resistance is required.

Thus M N , z , Rd = M pl , z , Rd = 32.7 kNm > 8.1 kNm = M z , Ed 6.2.5(2)

and the cross-section resistance is adequate.
Compression member buckling resistance.

N cr , z = L cr , z

Af y 1

λ 1 =

4500
( 3.48 × 10 )

1
93.9 × 0.924 = 1.490 6.3.1.3(1)

λ z =

i z

For a rolled UB section (with h / b > 1.2 and t f ≤ 40 mm), buckling about the
z -axis, use buckling curve (b) with α = 0.34 T6.2,T6.1

Φ z = 0.5 [ 1 + 0.34 ( 1.490 − 0.2 ) + 1.490 2 ]= 1.829 6.3.1.2(1)

χ z = 1 /( 1.829 +

1.829 2 − 1.490 2 ) = 0.346

6.3.1.2(1)

N b , z , Rd = χ z Af y /γ M 1 = 0.346 × 47.2 × 10 2 × 275 / 1.0 N
= 449 kN > 200 kN = N Ed

6.3.1.1(3)

Beam-column member resistance - simplified approach (Annex B).
Because the member is bent about the minor axis, beam lateral buckling need not
be considered, and e LT = 0.

M h =− 8.1 kNm, M s = 9 × 3.2 × 4.5 2 / 128 = 4.56 kNm, ψ = 0 TB.3
α s = M s / M h = 4.56 /( − 8.1 ) =− 0.563,

TB.3

C mz = 0.1 − 0.8 α s = 0.1 − 0.8 × ( − 0.563 ) = 0.550 > 0.40 TB.3

1 + ( 2 × 1.490 − 0.6 )

N Ed
χ z N Rk /γ M 1

C mz 1 + ( 2 λ z − 0.6 ) = 0.550 ×

200 × 10 3
0.346 × 47.2 × 10 2 × 275 / 1.0

× = 1.133