Steel Buildings in Europe

Part 5: Detailed Design of Trusses 5 - 38 The section is a Class 4 and it is therefore not fully effective in uniform compression. The effective area of the cross-section should be calculated with reference to EN 1993-1-5. Such a calculation leads to a fully effective area: A eff = A = 86 cm 2 Resistance of the cross-section The resistance of the section in uniform compression is therefore given by: 3053 kN 1,0 8600 0,355 M0 y c,Rd      Af N Buckling resistance of member Buckling resistance in the plane of the truss The buckling length is equal to: 0,9 × 5,464 = 4,918 m The elastic critical force is: 1539 kN 491,8 1796 21000 π π 2 2 2 y z 2 cr,z      l EI N The slenderness is given by: 1,408 1539 8600 0,355 cr,z y z     N Af  The buckling curve is curve b (EN 1993-1-1 Table 6.2), and the imperfection factor is: 0,34   ) 1,697 0,5 (1 ( 0,2) 2 z z          z Φ 0,378 1,697 1,408 1,697 1 1 2 2 2 2          z z z z   And the buckling resistance is then: 1154 kN 1,0 8600 0,355 0,378 M1 z y b,z,Rd        Af N Buckling resistance out of plane of the truss The buckling length is equal to the system length: L cr,y = 5,464m. The critical axial force is: 2594 kN 546,5 3737 21000 π π 2 2 2 y y 2 cr,y      l EI N