Steel Buildings in Europe

Part 5: Detailed Design of Trusses 5 - 34 Buckling resistance out of the plane of the truss, i.e. about the strong axis of the cross-section (EN 1993-1-1 § 6.3.1) The lateral supports of the upper chord are composed of truss purlins at 8504 mm intervals. The normal compression force is almost constant between lateral supports (see 3.2). There is therefore no need to use a method which allows for non-uniform force. The elastic critical force is: 3373 kN 850,4 11770 21000 π π 2 2 2 y y 2 cr,y      l EI N The slenderness is given as: 0,8009 3373 6095 0,355 cr,y eff y y     N A f  The buckling curve is curve a (EN 1993-1-1 Table 6.2), and the imperfection factor is:  = 0,21 ) 0,8838 0,5(1 ( 0,2) 2 y y         y Φ 0,7952 0,8009 0,8838 0,8838 1 1 2 2 2 y 2 y y y            And so the compression resistance is therefore: 1720 kN 1,0 6095 0,355 0,7952 M1 y eff y b,y,Rd        A f N N Ed / N b,y,Rd = 1477/1720 = 0,859 OK M-N interaction (EN 1993-1-1 §6.3.3): There is no effect of lateral torsional buckling to consider for a member in bending about its weak axis (no bending about the strong axis). The criteria are: 1 / / M1 eff,z y z,Ed yz M1 eff y y Ed      f W M k A f N (Eq. 6.61 in EN 1993-1-1) 1 / / eff,z y M1 z,Ed zz eff y M1 z Ed      f W M k A f N (Eq. 6.62 in EN 1993-1-1) Using resistances already calculated, these criteria can also be written as: