Steel Buildings in Europe

Part 5: Detailed Design of Trusses 5 - 25 Axial force (kN) Bending moment (kNm) Initial structure Modified structure Figure 3.11 Effects of the eccentricity of diagonal under ULS gravity loading The 300 mm eccentricity makes the triangulation imperfect. The main consequence of this arrangement is a significant increase in the bending moments in the lower chord that receives the eccentric diagonal. A 74,15 kNm moment is calculated in the second chord member from the right hand support, a 62,72 kNm moment in the first chord member, much higher than in the initial structure without eccentricity. The elastic moment resistance of an IPE 330 horizontal section is: 69,2  0,355 = 24,57 kNm The bending capacity is therefore greatly exceeded, apart from any other interactions. Reinforcement of the lower chord member will therefore be required in order to support the axis eccentricity introduced. 3.7.2 “Broken” diagonal (example 2) The panel of the penetration equipment is the same as in 3.6.1. Figure 3.12 is a diagram of the diagonal “breakage”.