Steel Buildings in Europe

Part 11: Moment Connections 11 - 10 2 JOINT STIFFNESS EN 1993-1-8 § 5.2 requires that all joints are classified, by strength or by stiffness. Classification by strength is appropriate for plastic global analysis. According to § 5.2.2.1(1), a joint may be classified according to its rotational stiffness, which should be calculated in accordance with the method described in Section 6.3 of EN 1993-1-8. It is recommended that software is used to calculate the initial joint stiffness. An introduction to the approach is given in Section 2.1. In § 5.2.2.1(2) it is noted that joints may be classified on the basis of experimental evidence, experience of previous satisfactory performance in similar cases or by calculations based on test evidence. Some countries will accept classification on the basis of satisfactory performance – this may even be confirmed in the National Annex, which may point to nationally accepted design methods or joint details, and allow these to be classified without calculation. 2.1 Classification by calculation In § 6.3.1(4) the initial stiffness, S j is given as: i i 2 j 1 k Ez S    where: E is the modulus of elasticity  is a stiffness ratio that depends on the ratio of the applied moment to the moment resistance of the joint z is the lever arm, given by § 6.2.7 k i is the stiffness of the basic joint component 2.1.1 Stiffness of basic joint components Table 6.10 of EN 1993-1-8 identifies the basic joint components to be considered. For a one-sided bolted end plate connection, such as in a portal eaves frame, the basic joint components to be considered are given in Table 2.1.