Steel Buildings in Europe

Part 5: Joint Design 5 – 2 Nominally pinned joints have the following characteristics: 1. they are assumed to transfer only the design shear reaction between members 2. they are capable of accepting the resulting rotation 3. they provide the directional restraint to members which has been assumed in the member design 4. they have sufficient robustness to satisfy the structural integrity requirements. EN 1993-1-8 [1] provides two methods to classify joints: stiffness and strength.  Classification by stiffness: the initial rotational stiffness of the joint, calculated in accordance with Section 6.3.1 of EN 1993-1-8 is compared with the classification boundaries given in Section 5.2 of the same document.  Classification by strength: the following two requirements must be satisfied in order to classify a joint as pinned:  the moment resistance of the joint does not exceed 25% of the moment resistance required for a full-strength joint  the joint is capable of accepting the rotation resulting from the design loads. Alternatively, joints may also be classified based on experimental evidence, experience of previous satisfactory performance in similar cases or by calculations based on test evidence. Generally, the requirements for nominally pinned behaviour are met by the use of relatively thin plates, combined with full strength welds. Experience and testing have demonstrated that the use of 8 mm or 10 mm end plates, fin plates and angles in S275, with M20 8.8 bolts leads to connections which behave as nominal pins. If details are chosen outside these recommended parameters, the connection should be classified in accordance with EN 1993-1-8. 1.3 Standardised joints In a typical braced multi-storey frame, the joints may account for less than 5% of the frame weight, but 30% or more of the total cost. Efficient joints will therefore have the lowest detailing, fabrication and erection labour content – they will not necessarily be the lightest. Use of standardised joints where the fittings, bolts, welds and geometry are fully defined offers the following benefits:  Reduces buying, storage, and handling time  Improves availability and leads to a reduction in material costs  Saves fabrication time and leads to faster erection  Leads to a better understanding of their performance by all sides of the industry