Steel Buildings in Europe

Part 11: Moment Connections 11 - 1 1 INTRODUCTION Manual design of moment-resisting bolted connections is laborious, particularly when there are several bolt rows acting in tension. Any iteration of connection geometry or connection component (such as changing the bolt setting out or bolt size) necessitates a full re-design. For these reasons, the design of moment-resisting bolted connections is generally carried out by using appropriate software. This Section aims to provide an introduction to the verification process described in EN 1993-1-8 [1] . 1.1 Design approach The verification of a bolted moment resisting connection involves three distinct steps: 1. Determine the potential resistance of the bolt rows in the tension zone, in isolation. 2. Check whether the total tension resistance can be realised, as it may be limited by the web panel shear resistance of the column, or the resistance of the connection in the compression zone. 3. Calculate the moment resistance as the sum of the tension forces multiplied by their respective lever arms. The key features of the approach are firstly that a plastic distribution of bolt row forces is allowed, as long as either the end plate or the column flange is sufficiently thin. The second key feature is that the complex yield line patterns in the tension zone are replaced by an equivalent, simple T-stub model which is more amenable to calculation. 1.2 Tension zone According to EN 1993-1-8 § 6.2.7.2(6), the effective design tension resistance F tr,Rd at each bolt row in the tension zone is the least of the following resistances:  Column flange bending and bolt strength ( F t,fc,Rd )  Column web in transverse tension ( F t,wc,Rd )  End plate bending and bolt strength ( F t,ep,Rd )  Rafter beam web in tension ( F t,wb,Rd ). For each bolt row, the effective design tension resistance may thus be expressed as: F t r ,Rd = min( F t,fc,Rd ; F t,wc,Rd ; F t,ep,Rd ; F t,wb,Rd ) The relevant clauses of EN 1993-1-8 for the above components are given in Table 1.1.