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6.! Design Resistance 6.!.1 Internal forces

(1) The stresses due to the internal forces and moments in a member may be assumed not to affect the design resistances of the basic components of a joint, except as specified in 6.2.1(2) and 6.2.1(3).

(2) The longitudinal stress in a column should be taken into account when determining the design resistance of the column web in compression, see 6.2.6.2(2).

(3) The shear in a column web panel should be taken into account when determining the design resistance of the following basic components:

- column web in transverse compression, see 6.2.6.2;

- column web in transverse tension, see 6.2.6.3.

6.2.2 Shear forces

(1) In welded connections, and in bolted connections with end-plates, the welds connecting the beam web should be designed to transfer the shear force from the connected beam to the joint, without any assistance from the welds connecting the beam flanges.

(2) In bolted connections with end-plates, the design resistance of each bolt-row to combined shear and tension should be verified using the criterion given in Table 3.4, taking into account the total tensile force in the bolt, including any force due to prying action.

NOTE: As a simplification, bolts required to resist in tension may be assumed to provide their full design resistance in tension when it can be shown that the design shear force does not exceed the sum of:

a) the total design shear resistance of those bolts that are not required to resist tension and;

b) (0,4/1,4) times the total design shear resistance of those bolts that are also required to resist tension.

(3) In bolted connections with angle flange cleats, the cleat connecting the compression flange of the beam may be assumed to transfer the shear force in the beam to the column, provided that:

- the gap g between the end of the beam and the face of the column does not exceed the thickness ta of the angle cleat;

- the force does not exceed the design shear resistance of the bolts connecting the cleat to the column;

- the web of the beam satisfies the requirement given in EN 1993-1-5, section 6.

(4) The design shear resistance of a joint may be derived from the distribution of internal forces within that joint, and the design resistances of its basic components to these forces, see Table 6.1.

(5) In base plates if no special elements for resisting shear are provided, such as block or bar shear connectors, it should be demonstrated that either the design friction resistance of the base plate, see 6.2.2(6), or, in cases where the bolt holes are not oversized, the design shear resistance of the anchor bolts, see 6.2.2(7), is sufficient to transfer the design shear force. The design bearing resistance of the block or bar shear connectors with respect to the concrete should be checked according to EN 1992.

(6) In a column base the design friction resistance Af,Rd between base plate and grout should be derived as follows:

Cf,d is the coefficient of friction between base plate and grout layer. The following values may be used:

- for other types of grout the coefficient of friction Cf,d should be determined by testing in accordance with EN 1990, Annex D;

1c,Ed is the design value of the normal compressive force in the column. NOTE: If the column is loaded by a tensile normal force, Af,Rd = 0.

(7) In a column base the design shear resistance of an anchor bolt AvbRd should be taken as the smaller of

- Ai,vbRd is the design bearing resistance of the anchor bolt, see 3.6.1

7m where:

ab = 0,44 - 0,0003 fyh fyb is the yield strength of the anchor bolt, where 235 N/mm2 <fyb <640 N/mm2

(8) The design shear resistance AvRd of a column base plate should be derived as follows:

where:

n is the number of anchor bolts in the base plate.

(9) The concrete and reinforcement used in the base should be designed in accordance with EN 1992. 6.2.3 Bending moments

(1) The design moment resistance of any joint may be derived from the distribution of internal forces within that joint and the design resistances of its basic components to these forces, see Table 6.1.

(2) Provided that the axial force 1Ed in the connected member does not exceed 5% of the design resistance iVp( Rd of its cross-section, the design moment resistance A/jRd of a beam-to column joint or beam splice may be determined using the method given in 6.2.7.

(3) The design moment resistance Hj,Rd of a column base may be determined using the method given in 6.2.8.

(4) In all joints, the sizes of the welds should be such that the design moment resistance of the joint Hj,Rd is always limited by the design resistance of its other basic components, and not by the design resistance of the welds.

(5) In a beam-to-column joint or beam splice in which a plastic hinge is required to form and rotate under any relevant load case, the welds should be designed to resist the effects of a moment equal to the smaller of:

the design plastic moment resistance of the connected member Mp[>Rd a times the design moment resistance of the joint M^m where a= 1,4 - for frames in which the bracing system satisfies the criterion (5.1) in EN 1993-1-1 clause 5.2.1(3) with respect to sway;

(6) In a bolted connection with more than one bolt-row in tension, as a simplification the contribution of any bolt-row may be neglected, provided that the contributions of all other bolt-rows closer to the centre of compression are also neglected.

6.2.4 Equivalent T-stub in tension

6.2.4.1 General

(1) In bolted connections an equivalent T-stub in tension may be used to model the design resistance of the following basic components:

- column flange in bending;

- end-plate in bending;

- flange cleat in bending;

- base plate in bending under tension.

(2) Methods for modelling these basic components as equivalent T-stub flanges, including the values to be used for emin, £eff and m, are given in 6.2.6.

(3) The possible modes of failure of the flange of an equivalent T-stub may be assumed to be similar to those expected to occur in the basic component that it represents.

(4) The total effective length X-Eeff of an equivalent T-stub, see Figure 6.2, should be such that the design resistance of its flange is equivalent to that of the basic joint component that it represents.

NOTE: The effective length of an equivalent T-stub is a notional length and does not necessarily correspond to the physical length of the basic joint component that it represents.

(5) The design tension resistance of a T-stub flange should be determined from Table 6.2.

NOTE: Prying effects are implicitly taken into account when determining the design tension resistance according to Table 6.2.

(6) In cases where prying forces may develop, see Table 6.2, the design tension resistance of a T-stub flange AT,Rd should be taken as the smallest value for the three possible failure modes 1, 2 and 3.

(7) In cases where prying forces may not develop, see Table 6.2, the design tension resistance of a T-stub flange ATRd should be taken as the smallest value for the two possible failure modes 1-2 and 3.

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