10.11.1 Bolt/Weld Group Subject to In-plane Loading
10.11.1.1 General method of analysis
The design force in a bolt/weld or design force per unit length in a bolt/weld group subject to in-plane loading shall be determined in accordance with the following:
- a) The connection plates shall be considered to be rigid and to rotate relative to each other about a point known as the instantaneous centre of rotation of the group.
- b) In the case of a group subject to a pure couple only, the instantaneous centre of rotation coincides with the group centroid. In the case of in-plane shear force applied at the group centroid, the instantaneous centre of the rotation is at infinity and the design force is uniformly distributed throughout the group. In all other cases, either the results of independent analyses for a pure couple alone and for an in-plane shear force applied at the group centroid shall be superposed, or a recognized method of analysis shall be used.
- c) The design force in a bolt or design force per unit length at any point in the group shall be assumed to act at right angles to the radius from that point to the instantaneous centre, and shall be taken as proportional to that radius.
10.11.2 Bolt/Weld Group Subject to Out-of-Plane Loading
10.11.2.1 General method of analysis
The design force of a bolt in bolt group or design force per unit length in the fillet weld group subject to out-of-plane loading shall be determined in accordance with the following:
- a) Design force in the bolts or per unit length in the fillet weld group resulting from any shear force or axial force shall be considered to be equally shared by all bolts in the group or uniformly distributed over the length of the fillet weld group.
- b) Design force resulting from a design bending moment shall be considered to vary linearly with the distance from the relevant centroidal axes:
- In bearing type of bolt group plates in the compression side of the neutral axis
and only bolts in the tension side of the neutral axis may be considered for calculating the neutral axis and second moment of area.
- In the friction grip bolt group only the bolts shall be considered in the calculation of neutral axis and second moment of area.
- The fillet weld group shall be considered in isolation from the connected element for the calculation of centroid and second moment of the weld length.
10.11.2.2 Alternative analysis
The design force per unit length in a fillet weld/bolt group may alternatively be determined by considering the fillet weld group as an extension of the connected member and distributing the design forces among the welds of the fillet weld group so as to satisfy equilibrium between the fillet weld group and the elements of the connected member.
10.11.3 Bolt/Weld Group Subject to In-plane and Out-of-Plane Loading
10.11.3.1 General method of analysis
The design force in a bolt or per unit length of the weld shall be determined by the superposition of analysis for in-plane and out-of-plane cases discussed in 10.11.1 and 10.11.2.
10.11.3.2 Alternative analysis
The design force in a bolt or per unit length in the fillet weld group may alternatively be determined by considering the fillet weld group as an extension of the connected member and proportioning the design force per bolt or unit length in the weld group to satisfy equilibrium between the bolt/weld group and the elements of the connected member.
Force calculated in the most stressed bolt or highest force per unit length of the weld shall satisfy the strength requirements of 10.3, 10.4 or 10.5, as appropriate.