7.2 Slipping and failure force 7.2.1 Slipping force Fs (RA,SW,PA,SF) To determine the resistance of Fs of a coupler to slipping along a tube and the relative displacements between the tube and the coupler. 7.2.2 Failure force Ff (RA,SW,PA) To determine the resistance of Ff, of a coupler at failure. 7.3 Pull-apart force Fp (RA) To determine the resistance of Fp of the coupler by separating into two parts. 7.4 Stiffnesses and ultimate moments 7.4.1 Cruciform bendingstiffness c1,MB and c2,MB and bending moment MB (RA) To determined the bending moment of resistance MB and the cruciform bending stiffness cϕ1,MB and cϕ2,MB of a coupler.W 7.4.2 Rotational moment MT and the stiffness cϕ,MT (RA) To determine the rotational moment resistance of MT and the stiffness c,MT to a coupler slipping around a tube. 7.4.3 Bending moment resistance (SF) To determine the ultimate bending moment resistance MB of a sleeve coupler. 7.5 Indentation (RA,SW,PA) To determine the local plastic deformation of tubes caused by forces transmitted by a coupler.