Torsion-bending moment interaction in the frictional contact of tuff blocks: Experimental and analytical results

Understanding the structural behaviour of dry-stacked masonry systems implies defining of the effective contact area at the joint interface and determining of the resulting stresses in the sections. In this paper the torsion-bending moment interaction is experimentally and analytically investigated with reference to the single contact interface of two dry-stacked tuff blocks. To experimentally evaluate the influence of bending moment on the torsion strength, a pair of horizontal forces are applied to the upper block in its midplane, in combination with a vertical overload with some eccentricity—small, medium and large—from the block centre of gravity. The results are compared with those obtained by the analytical model of two overlapped rigid blocks, based on the assumptions of infinite compressive strength for blocks and no-tension and frictional behaviour at their contact. In particular, a linearized yield criterion is compared with a non-linear model in order to take advantage of using simplified expressions in limit analysis formulations based on linear programming.