Openings in Masonry Walls on Settling Supports

Half-scale models of point-supported concrete block walls with openings, stiffened by reinforced concrete beams and ties, were submitted to differential foundation settlements. The influence of apertures, of stiffening ties and their reinforcement, and of vertical prestressing of masonry on deflections, cracking, and strength were studied. Test results tend to confirm a proposed theory stating that the statical action of a masonry wall with reinforced concrete ties is comparable with that of a truss. The horizontal ties provide couples for taking up the exterior bending moments, the vertical ties take up vertical tension and the masonry diagonal compression. Tests indicate that weakening of walls by openings can be offset by vertical reinforced concrete tension ties on the sides of the opening or by vertical prestressing of the sides of openings. The vertical prestressing proved to be effective also in repairing cracked masonry. The dimensions and reinforcement of horizontal and vertical ties can be calculated and the strength of the wall predicted by use of the proposed truss analogy.