(1) When the eccentric or lateral forces, together with axial loads, have to be taken into account in walls, piers or columns, the stresses shall be calculated on the assumption that the straight-line theory applies to such walls, piers or columns as are subject to bending moments, that is to say that planes in the cross-section remain places after bending.

(2) On this assumption, the maximum stresses in any part of the walls, piers or columns aforesaid resulting from eccentric loads and lateral forces, together with the axial loads, shall not exceed those set out in Table XXV:

Provided that any excess in compressive stress over that permitted for axial vertical force is due entirely to the eccentricity of forces or to lateral forces.

TABLE XXV

PERMISSIBLE STRESSES, OTHER THAN AXIAL COMPRESSIVE, IN MASONRY