Doors and service openings in structural walls introduce weaknesses that are not
confined merely to the consequential reduction in cross-section. Stress
concentrations are developed at the corners, and adequate reinforcement needs to
be provided to cater for these stresses. This reinforcement should take the form
of diagonal bars positioned at the corners of the openings as illustrated in the
figure below. The reinforcement will generally be adequate if it is designed to
resist a tensile force equal to twice the shear force in the vertical component
of the wall as shown, but should not be less than two size 16 bars across corner
of the opening.