Masonry Design and Construction
Materials and behavior
Masonry is an assemblage of units (brick, block) and mortar, sometimes with grout and reinforcement. Compressive strength depends on the unit and mortar type. Masonry is strong in compression and weak in tension, so reinforcement and grout are used for flexural and seismic resistance. Key concepts include the slenderness of walls, the difference between reinforced and unreinforced masonry, and the role of the mortar joint in bond.
Design checks
Design uses allowable stress or strength methods depending on the code. Axial compression capacity depends on wall thickness, effective height, and end conditions. Flexural tension is checked against the modulus of rupture for unreinforced walls. Traps include ignoring the effect of openings on wall capacity, forgetting that a wall braced only at the top is a cantilever, and confusing nominal with allowable stresses.
Construction
Key construction points: mortar mixing and curing, grouting procedures, flashing and weep holes for water management, and movement joints for expansion and shrinkage. Candidates should know that grout must be consolidated and that reinforcement must be properly positioned in the cells.
Worked rule of thumb
For an unreinforced wall in compression, the allowable stress is reduced by a slenderness factor. If a nominal allowable is 250 psi and the slenderness reduction is 0.7, the design stress is 175 psi. Multiply by the net area to get capacity, and always verify that the wall is braced at intervals that keep the effective height within the slenderness limit.