Masonry Shear Calculator

Example data table

Example rows illustrate typical input ranges; always verify against project standards.

Formula used

This calculator uses a cohesion-plus-friction model with an optional strength cap.

How to use this calculator

1. Select your unit system first.
2. Enter wall length, thickness, and net area ratio.
3. Provide axial load and shear demand for the segment.
4. Set cohesion, friction coefficient, and strength reduction factor.
5. Click Calculate to view utilization and pass or fail.
6. Use CSV or PDF export for project documentation.

Professional article: masonry shear capacity

1) Purpose of the shear check

Masonry walls resist in‑plane lateral actions from wind, seismic forces, soil pressure, and diaphragm transfer. A frequent limit state is diagonal cracking along mortar joints and unit interfaces. For streamlined design checks, shear strength is represented with a cohesion term plus a friction term that increases with compressive stress. This calculator applies that model and also caps the strength as a fraction of masonry compressive strength to avoid overestimation.

2) Geometry and net area

Strength scales with effective net area. Openings, chases, weak piers, and local damage reduce the working section and can concentrate stress. The net area ratio in this tool lets you approximate those effects quickly. Reducing the ratio raises shear stress demand for the same applied shear, which increases utilization. Use a ratio near 1.0 for solid walls and reduce it when openings significantly cut the resisting area.

3) Demand definition

Enter axial load and the controlling shear demand for the segment being checked. If shear demand is already factored, keep the demand factor at 1.0. If you enter an unfactored shear and apply a multiplier, set the demand factor to match your load combination method. The report shows factored demand, shear stress demand, nominal shear stress, and strength‑reduced capacity for transparent review.

4) Material inputs

Material parameters should follow your governing standard, test data, or clearly documented assumptions. Cohesion reflects bond and mortar contribution at low compression. The friction coefficient represents sliding resistance that grows with normal stress. The strength reduction factor reflects desired reliability. The cap ratio limits nominal shear stress to a selected fraction of f′m; choose it to align with your design guidance and to prevent unrealistic friction‑based values.

5) Example data walkthrough

Example (SI): L = 3000 mm, t = 200 mm, net ratio = 1.00, P = 450 kN, Vu = 120 kN, v0 = 0.20 MPa, μ = 0.70, f′m = 10 MPa, cap ratio = 0.25, ϕ = 0.75. The calculator computes net area, axial stress, shear stress demand, capped nominal shear stress, and utilization. Use the margin output to see remaining capacity or required strengthening.

6) Using utilization and margin

Interpret utilization as demand divided by design capacity. Values below 1.0 indicate reserve capacity; values above 1.0 suggest redesign. If the wall fails, increase thickness, reduce openings, add reinforcement or boundary elements, or redistribute forces through the layout. Even when utilization passes, confirm anchorage and load paths, because local concentrations around openings and connections can govern behavior. Document assumptions and coordinate with detailing requirements for durability and constructability.

FAQs

1) Does axial compression always increase shear capacity?

Compression can increase frictional resistance, but codes often cap the benefit. Excessive compression may trigger other limit states, so use realistic load combinations and apply the cap ratio and reduction factor for conservatism.

2) What should I enter for cohesion and friction?

Use values from your governing standard, project specifications, or material testing. If none exist, select conservative parameters based on unit type, mortar, and workmanship, and document your assumptions in the report.

3) How do openings affect the calculation?

Openings reduce the effective shear area and can create stress concentrations. Represent the overall reduction using the net area ratio, then separately check critical piers, lintels, and boundary zones where forces concentrate.

4) What is the demand factor used for?

It scales the entered shear demand to a factored demand. Set it to 1.0 if your shear demand is already factored, or apply a multiplier consistent with your load combination method.

5) Why is shear stress capped by a fraction of f′m?

At high compression, the simple friction model can overpredict capacity. A cap linked to compressive strength limits the nominal shear stress to a reasonable upper bound commonly used in design guidance.

6) Can I use this for reinforced masonry shear walls?

You can use it as a baseline check, but reinforced systems often require additional mechanisms and code-specific equations. For final design, follow the reinforcement-based provisions and detailing rules in your standard.

7) What does a negative margin mean?

Negative margin indicates demand exceeds design capacity. Increase capacity by changing geometry or materials, add reinforcement, reduce demand through load redistribution, or revise the structural layout to lower shear in the segment.