What it checks
The module designs rectangular CMU lintels that are grouted and reinforced at the bottom. It applies strength design methods to evaluate the member's performance under specified loads. The engine calculates section and masonry capacities using closed-form equations, noting that loads are ignored in the capacity calculation itself.
The design sequence involves checking flexural strength, shear strength, and deflection. The module accounts for arching-action reduction where the geometry allows. It determines the governing load combination and reports the resulting deflections and capacity values for the engineer's review.
Inputs
- Geometry - Clear span of opening (ft), width of lintel equal to wall nominal thickness (in), and number of CMU courses deep (count).
- Reinforcement - Cover to centroid of tension steel (in), bar size number, and number of longitudinal bars.
- Material Properties - Masonry specified compressive strength f'm (psi) and rebar yield strength fy (psi).
- Loads - Service dead load (klf), service live load (klf), and optional pre-factored uniform load (klf) which overrides standard combinations.
- Deflection Limits - Deflection limit denominator for live load (default 360) and total load (default 240).
- Seismic - Optional Ev toggle for vertical seismic effect, which folds 0.2*SDS*D into seismic combinations if provided.
What it reports
- Masonry Shear Capacity - The calculated shear capacity Vm (kips) for the masonry section.
- Effective Moment of Inertia - The effective moment of inertia (in⁴) based on a cracked-section approximation.
- Live-Load Deflection - The deflection (in) resulting from the live load alone.
- Total Load Deflection - The deflection (in) resulting from the combination of dead and live loads.
- Governing Combination - A label identifying which load combination governed the design and the source of its factors.
Code references
The engine cites TMS 402-22 §9.3.3 for flexural strength and §9.3.4 for shear strength. It also references TMS 402-22 §4.1.2.1 for the modulus of elasticity, defined as Em = 900·f'm. Load combinations default to the ASCE 7-22 §2.3.1 strength set if project-specific combinations are not provided.
Limits
The module performs strength design only; ASD is available in the future. It covers rectangular CMU lintels that are grouted and reinforced at the bottom. The capacity calculation ignores loads. Results are engineering aids; the engineer of record is responsible for the design.