Masonry Shear Wall (LRFD)

How it calculates

Masonry and reinforcement properties

Inputs establish the material model: masonry type (clay or concrete masonry), CMU nominal size, specified compressive strength f'm, unit weight, mortar type, and grout condition (partial or full). Reinforcement grade (Grade 60 standard) and bar layout complete the cross-section definition. The calculator derives net and gross section properties from these inputs, applying the correct maximum usable strain at the extreme compression fiber: ε_mu = 0.0035 for clay masonry and ε_mu = 0.0025 for concrete masonry, per TMS 402/602-22 assumptions.

Geometric properties and wall configuration

Wall height per story, number of stories, opening locations, and CMU pattern (running bond assumed) define the structural geometry. The segmented pier method splits walls with openings into individual piers for analysis. Each pier carries its tributary axial load and the lateral shear from above, with results combined to govern the wall design.

Load combination analysis

Factored gravity loads (dead, live, roof) and lateral demands (wind or seismic per story) are assembled into ASCE 7 load combinations. The calculator accumulates axial demand Pu at each story level and resolves in-plane lateral demands Vu and moment demand Mu at the critical section. Dynamic load linking allows wind and seismic inputs to propagate from upstream analysis calculators without manual re-entry.

In-plane shear (TMS 402/602-22, Section 9.3.3.1.2)

Nominal shear strength combines masonry and horizontal reinforcement contributions:

Vn = Vm + Vs

where Vm depends on the factored axial stress, f'm, and wall geometry, and Vs = 0.5·As·fy·(d/s). The design check is:

φVn ≥ Vu, with φ = 0.80 for shear

Separate limits apply to Ordinary, Intermediate, and Special walls. For Special Reinforced Shear Walls the code caps the total Vn at a fraction of f'm·An to ensure ductile flexural yielding governs over shear failure.

Interaction diagram (axial and flexure)

The P-M interaction envelope is built using a rectangular equivalent stress block (0.80·f'm over depth a = 0.80·c) with the neutral axis located by strain compatibility. Vertical reinforcement is modeled as uniformly distributed along the wall length. For each point on the envelope, the calculator checks P-delta amplification of moment demand using the magnified moment approach so slenderness effects are included at every load combination.

The governing interaction check is:

utilization = Mu / φMn (at Pu) ≤ 1.0

Maximum flexural reinforcement (Section 9.3.5.6.1)

To ensure ductile wall behavior, TMS 402-22 limits the maximum area of flexural tensile reinforcement based on the strain compatibility condition at the balanced point. The calculator enforces this limit automatically, flagging configurations where the reinforcement ratio would prevent adequate rotation capacity before masonry crushing.

Seismic detailing checks

For Intermediate and Special walls, the calculator validates minimum bar sizes at wall boundaries and maximum spacing of both vertical and horizontal reinforcement. These detailing checks are filtered by the SDC you enter, so only the requirements that apply to your wall type and seismic category are shown.