Shear Wall

Shear Wall#

The ShearWall class models a reinforced-concrete structural wall for in-plane shear analysis and design per ACI 318-19 Chapter 11.

Concrete shear capacity follows ACI 318-19 §11.5.4.6 with the aspect-ratio factor α_c, instead of a longitudinal-reinforcement term.
Reinforcement is distributed mesh in two orthogonal directions (ρt horizontal, ρl vertical), placed on both faces of the wall (E.F. — each face), not stirrups.
The minimum horizontal ratio is ρt,min = 0.0025 (§11.6.1). The minimum vertical ratio follows the §11.6.2 interpolation ρl,min = max(0.0025, 0.0025 + 0.5·(2.5 − hw/lw)·(ρt,req − 0.0025)), with hw/lw clamped to [0.5, 2.5].

The same shear provisions serve both ACI 318-19 and CIRSOC 201-25; CIRSOC differs only in the reinforcing-bar catalogue used for design (it allows Ø6 mm for the transverse mesh and Ø10 mm minimum for the vertical mesh).

Note

The module covers shear check and design only. Flexure design for shear walls is not implemented yet. Inherited flexure methods from RectangularBeam are not validated for wall geometry and should not be used.

Key Concepts#

Geometry:
- thickness (t) — out-of-plane dimension
- length (lw) — in-plane length, resists in-plane shear
- height (hw) — story / overall wall height, used for the hw / lw aspect ratio
Material Properties: requires a Concrete object (currently Concrete_ACI_318_19 or Concrete_CIRSOC_201_25) and a SteelBar object.
Reinforcement: distributed bars defined by bar diameter + spacing in each direction.
Forces: a list of Forces objects passed to check_shear() or design_shear() — either directly on the wall or through a Node. V_z is the in-plane lateral shear demand at the section.

Usage#

Below is a step-by-step guide on how to use the ShearWall class.

1. Creating a Shear Wall Object#

Specify the geometry, materials, and clear cover using the wall-friendly constructor parameters thickness, length, and height.

from mento import ShearWall, Concrete_ACI_318_19, SteelBar
from mento import MPa, cm, mm, m

concrete = Concrete_ACI_318_19(name="H25", f_c=25 * MPa)
steel    = SteelBar(name="ADN 420", f_y=420 * MPa)

wall = ShearWall(
    label="W1",
    concrete=concrete,
    steel_bar=steel,
    thickness=25 * cm,   # t
    length=4.0 * m,      # lw (in-plane length)
    height=3.5 * m,      # hw (story height; hw/lw = 0.875)
    c_c=20 * mm,
)

After construction, the dimensions are accessible as wall.thickness, wall.length, and wall.height.

2. Setting the Distributed Reinforcement#

Use set_horizontal_rebar(d_b, s) for the horizontal (transverse) mesh that resists in-plane shear, and set_vertical_rebar(d_b, s) for the vertical (longitudinal) mesh. The mesh is placed on both faces of the wall (E.F. — each face), so the reinforcement ratio counts both curtains: ρ = 2 · Ab / (t × s).

# Ø12 @ 150 mm in both directions
wall.set_horizontal_rebar(d_b=12 * mm, s=150 * mm)
wall.set_vertical_rebar(d_b=12 * mm, s=150 * mm)

3. Performing the Shear Check#

Call check_shear() with a list of Forces — either directly on the wall or through a Node. The returned DataFrame has one header row (units) followed by one row per combination.

from mento import Forces, Node, kN

f1 = Forces(label="1.2D+1.0E", V_z=800  * kN)
f2 = Forces(label="0.9D+1.0E", V_z=1200 * kN)

# Directly on the wall ...
wall.check_shear([f1, f2])

# ... or via a Node (recommended — enables results / detailed reports)
node = Node(section=wall, forces=[f1, f2])
node.check()
node.results

Returned columns:

Column	Meaning
`ρt,min`	Minimum horizontal reinforcement ratio (0.0025)
`ρt,req`	Required horizontal reinforcement ratio
`ρt`	Provided horizontal reinforcement ratio
`ρl,min`	Minimum vertical reinforcement ratio
`ρl`	Provided vertical reinforcement ratio
`Vu`	Demand shear
`ØVc`	Concrete shear strength (factored)
`ØVs`	Steel shear strength (factored)
`ØVn`	Total nominal shear strength (factored)
`ØVn,max`	Section-crushing limit (factored)
`DCR`	Demand-to-capacity ratio

4. Designing the Shear Reinforcement#

design() is fully automatic: it sizes both meshes against the worst-case force combination, applies them to the wall, and returns the re-evaluated check DataFrame.

result = wall.design([f1, f2])
# The wall now carries a designed mesh:
print(wall._d_b_h, wall._s_h)   # horizontal (shear) bar + spacing
print(wall._d_b_v, wall._s_v)   # vertical (minimum) bar + spacing

What it does:

Runs the check for every force and tracks the worst-case ρt,req.
Derives the worst-case ρl,min from §11.6.2.
Selects a bar diameter and spacing for the horizontal mesh (against ρt,req) and the vertical mesh (against ρl,min).
Applies both via set_horizontal_rebar / set_vertical_rebar and re-runs the check.

Vertical mesh. Because for now mento does not check flexure, the vertical mesh is always sized to the §11.6.2 minimum — it is reported and plotted as “Minimum vertical rebar”.

Note

For CIRSOC 201-25, design automatically uses the CIRSOC bar catalogue (Ø6 mm minimum transverse, Ø10 mm minimum vertical). No extra configuration is needed — the design code is read from the Concrete object.

5. Inspecting Intermediate Quantities#

After running a check, the relevant ACI 318-19 quantities are available as attributes on the wall:

Attribute	Meaning
`_hw_lw`	Aspect ratio `hw / lw`
`_alpha_c`	`α_c` factor (0.25 → 0.17 metric)
`_Acv`	Gross shear area `lw × t`
`_V_c_wall`	Nominal concrete shear strength
`_V_s_wall`	Nominal steel shear strength
`_phi_V_n_wall`	Factored total shear strength
`_phi_V_n_max_wall`	Factored crushing-limit shear strength
`_DCRv_wall`	Demand-to-capacity ratio for shear
`_rho_t_req`	Required horizontal reinforcement ratio
`_rho_l_min`	Minimum vertical reinforcement ratio
`_s_h_max`	§11.7.3 horizontal spacing limit
`_s_v_max`	§11.7.3 vertical spacing limit
`_d_b_h` / `_s_h`	Designed horizontal bar diameter / spacing
`_d_b_v` / `_s_v`	Designed vertical bar diameter / spacing

All reinforcement ratios (ρt, ρl) account for the mesh on both faces — ρ = 2 · Ab / (t · s).

A worked example with full output is available in the Shear Wall ACI 318-19 example.