AS 3700:2018 · §7.3 · Unreinforced
Masonry Compression
f′m
—
Srs
—
k · φ
—
Capacity
—
per metre
—
Util.
—
Masonry · Unreinforced
Compression — Design by Simple Rules
AS 3700:2018 §7.3.3 Unreinforced masonry walls & piers

Characteristic Compressive Strength f′m — §3.3.2

Table 3.1 → f′mb
— MPa
mm
mm
f′m = kh × f′mb
— MPa —

Masonry Section

— MPa
mm

Height & Support Conditions

mm

Applied Loading

kN
Srs > 36 — Simple rules do not apply. Use refined calculation per Cl. 7.3.4, or reduce height / increase thickness.
Wall thickness < 90 mm — Minimum 90 mm required for compression members per Cl. 7.3.1.

Calculation — Design by Simple Rules

AS 3700:2018 Cl. 7.3.3
0 · Material Strength — §3.3.2
Unit type & bedding — Table 3.1
Mortar class — Table 3.1
Unit strength f′uc — MPa Input
Tabulated strength f′mb — MPa
from Table 3.1
 Table 3.1
Unit height hu — mm Input
Joint thickness tj — mm Input
hu / tj ratio — Table 3.2 entry
Joint thickness factor kh —
—
 Table 3.2
f′m = kh × f′mb — MPa
—
 Cl. 3.3.2
1 · Section Properties
Masonry type — Unreinforced
Wall thickness t — mm Input
Wall length L — mm Input
Bedded area fraction fn — Input
Net bedded area An — mm² fn × L × t
2 · Basic Compressive Capacity (Cl. 7.3.2)
Characteristic strength f′m — MPa Tables 3.1 & 3.2
Basic capacity Fuc — kN
= f′m × An
 Cl. 7.3.2(a)
Capacity per metre Fuc/L — kN/m Reference
3 · Simplified Slenderness Ratio (Cl. 7.3.3.4)
Clear height H — mm Input
Vertical slenderness coeff. av — Cl. 7.3.3.4
Thickness coefficient kt — Table 7.2
Simplified slenderness ratio Srs —
= av × H / (kt × t)
 Cl. 7.3.3.4
4 · Reduction Factor k (Cl. 7.3.3.3, Table 7.1)
Load source / column — Cl. 7.3.3.3
k factor (interpolated) —
—
 Table 7.1
5 · Design Check (Cl. 7.3.3.2)
Design force F*d — kN Input
Capacity reduction factor φ 0.75 AS 3700 Table 4.1
Design capacity φ · k · Fuc — kN  
= φ × k × Fuc
 Cl. 7.3.3.2
Utilisation F*d / (φ · k · Fuc) — ≤ 1.0 required
F*d ≤ φ · k · Fuc —
0 %100 %

Table 7.1 — Reduction Factor k

AS 3700:2018 §7.3.3.3
Srs Col. a — Concrete slab Col. b — Other system Col. c — Load on face
Notes: 1 · Linear interpolation within each category is permitted.
2 · This Table does not cover load applied to one face at roof level — use a detail minimising load eccentricity.

Table 3.1 — f′mb for Selected Column

AS 3700:2018 §3.3.2
—
f′uc (MPa) f′mb (MPa)
Note: Linear interpolation of f′uc is permitted (Note 1). Mortar class per Table 11.1.

Table 3.2 — Joint Thickness Factor kh

AS 3700:2018 §3.3.2
hu / tj kh
hu = masonry unit height (mm) · tj = mortar bed joint thickness (mm). Standard clay brick: hu = 76 mm, tj = 10 mm → ratio = 7.6 → kh = 1.00. Linear interpolation permitted.
Scope: Design by simple rules per AS 3700:2018 Clause 7.3.3. Applies to unreinforced masonry walls and piers of rectangular cross-section. Minimum thickness 90 mm (Cl. 7.3.1). Where Srs > 36, use refined calculation per Cl. 7.3.4. The capacity reduction factor φ = 0.75 is applied separately from the slenderness/eccentricity factor k (AS 3700 Table 4.1); the design check is F*d ≤ φ · k · Fuc. Not for grouted or reinforced masonry — see Cl. 7.3.2(b) and Cl. 7.3.4.