Rod Cross-Bracing — Structopedia

Bay width W (mm) Centre-to-centre of posts

Bay height H (mm) Base to rod connection level

Cross (X) rods are tension-only members — the slender rod is assumed to buckle and carry no compression, so one diagonal resists each direction of loading. The system capacity is identical for load applied in either direction.

Rod size (ISO metric coarse thread) Threaded ends — A_n = tensile stress area A_s per AS 1275

Rod steel f_y / f_u from AS 4100 Table 2.1 & Table 9.2.1

Correction factor k_t 1.0 for symmetric end connections (nut & washer each end) — Cl 7.3.1

Design horizontal force H* (kN) — optional Strength limit state action for utilisation check — Cl 7.1

Diagonal angle θ

—

from horizontal

Rod capacity φN_t

—

Cl 7.2

Horizontal capacity φH

—

φN_t · cos θ

Vertical component at φH

—

φN_t · sin θ — post download / anchor uplift

Areas A_g / A_s

—

gross / tensile stress area

Utilisation H* / φH

—

enter H* above

Scope & assumptions — This calculator determines the horizontal racking capacity of a single braced bay (two posts with cross rod bracing) governed by the tension capacity of one rod diagonal per AS 4100:2020 Section 7, with capacity factor φ = 0.90 (Table 3.4). Rods are treated as tension-only: the compression diagonal is assumed ineffective. The net area of the threaded rod is taken as the tensile stress area per AS 1275 (Cl 7.2). It does not check the end connections (nuts, washers, gusset/cleat plates, welds, bolts — AS 4100 Section 9), the posts, the top chord/strut, anchorage of uplift and download forces, or serviceability (rod sag — light pre-tension via turnbuckle is normal practice and does not add to member force capacity). Round bar strengths apply to bar diameters ≤ 50 mm (Table 2.1). All checks must be verified by a qualified structural engineer.