📐 Truss Member Analysis

Written and maintained by the PhDino author · Last reviewed 21 September 2026 · A documented rule of thumb, pinned by automated tests · how PhDino checks its numbers

Related standards: AISC 360

Checking whether a truss member can carry its axial tension or compression force.

Truss members are idealized as two-force members — pinned at both ends, loaded only at the joints — so each member carries pure axial tension or compression with no bending. Member forces are typically found by the method of joints or method of sections; once you have the axial force, checking the member is a straightforward stress or capacity check.

Tension and compression capacity are not the same: a member in compression can fail by buckling before it ever reaches the material's yield stress, especially if it's slender (see Column Buckling) — this calculator applies simplified reduction factors to approximate that difference.

Key formula

Tension capacity ≈ 0.9 × F_y × A
Compression capacity ≈ 0.85 × F_y × A

Variables

F_y

yield strength of the member material

A

cross-sectional area of the member

Notes & limitations

• The compression factor here is a simplification — real compression capacity depends heavily on the member's slenderness ratio (see Column Buckling) and should be checked against AISC 360 Chapter E for anything but very stocky members.
• Finding the actual member force in the first place (method of joints/sections, or a full truss analysis) is a separate step not performed by this calculator — the "Applied Load" input here is the member's own axial force, however it was determined.