BuckIO — Elastic Buckling Checks

Analytical plate & column theory • MMPDS 2024-T3 Al defaults • Units: in, ksi, k (1000 lb)

BuckIO evaluates elastic buckling capacity for common structural elements. Pick the mode that matches your component, enter geometry and applied stress, and compare utilization against the critical value.

Buckling Modes

• Column (AISC E3)

  Overall flexural buckling of a compression member about its weak or strong axis. Uses slenderness KL/r and the column curve to find critical stress and axial capacity.

• Plate Compression

  Uniform in-plane compression on a flat plate panel. Compression is assumed along the longer side; elastic buckling uses the shorter span and edge-restraint k-factor.

• Web / Shear Panel

  Shear buckling of a web or plate panel under in-plane shear. Critical shear stress depends on panel aspect ratio and thickness.

• Flange Local

  Local buckling of a compression flange outstand (half-width from web to tip). Common in beams and built-up sections under bending or axial load.

• Web Compression + Shear

  Web slenderness with compression across hw and shear along the panel. Long beam webs use ks = 5.34; enter panel length for short segments. Von Kármán interaction (σ/σcr)² + (τ/τcr)² when both loads are present.

• Inter-Rivet (Bruhn)

  σ_ir depends on c and s only. Bruhn effective width W = t·K·√(E/F_cs) is independent of bay width b (b only caps W when the bay is narrow). Elastic panel-bay σ_panel ∝ (t/b)² is a separate limit that governs only at full panel analysis — wider bays buckle at lower σ_panel, which is not the same as effective width. Governing allowable is the minimum of applicable limits at your chosen analysis level.

Linear elastic buckling only. No post-buckling, no geometric imperfection knockdown unless you apply it manually to applied stress.