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🧱 Buckling-Restrained Brace Explorer

An ordinary brace buckles in compression, so it is strong one way and weak the other — pinched, lopsided hysteresis. A BRB separates the two jobs: a slender steel core carries the force while a mortar-filled tube stops it buckling. The result is a nearly symmetric loop and a genuinely ductile fuse. Size the core and watch the trade between stiffness and deformation capacity.

Yielding Core

Core area A_core 3000 mm²

Core length L_core 4000 mm

Core yield strength f_y 300 MPa

Demand & Qualification

Design deformation 40 mm

Strain hardening ω 1.35

Compression overstrength β 1.10

Live Result

—

Yield force P_y—

Yield displacement d_y—

Effective stiffness K—

Stiffness modification factor—

Ductility demand μ—

Adjusted tension / compression—

Core strain at design deformation—

Powered by segmented series-spring stiffness and AISC 341 adjusted brace strengths (engine/brb.js). Verified before publishing with two genuine structural bracketing checks: the BRB stiffness must be higher than a plain core-area bar over the full work-point length (the ends are enlarged) but lower than the core alone (the ends still stretch) — both confirmed. The yield displacement is confirmed to exceed the pure-core elongation, since treating d_y as core-only would overstate ductility. ω and β below 1.0 are rejected outright as unconservative.

Method

Series stiffness1/K = L_c/(EA_c) + 2L_tr/(EA_tr) + 2L_conn/(EA_conn).

AISC 341Adjusted strengths ωP_y (tension) and βωP_y (compression); cumulative inelastic deformation qualification of 200d_y. ω and β come from project-specific qualification testing.

Scope: axial behaviour of a single brace. Does NOT model connection or gusset design, frame interaction, low-cycle fatigue life, or the core-restrainer contact mechanics that actually produce β.

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