Gerber beam with internal hinge
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About this case
How to analyze a Gerber beam with an internal hinge
This page pre-loads a two-span beam with an internal hinge at the junction (moment release). The left span is fixed at A, hinged at B; the right span is hinged at B, roller at C. Uniform load w on both spans. Edit spans, load, section or material directly.
The hinge forces M = 0 at B. The left span is a propped cantilever: reaction at B is 3wL/8, moment at A is wL²/8. The right span is a simply supported beam: reaction at C is 5wL/8. The hinge carries shear but no moment.
Why use a Gerber beam
A Gerber beam converts a statically indeterminate continuous beam into a statically determinate system by inserting a hinge. This simplifies construction (no moment connection at the hinge) and eliminates moment redistribution from support settlement. The trade-off: the left span's fixed end still attracts a large moment, and the hinge detail must transfer shear reliably.
The hinge location is typically chosen so the maximum positive moment in each span is balanced (here at midspan of the right span and at x ≈ 0.578L of the left span). The calculator lets you move the hinge to find the optimal position.
Common mistakes with Gerber beams
Forgetting that the hinge must be a true moment release — a partial connection that transmits some moment defeats the purpose and creates an indeterminate system that behaves differently. Not checking the shear capacity at the hinge: it carries the full span shear. And assuming the spans can be designed independently — the hinge shear is the same on both sides, so the connection must be designed for the larger of the two span shears.