First sizing of a cantilever abutment on a spread footing. Set the superstructure reactions, height, abutment length and soil — the tool proposes footing dimensions that pass the classic stability checks (bearing, middle-third, sliding FS 1.5, overturning FS 2.0, Rankine earth pressure), and estimates the main reinforcement. Planning-level screening; wing walls, seismic and detailed RC checks belong to final design.
First sizing of a cantilever abutment on a spread footing. Set the superstructure reactions, height, abutment length and soil — the tool proposes footing dimensions that pass the classic stability checks (bearing, middle-third, sliding FS 1.5, overturning FS 2.0, Rankine earth pressure), and estimates the main reinforcement. Planning-level screening; wing walls, seismic and detailed RC checks belong to final design.
| Step | Quantity | Value | Note |
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Sliding governs more abutments than overturning — if the base is short on friction, a shear key is cheaper than a longer heel. The soil parameters move the answer far more than any structural choice: φ of 30° versus 34° changes the pressure by a fifth. Spend your effort on the geotech report, not the concrete.
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This sizer covers the conventional cantilever abutment with bearings and an expansion joint. Many short and medium bridges now avoid both by making the deck continuous with the abutment. Read integral vs semi-integral abutments for how the two jointless types work, their length limits and when to choose them, and the substructure chapter of the Bridge Book for the full background. Related tools: spread footing, pile capacity, bearing pad, expansion joint.