A torque-controlled expansion anchor uses a tapered member and expansion element to convert axial draw-in into radial motion against a drilled bore. Structural resistance is product- and condition-specific; it cannot be estimated safely from diameter, embedment and concrete strength with one generic scaling rule.
Expansion Anchor Bolt Interactive Calculator
Explore ideal wedge displacement only: axial draw-in, taper half-angle and initial radial gap determine the sleeve's geometric radial motion.
Equation Used
- Rigid, symmetric taper and sleeve displacement.
- Entered gap is radial and uniform.
- No friction, deformation, concrete response or load-capacity model.
- Use the exact evaluated product and manufacturer instructions for real work.
Educational kinematics only. This calculator does not predict anchor capacity, installation torque, concrete breakout, pullout, pryout, splitting, shear, edge or spacing effects, cracked-concrete behaviour, seismic performance or suitability. Use the exact evaluated product, construction documents and manufacturer instructions.
Taper and expansion element
Tightening the nut draws the tapered anchor body relative to its expansion element. The taper converts axial motion into radial movement that engages the bore wall. The exact working parts and installation sequence depend on the evaluated anchor product.
Use only an evaluated system
Mechanical anchors are qualified through prescribed testing and evaluation. Selection and design depend on the exact product, concrete condition, load direction, edge distances, spacing, embedment, installation and applicable code. A generic mechanism page cannot assign a structural capacity.
Ideal wedge geometry shown here
For axial draw-in x and taper half-angle alpha, ideal radial movement is y=x tan(alpha). Diametral growth is 2y, geometric contact margin is y minus the entered initial radial gap g, and ideal draw-in to close that gap is g/tan(alpha). These are displacement relations only, not anchor-force or holding-capacity results.
How to interpret the animation
The moving cone and split sleeve show axial-to-radial displacement. Reaching the drawn bore means only that the idealized geometry has closed the entered gap. It does not establish preload, friction, concrete stress or resistance.
Safety boundary
Do not use this page to select an anchor, drill size, embedment, torque or allowable load. Use the current evaluation report and installation instructions for the exact anchor, and obtain engineering review where required.
Frequently asked questions
Can the calculator determine anchor holding capacity?
No. It calculates ideal taper displacement. Anchor resistance requires the exact product evaluation, installation conditions and checks for the relevant failure modes.
Does a positive contact margin prove the anchor is set?
No. It only shows that the requested free displacement exceeds the entered gap. It does not calculate deformation, preload or holding force.
Authoritative references
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