Translating test loads to footing design checks.
Translate rating reports into design actions. We show how to convert crash rated bollard test outputs into overturning, shear, and bearing checks for real soils and concrete. Group effects, edge distance, and spacing must align with array pages (321–326) and clear-gap rules (232). Subgrade improvement and rebar strategies tie to foundation types (332) and verification (333). Include one-sentence context that naturally links upward to the parent hubs (this section and the chapter hub). For UAE projects, approvals can involve evidence for authorities—see SIRA Bollards (UAE) when relevant. Link installation pages only if helpful: What to Expect and Installation Guide.
Important: This is a general guide. For live projects we develop a tailored
Method Statement & Risk Assessment (MS/RA) and align with authority approvals (e.g., SIRA) where in scope.
331.1 Interpreting test data
Extract impact energy, penetration, and residual set (411–413). Convert to forces/moments for real soils. This bridges lab results to site design for any crash rated bollard.
Start with the certificate and test report values for penetration and debris classes (413). From the stated vehicle mass and impact speed you can compute nominal impact energy and derive a conservative crash standard–consistent force envelope. Translate the reported dynamic deflection and permanent set into allowable rotation at the base.
Use the as-tested geometry (socket depth, embedment, and concrete grade) and note any rating-critical dependencies (421). Where soil or groundwater differs, flag adjustments early and cross-reference ground conditions effects (423).
| Aspect | What matters | Where to verify |
|---|---|---|
| Performance | Tested system (bollard + footing) | Crash standards overview |
| Operations | Duty, fail-state, safety devices & measures | Installation Guide |
331.2 Equivalent design actions
Transform dynamic impact into conservative static actions using factors (228). These actions size bases so an HVM bollard line keeps pass/fail gaps (232).
Adopt a two-step approach: (a) derive a peak horizontal force and base moment from test energy/speed; (b) apply project-level safety factors (228) to form an ultimate action set. The resulting design actions are then checked against allowable clear-gap compliance (232, 322). Document all assumptions and keep them aligned with your modelling/correlation approach (416) if used.
331.3 Overturning & bearing
Check overturning against base weight/anchor and soil bearing (423). Adequate margins stop a crash rated bollard rotating beyond residual set limits (314).
Verify the resisting moment from concrete self-weight, passive soil pressure and any anchor contribution exceeds the factored base moment. Bearing checks should confirm allowable contact pressure under the footing is not exceeded for the chosen foundation type (332) and site soil class (423). Tie the rotation limit to the permitted permanent set so clear gaps remain within acceptance bands.
331.4 Group effects in arrays
Adjacent posts share soil and concrete. Model group stiffness so HVM bollard arrays don’t magnify rotation at corner units (321, 324).
Where bollards share a grade beam or overlapping pressure bulbs, treat the line as a coupled system. Corner and end posts can see higher rotations—cross-check against your chosen array pattern (321) and any corner/island treatment (324). If stiffness differences are large (e.g., mixed types), consider mixed-type array redistribution checks (326).
331.5 Edge distance & spacing
Respect clear cover and edge distances to prevent cone failures (333). Spacing coordinates with HVM bollard gap math (322).
Maintain minimum edge distances for anchors and reinforcing to avoid concrete breakout and ensure ductility. Align centre-to-centre spacing with spacing rules (232) and verify the clear-gap calculation (322) under deflection and set. Where utilities force offsets, escalate to the checks in foundation design checks (333).
331.6 Subgrade improvement
Stabilize weak soils with lean mix, geogrid, or stone columns. Improvement preserves crash rated bollard performance without changing array geometry.
When allowable bearing or stiffness is low, introduce improvement at controlled depth: lean-mix blinding for uniform bedding, compacted granular layers with verified compaction (628), or engineered solutions (geogrid base layers, stone columns). Record the chosen method in drawings and your ITP (714) so site tests prove the target modulus before pours.
331.7 Reinforcement strategies
Design cages for shear/punching and tie anchors to rebar (621). Good detailing protects HVM bollard sockets from cracking.
Provide shear links and punching shear capacity around sockets/plates; ensure development length and bar bends clear the socket and any drainage path. Where anchors are used, connect them into the rebar cage (621) to mobilise concrete and steel together. Use cover distances and formwork (623) that keep durability and breakout margins intact.
331.8 Verification methods
Use simplified checks plus FE where needed (416). Verify that chosen crash rated bollard loads are met with tolerance.
Begin with closed-form checks for overturning, bearing and rotation using conservative parameters. Where geometry is complex (shared beams, utility voids, mixed soils), supplement with calibrated finite element models per your modelling correlation strategy (416). Capture tolerances from tolerances & manufacturability (315) so worst-case rotations still preserve the acceptance band.
331.9 Worked calc outline
Inputs → dynamic→static factors → shear/bending → bearing/rotation → crack checks → drawings (931). Tie outputs to HVM bollard spacing (232).
(a) Inputs: certificate values, geometry, soil class; (b) Convert impact to design actions with project factors (228); (c) Check shear/bending, clear-gap (232) under rotation, bearing and punching; (d) Detail cages/anchors and specify subgrade improvement; (e) Issue drawings per CAD/BIM standards (931) and list field verification in the ITP and SAT (714, 638).
Related
External resources
- ASTM F2656 — Crash testing of vehicle security barriers
- BSI — Impact test specifications for VSB systems
- NPSA — Hostile Vehicle Mitigation guidance
331 Impact loads & foundations for Crash-Rated Bollards — FAQ
How do I turn a crash test into a base moment for design?
Use vehicle mass and impact speed to estimate energy, then derive a conservative horizontal force and base moment. Apply project safety factors (228) and check rotation against permanent-set limits from the certificate and deflection vs permanent set (314).
What if my soil and groundwater differ from the test?
Adjust bearing and passive resistance to local conditions and consider subgrade improvement. Document the change and confirm that rating-critical dependencies still hold; see groundwater/soil effects (423).
Do arrays behave differently from single bollards?
Yes. Shared concrete and soil stiffness can redistribute loads, especially at corners and ends. Check group effects alongside array pattern (321) and clear-gap calculations (322).
When should I use finite element (FE) modelling?
Use FE when simple checks are insufficient—e.g., mixed soils, large openings for utilities, deep grade beams, or non-standard sockets. Calibrate models and document correlation per Numerical Simulation & Correlation (416).