923.1 Purpose & scope

Rapid moment/overturning checks to size foundations for crash rated bollard cores (331–333).

This quick-estimator converts a chosen crash rating into a conservative overturning moment at the bollard base and spreads it over a candidate footing. It’s designed for fast feasibility: shortlisting suitable foundation classes and spotting red flags such as excessive bearing pressure or edge proximity. Use it to brief stakeholders and narrow options before committing to detailed calculations or ground investigation.

The scope covers typical single- and grouped-bollard arrangements for crash-rated systems, with presets aligned to common depth classes and soils. It does not replace structural design or geotechnical assessment; see Impact loads & foundations and Design checks for the engineering background.

923.2 Inputs

Vehicle energy proxy, spacing/grouping, soil/bearing class, embedment (331, 423). Aids HVM bollard feasibility.

Start by selecting a rating string (e.g., ASTM F2656 or IWA 14-1) and the relevant vehicle/speed envelope. The tool maps this to an equivalent horizontal action at capture height, adds a lever arm to estimate base moment, and applies a conservative factor for group stiffness when bollards share a grade beam. Then choose a soil preset representing typical allowable bearing (e.g., dense sand vs. stiff clay) and set the trial embedment depth or footing dimensions.

Geometry inputs include clear-gaps, edge distances, and slab thickness where shallow rails are considered (see Shallow foundations). Utility conflict flags can be toggled to preview clashes with ducts or drainage sumps.

923.3 Method

Converts rating outputs to equivalent actions; applies group/edge effects (331.2–331.5). Conservative by design.

The estimator uses a simplified energy-to-force translation consistent with how ratings are interpreted for foundation checks. It resolves the impact into a horizontal line load at the bollard’s effective height and computes the base moment using capture-height × force. For grouped arrays, a distribution factor estimates how much load the neighboring posts and any grade beam pick up.

Edge influences (near slab or excavation faces) are handled with reduction factors and warnings where rotation limits could be exceeded. Soil presets assign allowable bearing and a nominal modulus for rotation checks. All factors are intentionally on the safe side to prevent screening-stage underestimation.

923.4 Outputs

Indicative moments, bearing/rotation flags, depth options (332). Shortlist crash rated bollard base types.

Primary outputs include base moment (kN·m), estimated bearing pressure (kPa), and a qualitative rotation indicator at service level. Where values exceed defaults, the tool suggests deeper sockets, wider pads, or switching to reinforced rails. A comparison view lists viable foundation classes with pros/cons and notes on construction complexity and utility clearance.

Exportable summary rows show assumptions (rating, soil preset, geometry) and a pass/fail note for bearing and rotation. Use these to guide conversations during optioneering and to cue next-level design actions.

923.5 Limits

Not a replacement for detailed design; ignores complex soil–structure interaction (333, 423). Use for screening.

This is a hand-calc oriented quick check. It does not perform finite element soil–structure interaction, detailed sliding/uplift verifications, or punching checks for slabs. Parameters such as groundwater position, partial factors, and local detailing must be addressed by the designer—see Design checks for foundations and Groundwater/soil effects.

923.6 Validation

Compare against tested configurations and dependencies (421, 431). Keep HVM bollard integrity.

Use the tool’s “as-tested configuration” notes to align with certification dependencies (foundation size/rebar, backfill, and concrete grade). Cross-check with supplier literature and the rating-critical dependencies page, and ensure documentation captured in Documentation & certificates supports the chosen option.

923.7 Drainage & utilities notes

Warn on sump/outfall and clash risks (334, 245, 241–243). Practical foundations.

Foundation choices interact with drainage and services. Where a sump is required for automatic systems, include a weep hole or outfall and check freeboard and hydrostatic head. Respect the utility avoidance zone from survey outputs (see Utility search methods and Underground detection), and switch to shallow rails or micro-piles where conflicts persist.

923.8 Save/Export

Calc sheet with assumptions and IDs (911). Reviewer traceable for crash rated bollard decisions.

Each run can be saved with a unique page-ID and timestamp, including the rating string, geometry, soil preset, and foundation class shortlist. Export CSV and a snapshot PDF for inclusion in your ITP and specification template. For submission packs, add the export to the Submission-Pack Guidance.

923.9 Next steps

Hand off to detailed calcs (914) and drawings (931). Close evidence loop.

Use the shortlist to select a target foundation class and proceed to detailed checks (bearing, sliding, uplift, rotation, punching). Incorporate into the Calculations Pack, then coordinate CAD/BIM with CAD/BIM Standards and foundation typicals (933). In the UAE, verify any SIRA implications early in design.

923 Foundation Moment Quick-Estimator — FAQ