Concentrated Load Design for FRP Grating: Point Loads & Wheel Loads

A person standing still on a grating exerts roughly the same pressure as a heavy-duty pallet truck rolling across it — yet the two are treated very differently in design. Uniform load asks the whole panel to share; a concentrated load asks a few bars to carry everything. For high load pultruded FRP grating and industrial fiberglass flooring grating exposed to forklifts, carts and maintenance vehicles, the point-load case — not the uniform-load case — usually controls the panel selection.

This article explains how a point or wheel load actually travels through a grating panel, why the contact footprint matters, and why pultruded I-bar and T-bar sections are the right answer for heavy duty pultruded FRP grating applications.

1 · Uniform Load vs Concentrated Load

Uniformly distributed load (UDL) spreads over the entire deck — a 5 kN/m² walkway load means every square metre contributes and every load bar takes a small share. A concentrated load is the opposite: it is applied through a small contact area (a shoe, a wheel, a foot of equipment) and transferred to only the bars directly beneath it, plus a few neighbours through the cross-bars or cross-rods.

Load Case	Example	Design Driver
Uniform (kN/m²)	Pedestrian occupancy, live load	Panel deflection over span
Point / concentrated (kN)	A worker with tools, a machine foot	Local bending + shear in a few bars
Wheel / moving (kN per wheel)	Forklift, pallet jack, cart	Contact pressure + repeated fatigue

A common mistake is to size a deck for UDL and then discover a pallet truck wheel creates a local bar deflection the uniform table never checked. Always design for the most severe of the two cases.

2 · How a Point Load Distributes Through the Bars

When a load lands on the top surface, it first contacts the surface layer (grit, concave or convex meniscus) and then transfers into the nearest load bars. In molded grating, the interwoven continuous glass in both directions spreads the load across roughly three to five adjacent bars because the grid is monolithic. In pultruded grating, the longitudinal load bars are the primary members and the transverse tie bars are not designed to carry bending — so the effective distribution depends on how many load bars the contact footprint covers.

• Bigger contact area = more bars share. A wide forklift tyre spreads its load over more bars than a narrow caster wheel of the same load.
• Smaller mesh = shorter lever arm. A 38×38 mm mesh engages bars more densely than a 50×50 mm opening, reducing local stress.
• Bar depth governs local bending. A deeper bar spreads the point load further toward the supports and deflects less under it.

3 · Wheel Load Scenarios

Wheel loads are the harshest concentrated case because they are moving, repeated and applied through a small rubber contact patch. Typical scenarios on industrial fiberglass flooring grating:

• Pedestrian and hand cart: light casters; molded 25–30 mm grating is usually sufficient.
• Pallet jack / maintenance trolley: steel or nylon wheels of 1–3 kN per wheel; 38–40 mm grating with grit-top surface is typical.
• Electric walkie / small forklift: 3–5 kN per wheel over a small tyre contact; specify pultruded grating and confirm against the wheel-load rating.
• Heavy forklift / lift truck: exceeds standard deck ratings — use a dedicated equipment plate, a steel plate overlay, or a heavy-duty pultruded section rated for the axle load.

For any wheeled traffic, state the wheel load, tyre contact dimensions and tyre pressure in the RFQ. ZeAllgrate engineers convert these into an equivalent point load and check both local bar stress and panel deflection over the actual span. Do not assume a pedestrian-rated deck is forklift-rated. When a maintenance vehicle crosses a walkway only occasionally, it is still worth rating that stretch of deck: a single overloaded pass can permanently set a bar that would otherwise last decades, and FRP does not show visible yielding — the damage only appears as a slow, unexpected sag later.

4 · Contact Area and Bearing onto Supports

Two local details matter beyond the bar itself. First, the contact area: a sharp equipment foot can concentrate enough pressure to crush the top of a bar even when the global panel is fine — fit a foot plate or sole board to spread the load. Second, the support bearing: each loaded bar must sit on a support with the required minimum 40 mm bearing, otherwise the point load reacts as a knife-edge and crushes the bar end. Panel clips (SS304/SS316) at each loaded bar-to-beam intersection prevent lateral movement and keep the bearing line true.

5 · Why Pultruded I-Bar / T-Bar Wins Point-Load Duty

Pultruded grating is built around deep, unidirectional load bars with glass content near 70%, and a flexural modulus about twice that of molded grating. I-bar and T-bar sections put the glass where bending needs it — in the top and bottom flanges — rather than wasting resin in a thin web. For point loads and wheel loads, this means:

• Higher section depth (up to 60 mm) resists local sag under a wheel.
• Unidirectional high-glass bars carry the concentrated moment to the supports with less deflection.
• Repeat wheel passes do not fatigue the bars the way they can a more resin-rich molded section.

Factor	Molded Grating	Pultruded I/T-Bar
Glass content	~30–35%	~70%
Relative stiffness	1×	~2×
Max load-bar depth	50 mm	60 mm
Best at point/wheel loads	Light carts, pedestrian	Forklifts, equipment feet, heavy duty

6 · Design Example and Heavy-Duty Applications

Example: a maintenance walkway crossed by an electric walkie pallet truck with a 2.5 kN wheel load and a 100×80 mm tyre contact, span 1.0 m. The engineered solution is ZeAllgrate pultruded grating with 50 mm I-bars on the 1.0 m support spacing, grit-top surface for wet grip, SS316 clips at every bar intersection, and a small steel wear plate at the truck parking zone where wheels stop repeatedly. The same deck in molded 38 mm would pass the 5 kN/m² pedestrian UDL but show excessive local deflection under the 2.5 kN wheel — which is exactly the failure mode point-load design prevents.

Typical heavy duty pultruded FRP grating installations include offshore equipment access platforms, chemical plant truck crossings, wastewater treatment maintenance decks, and factory mezzanine floors where pallet traffic is expected. ZeAllgrate supplies load bars up to 60 mm deep in ISO polyester, vinyl ester and fire-retardant resins for these duties.

7 · Fatigue, Impact and Dynamic Loading

A single forklift pass is a static point load; a deck crossed by forklifts every hour for ten years is a fatigue problem. FRP bars are remarkably fatigue-resistant compared with metals, but repeated wheel passes over the same bar — especially where the tyre contact patch lands repeatedly on the same spot — can work the resin-rich surface and eventually crack the top flange. Three design choices control this. First, rate the cover or deck for the repeated wheel load, not just the first pass, and keep the working stress well below the ultimate. Second, add a steel or FRP wear plate at the parking and turning zones where wheels stop and pivot — that is where the highest local damage accumulates. Third, account for impact: a dropped drum, a bump over a clip, or a truck hitting a curb introduces a short dynamic load that a static rating underestimates. Where impact is expected, derate the working load or specify a deeper pultruded section with reserve stiffness. ZeAllgrate can provide batch load-test reports (ASTM D790 flexural) so you can verify the as-produced bar stiffness against the design assumption.

8 · Conclusion

Concentrated and wheel loads are a local, few-bar problem, not a whole-panel problem. Size for the heaviest expected point or wheel load, specify the contact footprint and tyre pressure up front, spread sharp feet with plates, guarantee 40 mm bearing at each support, and choose the ~2× stiffer pultruded I/T-bar family — with load bars to 60 mm — whenever a deck sees forklifts, carts or equipment feet. Send the axle loads and support drawing to ZeAllgrate for a verified rating before procurement.

Frequently Asked Questions

Q: Is a pedestrian-rated FRP grating safe for a pallet truck?

A: Usually no. Pedestrian ratings are based on uniform live load; a pallet truck applies a concentrated wheel load that deflects only a few local bars. You must rate the deck against the actual wheel load and contact area — typically with pultruded grating — before allowing cart or truck traffic.

Q: How do I calculate the point load from a forklift?

A: Take the axle load, divide between the wheels on that axle, and account for dynamic impact during braking or lifting. Provide the wheel load, tyre contact dimensions and tyre pressure to ZeAllgrate; our engineers convert these into an equivalent design point load and check local bar bending and deflection.

Q: Does a grit-top surface help with wheel loads?

A: Grit-top improves slip resistance (dry COF 0.6–0.8, wet 0.5–0.7) and wears well under foot traffic, but it does not by itself increase the structural point-load rating. The structural rating comes from bar depth, glass content and span; grit-top is chosen for the surface zone that people walk on.