FRP Design Manuals and Load Tables: What They Contain and How to Use Them

In short: An FRP design manual is the supplier's technical document for designing with its grating, profiles or other products. It contains material properties, section properties, load tables, connection details and design guidance. Load tables give the safe load for each product and span, usually limited by a deflection limit and a factor of safety. For example, some grating manufacturers publish recommended loads at about one fifth of the ultimate load, and another describes a 4:1 factor of safety for its grating tables. For pultruded structures, published design standards now exist: ASCE/SEI 74-23 in the United States and CEN/TS 19101:2022 in Europe, while EN 13706 specifies pultruded profiles. Always use the manual for the exact product you buy.

What a design manual contains

How load tables work

A grating load table typically lists, for each product and clear span:

• uniform loads (psf or kPa) and the resulting deflection;
• concentrated loads (lb or kN), often as a line load across the panel width;
• a maximum recommended load derived from the ultimate load and a factor of safety.

Deflection limits

FRP is stiff for its weight, but less stiff than steel, so deflection often governs. One US grating manufacturer describes common limits of span/120 or 3/8 in, with a firmer feel at span/200 or 1/4 in. For walkways, a common comfort criterion is span/200 or 6 mm (1/4 in), whichever is less. Follow your project specification.

Factor of safety

Load tables give recommended loads well below the ultimate. A second US grating manufacturer's published tables show maximum recommended loads at about one fifth of the ultimate load (for example 3,200 psf recommended against 16,000 psf ultimate for one product at a 12 in span). The first manufacturer describes a 4:1 factor of safety. Factors differ between manufacturers, so read the notes on each table.

Dynamic and impact loads

The first manufacturer notes that deflections under impact or dynamic loads should be taken as twice the tabulated static values. Wheeled carts and impact loads need special attention.

Temperature and resin

Strength and stiffness fall at elevated temperature. Load tables are usually given at room temperature, so check derating if your service temperature is high.

Test methods

Grating load tables are normally based on testing. The first manufacturer refers to the test method published by the Fiberglass Grating Manufacturers Council (FGMC) of the American Composites Manufacturers Association (ACMA).

See How to Read FRP Grating Load Tables for a worked example.

Design standards for FRP structures

ASCE/SEI 74-23 gives a code-based design method for pultruded FRP members and connections. CEN/TS 19101 is a European Technical Specification for the design of fiber-polymer composite structures. EN 13706 specifies requirements for pultruded profiles, including grades.

How to use supplier data correctly

1. Use the manual for the exact product. Values differ between manufacturers, meshes and resins.
2. Use clear span. The distance between supports, not center to center.
3. Check units. psf and kPa: 1 kPa ≈ 20.9 psf.
4. Apply the right deflection limit.
5. Include dynamic and concentrated loads.
6. Check temperature and chemical exposure.
7. Ask the supplier when in doubt.

FIBROVX technical data

We provide product datasheets, load data and drawings on request through our Technical Resources page. Send your spans, loads and environment and we will confirm a suitable product. See also FRP molded grating, pultruded grating and pultruded profiles.

Common mistakes

• Using another manufacturer's table.
• Using center-to-center span.
• Ignoring deflection.
• Confusing ultimate and recommended loads.
• Mixing units.

Key terms

• Ultimate load: Load at which the product fails in test.
• Factor of safety: Ratio of ultimate load to allowable load.
• Deflection limit: Maximum allowed bending, expressed as a fraction of span or a fixed value.
• LRFD: Load and Resistance Factor Design.

FAQ

What is the factor of safety for FRP grating?

It varies by manufacturer. Published examples include about 5:1 and 4:1. Read the notes on the table.

What deflection limit should I use?

Follow your specification. A common walkway criterion is span/200 or 6 mm (1/4 in), whichever is less.

Is there a design code for FRP?

Yes. ASCE/SEI 74-23 in the USA and CEN/TS 19101:2022 in Europe for pultruded and composite structures.

Can I use a steel grating table for FRP?

No. FRP and steel behave differently.

Do you provide load data?

Yes, on request.

Related guides

• How to Read FRP Grating Load Tables
• FRP Pultruded Profiles Guide
• FRP CAD Drawings Guide
• Technical Resources: datasheets and drawings on request
• FRP Structural Design Basics: Deflection, Creep and Safety Factors
• FRP Grating Thickness Selection: 25, 30, 38 and 50 mm Compared

Sources

• ASCE/SEI 74-23, Load and Resistance Factor Design (LRFD) for Pultruded Fiber Reinforced Polymer (FRP) Structures: https://ascelibrary.org/doi/book/10.1061/9780784415771
• CEN/TS 19101:2022, Design of fiber-polymer composite structures (CEN Technical Specification)
• EN 13706, Reinforced plastics composites: Specifications for pultruded profiles (CEN standard)
• A US FRP grating manufacturer, square grid load table notes (4:1 factor of safety, span/120 or 3/8 in, span/200 or 1/4 in, dynamic-load deflections ×2, FGMC/ACMA test method)
• A US FRP grating manufacturer, molded grating load tables (5:1; 1-1/2 in 1-1/2 × 1-1/2 at 12 in span: 3,200 psf recommended, 16,000 psf ultimate)