FRP Structural Profiles: Sizes, Standards and a Structural Engineer's Selection Guide

When a steel beam or angle will rust, conduct or weigh down the structure, engineers reach for pultruded composite framing. FRP structural profiles - the same product called GRP structural profiles, GFRP structural profiles and fiberglass structural profiles, and equivalently composite structural profiles in fiber reinforced plastic - are continuous-fiber shapes that drop into familiar beam-and-post layouts without the corrosion, electrical conduction or dead load of steel. In British engineering writing they appear as fibreglass profiles or fibre reinforced polymer sections. This guide explains the standard structural sections and structural shapes ZeAllgrate stocks, how to read their dimensions and section properties, how resin choice drives corrosion and fire performance, and how to size a real beam against its span and load.

Manufactured by pultrusion, these pultruded FRP profiles use the same names a structural engineer already knows - beam, channel, angle, tube, bar - so a project does not need a new design language. What changes is the material: a corrosion resistant, lightweight, high strength frame that is also non-conductive, UV resistant and flame retardant where the specification demands it.

Why Specify FRP Structural Profiles Instead of Steel

Steel framing is cheap and stiff, but it loses both arguments in the environments that matter. In chemical processing, water and wastewater treatment, pulp and paper, coastal and offshore service, and cable trays next to live equipment, steel rusts, requires painting and touches nothing safely live. FRP reinforced plastic profiles solve all three at once.

• Corrosion resistant and anti-chemical - the resin matrix, not the glass, resists acids, alkalis, bleach and brine; there is no rust to paint or strip.
• High strength with a superior strength-to-weight ratio - pultruded laminates reach roughly 22-28 GPa longitudinal flexural modulus at a density of about 1.7-1.9 g/cm³, around a quarter of steel density, so sections are light enough to handle by hand and to bolt onto existing structures.
• Non-conductive with built-in electrical insulation - dielectric strength above 10 kV/mm, making these sections the safe choice for substations, busbar supports and rail electrification zones.
• Low maintenance - no painting, no rust-through, no galvanic corrosion at the fasteners.
• UV resistant and fire retardant - a C-glass or synthetic surface veil protects against fiber bloom outdoors, and fire retardant / flame retardant resins meet ASTM E84 Class A where code requires it.

The result is framing that survives wash-down, salt air and chemical spill that would eat a steel frame in a single maintenance cycle. These are the properties that make pultruded fiberglass structural profiles the default choice for platform support framing, conveyor supports, pipe racks, pedestrian bridge girders, equipment skids and cooling tower structure.

How Pultrusion Makes These Sections

All of these shapes are produced on a pultrusion line. Continuous glass rovings, mats and a surface veil are pulled through a resin bath, then through a heated steel die that consolidates the laminate to a precise cross-section and cures it in line. This is what Pultrusion FRP Profiles, Pultruded Fiberglass Profiles and Pultruded GRP Sections have in common: unidirectional reinforcement along the length, a consistent web and flange thickness, and a finished surface veil as standard.

Because the fibers run the full length, longitudinal stiffness and strength are high; transverse performance is deliberately lower and must be respected in design. ZeAllgrate pultruded shapes run roughly 65-70% glass by weight (about 70% ± 5% on the structural laminate), wall thicknesses from 3 to 25 mm per profile, and standard stock lengths of 6 m and 12 m with custom cut lengths on request. Colors are gray, green or black as standard, with custom RAL/Pantone matching available.

The Shape Range - Structural Sections and Structural Shapes

The catalog covers the full vocabulary of structural shapes. On the beam line you will find the FRP I Beam, the deeper FRP H Beam, the symmetric FRP Wide Flange Beam, and the equivalent fiberglass I-beam. On the secondary line there are channels and angles - the FRP U Channel, FRP C Channel, GRP Channel and fiberglass U section, together with the FRP L Profile, FRP Equal Angle and FRP Unequal Angle. Hollow sections cover the FRP Square Tube, FRP Rectangular Tube, FRP Round Tube, GRP Square Hollow Section and fiberglass rectangular hollow tube. Solid shapes include the FRP Flat Strip, FRP Flat Bar, FRP Solid Round Rod, FRP T Profile and FRP Z Profile, with FRP Custom Profiles and Special Shaped sections engineered to customer drawings where a standard shape will not do.

Dimensions and weights above are ZeAllgrate's nominal pultruded catalog; certified section data accompanies each order. FRP rectangular tube, fiberglass rectangular hollow tube, FRP unequal angle, FRP T profile, FRP Z profile and special shaped sections are available to drawing where the standard range does not match the requirement.

Beam Sections: I-Beam, H-Beam and Wide-Flange

The distinction matters more than engineers expect. An FRP I Beam has narrow flanges relative to its depth and is optimized for bending about the strong axis - it is the right member for a platform beam spanning between columns. The FRP Wide Flange Beam (a symmetric H-shape) has flanges almost as wide as the beam is deep, so its strong- and weak-axis properties are nearly equal; that makes it the correct choice for a column or a beam where lateral bending cannot be fully braced. The FRP H Beam term is often used interchangeably with the wide-flange form. The fiberglass I-beam is simply the same pultruded I-section named for the glass reinforcement rather than the plastic matrix.

Stocked I-sections run from I-100×50 (100 mm deep, 50 mm flange, 6 mm web, 8 mm flange, about 2.35 kg/m) up to I-250×125 (250 mm deep, 125 mm flange, 8 mm web, 12 mm flange, about 8.65 kg/m). Wide-flange sections run from WF-150×150 to WF-250×250. Across the catalog, section depth spans 100-250 mm, flange width 50-250 mm, web thickness 6-12 mm and flange thickness 8-15 mm.

Secondary Shapes: Channels, Angles, Tubes, Bars and Rods

Channels - the FRP U Channel, FRP C Channel, GRP Channel and fiberglass U section - are stocked as C-100×50, C-150×75 and C-200×100. They bolt easily to flat faces and carry torsional and edge-rail duty that an I-beam is over-specified for. Angles are stocked as equal-leg FRP Equal Angle sections (L-50×50×5 through L-100×100×8); FRP Unequal Angle and custom FRP L Profile legs are produced to drawing.

Hollow sections are where the family is most versatile. The FRP Square Tube and GRP Square Hollow Section are the workhorse posts and handrail legs; the FRP Round Tube gives a clean rail; and the FRP Rectangular Tube and fiberglass rectangular hollow tube are ordered where a flat face or a deeper section is needed. The FRP Flat Strip and FRP Flat Bar form grating borders, stiffeners and gussets, while the FRP Solid Round Rod supplies tie rods and dowels. FRP T Profile and FRP Z Profile sections fill ledge and interlocking roles, and anything outside this vocabulary is handled as FRP Custom Profiles or a Special Shaped pull.

Reading Section Properties (Ix, Zx and EI)

Selecting a composite beam is a section-property calculation, not a guessing game. Each catalog row lists area, weight per metre, moment of inertia Ix and section modulus Zx = Ix/(h/2) about the strong axis. For example, the I-200×100 carries Ix ≈ 2195 cm&sup4; and Zx ≈ 219.5 cm³; the WF-200×200 is nearly symmetric, with Ix = Iy ≈ 4701 cm&sup4;.

On the material side, a typical unidirectional pultruded laminate sits at about 70% ± 5% glass by weight, tensile strength around 350-450 MPa longitudinal (ASTM D638), flexural strength around 400-500 MPa and flexural modulus around 22-28 GPa (ASTM D790), compressive strength around 250-300 MPa (ASTM D695), density 1.7-1.9 g/cm³ (ASTM D792) and dielectric strength above 10 kV/mm (ASTM D149). For design, ZeAllgrate uses a representative modulus near 24 GPa and an allowable bending stress around 69 MPa with a safety factor of about 3 - and always recommends confirming with certified EI data for the exact resin and section before final sizing.

Sizing Beams by Load and Span

Because FRP is less stiff than steel, long beams are usually deflection-limited, not stress-limited. ZeAllgrate's allowable uniform load for a simply supported I-beam uses a deflection limit of L/240, includes a long-term creep factor, and is computed from δ = 5wL&sup4;/(384EI) with E ≈ 24 GPa. Short spans are stress-limited; long spans are deflection-limited.

Values are allowable uniformly distributed load in kN/m by clear span, indicative for specification-level sizing. Two rules follow. First, brace the compression flange: lateral-torsional buckling governs unbraced long beams, so provide lateral-torsional restraint at supports and brace the compression flange on long spans. Second, expect the allowable load to fall steeply as span grows - the I-250×125 carries 154 kN/m at 1 m but only 5.7 kN/m at 3 m. Never extrapolate beyond the tabulated span; send the actual span, load and deflection limit to ZeAllgrate engineering for a certified take-off.

Resin Systems: Corrosion, Fire, UV and Electrical

Corrosion performance is set by the resin, not the glass - glass fibers are chemically inert in most service; it is the matrix that fails. ZeAllgrate builds structural profiles in four families. Isophthalic polyester is the cost-effective workhorse for atmospheric corrosion, water, wastewater and mild acids/bases. Vinyl ester is the anti-chemical upgrade for chemical, coastal and offshore service, excellent against bleach, oxidizers and concentrated acids. A fire retardant / flame retardant vinyl ester meets ASTM E84 Class A with low smoke for metro, marine and enclosed structures. Novolac vinyl ester is reserved for strong oxidizers, high-temperature acids and chlorine service. UV-stabilized formulations and a C-glass surface veil keep outdoor sections UV resistant and prevent fiber bloom.

The same material is non-conductive by nature - dielectric strength above 10 kV/mm and arc resistance around 120 s - which is why FRP framing surrounds live switchgear and railway electrification rather than steel. For flammable or vapor atmospheres a conductive (static-dissipative) surface can be specified instead. Because the sections are lightweight and need no painting, they stay low maintenance for the life of the structure.

Standards, Tolerances and Certification

Pultruded profiles are manufactured to dimensional tolerances under the ASTM D3917 profile standard, with section dimensions held to about ±1.5-2% or ±0.8-1.5 mm (whichever is greater) and cut lengths to about ±3 mm. Mechanical data on every certificate is traceable to ASTM test methods - tensile to D638, flexure to D790, compression to D695, density to D792, water absorption to D570 and Barcol hardness to D2583 - while fire performance is measured to ASTM E84. Where the structure is an access platform, ISO 14122 (parts 1-4) and OSHA 1910.23 govern walkway, stair and handrail geometry, with AS 1657 and BS 4592 as regional references. Each profile lot carries batch traceability; request the material certificate, E84 report and load test report for the exact resin and section you are ordering rather than relying on a generic brochure value.

Connections: Bolted, Bonded - Never Weld

FRP cannot be welded, and anyone who tries will destroy the laminate. Joints are bolted or adhesively bonded. For bolted connections use oversized holes (+2 mm), a minimum edge distance of twice the bolt diameter, stainless-steel side plates or FRP angle brackets, and torque to about 25-30 N·m. Spread bearing loads with side plates to avoid local crushing - allowable bearing stress is around 69 MPa with a safety factor near 3. For flush, permanent joints, bond with vinyl ester or epoxy: abrade the surface, apply per the adhesive datasheet and design the lap length for shear. Always provide full-section bearing at supports; partial seats concentrate stress at the web. Cut edges in chemical service should be sealed with a matching resin.

Choosing the Right Section

Frequently Asked Questions

Q: How do pultruded FRP profiles compare structurally with steel?

A: They are lighter - roughly a quarter of steel density at 1.7-1.9 g/cm³ - and corrosion resistant and non-conductive where steel cannot go. They are also less stiff: design modulus is around 22-28 GPa longitudinal versus steel's ~200 GPa, so long spans are deflection-limited and need deeper sections and lateral bracing. Treat them as a deflection-driven composite beam design, not a direct one-for-one steel swap.

Q: Can FRP structural profiles go outdoors and into fire-rated areas?

A: Yes. A C-glass/synthetic surface veil plus UV-stabilized resin keeps outdoor sections UV resistant and prevents fiber bloom. For code-required fire performance, specify the flame retardant / fire retardant vinyl ester, which meets ASTM E84 Class A (flame spread ≤25); phenolic is reserved for low-smoke, fire-critical escape routes.

Q: What is the maximum span for a pultruded FRP I-beam?

A: It depends on the load and the deflection limit. At a typical L/240 limit, the I-200×100 carries about 8.4 kN/m at a 2 m span but only 2.5 kN/m at 3 m. Short spans are stress-limited; long spans are deflection-limited, and the compression flange must be braced. Send your span, load and deflection limit to ZeAllgrate for a certified section schedule rather than extrapolating.