Free FRP Profile Calculator
LRFD and ASD design checks for pultruded FRP — bending, shear, Timoshenko-corrected deflection, orthotropic E_L/E_T/G_LT, environmental knockdown, and steel/aluminum equivalence. Switch between EN 13706, GB 50608-2020 / T/CECS 692-2020, ASCE/SEI 74-23, and CEN/TS 19101:2022. Free, no login.
Published
May 16, 2026
Updated
Jul 8, 2026
Technical Review
Yifan Liu, Application Engineer
Standards and application check
Standards and References
Material spec: EN 13706-3:2002 · Method: ASCE/SEI 74-23 — φ·R_n ≥ γ·Q (γ_Q = 1.6 live-dominated; λ not modeled) · Env knockdown: ×0.85 (Long-term UV + moisture exposure)
Reference: EN 13706-3 · GB 50608-2020 / T/CECS 692-2020 · ASCE/SEI 74-23 · CEN/TS 19101:2022 · ASTM D3917. Calculator performs global bending (vs min tensile/compressive strength), average shear, and load-case-matched Timoshenko deflection only. Not modeled: local buckling, lateral-torsional buckling, web crippling, long-term creep deflection, the ASCE 74-23 time-effect factor λ, principal-axis bending of single angles, and connection design — these require dedicated analysis; contact F1 Composite engineering.
How to use the FRP profile calculator
Prefer precomputed numbers? The FRP span tables publish the allowable uniform load for every standard I-beam, channel, and tube over 1–6 m spans on the same design basis — each row opens here pre-loaded for verification. And once a section passes, the pultruded profile price estimator gives you its budgetary USD/meter range before you send the RFQ.
This calculator solves three recurring questions in FRP structural selection: whether a pultruded FRP beam satisfies bending and shear at factored load, whether deflection at service load meets the L/n limit (including the Timoshenko shear correction that matters for short-span FRP beams), and what cross-section is needed to replace a steel or aluminum member at equal stiffness or equal strength — whichever governs. Select the design framework (ASCE/SEI 74-23 LRFD, CEN/TS 19101:2022 partial-factor, GB 50608-2020 LRFD, or legacy ASD) and an environmental class; the calculator applies the appropriate resistance factor and FRP environmental knockdown to characteristic strengths.
Input example — walkway beam
A pedestrian walkway requires a 3 m simply-supported FRP beam carrying 5 kN/m service UDL (live-load governed). With LRFD ASCE/SEI 74-23 (γ_Q = 1.6, φ_b = 0.65) and outdoor exposure (Ω_E = 0.85), an EN 13706 E23 I-beam 240×120×12 (I ≈ 4.75×10⁷ mm⁴) returns factored bending stress near 23 MPa vs ~110 MPa allowable (min(F_tL, F_cL) = 200 MPa × 0.65 × 0.85), and service deflection near 5.4 mm = L/550 with a Timoshenko shear contribution of ~13% — within the L/360 walkway limit per IBC 1604.3 / GB 50352. Comfortable margin on strength, deflection-governed as expected — this is the calculator's Walkway preset, so you can reproduce it in one click.
How to interpret the results
- Deflection almost always governs. FRP E_L is 17–28 GPa — roughly 1/10 of steel. Members sized for steel-equivalent strength deflect about 10× more. Check L/240 or L/360 first; if it passes, the bending and shear checks usually pass too. The Timoshenko shear-deflection share (shown below the load summary) is non-trivial for short-span beams because FRP G_LT is only ~1/6 of E_L.
- Equivalent section is deeper, not heavier. Replacing a W6×12 (152×76) steel beam at equal stiffness needs roughly ×1.7 on every dimension under geometric scaling (≈ 265 mm deep) and still lands ~25–30% lighter. Practical replacements deepen the web instead of scaling every wall, which is how optimized FRP substitutions reach 40–60% weight savings — the equivalence tab shows the conservative geometric-scaling figure.
- Why allowables look low. Allowable strength = φ × min(F_tL, F_cL) × Ω_E — pultruded FRP typically fails on the compression face first, so the lower compressive strength governs bending. The resistance factor (φ_b = 0.65 in ASCE/SEI 74-23, 1/γ_M ≈ 0.67 in CEN/TS 19101, 1/γ_R ≈ 0.63 in GB 50608) covers material and manufacturing variability; Ω_E (0.70–1.00) adds long-term environmental knockdown for outdoor/wet/hot/chemical service. Long-term creep and the ASCE 74-23 time-effect factor λ are separate checks the calculator does not model. Together these explain why the design allowable is 25–40% of the characteristic strength reported by the material spec.
Common specification mistakes
- Using steel allowables for FRP. FRP must never be designed using AISC 360, Eurocode 3, or GB 50017 steel allowables. Pultruded profiles follow ASCE/SEI 74-23 (US), CEN/TS 19101:2022 (Europe), or GB 50608-2020 with T/CECS 692-2020 (China). All three use distinctly different resistance factors and explicitly cap long-term stress at 20–35% of ultimate.
- Ignoring local buckling. Thin-walled FRP sections can buckle locally before reaching calculated bending capacity. The calculator flags an outstanding-flange b/t advisory (limit ≈ 18 for E-glass pultruded), but a full check per ASCE/SEI 74-23 Ch.3 or CEN/TS 19101 §6 is still required — for compression-governed members the limit tightens further.
- Treating FRP as isotropic. Pultruded FRP is strongly orthotropic: longitudinal tensile strength (F_tL) is 4–5× the transverse value, and E_T is only 25–35% of E_L. Connections that load in the transverse direction (drilled holes, notches, brackets) need special detailing per ASCE/SEI 74-23 Ch.8 or T/CECS 692-2020 §7.
- Skipping shear deflection. Because G_LT is only ~3 GPa, FRP shear deflection typically contributes 5–15% of total mid-span deflection at common span-to-depth ratios — and over 20% on very short spans (L/h ≲ 10). The calculator applies a load-case-matched Timoshenko correction on the shear area automatically and reports the shear share — pure Euler-Bernoulli (Δ = 5wL⁴/384EI) under-predicts.
Referenced standards
- EN 13706-2/-3:2002 — Reinforced plastic composites — Pultruded profiles — General requirements and Specific requirements (E17 / E23 minimum-modulus grades)
- ASTM D3917 — Standard Specification for Dimensional Tolerance of Thermosetting Glass-Reinforced Plastic Pultruded Shapes
- ASCE/SEI 74-23 — Standard for the Load and Resistance Factor Design of Pultruded Fiber Reinforced Polymer Structures (2023, supersedes the 2010 ACMA Pre-Standard)
- CEN/TS 19101:2022 — Design of fibre-polymer composite structures (Eurocode-track Technical Specification preparing prEN 19101)
- GB 50608-2020 — Technical Standard for the Engineering Application of Fiber-Reinforced Composite Materials
- T/CECS 692-2020 — Technical Regulation for Structures of Pultruded Profiles
- Eurocomp Design Code and Handbook — Structural Design of Polymer Composites (companion to CEN/TS 19101)
Frequently Asked Questions
Is this FRP profile calculator free?
Yes. The FRP profile calculator is fully free, runs in your browser without login or sign-up, and is available worldwide. F1 Composite publishes it as an engineering reference for specifiers selecting pultruded FRP profiles.
Which standards does the FRP calculator follow?
The calculator supports four design frameworks: LRFD per ASCE/SEI 74-23 (US official FRP standard, published 2023 — superseding the 2010 ACMA Pre-Standard); the partial-factor method per CEN/TS 19101:2022 (the Eurocode-track Technical Specification for FRP structures); LRFD per GB 50608-2020 (China FRP application code) together with T/CECS 692-2020 for pultruded profiles; and legacy ASD using a 2.5 bending / 3.0 shear factor of safety. Load factors use each code's variable-action value (γ_Q = 1.6 / 1.5 / 1.5) since the tool's scenarios are live-load governed. Material specifications include EN 13706-3 (E17/E23 minimum-modulus grades) and ASTM D3917 (dimensional tolerance).
Does the calculator handle orthotropic FRP properties?
Yes. For every FRP grade the calculator reports the longitudinal modulus E_L (fiber direction), transverse modulus E_T (typically 0.25–0.35 × E_L for E-glass pultruded), in-plane shear modulus G_LT (typically 3–4 GPa), and both tensile and compressive strengths (bending is checked against the lower of the two). Deflection includes a load-case-matched Timoshenko shear correction driven by the E_L / G_LT ratio — typically adding 5–15% at common span-to-depth ratios, and more on very short spans (L/h ≲ 10).
How are environmental knockdowns applied?
FRP characteristic strengths are multiplied by an environmental factor selected from the dropdown: 1.00 indoor dry, 0.85 outdoor exposed (UV + humidity), 0.80 wet / immersion, 0.75 mild chemical exposure (per T/CECS 692-2020 Annex), and 0.70 elevated temperature 30–60°C (approaching glass transition per ASCE/SEI 74-23 §3.5.4). Metals are unaffected. For acid resistance class selection, see T/CECS 692-2020 Annex.
Can I use this calculator for vinyl ester, polyurethane, or phenolic FRP profiles?
The EN 13706 E17/E23 and GB 50608 Class I/II material properties reflect E-glass / polyester pultruded profiles. Vinyl ester and polyurethane FRP have similar modulus and slightly different strength; phenolic FRP has lower modulus and significantly better fire performance. For non-default resin systems, contact F1 Composite engineering for project-specific characteristic values.
Does this calculator handle local buckling, lateral-torsional buckling, and connections?
Not as full design checks. The calculator flags a wall-slenderness advisory per shape — outstanding flanges and angle legs at b/t > 18, box flat widths and tube D/t at > 40 (E-glass pultruded typical) — prompting a dedicated local-buckling review per ASCE/SEI 74-23 Ch.3 or CEN/TS 19101 §6. Lateral-torsional buckling, web crippling, single-angle principal-axis bending, long-term creep, and bolted/bonded connection design (ASCE/SEI 74-23 Ch.8) are out of scope — these need a dedicated tool such as PulCalc 3.x or project-specific engineering. F1 Composite engineering supports these checks on request.
Why does FRP need a deeper section than steel for the same deflection?
FRP elastic modulus is 17–28 GPa versus steel's 200 GPa — about 1/8 to 1/10 of steel. To match steel's deflection, the FRP section needs roughly 8–10× the second moment of area, achieved by going deeper (stiffness scales with depth cubed). The FRP replacement is still lighter because FRP density is 1.9 g/cm³ versus 7.85 g/cm³ for steel: ~25–30% lighter under uniform geometric scaling (the calculator's conservative figure), and 40–60% lighter when the section goes deeper rather than uniformly larger.
Want the AI to walk you through the inputs?
Open the FRP Engineering Advisor — describe your span, load, and exposure, and it will recommend a profile, deflection check approach, and standards path.
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