Overview
ISO 12122-3:2016 - Timber structures - Determination of characteristic values - Part 3: Glued laminated timber (glulam) - defines standardized methods to derive characteristic values from test results on a defined population of glued laminated timber products. It provides procedures for calculating both mean‑based and 5th‑percentile‑based characteristic properties and references analytical models (Annex B) used to estimate glulam properties from laminates.
Key topics and requirements
- Reference population: Define the population attributes (raw material sources, seasoning, laminate grading and layup, adhesives, finger joints, quality control, etc.) so sampling represents production variants.
- Sampling: Follow the sampling performance objectives in ISO 12122‑1; sample composition must approximate variant representation. Sample size is chosen with regard to expected coefficient of variation.
- Sample conditioning: Conditioning must match the reference population. For large glulam, testing at as‑tested conditions is acceptable if data are adjusted as required.
- Test methods: Use ISO 8375 or an equivalent standard with established equivalency factors. Test variables (loading, positioning, measurement) must be appropriate to objectives.
- Test data handling:
- Adjust raw data to standard size/moisture where applicable (per ISO 12122‑1).
- Record failure modes; include only tests that produced the failure mode appropriate to the property.
- Evaluation of characteristic values:
- Modulus of elasticity / stiffness: For serviceability use the mean of test values; for ultimate limit state use either the mean or the 5th percentile (depending on design needs).
- Bearing strength (parallel & perpendicular to grain): Characteristic value is the mean.
- Other strength/capacity properties: Evaluate the 75% lower one‑sided confidence limit of the test 5th percentile; methods are given in ISO 12122‑1.
- Reporting: Reports must comply with ISO 12122‑1 and document sampling, adjustments, test details and failure modes.
Practical applications and users
ISO 12122‑3:2016 is intended for:
- Structural engineers and designers verifying glulam material properties for design and serviceability checks.
- Manufacturers and quality control teams establishing in‑house characteristic values for production runs.
- Test laboratories and certification bodies performing type testing, verification and product conformity assessments.
- Researchers and product developers using Annex B analytical models to relate laminate properties to full‑scale glulam behavior.
Use cases include deriving certified material properties for design, validating analytical models, supporting product certification, and informing production quality strategies.
Related standards
- ISO 12122‑1 - Basic requirements for determination of characteristic values
- ISO 8375 - Test methods for physical and mechanical properties of glued laminated timber
- Terms/definitions reference: ISO 12578
Keywords: ISO 12122-3:2016, glued laminated timber, glulam, characteristic values, timber structures, modulus of elasticity, 5th percentile, ISO 8375, sampling, testing, bearing strength.