Overview
ISO 12122-5:2018 - "Timber structures - Determination of characteristic values - Part 5: Mechanical connections" provides standardized methods to derive characteristic values (statistical design properties) for mechanical connections between timber components from full‑scale test results. The document covers calculation of the slip modulus and characteristic strength for connections under monotonic and cyclic loading. Glued connections are excluded. The standard assumes a consistent failure mode across specimens and references ISO 12122‑1 for basic requirements.
Key topics and requirements
- Reference population definition: Describe connector materials, dimensions, assembly method, timber species and density range, geometric details (end/edge distances, spacings), and moisture exposure conditions.
- Sampling and sample size: Sampling must represent the reference population and follow ISO 12122‑1. Sample size should account for expected coefficient of variation.
- Sample conditioning: Test specimens must be conditioned to match the declared reference population. For connectors driven into timber (nails, toothed plates) allow a minimum of seven days between assembly and testing for fibre relaxation.
- Test methods and data:
- Monotonic tests - follow ISO 6891 or equivalent.
- Cyclic tests - follow ISO 16670 or equivalent.
- Record peak (maximum) loads, stiffness (slip modulus), yield/ultimate displacements and failure modes.
- Only include data where the observed failure mode is appropriate to the measured property.
- Evaluation of characteristic values:
- Calculate mean, 5th percentile (lower characteristic for strength), and 95th percentile (upper characteristic for stiffness) with prescribed confidence limits.
- When sample size is small, use ISO 12122‑6 for estimating mean and 5th percentile.
- Reporting: Test conditions, adjustments, failure modes and statistical treatment must be documented; Annex A provides informative commentary.
Applications and users
ISO 12122‑5 is used by:
- Test laboratories performing connector performance tests.
- Manufacturers of mechanical fasteners, plates, bolts, screws and connector assemblies for timber.
- Structural engineers and designers validating connector capacities for design or for producing calibrated design values.
- Certification bodies and researchers establishing performance data for timber connections.
Practical uses include generating validated slip modulus and capacity data for structural calculations, product datasheets, and regulatory compliance.
Related standards
- ISO 12122‑1 (Basic requirements for determining characteristic values)
- ISO 12122‑6 (Small sample procedures)
- ISO 6891 (Mechanical fastener joint testing principles)
- ISO 16670 (Quasi‑static reversed‑cyclic test method)
- ISO 8970 (Timber density declaration)
Keywords: ISO 12122‑5:2018, timber structures, mechanical connections, characteristic values, slip modulus, monotonic loading, cyclic loading, connector testing, sample conditioning.