Overview
ISO 16670:2003 specifies a quasi-static reversed‑cyclic test method for evaluating joints in timber structures made with mechanical fasteners under seismic (earthquake) loading. The standard provides a repeatable cyclic displacement schedule and procedures to derive envelope (backbone/skeleton) curves and joint parameters used in seismic design. It applies to joints subjected to lateral loads (not to withdrawal forces) and is intended to produce representative elastic and inelastic demands on connections.
Key topics and technical requirements
- Scope and applicability: Joints with mechanical fasteners in timber structures under seismic action; lateral loads only.
- Test specimens and conditioning: Conditioning to realistic service conditions (ISO 554 recommended: 20 °C, 65 % RH when comparing joints); density requirements per ISO 8970; representative joint geometry and fabrication details.
- Static (monotonic) pre‑tests: Determine mean ultimate displacement (νu) from matched monotonic tests (ISO 6891 principles) to scale the cyclic schedule.
- Cyclic displacement schedule: Reversed cycles scaled to percentages of νu with an example amplitude sequence (1.25%, 2.5%, 5%, 7.5%, 10%, then multiple cycles at 20%, 40%, 60%, 80%, 100% and further increments). Test rate: 0.1 mm/s to 10 mm/s to avoid dynamic effects.
- Data and outputs:
- Full hysteresis (load–displacement or moment–rotation) records.
- Three envelope curves (first, second, third) constructed from peak loads at each slip level.
- Reported joint properties: maximum loads, ultimate displacements, stiffness, failure modes.
- Apparatus and accuracy: Continuous recording of load and displacement with ±1% accuracy; minimize member deformation in displacement measurements.
- Replication: Minimum recommended replicates: 6 for static and cyclic tests to estimate mean properties reliably.
- Test report requirements: Timber and fastener specifications, joint geometry, fabrication details, test matrix, apparatus and measuring locations, cyclic schedule, deviations, hysteresis plots and tabulated envelope data.
Applications and users
ISO 16670 is primarily used for:
- Structural engineers and researchers developing seismic design parameters for timber connections.
- Product manufacturers and test laboratories validating connection performance and generating backbone curves for design models.
- Code developers and consultants needing standardized joint data for performance-based seismic design or for adoption into national standards.
Practical uses include deriving joint stiffness, strength degradation, ductility measures and energy dissipation characteristics for use in seismic analysis, nonlinear modelling, and design verification.
Related standards
- ISO 554 - Standard atmospheres for conditioning/testing
- ISO 3131 - Wood density determination
- ISO 6891 - General principles for strength and deformation of joints
- ISO 8970 - Requirements for wood density in joint testing
Keywords: ISO 16670, timber structures, cyclic test method, quasi‑static reversed‑cyclic, mechanical fasteners, seismic design, joint testing, backbone curve, hysteresis, envelope curves, ultimate displacement.