ISO 16670:2003

Timber structures - Joints made with mechanical fasteners - Quasi-static reversed-cyclic test method

ISO 16670:2003 is intended to provide a cyclic test method as a basis for the derivation of parameters which are required in seismic design of timber structures. The method includes procedures to develop the envelope curves (backbone or skeleton curves, an example is given in Clause A.5.) for joints subjected to a cyclic displacement schedule which produces representative demands imposed on the joints by earthquakes. It does not include criteria for parameters which are, at times, stipulated in national standards or building codes. ISO 16670:2003 is intended for joints subjected to lateral load and is not applicable to joints subjected to withdrawal forces. ISO 16670:2003 is applicable to joints made with mechanical fasteners used in timber structures loaded under seismic action.

Structures en bois — Joints réalisés avec des connecteurs mécaniques — Méthode d'essai cyclique réversible quasi statique

General Information

• Status: Published
• Publication Date: 11-Dec-2003
• ICS: 91.080.20 - Timber structures
• Technical Committee: ISO/TC 165 - Timber structures
• Drafting Committee: ISO/TC 165/WG 7 - Connections and assemblies
• Current Stage: 9092 - International Standard to be revised
• Start Date: 20-Oct-2025
• Completion Date: 13-Dec-2025

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.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 16670
First edition
2003-12-15
Timber structures — Joints made with
mechanical fasteners — Quasi-static
reversed-cyclic test method
Structures en bois — Joints réalisés avec des connecteurs
mécaniques — Méthode d'essai cyclique réversible quasi statique

Reference number
©
ISO 2003
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ii © ISO 2003 — All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references. 1
3 Symbols and definitions. 1
4 Test specimens. 2
4.1 Conditioning. 2
4.2 Form and dimension. 2
4.3 Sampling. 2
4.4 Number of replicates . 2
5 Apparatus. 2
6 Test procedure. 2
6.1 Properties from static (monotonic) tests. 2
6.2 Cyclic displacement schedule. 3
7 Test results. 5
7.1 Hysteresis data. 5
7.2 Envelope curves. 5
7.3 Joint properties. 5
8 Test report. 5
Annex A (informative) Additional information. 6
Bibliography . 9

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 16670 was prepared by Technical Committee ISO/TC 165, Timber structure.
iv © ISO 2003 — All rights reserved

Introduction
Evaluation of the structural performance of joints under reversed-cyclic loading has become a requirement in
seismic design. The objective of this International Standard is to provide a cyclic test procedure as a basis for
the development of characteristics of joints for use in seismic design. The cyclic displacement schedule was
developed in consultation with a group of international experts with the intention that the cyclic displacement
schedule shall produce
a) data that sufficiently describes the elastic and inelastic properties of the joint, and
b) representative demands imposed on joints by earthquakes.
Supplementary information is given in Annex A to provide the rationale behind the cyclic displacement
schedule, recommendations for cases for which a modified schedule would be more appropriate, and typical
test results obtained on a joint by following this cyclic displacement schedule.

INTERNATIONAL STANDARD ISO 16670:2003(E)

Timber structures — Joints made with mechanical fasteners —
Quasi-static reversed-cyclic test method
1 Scope
This International Standard is intended to provide a cyclic test method as a basis for the derivation of
parameters which are required in seismic design of timber structures. The method includes procedures to
develop the envelope curves (backbone or skeleton curves; an example is given in Clause A.5.) for joints
subjected to a cyclic displacement schedule which produces representative demands imposed on the joints by
earthquakes. It does not include criteria for parameters which are, at times, stipulated in national standards or
building codes.
This standard is intended for joints subjected to lateral load ans is not applicable to joints subjected to
withdrawal forces.
This International Standard is applicable to joints made with mechanical fasteners used in timber structures
loaded under seismic action.
NOTE 1 In the context of this Standard, the term “joint” means “connection” in present-day North-American English.
NOTE 2 It is recognized that, for some special types of joints, modification of the test method may be necessary
provided the test objectives in this clause and the principles in Clause 6 are achieved. See Clause A.2 for details.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 554, Standard atmospheres for conditioning and/or testing — Specifications
ISO 3131, Wood — Determination of density for physical and mechanical tests
ISO 8970, Timber structures — Testing of joints made with mechanical fasteners — Requirements for wood
density
ISO 6891, Timber structures — Joints made with mechanical fasteners — General principles for the
determination of strength and deformation characteristics
3 Symbols and definitions
F Applied load, in newtons, or newton-millimetres in the case of joint rotation
F Maximum load, in newtons, or newton-millimetres in the case of joint rotation (as defined in Figure 1)
max
k Joint stiffness, in newtons per millimetre, or newton-millimetres per radian in the case of joint rotation
ν Joint displacement, in millimetres, or radians in the case of joint rotation
ν Ultimate joint displacement, in millimetres, or radians in the case of joint rotation (as defined in Figure 1)
u
NOTE “Load” and “displacement” are taken as generic terms. Load could be axial, shear, moment or torsion.
Displacement could be any displacement (or slip) or rotation.
4 Test specimens
4.1 Conditioning
Attention shall be given to the conditioning of the timber before the manufacture of the joint and also to the
conditioning of the joints after their fabrication.
The conditioning shall be conducted in such a way that the test conditions correspond in a realistic manner to
the in-service conditions of joints in structures.
Where the purpose of testing is to compare joints under similar conditions, the standard atmosphere of 20 °C
and 65 % relative humidity according to ISO 554 shall be used for conditioning. Density of the specimens shall
comply with the requirements given in ISO 8970.
4.2 Form and dimension
Joint geometry, loading configuration and fabrication details (e.g. elapsed time between the fabrication and
test, predrilling of holes, tolerances, conditioning details before and after fabrication) shall be representative of
the intended end use.
4.3 Sampling
Sampling should provide for selection of representative test material on an objective and unbiased basis,
covering an appropriate range in density and properties as circumstances suggest.
4.4 Number of replicates
The number of replicates depends on the specific objectives and desired reliability.
NOTE A minimum of 6 replicates is recommended for each of the static and cyclic tests to obtain a reliable estimate
of mean mechanical properties.
5 Apparatus
The test apparatus, tolerances and restraints shall be of realistic forms that are representative of the intended
end use.
The testing machine shall be able to apply and continuously record load and joint displacement with an
accuracy of ± 1 % of the estimates of F and ν or better.
max u
It is recommended that displacement measurements be made in such a way that the amount of member
deformation included in displacement readings is minimized.
6 Test procedure
6.1 Properties from static (monotonic) tests
Static (monotonic) tests shall be conducted on a match
...