ISO/TS 18973:2025

Technical
Specification
ISO/TS 18973
First edition
Railway infrastructure — Rail
2025-04
fastening systems — Two
directional test method for
resistance to repeated loading
Infrastructure ferroviaire — Systèmes d'attache — Méthode
d’essai bidirectionnel pour la determination de résistance aux
charges répétitives
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 1
5 Principle . 3
6 Apparatus . 4
6.1 General arrangement .4
6.2 Rail .4
6.3 Actuator .5
6.4 Load application head .6
6.5 Displacement measuring instruments .6
6.5.1 Calibration procedure.6
6.5.2 Calibration requirement .6
6.5.3 Fixtures for mounting displacement measuring instruments .6
6.6 Force measuring instruments .6
6.6.1 Instruments .6
6.6.2 Verification of calibration . . .6
6.7 Strain gauges for rail clips .6
7 Test specimens . 6
8 Test procedure . 7
8.1 General .7
8.2 Preparation for test .7
8.3 Clamping force and uplift stiffness .7
8.4 Longitudinal rail restraint .7
8.5 Vertical stiffness .7
8.6 Lateral stiffness .7
8.7 Calculation of test loads and test loading angles .8
8.8 Two directional static load test .8
8.8.1 Preparation for the static load test .8
8.8.2 Loading procedure .10
8.8.3 Results required from the static load test .11
8.9 Two directional repeated load test . 12
8.9.1 Preparation for the repeated load test . 12
8.9.2 Loading conditions of the repeated load test. 12
8.9.3 Results required from the repeated load test . 13
8.9.4 Repeat tests . . 13
9 Test report . 14
Annex A (normative) Test method for lateral stiffness .15
Annex B (informative) Calculation method of test loads and test loading angles . 19
Bibliography .28

iii
Foreword
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iv
Technical Specification ISO/TS 18973:2025(en)
Railway infrastructure — Rail fastening systems — Two
directional test method for resistance to repeated loading
1 Scope
This document describes a test procedure for the determination of resistance to repeated loading by –
amongst others – applying out-of-phase load cycles which generate forces in two directions, representative
of those caused by traffic on railway track, taking into account the effect of two consecutive axles of passing
railway vehicles.
The document applies to surface mounted rail on sleepers, bearers and slab track.
The test procedure applies to a complete fastening assembly.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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 22074-1, Railway infrastructure — Rail fastening systems — Part 1: Vocabulary
ISO 22074-2, Railway infrastructure — Rail fastening systems — Part 2: Test method for longitudinal rail
restraint
ISO 22074-4:2022, Railway infrastructure — Rail fastening systems — Part 4: Test methods for resistance to
repeated loading
ISO 22074-7, Railway infrastructure — Rail fastening systems — Part 7: Test method for clamping force and
uplift stiffness
ISO 22074-8:2022, Railway infrastructure — Rail fastening systems — Part 8: Test method for vertical stiffness
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 22074-1 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Symbols
Symbol Description First appearance
h height of loading position for normal rail, in mm; 6.2
N
h height of loading position for test rail, in mm; 6.2
T
P clamping force, in kN; 8.3
F maximum axial load on the rail without non-elastic displacement occurring, in kN; 8.4
F the lower limit of force for determining the static stiffness, in kN; 8.5
SA1
Symbol Description First appearance
F the reference force for measurement of static stiffness, in kN/mm; 8.5
SA max
k vertical stiffness of fastening assembly, in kN/mm; 8.5
SA
k lateral stiffness of fastening assembly, in kN/mm; 8.6
LA
e eccentricity of loading position from centre for test rail, in mm; 8.8.1
T
θ test loading angle applied from gauge side (A load), in radians; 8.8.1
A
θ test loading angle applied from field side (B load), in radia
...