ISO 18900

Steel structures — Structural bolting — Test method for determining the slip factor for faying surfaces of slip-resistant connections

The standard is to provide a test method and associated criteria to determine the slip factor for a particular faying surface treatment, with or without a faying surface coating.

Structures en acier — Boulonnerie de construction métallique — Méthode d’essai pour déterminer le coefficient de frottement des surfaces en contact pour les assemblages résistant au glissement

General Information

• Status: Not Published
• ICS: 91.080.13 - Steel structures
• Technical Committee: ISO/TC 167 - Steel and aluminium structures
• Drafting Committee: ISO/TC 167 - Steel and aluminium structures
• Current Stage: 6000 - International Standard under publication
• Start Date: 21-Oct-2025
• Completion Date: 26-Oct-2025

Standards Content (Sample)

FINAL DRAFT
International
Standard
ISO/FDIS 18900
ISO/TC 167
Steel structures — Structural
Secretariat: SN
bolting — Test method for
Voting begins on:
determining the slip factor for
2025-08-25
faying surfaces of slip-resistant
Voting terminates on:
connections
2025-10-20
Structures en acier — Boulonnerie de construction métallique —
Méthode d’essai pour déterminer le coefficient de frottement des
surfaces en contact pour les assemblages résistant au glissement
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 18900:2025(en) © ISO 2025

FINAL DRAFT
ISO/FDIS 18900:2025(en)
International
Standard
ISO/FDIS 18900
ISO/TC 167
Steel structures — Structural
Secretariat: SN
bolting — Test method for
Voting begins on:
determining the slip factor for
faying surfaces of slip-resistant
Voting terminates on:
connections
Structures en acier — Boulonnerie de construction métallique —
Méthode d’essai pour déterminer le coefficient de frottement des
surfaces en contact pour les assemblages résistant au glissement
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/FDIS 18900:2025(en) © ISO 2025

ii
ISO/FDIS 18900:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 1
5 General . 2
6 Significant variables . 2
7 Test specimens . 2
8 Slip test procedure and evaluation of results . 4
9 Extended creep test procedure and evaluation. 5
10 Test results . . 7
11 Test report . 8
Bibliography . 9

iii
ISO/FDIS 18900:2025(en)
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.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 167, Steel and aluminium structures.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/FDIS 18900:2025(en)
Introduction
This document has been prepared to provide provisions and guidance in the testing of slip-resistant
connections made of steel for providing slip factors to be used in structural steelwork.

v
FINAL DRAFT International Standard ISO/FDIS 18900:2025(en)
Steel structures — Structural bolting — Test method for
determining the slip factor for faying surfaces of slip-resistant
connections
1 Scope
This document specifies a procedure to determine the slip factor of faying surfaces in slip-resistant (friction)
connections to be used in structural steelwork.
The method is mainly applicable to uncoated and coated components made of steel with different surface
treatments.
This document applies mainly to carbon steels but can be used for other type of steels as appropriate.
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 17607-1, Steel structures — Execution of structural steelwork — Part 1: General requirements and terms
and definitions
ISO 17607-3, Steel structures — Execution of structural steelwork — Part 3: Fabrication
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 17607-1 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
F specified pretension of the bolts
p,C
F individual slip load
Si
F mean value of the slip load
Sm
n number of test specimens
s standard deviation s for the slip load from the first five specimens (ten values), expressed percentage
Fs
of the mean slip load value
s standard deviation for the slip load
Fs
s standard deviation for the slip factor
μ
ISO/FDIS 18900:2025(en)
μ characteristic value of the slip factor
μ individual slip factor
i
μ mean value of the slip factor
m
5 General
The purpose of this test is to determine the slip factor for a particular surface treatment, often involving a
surface coating.
The test procedure is intended to ensure that account is taken of the possibility of creep deformation of the
connection.
The validity of the test results is limited to cases where all significant variables are similar to those of the
test specimens.
6 Significant variables
The following variables shall be taken as significant on the test results:
a) property class of the bolt;
b) number and configuration of washers;
c) grade of steel plates;
d) composition of the coating;
e) maximum thickness of the coating;
f) surface treatment of the faying surfaces prior to coating and resulting surface conditions including
roughness and surface profile;
g) parameters of primary layers in case of multi-layer systems;
h) curing parameters.
7 Test specimens
The test specimens shall conform to the dimensional details shown in Figure 1.
The steel material shall conform to any structural steel between 350 MPa and 700 MPa minimum specified
yield strength, inclusive.
The plates shall have accurately cut edges that do not interfere with contact between the plate surfaces.
They shall be sufficiently flat to permit the prepared surfaces to be in contact when the bolts have been
pretensioned. The plate edges in contact with the testing machine shall be flat and parallel to the contact
surface.
ISO/FDIS 18900:2025(en)
Dimensions in millimetres
A A-A A A-A
S1
S1 S2 S2
b b
a 1 a
1 c
c
1 1
50 50
40 40 8
A
A
a) M20 bolts in 22 mm diameter hole b) M16 bolts in 18 mm diameter hole
Key
S1 slip plane 1
S2 slip plane 2
Figure 1 — Compression type test specimens for static slip factor test
The surface treatment and coating to be tested shall be applied to the contact surfaces of the test specimens
in a manner consistent with the intended structural application. The mean dry film thickness of the coating
on the contact surface of the test specimens, measured according to the relevant standard, shall be at least
25 % thicker than the nominal dry film thickness specified for use in the structure.
The curing procedure shall be documented, either by reference to published recommendations or by
description of the actual procedure.
The tolerances of the bolt holes shall conform with ISO 17607-3. Burrs and shear lips at bolt holes shall be
removed.
The specimens shall be assembled such that the bolts are bearing in the opposite direction to the applied force.
The time interval (in hours) between coating, assembling and testing shall be recorded.
The bolts shall be tightened to within ±5 % of the specified pretension, F , for the size and property class
p,C
of the bolt used.
The pretension in the bolts shall be directly measured with equipment that is accurate to ±4 %.
If it is required to estimate bolt pretension losses over time, the test specimens may be left for a specified
period at the end of which the pretensions may be again measured.
The bolt pretensions in each test specimen shall be measured just prior to testing and, if necessary, the bolts
shall be retightened to the required ±5 % accuracy.
The tension-type test specimen for creep test, as shown in Figure 2, is an alternative test setup for static
test. To ensure that the two inner plates have the same thickness, they shall be produced by cutting them
consecutively from the same piece of material and assembled in their original relative positions.
NOTE 1 The compression-type and tension-type test specimen with one single bolt lead to comparable static slip
[2]
factors, even with those test specimens consisting of multiple bolts .

a , b , c
1 1 1
a , b , c
2 2 2
40 40
20 20
a , b , c
1 1 1
a , b , c
2 2 2
35 35
...

ISO/FDIS 18900:2025(en)
ISO/TC 167/WG 4
Secretariat: SN
Date 2025-06-24:
Steel structures – — Structural bolting –— Test method for
determining the slip factor for faying surfaces of slip-resistant
connections
Structures en acier – — Boulonnerie de construction métallique –— Méthode d’essai pour déterminer le
coefficient de frottement des surfaces en contact pour les assemblages résistant au glissement
FDIS stage
ISO/FDIS 18900:2025(en)
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Fax: [phone]
EmailE-mail: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO/FDIS 18900:2025(en)
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 1
5 General . 2
6 Significant variables . 2
7 Test specimens . 2
8 Slip test procedure and evaluation of results . 4
9 Extended creep test procedure and evaluation . 7
10 Test results . 11
11 Test report . 11
Bibliography . 13

iii
ISO/FDIS 18900:2025(en)
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.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 167, Steel and aluminium structures.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
ISO/FDIS 18900:2025(en)
Introduction
This document has been prepared to provide provisions and guidance in the testing of slip-resistant
connections made of steel for providing slip factors to be used in structural steelwork.
v
ISO/FDIS 18900:2025(en)
Steel structures – — Structural bolting –— Test method for
determining the slip factor for faying surfaces of slip-resistant
connections
1 Scope
This document specifies a procedure to determine the slip factor of faying surfaces in slip-resistant (friction)
connections to be used in structural steelwork.
The method is mainly applicable to uncoated and coated components made of steel with different surface
treatments.
This document applies mainly to carbon steels but can be used for other type of steels as appropriate.
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 17607--1, Steel structures — Execution of structural steelwork — Part 1: General requirements and terms
and definitions
ISO 17607--3, Steel structures — Execution of structural steelwork — Part 3: Fabrication
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 17607-1 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
F specified pretension of the bolts
p,C
F individual slip load
Si
F mean value of the slip load
Sm
n number of test specimens
s standard deviation s for the slip load from the first five specimens (ten values), expressed
Fs
percentage of the mean slip load value
s standard deviation for the slip load
Fs
s standard deviation for the slip factor
μ
μ characteristic value of the slip factor
μ individual slip factor
i
μ mean value of the slip factor
m
ISO/FDIS 18900:2025(en)
5 General
The purpose of this test is to determine the slip factor for a particular surface treatment, often involving a
surface coating.
The test procedure is intended to ensure that account is taken of the possibility of creep deformation of the
connection.
The validity of the test results is limited to cases where all significant variables are similar to those of the test
specimens.
6 Significant variables
The following variables shall be taken as significant on the test results:
a) a) property class of the bolt;
b) b) number and configuration of washers;
c) c) grade of steel plates;
d) d) composition of the coating;
e) e) maximum thickness of the coating;
f) f) surface treatment of the faying surfaces prior to coating and resulting surface conditions
including roughness and surface profile;
g) g) parameters of primary layers in case of multi-layer systems;
h) h) curing parameters.
7 Test specimens
The test specimens shall conform to the dimensional details shown in Figure 1Figure 1.
The steel material shall conform to any structural steel between 350 MPa and 700 MPa minimum specified
yield strength, inclusive.
The plates shall have accurately cut edges that do not interfere with contact between the plate surfaces. They
shall be sufficiently flat to permit the prepared surfaces to be in contact when the bolts have been
pretensioned. The plate edges in contact with the testing machine shall be flat and parallel to the contact
surface.
ISO/FDIS 18900:2025(en)
Dimensions in millimetres
a) M20 bolts in 22 mm diameter hole b) M16 bolts in 18 mm diameter hole
Key
S1 slip plane 1
S2 slip plane 2
S1 slip plane 1
S2 slip plane 2
Figure 1 — Compression type test specimens for static slip factor test
The surface treatment and coating to be tested shall be applied to the contact surfaces of the test specimens
in a manner consistent with the intended structural application. The mean dry film thickness of the coating on
the contact surface of the test specimens, measured according to the relevant standard, shall be at least 25 %
thicker than the nominal dry film thickness specified for use in the structure.
The curing procedure shall be documented, either by reference to published recommendations or by
description of the actual procedure.
The tolerances of the bolt holes shall conform with ISO 17607-3. Burrs and shear lips at bolt holes shall be
removed.
The specimens shall be assembled such that the bolts are bearing in the opposite direction to the applied force.
The time interval (in hours) between coating, assembling and testing shall be recorded.
ISO/FDIS 18900:2025(en)
The bolts shall be tightened to within ±5 % of the specified pretension, F , for the size and property class of
p,C
the bolt used.
The pretension in the bolts shall be directly measured with equipment that is accurate to ±4 %.
If it is required to estimate bolt pretension losses over time, the test specimens may be left for a specified
period at the end of which the pretensions may be again measured.
The bolt pretensions in each test specimen shall be measured just prior to testing and, if necessary, the bolts
shall be retightened to the required ±5 % accuracy.
The tension-type test specimen for creep test, as shown in Figure 2Figure 2,, is an alternative test setup for
static test. To ensure that the two inner plates have the same thickness, they shall be produced by cutting them
consecutively from the same piece of material and assembled in their original relative positions.
NOTE 1 The compression-type and tension-type test specimen with one single bolt lead to comparable static slip
[2[2] ]
factors, even with those test specimens consisting of multiple bolts . .
8 Slip test procedure and evaluation of results
In a first step, four static tests shall be tested in compression at a test speed such that the duration of the test
is approximately 10 min to 15 min. The specimens shall be tested in a universal testing machine. The load-slip
relationship shall be recorded.
The load-slip relationship can be determined from a tension-type test setup as an alternative test method, as
long as the contact surface area per bolt remains the same in comparison with test specimens presented in
Figure 2Figure 2.
In the second step, the fifth test specimen shall be tested in tension in a creep test.
ISO/FDIS 18900:2025(en)
Dimensions in millimetres
a) M20 bolts in 22 mm hole diameter b) M16 bolts in 18 mm hole diameter
Key
1 specimen (in gray) S1 slip plane 1
2 loose bolt S2 slip plane 2
1 specimen (in grey)
2 loose bolt
S1 slip plane 1
S2 slip plane 2
Figure 2 — Tension-type test specimen for creep test
ISO/FDIS 18900:2025(en)
In a test specimen, two slip planes exist: slip planes 1 and 2 according to Figure 1Figure 1.
The slip shall be taken as the relative displacement between adjacent points on an inner plate (positions b
and b , Figure 1Figure 1)) and a cover plate (positions a , a ,c and c , Figure 1Figure 1),), in the direction of
2 1 2 1 2
the applied load. The slip displacement shall be measured on both sides of the specimen.
Slip occurs in a failure mode of combination of slip in slip planes 1 and 2. The slip must be evaluated according
to this failure mode, so that finally one mean slip value shall be determined on the basis of two measured
displacements.
The individual slip load for a connection, F , is defined as the load at 0,15 mm displacement or at the peak
Si
load before 0,15 mm displacement according to the load-displacement diagram as given in Figure 3Figure 3.

Key
I slip load is the peak load before slip of 0,15 mm X slip displacement (mm)
II slip load is load at sudden slip before 0,15 mm Y load
III slip load is the load at slip of 0,15 mm.
ISO/FDIS 18900:2025(en)
X slip displacement (mm)
Y load
I slip load is the peak load bef
...