ISO 20895:2026

International
Standard
ISO 20895
First edition
Welded joints performance for
2026-04
seismic steel structures
Reference number
© ISO 2026
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
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Welded joints . 2
4.1 Applicable structural performance .2
4.2 Mechanical properties of base metal . .3
4.2.1 Toughness of base metal.3
4.2.2 Tensile strength of base metal .3
5 Mechanical testing . 3
5.1 Type of testing . .3
5.2 Test specimens.3
5.2.1 Shape and dimensions of specimens .3
5.2.2 Specimen location, notch orientation and number of specimens .4
5.2.3 Preparation of specimens . . . 15
5.3 Testing procedure . 15
5.3.1 Weld metal longitudinal tensile testing . 15
5.3.2 Charpy impact tests .16
6 Acceptance criteria . 16
6.1 Basic Demand .16
6.1.1 General .16
6.1.2 Acceptance criteria for tensile tests .16
6.1.3 Acceptance criteria for impact tests .16
6.2 Critical Demand .16
6.2.1 General .16
6.2.2 Acceptance criteria for tensile test .16
6.2.3 Acceptance criteria for impact test .16
7 Re-testing . 17
8 Test reports . 17
Annex A (informative) Example welded joints of steel structures .18
Annex B (informative) Relationship between the structural performance and the acceptance
criteria for Critical Demand .27
Bibliography .30

iii
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
Introduction
Structural safety is needed in high public occupancy facilities, tall or large-scale structures, and other
important facilities. Higher performance is needed for structures subjected to seismic actions. In the case
of steel frame structures, integrity of welded joints determines the structural safety of these structures,
because welding is often used with beam to column connections, joints of steel members, member assembly,
etc. It is especially important to ensure the strength and toughness of the welds.
This document addresses the mechanical testing methods and acceptance criteria for weld metal and heat
affected zones. These mechanical properties, coupled with appropriate designs for the seismic force resisting
system, proper connection designs and detailing, as well as appropriate weld quality and inspection criteria
are essential to ensuring the high structural safety of steel structures of seismic design.
This document specifies the target performance regarding the strength and toughness of welded joints in
the acceptance criteria, but does not mention the means for realizing the performance. Rather, the document
intends to present the performance-based standards, in recognition of diverse construction methods and
the need to promote and disseminate new technologies.

v
International Standard ISO 20895:2026(en)
Welded joints performance for seismic steel structures
1 Scope
This document defines two performance levels for welded joints, namely Basic Demand and Critical Demand,
for longitudinal tensile strength of weld metals, impact toughness of weld metals and heat affected zones
(HAZ) to suit the level of seismic performance specifications required for welded steel structures.
This document supplements the provisions of the standards or codes for welding procedure qualification
in the application of new steel materials, welding consumables, or complex joints, for welds that require the
performance of Basic or Critical Demands as specified by the engineer in the contract.
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 148-1, Metallic materials — Charpy pendulum impact test — Part 1: Test method
ISO 4063:2023, Welding, brazing, soldering and cutting — Nomenclature of processes and reference numbers
ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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/
3.1
structural performance
qualitative or quantitative representation of the behaviour of a structure related to its safety and
serviceability, durability, and robustness under various actions
3.2
basic demand
required properties of welded joints based on the conventional welding parameters and specifications of
materials used
3.3
critical demand
required properties of welded joints that prevent brittle fracture and ensure sufficient level of cumulative
plastic deformation capacity expected of beams welded to beam-to-column connections
3.4
sequential testing
group or set of tests for which either a certain average or an individual test results, or both, are required, for
demonstrating that the specification requirements have been satisfied

4 Welded joints
4.1 Applicable structural performance
This document specifies the two structural performance levels, namely Basic Demand and Critical Demand,
for welded joints of steel structures listed below:
— beam to column;
— column to column, beam to beam;
— welded built-up box section column, H-beam and H-column.
The Basic Demand is a performance category considered to be exhibited at a minimum based on the
specifications of materials used as base materials. This refers to the performance level that can be ensured
even if it is not specified in the design drawing as a special specification, etc., and it is set on the assumption
that the performance obtained by the general construction method in the steel frame manufacturing
exceeds this. This performance category represents the minimum requirements for mechanical properties
of steel structure welded joints for which seismic performance is required.
The Critical Demand is a performance category recommended by various advanced research efforts to
ensure higher safety. This is the performance level that is applied when it is specified in the design drawing
as a special specification, and to realize this goal, it is necessary to designate special materials for use and to
manufacture them with the higher technological system.
This document may be applied to various types of welded joints of steel structures (see Annex A), but the
definitive rules on the level of performance to be adopted in individual circumstances of welded joints are
not given in this clause. The levels of required performances applicable to various welded joints shall be in
accordance with Table 1.
The range of plate thicknesses of welded joints to which this standard applies are the base metal plate
thicknesses shown in Table 2 or Table 3. Application to members exceeding this thickness range can be
determined by engineers based on structural tests.
Table 1 — Applicable structural performance
b
Performance
a
Welding process
Type of welded joint
Basic De- Critical De-
(ISO 4063:2023)
mand mand
Single-bevel-groove, butt joint
Beam flange to through diaphragm (see Figures A.1 and
111,114, 135,136,138 X X
A.2)
Beam to beam (see Figure A.3) 111,114, 135,136,138 X ―
Column to column (see Figure A.4) 111,114, 135,136,138 X ―
Single-bevel-groove, T-joint and corner joint
Beam flange to column (see Figures A.5 and A.6) 111,114, 135,136,138 X X
Column to through diaphragm (see Figure A.7) 111,114, 135,136,138 X ―
Welded built-up box section column (Corner welding, see
111,114,12,135,136,138 X ―
Figure A.8)
Square-groove, T-joint
a
The most commonly applied welding processes, but not limited to those shown in this table.
b
X : applicable; ― : not generally applicable.

TTabablele 1 1 ((ccoonnttiinnueuedd))
b
Performance
a
Welding process
Type of welded joint
Basic De- Critical De-
(ISO 4063:2023)
mand mand
Inner diaphragm for welded built-up box section column
772 X X
(see Figure A.9)
Double-bevel-groove, T-joint
Welded built-up H-beam and H-column (T-joint, groove
111,114,12,135,136,138 X ―
welding, see Figure A.10)
a
The most commonly applied welding processes, but not limited to those shown in this table.
b
X : applicable; ― : not generally applicable.
NOTE The Critical Demand is established because brittle fractures of welded joints were conspicuously observed
in the damage caused by the Great Hanshin Earthquake in 1995 and subsequent experimental research. In the series
of research efforts, brittle fracture of beam flange welds for beam to column connections and inner diaphragm
electroslag welds for welded built-up box section columns were regarded especially problematic. In order to prevent
such fractures, it has been found that a considerably higher Charpy absorption energy than has conventionally been
[2-6]
considered needs to be secured in the welded joints .
4.2 Mechanical properties of base metal
4.2.1 Toughness of base metal
The steel materials constituting welded joints of seismic steel structures, to which this document applies,
shall be structural steels for which the lower limit values of toughness have been specified regarding the
Charpy impact absorption energy. The lower limit values shall be greater than or equal to the acceptance
criteria regarding Charpy impact tests on welded joints specified in Clause 6. The test temperature shall
be the lowest service temperature of the steel structure determined by the engineer based on national
regulations, codes, standards, etc. Steel materials for which the lower limit value of Charpy impact
absorption energy is not specified may be used if a toughness value was added optionally to the steel
material specifications.
4.2.2 Tensile strength of base metal
The range of tensile strength R of steel materials constituting welded joints is from 400 MPa to 740 MPa,
m
for which the Basic Demand or Critical Demand defined in this document is required.
5 Mechanical testing
5.1 Type of testing
Two types of mechanical testing performed shall be a weld metal longitudinal tensile test and an impact test.
5.2 Test specimens
5.2.1 Shape and dimensions of specimens
5.2.1.1 Tensile test specimens
The dimensions of test specimens shall be as shown in Figure 1, Type A or Type B test specimen, to suit the
plate thickness of the base material.

Unit (mm)
Type of specimen d L R
0 c
Type A 12,5 60 ≤ 15 ≤
Type B 6 32 ≤ 6 ≤
Key
d original diameter of the parallel length of a circular specimen
L parallel length
c
R radius of shoulder
Figure 1 — Schematic of weld metal longitudinal tensile strength test specimen
5.2.1.2 Impact test specimens
Test specimen designation is expressed using VWT and VHT according to ISO 9016. Size and tolerance shall
be in accordance with ISO 148-1.
5.2.2 Specimen location, notch orientation and number of specimens
5.2.2.1 General
Test specimens shall be taken in accordance with 5.2.2.2 and 5.2.2.3. Location for extraction of mechanical
test specimen shall be in accordance with Figure 2.
The specific requirements for each welded joint apply:
a) The specimens for longitudinal tensile test shall be extracted from a location of the weld metal, if the
entire cross-section of the joint is welded with single process. If welded with multiple processes, the
test specimens shall be extracted from the location of each weld metal made by the respective welding
process.
b) The specimens for impact test shall be extracted from the vicinity of a location that could be the point of
fracture origin.
c) For beam flange to through diaphragm weld, beam flange to column weld, or beam to beam weld, in
the case of shop welding where the upper flange and lower flange are welded by the same welding
parameters with a metal backing plate placed on an inner side of beam joint, the specimens shall be
extracted from the weld metal of either the upper or lower flange.
In the case of site welding that is performed with a metal backing plate placed on an outer side of the
beam joint for lower flange welding, the specimens shall be extracted from the weld metals of both
upper and lower flanges, because the welding parameters differ between the upper and lower flanges.
d) Test specimens may be taken from full-scale test piece of the joints or simplified test pieces made from
plate-to-plate or tube-to-tube groove welds with steel materials actually used in the structure. When
simplified test pieces are used, the impact test specimens shall be taken from the locations specified by
the type of joint being simulated (upper flange or lower flange).

Dimensions in millimetres
a) Beam flange to through diaphragm weld, b) Square steel tube column to diaphragm weld, or
beam flange to column weld, or beam to beam column to column weld
weld
c) Welded built-up box section column d) H-column to diaphragm weld, or column to col-
umn weld
e) Circular steel tube column to diaphragm f) Inner diaphragm for welded built-up box section
weld or column to column weld column (ESW)
g) Welded built-up box section column
(corner welding)
h) Welded built-up H-beam and H-column (T-joint, groove welding)

Key
1 location for extraction of mechanical test specimen
2 beam flange
3 seam weld
4 flange
5 web
6 box column plate
Figure 2 — Location for mechanical test specimens
5.2.2.2 Tensile test specimen
Tensile test specimens shall be taken in accordance with Table 2 and Figure 3.
If a test joint is welded with multiple processes, tensile test specimens shall be extracted from locations that
can yield complete specimens with the reduced section completely in weld metal deposited by each single
process.
Table 2 — Tensile test specimen location and number of specimen
Nominal thick- Location
ness of base
Type of spec- Distance
metal
Type of welded joint Number of specimens
a
imen b, f
y Figure
t
mm
mm
Single-bevel-groove, Butt joint (Including single-V-groove)
c
Beam flange to through dia- 9 ≤ t ˂ 20 Type B 0,5t
1 specimen from upper
phragm, Beam to beam
c b
or lower flange
20 ≤ t ≤ 100 Type A 10
(shop welding)
c
Beam flange to through dia- 9 ≤ t ˂ 20 Type B 0,5t
1 specimen from upper
phragm, Beam to beam
and lower flange each
c b
20 ≤ t ≤ 100 Type A 10
(total 2 specimens)
(field welding)
Figure 3
d
a)
Column to column 9 ≤ t ˂ 20 Type B 0,5t
(Welded built-up box section
1 specimen
d b
column, Square or rectangular
20 ≤ t ≤ 100 Type A 10
steel tube, H-column)
d, h b
16 ≤ t ˂ 30 Type B 10
Column to column
1 specimen
d, h b
(Circular steel tube)
30 ≤ t ≤ 100 Type A 15
Single-bevel-groove, T-joint and corner joint (Including single-V-groove corner joint)
a
See 5.2.1.1.
b
Distance from the weld joint face side to the centre of specimen, y
F.
c
Thickness of the thinner of the two welded plates.
d
Thickness of column.
e
Thickness of beam flange.
f
Distance from the centre of specimen to the weld joint face of root side, y .
R
g
Thickness of box column plate.
h
Outer diameter of circular steel tube; 400 mm or more.

TTabablele 2 2 ((ccoonnttiinnueuedd))
Nominal thick- Location
ness of base
Type of spec- Distance
metal
Type of welded joint Number of specimens
a
b, f
imen
y Figure
t
mm
mm
e
9 ≤ t ˂ 20 Type B 0,5t
Beam flange to column
1 specimen from upper
e b
or lower flange
(shop welding)
20 ≤ t ≤ 100 Type A 10
e
1 specimen from upper 9 ≤ t ˂ 20 Type B 0,5t
Beam flange to column
and lower flange each
e b
(field welding)
20 ≤ t ≤ 100 Type A 10
Figure 3
(total 2 specimens)
b)
d
9 ≤ t ˂ 20 Type B 0,5t
Column to through diaphragm
1 specimen
d b
(Square steel tube, H-column)
20 ≤ t ≤ 60 Type A 10
d, h b
16 ≤ t ˂ 30 Type B 10
Column to through diaphragm
1 specimen excluded
d, h b
seam weld of tube
(Circular steel tube)
30 ≤ t ≤ 100 Type A 15
Single process
b
22 ≤ t ≤ 100 Type A 10
1 specimen
Welded built-up box section Figure 3
Multiple process
b
column c)
1 specimen from each
50 ≤ t ≤ 100 Type A
f
process (total 2 speci- 20
mens)
Square-groove, T-joint
Inner diaphragm for welded Centre of weld Figure 3
g
1 specimen 22 ≤ t ≤ 100 Type A
built-up box section column metal d)
Double-bevel-groove, T-joint
22 ≤ t ˂ 28 Type B
Welded built-up H-beam and Centre of weld Figure 3
1 specimen
H-column metal e)
28 ≤ t ≤ 40 Type A
a
See 5.2.1.1.
b
Distance from the weld joint face side to the centre of specimen, y
F.
c
Thickness of the thinner of the two welded plates.
d
Thickness of
...