ISO/FDIS 25780

FINAL DRAFT
International
Standard
ISO/TC 138/SC 6
Plastics piping systems for
Secretariat: ASI
pressure and non-pressure water
Voting begins on:
supply, drainage or sewerage —
2026-08-24
Glass-reinforced thermosetting
Voting terminates on:
plastics (GRP) systems based on
2026-10-19
unsaturated polyester (UP) resin —
Pipes with flexible joints intended
to be installed using jacking
techniques
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
FINAL DRAFT
International
Standard
ISO/TC 138/SC 6
Plastics piping systems for
Secretariat: ASI
pressure and non-pressure water
Voting begins on:
supply, drainage or sewerage —
Glass-reinforced thermosetting
Voting terminates on:
plastics (GRP) systems based on
unsaturated polyester (UP) resin —
Pipes with flexible joints intended
to be installed using jacking
techniques
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 2026
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.
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ii
Contents Page
Foreword .v
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms . 2
3.1 Terms related to design values declared by the manufacturer .2
3.2 Terms related to measured values .4
3.3 General terms .5
3.4 Symbols and abbreviated terms .11
4 Requirements .13
4.1 Pipe properties . 13
4.1.1 Manufacturer's declared diameters . 13
4.1.2 Design jacking load for closed joint . 13
4.1.3 Nominal stiffness . 13
4.1.4 Nominal pressure . 13
4.1.5 Appearance . 13
4.2 Materials .14
4.2.1 General .14
4.2.2 Reinforcement .14
4.2.3 Resin .14
4.2.4 Aggregates and fillers .14
4.2.5 Thermoplastics liners .14
4.2.6 Elastomers .14
4.2.7 Metals . 15
4.3 Pipe wall construction . 15
4.3.1 Inner layer . 15
4.3.2 Structural layer . 15
4.3.3 Outer layer . 15
4.4 Reference conditions for testing . 15
4.4.1 Temperature . 15
4.4.2 Properties of water for testing . 15
4.4.3 Loading conditions .16
4.4.4 Preconditioning .16
4.4.5 Measurement of dimensions .16
4.5 Elapsed time, x, for determination of long-term properties .16
4.6 Joint properties .16
4.6.1 Types of joint .16
4.6.2 Flexibility of the jointing system .17
4.6.3 Sealing ring . . .18
4.6.4 Effect on water quality .18
4.7 Assessment of conformity .18
5 Pipes . 19
5.1 Geometrical characteristics .19
5.1.1 Wall thickness .19
5.1.2 Nominal length, L .19
5.1.3 Straightness .19
5.1.4 Squareness of end faces.19
5.2 Mechanical characteristics .21
5.2.1 Initial ring stiffness .21
5.2.2 Long-term creep stiffness .21
5.2.3 Initial resistance to failure in a deflected condition .21
5.3 Resistance to strain corrosion .21
5.4 Longitudinal compressive strength .21

iii
5.4.1 General .21
5.4.2 Initial longitudinal compressive stress at break (prism test pieces) . 22
5.4.3 Initial longitudinal compressive stress at break (spool test pieces) . 22
5.4.4 Requirements . 22
5.5 Design loads . 22
5.5.1 Design longitudinal load . . 22
5.5.2 Design jacking load . . 22
5.6 Longitudinal compressive modulus . 22
5.6.1 Initial longitudinal compressive modulus (prism test pieces). 22
5.6.2 Initial longitudinal compressive modulus (spool test pieces) . 22
5.6.3 Declared value . 23
5.7 Resistance of pressure pipes to internal pressure . 23
5.8 Marking . 23
6 Joints .23
6.1 General requirements . 23
6.2 Performance requirements .24
6.3 Geometrical characteristics .24
6.4 Interchangeability . 25
6.5 Marking . 25
Annex A (normative) Determination of the longitudinal compressive properties of a pipe, using
a sample of prism test pieces cut from a ring from the pipe .26
Annex B (normative) Determination of the longitudinal compressive properties of pipes, using
spool test pieces .32
Annex C (normative) Procedure for the calculation of the design jacking load on a GRP (UP)
pipe, F .38
j,d
Bibliography .43

iv
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 138, Plastics pipes, fittings and valves for the
transport of fluids, Subcommittee SC 6, Reinforced plastics pipes and fittings for all applications.
This second edition cancels and replaces the first edition (ISO 25780:2011), which has been technically
revised.
The main changes are as follows:
— Clause 3 has been restructured to distinguish measured values and declared values (see 3.1 and 3.2).
— An overview of symbols and abbreviated terms has been introduced (see 3.4).
— The limit state concept used in conjunction with a partial factor method has been introduced.
— The nominal pressure classes have been reduced (see Table 1).
— Type “R” and type “E-CR” have been added as additional reinforcement types (see 4.2.2).
— Requirements for thermoplastic liners have been introduced (see 4.2.5).
— Requirements for the assessment of conformity have been introduced (see 4.7).
— The parameters “jacking diameter” and “laying length” have been deleted.
— The requirements on longitudinal compressive strength as well as design loads have been completely
revised (see 5.4 and 5.5).
— The determination of the initial longitudinal compressive modulus by testing has been introduced.
— Clause 6 on joints has been restructured.
— Annexes A to C have been completely updated.
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.

v
vi
Introduction
A jacking technique is a trenchless construction method which installs a pipeline by inserting pipes one
by one under the ground by pressing with one or more hydraulic jacks, while the excavated ground is
simultaneously evacuated.
In this document, the requirements for design jacking load on glass-reinforced thermosetting plastics (GRP)
pipes are based on the general principle for the reliability of structures detailed in ISO 2394 and in EN 1990.
These reference documents provide procedures for the harmonization of design practices and address the
probability of failure, as well as possible consequences of failures. The design practices are based on a partial
safety factor concept, as well as on risk management engineering.

vii
FINAL DRAFT International Standard ISO/FDIS 25780:2026(en)
Plastics piping systems for pressure and non-pressure
water supply, drainage or sewerage — Glass-reinforced
thermosetting plastics (GRP) systems based on unsaturated
polyester (UP) resin — Pipes with flexible joints intended to
be installed using jacking techniques
1 Scope
This document specifies the properties of the piping system and its components made from glass-reinforced
thermosetting plastics (GRP) based on unsaturated polyester (UP) resin. It is suited for all types of water
supply, drainage and sewerage with or without pressure. Types of water supply include, but are not limited
to, raw water, irrigation, cooling water, potable water, salt water, sea water, penstocks in power plants,
processing plants and other water-based applications.
This document is applicable to GRP-UP piping systems, with flexible joints, intended to be installed using
jacking techniques. It specifies the characteristics of pipes made from GRP-UP, with or without aggregates
or fillers. It also specifies the test parameters for the test methods referred to in this document.
This document is applicable to circular pipes and joints with a size range from DN 100 to DN 4 000 at normal
service conditions.
This document covers requirements to demonstrate the adequacy of the design of the joint and specifies
type test performance requirements for the joints as a function of the declared nominal pressure rating of
the pipeline system and the required joint deflection capability of the system.
The determination of longitudinal compressive properties of a pipe are given in Annex A and Annex B.
The procedure for the calculation of the design jacking load on a GRP (UP) pipe is given in Annex C.
Requirements for GRP-fittings, used between pipe systems covered by this document, are given in ISO 23856.
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 75-2:2013, Plastics — Determination of temperature of deflection under load — Part 2: Plastics and ebonite
ISO 604:2002, Plastics — Determination of compressive properties
ISO 3126, Plastics piping systems — Plastics components — Determination of dimensions
ISO 4633, Rubber seals — Joint rings for water supply, drainage and sewerage pipelines — Specification for
materials
ISO 7685, Glass-reinforced thermosetting plastics (GRP) pipes — Determination of initial ring stiffness
ISO 8639, Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Test methods for leaktightness and
proof of structural design of flexible joints
ISO 10466, Glass-reinforced thermosetting plastics (GRP) pipes — Test method to prove the resistance to initial
ring deflection
ISO 10468, Glass-reinforced thermosetting plastics (GRP) pipes — Determination of the ring creep properties
under wet or dry conditions
ISO 10952, Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Determination of the resistance
to chemical attack for the inside of a section in a deflected condition
ISO 23856, Plastics piping systems for pressure and non-pressure water supply, drainage or sewerage — Glass-
reinforced thermosetting plastics (GRP) systems based on unsaturated polyester (UP) resin
CEN/TS 14632, Plastics piping systems for drainage, sewerage and water supply, pressure and non-pressure —
Glass-reinforced thermosetting plastics (GRP) based on unsaturated polyester resin (UP) — Guidance for the
assessment of conformity
3 Terms, definitions, symbols and abbreviated terms
For the purposes of this document, the following terms and definitions, symbols and abbreviated terms
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 Terms related to design values declared by the manufacturer
3.1.1
pipe outside diameter
jacking diameter
d
OD
manufacturer's declared value for the maximum external diameter of the pipe barrel
Note 1 to entry: The pipe outside diameter is expressed in millimetres (mm).
Note 2 to entry: See Figure 1.
3.1.2
maximum spigot inside diameter
d
i,max
manufacturer's declared value for the maximum internal diameter of the pipe spigot, at the groove location
where applicable
Note 1 to entry: See Figure 1.
3.1.3
minimum spigot or groove diameter
d
g,min
manufacturer's declared value for the minimum external diameter of the spigot (see Figure 1 a) diameter),
or in the groove of the spigot (see Figure 1 b) diameter, if applicable)
Note 1 to entry: Spigot or groove diameter is expressed in millimetres (mm).
Note 2 to entry: See Figure 1.
3.1.4
minimum wall thickness
e
min
manufacturer's declared value for the minimum wall thickness of the pipe barrel
Note 1 to entry: The minimum wall thickness is expressed in millimetres (mm).
Note 2 to entry: See Figure 1.

3.1.5
cross-sectional area at the spigot
A
s
minimum area of the cross-section of the pipe at the spigot, or in the groove of the spigot, if applicable
Note 1 to entry: Minimum cross-sectional area at the spigot is derived using the following formula and is expressed in
square millimetres (mm ):
 
Ad  05,, 05d .


sg i 
 
Note 2 to entry: See Figure 1.
3.1.6
cross-sectional area at the barrel
A
b
area of the cross-section of the pipe barrel
Note 1 to entry: The cross-sectional area at the pipe barrel is derived using the following formula and is expressed in
square millimetres (mm ):
 
Ad  05,, 05d .
 
bO Di,max 
 
Note 2 to entry: See Figure 1.
a) Section through a rebated un-grooved spigot b) Section through a rebated grooved spigot
Key
d pipe outside diameter, in mm
OD
d maximum spigot inside diameter, in mm
i,max
d minimum spigot or groove diameter, in mm
g,min
e minimum wall thickness of pipe, in mm
min
Figure 1 — Diameters declared by the manufacturer
3.1.7
declared initial longitudinal compressive stress at break
σ
b
manufacturer's declared minimum value, derived from tests, for the initial longitudinal compressive stress
at break of the pipe
Note 1 to entry: When tested in accordance with Annex B, the minimum initial longitudinal compressive stress at
break is expressed in megapascals (MPa).

3.1.8
declared initial longitudinal compressive modulus
E
c
manufacturer's declared value, derived from tests, for the initial longitudinal compressive modulus
Note 1 to entry: When tested in accordance with Annex A or Annex B, the declared initial longitudinal compressive
modulus is expressed in megapascals (MPa).
3.2 Terms related to measured values
3.2.1
mean diameter
d
m
diameter of the circle corresponding to the middle of the pipe wall cross-section and given by the following
formula:
dde
me
where
d is the measured external diameter, in mm;
e
e is the measured wall thickness of the pipe, in mm
Note 1 to entry: The mean diameter is expressed in millimetres (mm).
Note 2 to entry: If measured values are not available (e.g. for design purposes) declared values may be used.
Note 3 to entry: See Figure 2.
[SOURCE: ISO 23856:2021, 3.3, modified — the first formula has been removed and Notes 2 and 3 to entry
have been added.]
a) Section through a rebated un-grooved spigot b) Section through a rebated grooved spigot
Key
d measured external diameter, in mm
e
d measured spigot inside diameter, in mm
i
d measured spigot or groove diameter, in mm
g
d mean diameter, in mm
m
e measured wall thickness of pipe, in mm
Figure 2 — Measured diameters
3.3 General terms
3.3.1
jacking
trenchless construction method which installs a pipeline by inserting pipes one by one under the ground by
pressing with one or more hydraulic jacks, while the excavated ground is simultaneously evacuated from
the cutting head
3.3.2
nominal length
pipe length without tolerance
Note 1 to entry: The nominal length is expressed in metres (m).
3.3.3
initial longitudinal compressive modulus (prism test piece)
E
c,p
ratio of the applied stress to the resulting strain below the elastic limit, both measured concurrently during
a short-term compression test with prism
Note 1 to entry: When tested in accordance with Annex A, the initial longitudinal compressive modulus is expressed
in megapascals (MPa).
3.3.4
initial longitudinal compressive modulus (spool test piece)
E
c,s
ratio of the applied stress to the resulting strain below the elastic limit, both measured concurrently during
a short-term compression test with spool
Note 1 to entry: When tested in accordance with Annex B, the initial longitudinal compressive modulus is expressed
in megapascals (MPa).
3.3.5
design longitudinal load
F
d
design value of the concentric longitudinal load that the pipe withstands, taking into account the material
partial factor
Note 1 to entry: The ultimate longitudinal load is determined using the following formula and is expressed in
kilonewtons (kN):
1 1
FA 
db s
1000 
M
where
σ is the declared minimum initial compressive stress at break, in MPa;
b
A is the pipe cross-sectional area at the spigot, in mm ;
s
γ is the material partial factor, γ = 1,37; see also Table C.1.
M M
3.3.6
design jacking load
F
j,d
longitudinal compressive load that a pipe can withstand during a jacking operation, taking into account the
installation partial factor and the stress eccentricity dependence factor
Note 1 to entry: The design jacking load is determined using the following formula and is expressed in kilonewtons
(kN):
F
d
F 
jd,
S 
 i
where
F is the design longitudinal load, in kN;
d
S is the stress eccentricity dependence factor, with S ≥ 2;
σ σ
γ is the installation partial factor, see Table C.1.
i
Note 2 to entry: For the design jacking load for closed joint (considering full contact between the spigots) the stress
eccentricity dependence factor S = 2.
σ
Note 3 to entry: For the design jacking load for open joint (considering incomplete contact between the spigots) the
stress eccentricity dependence factor S > 2. For the determination of S , see C.2.5.1.
σ σ
3.3.7
nominal stiffness
SN
alphanumerical designation for stiffness classification purposes, which has the same numerical value as the
minimum initial value required, when expressed in newtons per square metre (N/m )
Note 1 to entry: The designation for reference or marking purposes consists of the letters SN plus a number.
[SOURCE: ISO 23856:2021, 3.8, modified — Note 1 to entry has been removed.]
3.3.8
ring stiffness
S
physical characteristic of the pipe which is a measure of the resistance to ring deflection per metre length
under external load
Note 1 to entry: Ring stiffness is determined using the following formula and is expressed in newtons per square
metre (N/m ):
EI
S 
d
m
where
E is the apparent modulus of elasticity, which can be derived from the result of the ring stiffness
test, i.e. ISO 7685, in N/m ;
d is the mean diameter, in m;
m
I is the second moment of area in the longitudinal direction per metre length, in m /m;
e
I=
where e is the measured wall thickness of pipe, in m.
3.3.9
initial ring stiffness
S
value of ring stiffness, S, obtained when tested according to ISO 7685
Note 1 to entry: The initial stiffness is computed by:

  
 y 
5
1860 2500 10
 
 
 
d
 
  
m
S 
Ly kd
R mm
0,3927
F Ge
R
where
y is the measured deflection, in m;
d is the mean diameter, in m;
m
L is the length of the specimen, in m;
R
F is the measured load, in N;
R
k is a shape factor for the wall cross-section, which can be assumed to be equal to 1,2,
dimensionless;
G is the shear modulus, in N/m .
Note 2 to entry: The shear modulus to be used in the calculation can be determined through calibration between
measured and computed values on various products, or other suitable means.
Note 3 to entry: Initial ring stiffness is expressed in newtons per square metre (N/m ).
Note 4 to entry: The test shall be performed at relative deflection, y/d calculated by:
m
y
% 

d 3
m
SN
3.3.10
calculated long-term ring creep stiffness
S
x
calculated value of ring creep stiffness, S, at x years
Note 1 to entry: Long-term ring creep stiffness is obtained using the following formula:
SS
xx01,,creep
where
x is the elapsed time as specified in this document (see 4.5), in years;
α is the creep factor at x years, determined according to ISO 10468 under wet conditions;
x,creep
S is the ring stiffness at position 1 at 0,1 h.
0,1
3.3.11
pressure pipe
pipe having a nominal pressure (3.3.13) (PN) classification greater than 1 bar and which is intended to be
used with the internal pressure equal to or less than its nominal pressure when expressed in bars
5 2
Note 1 to entry: 1 bar = 0,1 MPa = 10 Pa; 1 MPa = 1 N/mm .
3.3.12
non-pressure pipe
pipe subjected to an internal pressure not greater than 1 bar
5 2
Note 1 to entry: 1 bar = 0,1 MPa = 10 Pa; 1 MPa = 1 N/mm .

3.3.13
nominal pressure
PN
alphanumeric designation for pressure classification purposes, which has a numerical value equal to the
resistance of a component of a piping system to internal pressure
Note 1 to entry: Nominal pressure is a designation for reference or marking purposes that consists of the letters PN
plus a number which is related to a component's pressure rating in bars.
5 2
Note 2 to entry: 1 bar = 0,1 MPa = 10 Pa; 1 MPa = 1 N/mm .
3.3.14
normal service conditions
conveyance of water or sewage, in the temperature range of 2 °C to 50 °C, with or without pressure, for
50 years
3.3.15
service temperature
maximum sustained temperature at which the system is expected to operate continuously
Note 1 to entry: Service temperature is expressed in degrees Celsius (°C).
3.3.16
rerating factor
R
RF
multiplication factor that quantifies the relation between a mechanical, physical or chemical property at the
service condition compared to the respective value at 23 °C and 50 % relative humidity (RH)
3.3.17
relative ring deflection
y/d
m
ratio of the change in diameter of a pipe, y, in metres, to its mean diameter, d , in metres
m
Note 1 to entry: Relative ring deflection is derived as a percentage, %, i.e.:
 
y
100 .
 
 
d
 
m
3.3.18
type test
TT
test carried out in order to assess the fitness for purpose of a product or assembly of components to fulfil its
or their function(s) according to this document
3.3.19
flexible joint
joint which allows relative movement between components being joined
3.3.20
flush coupling
joint component with either an external diameter equal to the pipe's outside diameter or an inside diameter
equal to the pipe's inside diameter
3.3.21
closed joint
joint condition where the pipe ends, with or without a transfer ring, are in full contact around the whole
circumference
3.3.22
open joint
joint condition where the pipe ends, with or without a transfer ring, are in incomplete contact with each
other thereby forming a gap
3.3.23
angular deflection
δ
angle between the axes of two adjacent pipes
Note 1 to entry: Angular deflection (see Figure 3 b)) is expressed in degrees (°).
3.3.24
draw
D
longitudinal movement of a joint
Note 1 to entry: Draw (see Figure 3 a)) is expressed in millimetres (mm).
3.3.25
total draw
T
sum of the draw, D, and the additional longitudinal movement, J, due to the presence of angular deflection
Note 1 to entry: Total draw (see Figure 3 c)) is expressed in millimetres (mm).
3.3.26
deformation
M
pipe deformation in the coupling as a result of a vertical force of 20 N/mm of the maximum spigot inside
diameter d , on the pipe and a supported coupling causing a step between the two pipe spigots at the
i,max
loading position
Note 1 to entry: Deformation (see Figure 3 d)) is expressed in millimetres (mm).
a) Draw
b) Angular deflection
c) Total draw
d) Deformation
Key
D draw
J longitudinal movement arising from angular deflection of the joint
δ angular deflection of the joint
T total draw
M deformation
NOTE The joint in this figure is an example of a typical joint but is not intended to fix design. Other joints are
available.
Figure 3 — Joint movements
3.3.27
break
condition where the test piece can no longer carry the load to which it is being subjected
3.3.28
thickness to diameter ratio
e /d
min OD
ratio between the minimum wall thickness of pipe, e , and the pipe outside diameter, d , expressed in per
min OD
thousand, ‰
3.3.29
controlled installation process
installation process during which the steering and jacking forces are continuously monitored and recorded
to ensure that design limits on angular deflection and jacking load are not exceeded
3.3.30
uncontrolled installation process
installation process during which the steering and jacking forces are not continuously monitored and
recorded
3.4 Symbols and abbreviated terms
A initial mean cross-sectional area
A cross-sectional area at the barrel
b
A cross-sectional area at the spigot
s
A calculated minimum area of the cross-section of the pipe at the spigot, or in the groove
spool
of the spigot
a deflection offset
D draw
d measured external diameter of the flush coupling
c
d measured external diameter
e
d measured spigot or groove diameter
g
d minimum spigot or groove diameter
g,min
d measured spigot inside diameter
i
d maximum spigot inside diameter
i,max
d mean diameter
m
d pipe outside diameter
OD
d deviation from squareness across a joint's external diameter
sq,d
d deviation from squareness across a joint's wall thickness
sq,e
E apparent modulus of elasticity
E declared initial longitudinal compressive modulus
C
E initial longitudinal compressive modulus (prism test piece)
c,p
E initial longitudinal compressive modulus (spool test piece)
c,s
e measured wall thickness of pipe
e/d thickness to diameter ratio
OD
e minimum wall thickness of pipe
min
F compressive load
F measured load
R
F maximum compressive force at failure
c
F design longitudinal load
d
F design jacking load
j,d
F load at fracture
fr
f test piece de-rating factor
s
G shear modulus
h measured height of test piece
I second moment of area in the longitudinal direction
J longitudinal movement arising from angular deflection of the joint
k shape factor for the wall cross-section
L nominal length
L actual length of the pipe
p
L length of the specimen
R
L length of the test spool
S
L measured length of coupling
c
M deformation
p probability of failure
f
R rerating factor
RF
R slenderness ratio
SL
r radius of gyration for a rectangle
G
S ring stiffness
S initial ring stiffness
S ring stiffness at position 1 at 0,1 h
0,1
S calculated long-term ring creep stiffness
x
S minimum long-term creep stiffness
x, creep, min
S stress eccentricity dependence factor
σ
T total draw
T measured spigot thickness
g
T minimum spigot thickness
g,min
w measured width of test piece
X coefficient
x elapsed time
x measured rebated length
x measured distance from the groove to spigot end
y measured deflection
y/d relative ring deflection
m
(y /d ) initial relative ring deflection at 2 min
2, bore m min
Z diametrical extent of compression in the joint segments
α creep factor at x years
x,creep
δ angular deflection
ε strain
x
ε strain at failure
b
γ total safety factor
γ installation partial factor
i
γ material partial factor
M
η coefficient
λ coefficient
φ angular deflection, in accordance with the design jacking load
v number equal to the component's nominal pressure
σ declared initial longitudinal compressive stress at break
b
σ initial longitudinal compressive stress at break (spool test piece)
b,s
σ individual value of the initial longitudinal compressive stress at break (prism test piec-
b,p;QC,i
es) for quality control
σ stress at the value of the strain ε = 0,000 5
1 1
σ stress at the value of the strain ε = 0,002 5
2 2
ξ coefficient
subscript referring to individual test piece
i
subscript referring to individual gauge
j
AT audit test
BRT batch release test
CC consequence class
GRP glass reinforced thermosetting plastics

DN nominal size
ITT initial type test
PN nominal pressure
PVT process verification tests
TT type test
SN nominal stiffness
UP unsaturated polyester
4 Requirements
4.1 Pipe properties
4.1.1 Manufacturer's declared diameters
The outside diameter d and its tolerances shall be designated by the manufacturer. The manufacturer
OD
shall also declare the maximum spi
...

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ISO /TC 138/SC 06 6
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Secretariat: ASI
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Date: 2026-04-1608-10
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Plastics piping systems for pressure and non-pressure water supply,
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drainage or sewerage — Glass-reinforced thermosetting plastics
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(GRP) systems based on unsaturated polyester (UP) resin — Pipes
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with flexible joints intended to be installed using jacking techniques
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FDIS stage
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St l D fi iti
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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,
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or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
Adjust space between Asian text and numbers
at the address below or ISO’s member body in the country of the requester.
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Header distance from edge: 1.27 cm, Footer distance
ISO copyright office
from edge: 0.5 cm
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
EmailE-mail: copyright@iso.org
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Website: www.iso.orgwww.iso.org
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Published in Switzerland
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ii
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Contents
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Foreword . iv
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms . 2
3.1 Terms related to design values declared by the manufacturer . 2
3.2 Terms related to measured values . 4
3.3 General terms . 5
3.4 Symbols and abbreviated terms . 13
4 Requirements . 16
4.1 Pipe properties . 16
4.2 Materials . 17
4.3 Pipe wall construction . 18
4.4 Reference conditions for testing . 18
4.5 Elapsed time, x, for determination of long-term properties . 19
4.6 Joint properties . 19
4.7 Assessment of conformity . 22
5 Pipes . 22
5.1 Geometrical characteristics . 22
5.2 Mechanical characteristics . 25
5.3 Resistance to strain corrosion . 26
5.4 Longitudinal compressive strength . 26
5.5 Design loads . 27
5.6 Longitudinal compressive modulus . 27
5.7 Resistance of pressure pipes to internal pressure . 28
5.8 Marking . 28
6 Joints . 29
6.1 General requirements . 29
6.2 Performance requirements . 29
6.3 Geometrical characteristics . 30
6.4 Interchangeability . 30
6.5 Marking . 30
Annex A (normative) Determination of the longitudinal compressive properties of a pipe, using
a sample of prism test pieces cut from a ring from the pipe . 32
Annex B (normative) Determination of the longitudinal compressive properties of pipes, using
spool test pieces . 41
Annex C (normative) Procedure for the calculation of the design jacking load on a GRP (UP)
pipe, F . 50
j,d
Bibliography . 58

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iii
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Foreword Formatted: Adjust space between Latin and Asian text,
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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).
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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)
Formatted: English (United Kingdom)
which may be required to implement this document. However, implementers are cautioned that this may not
Formatted: English (United Kingdom)
represent the latest information, which may be obtained from the patent database available at
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www.iso.org/patents.www.iso.org/patents. ISO shall not be held responsible for identifying any or all such
patent rights.
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Any trade name used in this document is information given for the convenience of users and does not
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constitute an endorsement.
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For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
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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 Formatted: English (United Kingdom)
www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.
Formatted: English (United Kingdom)
Formatted: English (United Kingdom)
This document was prepared by Technical Committee ISO/TC 138, Plastics pipes, fittings and valves for the
transport of fluids, Subcommittee SC 6, Reinforced plastics pipes and fittings for all applications.
Formatted: English (United Kingdom)
Formatted: English (United Kingdom)
This second edition cancels and replaces the first edition (ISO 25780:2011), which has been technically
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revised.
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The main changes are as follows:
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— — The complete clause on terms and definition have been Clause 3 has been restructured to distinguish
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measured values and declared values, (see 3.1 and 3.2.3.1 and 3.2).
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— — An overview of symbols and abbreviated terms has been introduced, (see 3.4.3.4).
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— — The limit state concept used in conjunction with a partial factor method has been introduced.
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— — The nominal pressure classes have been reduced, (see Table 1.Table 1). Formatted: English (United Kingdom)
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— — Type “R” and type “E-CR” have been added as additional reinforcement types, (see 4.2.2.4.2.2).
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— — Requirements for thermoplastic liners have been introduced, (see 4.2.5.4.2.5).
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— — Requirements for the assessment of conformity have been introduced, (see 4.7.4.7).
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— — The parameters “jacking diameter” and “laying length” have been deleted.
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iv
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— — The requirements on longitudinal compressive strength as well as design loads have been completely
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revised, see 5.4 and 5.5. (see 5.4 and 5.5).
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— — The determination of the initial longitudinal compressive modulus by testing has been introduced.
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— — Clause 6Clause 6 on joints has been restructured. Formatted: English (United Kingdom)
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— — All Annexes A to C wereAnnexes A to C have been completely updated.
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Any feedback or questions on this document should be directed to the user’s national standards body. A
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complete listing of these bodies can be found at www.iso.org/members.html.www.iso.org/members.html.

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v
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Introduction
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A jacking technique is a trenchless construction method which installs a pipeline by inserting pipes one by one
under the ground by pressing with one or more hydraulic jacks, while the excavated ground is simultaneously
evacuated.
In this document, the requirements for design jacking load on glass-reinforced thermosetting plastics (GRP)
pipes are based on the general principle for the reliability of structures detailed in ISO 2394 and in EN 1990.
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These reference documents provide procedures for the harmonization of design practices and address the
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probability of failure, as well as possible consequences of failures. The design practices are based on a partial
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safety factor concept, as well as on risk management engineering.
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vi
International Standard ISO 25780:2025(en)

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Plastics piping systems for pressure and non-pressure water supply,
drainage or sewerage — Glass-reinforced thermosetting plastics
(GRP) systems based on unsaturated polyester (UP) resin — Pipes
with flexible joints intended to be installed using jacking techniques
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1 Scope
Header distance from edge: 1.27 cm, Footer distance
from edge: 0.5 cm
This document specifies the properties of the piping system and its components made from glass-reinforced
thermosetting plastics (GRP) based on unsaturated polyester (UP) resin. It is suited for all types of water
supply, drainage and sewerage with or without pressure. Types of water supply include, but are not limited
to, raw water, irrigation, cooling water, potable water, salt water, sea water, penstocks in power plants,
processing plants and other water-based applications.
This document is applicable to GRP-UP piping systems, with flexible joints, intended to be installed using
jacking techniques. It specifies the characteristics of pipes made from GRP-UP, with or without aggregates or
fillers. It also specifies the test parameters for the test methods referred to in this document.
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This document is applicable to circular pipes and joints with a size range from DN 100 to DN 40004 000 at
normal service conditions.
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This document covers requirements to demonstrate the adequacy of the design of the joint and specifies type
test performance requirements for the joints as a function of the declared nominal pressure rating of the Formatted: Default Paragraph Font
pipeline system and the required joint deflection capability of the system.
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The determination of longitudinal compressive properties of a pipe are given in Annex A and Annex B.Annex A
and Annex B.
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The procedure for the calculation of the design jacking load on a GRP (UP) pipe is given in Annex C.Annex C. stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
Requirements for GRP-fittings, used between pipe systems covered by this document, are given in ISO 23856.
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2 Normative references
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The following documents are referred to in the text in such a way that some or all of their content constitutes
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requirements of this document. For dated references, only the edition cited applies. For undated references,
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the latest edition of the referenced document (including any amendments) applies.
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ISO 75--2:2013, Plastics — Determination of temperature of deflection under load — Part 2: Plastics and
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ebonite
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ISO 604:2002, Plastics — Determination of compressive properties
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
ISO 2602, Statistical interpretation of test results — Estimation of the mean — Confidence interval
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ISO 3126, Plastics piping systems — Plastics components — Determination of dimensions
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ISO 4633, Rubber seals — Joint rings for water supply, drainage and sewerage pipelines — Specification for
materials
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ISO 7685, Glass-reinforced thermosetting plastics (GRP) pipes — Determination of initial ring stiffness
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...
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ISO 8639, Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Test methods for leaktightness
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and proof of structural design of flexible joints .
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ISO 10466, Glass-reinforced thermosetting plastics (GRP) pipes — Test method to prove the resistance to
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...
initial ring deflection
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ISO 10468, Glass-reinforced thermosetting plastics (GRP) pipes — Determination of the ring creep properties
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...
under wet or dry conditions
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ISO 10952, Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Determination of the resistance
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to chemical attack for the inside of a section in a deflected condition
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ISO 23856, Plastics piping systems for pressure and non-pressure water supply, drainage or sewerage — Formatted
...
Glass-reinforced thermosetting plastics (GRP) systems based on unsaturated polyester (UP) resin
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...
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CEN/TS 14632, Plastics piping systems for drainage, sewerage and water supply, pressure and non-pressure
— Glass-reinforced thermosetting plastics (GRP) based on unsaturated polyester resin (UP) — Guidance for
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...
the assessment of conformity
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EN 681-1, Elastomeric seals — Material requirements for pipe joint seals used in water and drainage .
applications — Part 1: Vulcanized rubber
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3 Terms, definitions, symbols and abbreviated terms
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For the purposes of this document, the following terms and definitions, symbols and abbreviated terms apply.
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ISO and IEC maintain terminology databases for use in standardization at the following addresses:
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— — ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
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— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/ .
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3.1 Terms related to design values declared by the manufacturer
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3.1.1 3.1.1
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...
pipe outside diameter
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...
jacking diameter
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d .
OD
manufacturer's declared value for the maximum external diameter of the pipe barrel
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...
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...
Note 1 to entry: The pipe outside diameter is expressed in millimetres (mm).
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...
Note 2 to entry: See Figure 1.Figure 1.
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3.1.2 3.1.2 Formatted
...
maximum spigot inside diameter
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...
di,max
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...
manufacturer's declared value for the maximum internal diameter of the pipe spigot, at the groove location
where applicable
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...
Note 1 to entry: See Figure 1.Figure 1.
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...
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3.1.3 3.1.3
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minimum spigot or groove diameter
dg,min
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manufacturer's declared value for the minimum external diameter of the spigot [(see Figure 1Figure 1 a)
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diameter],), or in the groove of the spigot [(see Figure 1Figure 1 b) diameter, if applicable])
and Asian text, Adjust space between Asian text and
numbers
Note 1 to entry: Spigot or groove diameter is expressed in millimetres (mm).
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Note 2 to entry: See Figure 1.Figure 1.
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Subscript
3.1.4 3.1.4
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minimum wall thickness
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emin
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
manufacturer's declared value for the minimum wall thickness of the pipe barrel
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
Note 1 to entry: The minimum wall thickness is expressed in millimetres (mm).
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and Asian text, Adjust space between Asian text and
Note 2 to entry: See Figure 1.Figure 1.
numbers
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3.1.5 3.1.5
cross-sectional area at the spigot Formatted: Regular Sub, Font: Bold, Not Superscript/
A Subscript
s
minimum area of the cross-section of the pipe at the spigot, or in the groove of the spigot, if applicable
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Note 1 to entry: Minimum cross-sectional area at the spigot is derived using the following formula and is expressed in
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
square millimetres (mm )):
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
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 2 
A =π−05,,dd(05 ) and Asian text, Adjust space between Asian text and
( )
s  g i 
 
numbers
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2 2
𝐴𝐴 =𝜋𝜋[(0,5𝑑𝑑 ) −(0,5𝑑𝑑) ]
s g i
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.
Subscript
Note 2 to entry: See Figure 1.Figure 1.
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3.1.6 3.1.6
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
cross-sectional area at the barrel
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
A
b
Formatted
...
area of the cross-section of the pipe barrel
Formatted
...
Note 1 to entry: The cross-sectional area at the pipe barrel is derived using the following formula and is expressed in
Formatted: Regular Italic, Font: Bold, Not Italic
square millimetres (mm ).):
Formatted
...

Formatted
Ad=π 05, − 05, d .
( ) ( )
b OD i,max


2 2
𝐴𝐴 =𝜋𝜋[(0,5𝑑𝑑 ) −(0,5𝑑𝑑 ) ]
b OD i,max
.
Note 2 to entry: See Figure 1.Figure 1.
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...
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...
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Asian text, Adjust space between Asian text and
numbers
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between Latin and Asian text, Adjust space between
Asian text and numbers
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Adjust space between Asian text and numbers, Tab
stops: Not at 0.7 cm + 1.4 cm + 2.8 cm + 3.5 cm +
4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm

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a) Section through a rebated un-grooved spigot b) Section through a rebated grooved spigot
Asian text, Adjust space between Asian text and
numbers
Key
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d pipe outside diameter, in mm
OD
and Asian text, Adjust space between Asian text and
d maximum spigot inside diameter, in mm
i,max
numbers
dg,min minimum spigot or groove diameter, in mm
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emin minimum wall thickness of pipe, in mm
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Figure 1 — Diameters declared by the manufacturer
Subscript
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3.1.7 3.1.7
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declared initial longitudinal compressive stress at break
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
σb 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
manufacturer's declared minimum value, derived from tests, for the initial longitudinal compressive stress at
Formatted: TermNum3, Adjust space between Latin
break of the pipe
and Asian text, Adjust space between Asian text and
numbers
Note 1 to entry: When tested in accordance with Annex B,Annex B, the minimum initial longitudinal compressive stress
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at break is expressed in megapascals (MPa).
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3.1.8 3.1.8
Subscript
declared initial longitudinal compressive modulus
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E
c
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manufacturer's declared value, derived from tests, for the initial longitudinal compressive modulus
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
Note 1 to entry: When tested in accordance with Annex AAnnex A or Annex B,Annex B, the declared initial longitudinal
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compressive modulus is expressed in megapascals (MPa).
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stops: Not at 0.71 cm
3.2 Terms related to measured values
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3.2.1 3.2.1
and Asian text, Adjust space between Asian text and
mean diameter
numbers
dm
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diameter of the circle corresponding to the middle of the pipe wall cross-section and given by the following
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formula:
Subscript
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d de−
me
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𝑑𝑑 =𝑑𝑑 −𝑒𝑒
m e
where
Formatted: Equation Legend, Adjust space between
de is the measured external diameter, in mm;
Latin and Asian text, Adjust space between Asian text
e is the measured wall thickness of the pipe, in mm. and numbers
Note 1 to entry: The mean diameter is expressed in millimetres (mm).
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Adjust space between Asian text and numbers, Tab
Note 2 to entry: If measured values are not available (e.g. for design purposes) declared values may be used.
stops: Not at 0.7 cm + 1.4 cm + 2.8 cm + 3.5 cm +
4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
Note 3 to entry: See Figure 2.Figure 2.
[SOURCE: ISO 23856:2021, 3.3, modified — the first formula has been removed and Notes 2 and 3 to entry
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have been added.]
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stops: Not at 0.7 cm + 1.4 cm + 1.7 cm + 2.1 cm +
2.8 cm + 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3
cm + 7 cm
Formatted Table
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Asian text, Adjust space between Asian text and
numbers, Tab stops: Not at 1.7 cm

Formatted: Key Title, Space Before: 12 pt, Adjust space
a) Section through a rebated un-grooved spigot b) Section through a rebated grooved spigot
between Latin and Asian text, Adjust space between
Asian text and numbers
Key
Formatted: Adjust space between Latin and Asian text,
de measured external diameter, in mm
Adjust space between Asian text and numbers, Tab
di measured spigot inside diameter, in mm
stops: Not at 0.7 cm + 1.4 cm + 2.8 cm + 3.5 cm +
dg measured spigot or groove diameter, in mm 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
dm mean diameter, in mm
Formatted: None, Adjust space between Latin and
e measured wall thickness of pipe, in mm
Asian text, Adjust space between Asian text and
numbers
Figure 2 — Measured diameters
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Adjust space between Asian text and numbers, Tab
3.3 General terms stops: Not at 0.71 cm
Formatted
...
3.3.1 3.3.1
Formatted: Font: 10 pt
jacking
trenchless construction method which installs a pipeline by inserting pipes one by one under the ground by
Formatted
...
pressing with one or more hydraulic jacks, while the excavated ground is simultaneously evacuated from the
Formatted: Font: 11 pt
cutting head
Formatted
...
=
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Formatted: HeaderCentered
3.3.2 3.3.2
nominal length
pipe length without tolerance
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Note 1 to entry: The nominal length is expressed in metres (m).
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stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.3.3 3.3.3
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
initial longitudinal compressive modulus (prism test piece)
Formatted: TermNum3, Adjust space between Latin
E
c,p
and Asian text, Adjust space between Asian text and
ratio of the applied stress to the resulting strain below the elastic limit, both measured concurrently during a
numbers
short-term compression test with prism
Formatted: Regular Italic, Font: Bold, Not Italic
Note 1 to entry: When tested in accordance with Annex A,Annex A, the initial longitudinal compressive modulus is
Formatted: Regular Sub, Font: Bold, Not Superscript/
expressed in megapascals (MPa).
Subscript
3.3.4 3.3.4
Formatted: Adjust space between Latin and Asian text,
initial longitudinal compressive modulus (spool test piece)
Adjust space between Asian text and numbers, Tab
Ec,s stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
ratio of the applied stress to the resulting strain below the elastic limit, both measured concurrently during a 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
short-term compression test with spool
Formatted: TermNum3, Adjust space between Latin
and Asian text, Adjust space between Asian text and
Note 1 to entry: When tested in accordance with Annex B,Annex B, the initial longitudinal compressive modulus is
numbers
expressed in megapascals (MPa).
Formatted: Regular Italic, Font: Bold, Not Italic
3.3.5 3.3.5
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design longitudinal load
Subscript
F
d
Formatted: Adjust space between Latin and Asian text,
design value of the concentric longitudinal load that the pipe withstands, taking into account the material
Adjust space between Asian text and numbers, Tab
partial factor
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
Note 1 to entry: The ultimate longitudinal load is determined using the following formula and is expressed in
Formatted: TermNum3, Adjust space between Latin
kilonewtons (kN):
and Asian text, Adjust space between Asian text and
numbers
1 1
FA= σ ⋅ ⋅ ⋅
d bs Formatted: Regular Italic, Font: Bold, Not Italic
1 000 γ
M
Formatted: Regular Sub, Font: Bold, Not Superscript/
Subscript
1 1
𝐹𝐹 =𝜎𝜎 ⋅𝐴𝐴 ⋅ ⋅
d b 𝑠𝑠
Formatted: Adjust space between Latin and Asian text,
1000 𝛾𝛾
M
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where stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
σb is the declared minimum initial compressive stress at break, in MPa;
As is the pipe cross-sectional area at the spigot, in mm ;
Formatted: Equation Legend, Adjust space between
γ is the material partial factor, γ = = 1,37; see also Table C.1.Table C.1. Latin and Asian text, Adjust space between Asian text
M M
and numbers
3.3.6 3.3.6
design jacking load
Formatted: Adjust space between Latin and Asian text,
F
j,d Adjust space between Asian text and numbers, Tab
longitudinal compressive load that a pipe can withstand during a jacking operation, taking into account the stops: Not at 0.7 cm + 1.4 cm + 2.8 cm + 3.5 cm +
installation partial factor and the stress eccentricity dependence factor 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
Formatted
...
Note 1 to entry: The design jacking load is determined using the following formula and is expressed in kilonewtons (kN):
Formatted: Regular Italic, Font: Bold, Not Italic
F Formatted: Regular Sub, Font: Bold, Not Superscript/
d
F =
Subscript
jd,
S ⋅γ
σ i
Formatted
...
Formatted: FooterPageNumber
Formatted: Font: 11 pt, Bold
Formatted: Font: 11 pt, Bold
𝐹𝐹
d
𝐹𝐹 =
j,d
Formatted: Font: Bold
𝑆𝑆 ⋅𝛾𝛾
𝜎𝜎 i
Formatted: HeaderCentered, Left
where
Formatted: where_keep-with-next, Adjust space
between Latin and Asian text, Adjust space between
F is the design longitudinal load, in kN;
d
Asian text and numbers
Sσ is the stress eccentricity dependence factor, with Sσ ≥ ≥ 2;
Formatted: Adjust space between Latin and Asian text,
γi is the installation partial factor, see Table C.1.Table C.1.
Adjust space between Asian text and numbers, Tab
Note 2 to entry: For the design jacking load for closed joint (considering full contact between the spigots) the stress
stops: Not at 0.7 cm + 1.4 cm + 2.8 cm + 3.5 cm +
eccentricity dependence factor Sσ = = 2.
4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
Note 3 to entry: For the design jacking load for open joint (considering incomplete contact between the spigots) the
stress eccentricity dependence factor Sσ > > 2. For the determination of Sσ, see C.2.5.1.C.2.5.1.
3.3.7 3.3.7
Formatted: TermNum3, Adjust space between Latin
nominal stiffness
and Asian text, Adjust space between Asian text and
SN
numbers
alphanumerical designation for stiffness classification purposes, which has the same numerical value as the
Formatted: Regular, Font: Bold
minimum initial value required, when expressed in newtons per square metre (N/m )
Note 1 to entry: The designation for reference or marking purposes consists of the letters SN plus a number.
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers, Tab
[SOURCE: ISO 23856:2021, 3.8, modified — Note 1 to entry has been removed.]
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
3.3.8 3.3.8
Formatted: Default Paragraph Font
ring stiffness
Formatted: Default Paragraph Font
S
physical characteristic of the pipe which is a measure of the resistance to ring deflection per metre length
Formatted: Default Paragraph Font
under external load
Formatted: Default Paragraph Font
Note 1 to entry: Ring stiffness is determined using the following formula and is expressed in newtons per square metre
Formatted: Adjust space between Latin and Asian text,
(N/m ):
Adjust space between Asian text and numbers
Formatted: Regular Italic, Font: Bold, Not Italic
E ⋅ I
S =
Formatted: Font: Not Italic
d
m
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers, Tab
𝐸𝐸⋅𝐼𝐼
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
𝑆𝑆 =
𝑑𝑑
m 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
Formatted: where_keep-with-next, Adjust space
where
between Latin and Asian text, Adjust space between
Asian text and numbers
E is the apparent modulus of elasticity, which can be derived from the result of the ring stiffness test, i.e. ISO 7685, in
N/m ;
Formatted: Default Paragraph Font
dm is the mean diameter, in m;
Formatted: Default Paragraph Font
I is the second moment of area in the longitudinal direction per metre length, in m /m;
Formatted: Adjust space between Latin and Asian text,
e
Adjust space between Asian text and numbers, Tab
I =
stops: Not at 0.7 cm + 1.4 cm + 2.8 cm + 3.5 cm +
4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
𝑒𝑒
Formatted
...
𝐼𝐼 =
Formatted: Font: 10 pt
where e is the measured wall thickness of pipe, in m. Formatted
...
Formatted: Font: 11 pt
Formatted
...
Formatted: Font: Bold
Formatted: HeaderCentered
3.3.9 3.3.9
Formatted: TermNum3, Adjust space between Latin
initial ring stiffness
and Asian text, Adjust space between Asian text and
S
0 numbers
value of ring stiffness, S, obtained when tested according to ISO 7685
Formatted: Regular Italic, Font: Bold, Not Italic
Formatted: Regular Sub, Font: Bold, Not Superscript/
Note 1 to entry: The initial stiffness is computed by:
Subscript
  
y Formatted: Default Paragraph Font

−5
1 860+ 2500 ⋅10



d
 Formatted: Default Paragraph Font
  m 
S =
L ⋅⋅y kd
Formatted: Adjust space between Latin and Asian text,
Rm
−0,392 ⋅7
Adjust space between Asian text and numbers, Tab
F Ge⋅
R
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
𝑦𝑦
−5
{1860+(2500 )}⋅10
𝑑𝑑
𝑚𝑚
𝑆𝑆 =
𝐿𝐿 ⋅𝑦𝑦 𝑘𝑘⋅𝑑𝑑
R
𝑚𝑚
−0,3927⋅
𝐹𝐹 𝐺𝐺⋅𝑒𝑒
R
where
Formatted: where_keep-with-next, Adjust space
between Latin and Asian text, Adjust space between
y is the measured deflection, in m;
Asian text and numbers
dm is the mean diameter, in m;
Formatted: Adjust space between Latin and Asian text,
L is the length of the specimen, in m;
R
Adjust space between Asian text and numbers, Tab
F is the measured load, in N;
R
stops: Not at 0.7 cm + 1.4 cm + 2.8 cm + 3.5 cm +
k is a shape factor for the wall cross -section, which can be assumed to be equal to 1,2, dimensionless; 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
G is the shear modulus, in N/m .
Note 2 to entry: The shear modulus to be used in the calculation can be determined through calibration between
measured and computed values on various products, or other suitable means.
Note 3 to entry: Initial ring stiffness is expressed in newtons per square metre (N/m ).
Note 4 to entry: The test shall be performed at relative deflection, y/d calculated by:
m
y
% =
( )
d 3
m
SN
3.3.10
Formatted: Adjust space between Latin and Asian text,
𝑦𝑦
Adjust space between Asian text and numbers
(%) =
� 3
𝑑𝑑
m
𝑆𝑆𝑆𝑆
√
Formatted: Regular Italic, Font: Bold, Not Italic
3.3.10
Formatted: Regular Italic Sub, Font: Bold, Not Italic,
calculated long--term ring creep stiffness
Not Superscript/ Subscript
Sx
Formatted: Adjust space between Latin and Asian text,
calculated value of ring creep stiffness, S, at x years
Adjust space between Asian text and numbers, Tab
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
Note 1 to entry: Long-term ring creep stiffness is obtained using the following formula:
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
Formatted: where_keep-with-next, Adjust space
SS ⋅α
xx0,1 ,creep
between Latin and Asian text, Adjust space between
Asian text and numbers
𝑆𝑆 =𝑆𝑆 ⋅𝛼𝛼
𝑥𝑥 0,1 𝑥𝑥,creep
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers, Tab
where
stops: Not at 0.7 cm + 1.4 cm + 2.8 cm + 3.5 cm +
4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
x is the elapsed time as specified in this document (see 4.5),4.5), in years;
Formatted: FooterPageNumber
=
Formatted: Font: 11 pt, Bold
Formatted: Font: 11 pt, Bold
αx,creep is the creep factor at x years, determined according to ISO 10468 under wet conditions;
Formatted: Font: Bold
S0,1 is the ring stiffness at position 1 at 0,1 h.
3.3.11 3.3.11
Formatted: HeaderCentered, Left
pressure pipe
Formatted: Default Paragraph Font
pipe having a nominal pressure (3.3.13) (PN) classification greater than 1 bar and which is intended to be used
Formatted: Default Paragraph Font
with the internal pressure equal to or less than its nominal pressure when expressed in bars
Formatted: TermNum3, Adjust space between Latin
5 2
Note 1 to entry: 1 bar = = 0,1 MPa = = 10 Pa; 1 MPa = = 1 N/mm .
and Asian text, Adjust space between Asian text and
numbers
3.3.12 3.3.12
Formatted: TermNum3, Adjust space between Latin
non-pressure pipe
and Asian text, Adjust space between Asian text and
pipe subjected to an internal pressure not greater than 1 bar
numbers
5 2
Note 1 to entry: 1 bar = = 0,1 MPa = = 10 Pa; 1 MPa = = 1 N/mm .
3.3.13 3.3.13
Formatted: TermNum3, Adjust space between Latin
nominal pressur
...