ISO 10471:2018

Glass-reinforced thermosetting plastics (GRP) pipes - Determination of the long-term ultimate bending strain and the long-term ultimate relative ring deflection under wet conditions

This document specifies a method for determining by extrapolation the long-term ultimate ring bending strain and the calculation of the long-term ultimate relative ring deflection of glass-reinforced thermosetting plastics (GRP) pipes, under wet conditions. Two methods of loading are given, one using plates the other beam bars.

Tubes en plastiques thermodurcissables renforcés de verre (PRV) — Détermination de l'effort à la flexion ultime à long terme et réflexion annulaire relative ultime à long terme dans des conditions mouillées

General Information

• Status: Published
• Publication Date: 16-May-2018
• ICS: 23.040.20 - Plastics pipes
• Technical Committee: ISO/TC 138/SC 6 - Reinforced plastics pipes and fittings for all applications
• Drafting Committee: ISO/TC 138/SC 6/WG 1 - Methods of test
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 27-Aug-2025
• Completion Date: 13-Dec-2025

Relations

• Revised: ISO 10471:2025 - Glass-reinforced thermosetting plastics (GRP) pipes - Determination of the long-term ultimate bending strain and the long-term ultimate relative ring deflection under wet conditions
• Effective Date: 28-Oct-2023
• Revises: ISO 10471:2003/Amd 1:2010 - Glass-reinforced thermosetting plastics (GRP) pipes - Determination of the long-term ultimate bending strain and the long-term ultimate relative ring deflection under wet conditions - Amendment 1
• Effective Date: 05-Nov-2015
• Revises: ISO 10471:2003 - Glass-reinforced thermosetting plastics (GRP) pipes - Determination of the long-term ultimate bending strain and the long-term ultimate relative ring deflection under wet conditions
• Effective Date: 04-Nov-2015

Overview

ISO 10471:2018 specifies a laboratory test method to determine, by extrapolation, the long‑term ultimate bending strain and the long‑term ultimate relative ring deflection of glass‑reinforced thermosetting plastics (GRP) pipes under wet conditions. The procedure immerses horizontally supported pipe test pieces in water, applies a constant diametral compressive load and records progressive ring deflection until failure. Results are converted to bending strain and extrapolated to an agreed service life using regression procedures.

Key topics and requirements

• Scope: Long‑term ultimate ring bending strain and relative ring deflection of GRP pipes under wet conditions; two loading methods are allowed - bearing plates or beam bars.
• Test principle: Constant vertical compressive force applied while the pipe is immersed; measure vertical deflection vs time until structural failure.
• Loading surfaces:
  • Plates: minimum width 100 mm, length at least equal to test piece; used for deflections up to ~28%.
  • Beam bars: flat face width 15–55 mm, required when deflection is expected to exceed 28% (at least one beam bar must be used).
• Measurements and instrumentation:
  • Vertical deflection monitoring; waterproofed strain gauges may be used to measure bending strain directly.
  • For accurate failure times and deflections, automatic recording is recommended for short‑life, high‑force tests.
• Data processing:
  • Convert ultimate relative vertical deflection (y/dm) to ultimate bending strain using the strain factor and appropriate formulae for crown/invert or spring‑line failures.
  • Use regression and extrapolation procedures (see ISO 10928) to determine long‑term values at a specified time x.
• Test parameters to be specified by referring standard: extrapolation time x, test temperature, number and length of test pieces, water pH and distribution of times to failure.
• Reporting: Test report must include loading method, dimensions, test conditions, failure mode and extrapolated long‑term strain/deflection results.

Applications and users

• Manufacturers of GRP pipes for wastewater, drainage and buried applications use ISO 10471:2018 for product development and qualification.
• Independent testing laboratories and quality assurance departments apply the method to demonstrate long‑term mechanical performance in wet service conditions.
• Specifiers, engineers and regulators use the results for structural design inputs, service life assessments and compliance with product standards.
• Useful where long‑term bending performance and ring stiffness degradation in wet environments are critical to safety and durability.

Related standards

• ISO 10928 - regression analysis and extrapolation methods for long‑term properties.
• ISO 7685 - determination of initial specific ring stiffness for GRP pipes.
• ISO 3126 - measurement of pipe dimensions.

Keywords: ISO 10471:2018, GRP pipes, glass‑reinforced thermosetting plastics, long‑term bending strain, ring deflection, wet conditions, test method, beam bars, bearing plates, ISO 10928.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 10471
Second edition
2018-05
Glass-reinforced thermosetting
plastics (GRP) pipes — Determination
of the long-term ultimate bending
strain and the long-term ultimate
relative ring deflection under wet
conditions
Tubes en plastiques thermodurcissables renforcés de verre (PRV) —
Détermination de l'effort à la flexion ultime à long terme et réflexion
annulaire relative ultime à long terme dans des conditions mouillées
Reference number
©
ISO 2018
© ISO 2018
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: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
5 Apparatus . 5
5.1 Compressive loading machine . 5
5.2 Force application surfaces . 5
5.2.1 General arrangement . 5
5.2.2 Plates . 5
5.2.3 Beam bars . 5
5.3 Water container. 5
5.4 Measuring devices. 6
6 Test piece . 7
7 Number of test pieces . 7
8 Determination of the dimensions of the test piece . 7
8.1 Length . 7
8.2 Wall thickness . 7
8.3 Mean diameter . 7
9 Conditioning . 7
10 Procedure. 7
11 Calculation . 8
11.1 Extrapolation of the strain data to obtain the x-year value, ε . . 8
x, wet
11.2 Calculation of the long-term ultimate relative ring deflection under wet conditions,
y /d . 9
u, wet, x m
12 Test report . 9
Annex A (informative) Equal increments of lg (time in h) .10
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 documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on 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 the following
URL: 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 10471:2003), which has been technically
revised. It also incorporates the Amendment ISO 10471:2003/Amd1: 2010.
The major changes to this edition include:
— reference to ISO 3126 for dimension measurement;
— clarification of accuracy statements;
— inclusion of calculation procedure for spring-line failures.
iv © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 10471:2018(E)
Glass-reinforced thermosetting plastics (GRP) pipes —
Determination of the long-term ultimate bending strain
and the long-term ultimate relative ring deflection under
wet conditions
1 Scope
This document specifies a method for determining by extrapolation the long-term ultimate ring
bending strain and the calculation of the long-term ultimate relative ring deflection of glass-reinforced
thermosetting plastics (GRP) pipes, under wet conditions.
Two methods of loading are given, one using plates the other beam bars.
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 3126, Plastics piping systems — Plastics components — Determination of dimensions
ISO 7685, Plastics piping systems — Glass-reinforced thermosetting plastics (GRP) pipes — Determination
of initial specific ring stiffness
ISO 10928, Plastics piping systems — Glass-reinforced thermosetting plastics (GRP) pipes and fittings —
Methods for regression analysis and their use
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http: //www .electropedia .org/
— ISO Online browsing platform: available at https: //www .iso .org/obp
3.1
vertical compressive force
F
vertical force, applied to a horizontal pipe to cause a vertical deflection
Note 1 to entry: Vertical compressive force is expressed in newtons.
3.2
mean diameter
d
m
diameter of the circle corresponding with the middle of the pipe wall cross-section and given by either
of the following formulae:
dd=+e
mi
dd=−e
me
where
d is the internal diameter, in metres (m);
i
d is the external diameter, in metres (m);
e
e is the wall thickness of the pipe, in metres (m).
Note 1 to entry: Mean diameter is expressed in metres.
3.3
vertical deflection
y
vertical change in diameter of a pipe in a horizontal position in response to a vertical compressive
force (3.1)
Note 1 to entry: Vertical deflection is expressed in metres.
3.4
relative vertical deflection
y/d
m
ratio of the vertical deflection, y (3.3), to the mean diameter (3.2) of the pipe, d
m
3.5
ultimate vertical deflection under wet conditions
y
u, wet
vertical deflection (3.3) of the pipe, y, when failure occurs under wet conditions (see Clause 4)
Note 1 to entry: Ultimate vertical deflection under wet conditions is expressed in metres.
3.6
ultimate relative vertical deflection under wet conditions
y /d
u, wet m
ratio of the ultimate vertical deflection under wet conditions, y (3.5), to the mean diameter (3.2) of
u, wet
the pipe, d
m
3.7
long-term ultimate ring deflection under wet conditions
y
u, wet, x
extrapolated value of the ultimate vertical deflection under wet conditions (3.5) of the pipe, y , when
u, wet
failure is expected to occur at a time, x, specified in the referring standard
Note 1 to entry: Long-term ultimate ring deflection under wet conditions is expressed in metres.
3.8
long-term ultimate relative ring deflection under wet conditions
y /d
u, wet, x m
ratio of the long-term ultimate ring deflection under wet conditions (3.7) of the pipe, y , to the mean
u, wet, x
diameter (3.2) of the pipe, d
m
3.9
failure
loss of the structural integrity of a test piece as evidenced by the inability of the test piece to carry the load
2 © ISO 2018 – All rights reserved

3.10
time to failure
t
u
time elapsed until failure (3.9) occurs
Note 1 to entry: Time to failure is expressed in hours.
3.11
specific ring stiffness
S
physical characteristic of a pipe, that is a measure of the resistance to ring deflection per metre length
under external load and is defined by the following formulae
EI×
S =
d
m
where
E is the apparent modulus of elasticity, in newtons per square metre, determined by testing in
accordance with ISO 7685;
I is the second moment of area in the longitudinal direction per metre length, in metres to the
fourth power per metre (m /m), i.e.
e
I=
where
e is the wall thickness of the pipe, in metres (m);
d is the mean diameter of the pipe, in metres (m) (see 3.2).
m
Note 1 to entry: Specific ring stiffness is expressed in newtons per square metre.
3.12
initial specific ring stiffness
S
value of specific ring stiffness S (3.11), determined by testing in accordance with ISO 7685
Note 1 to entry: Initial specific ring stiffness is expressed in newtons per square metre.
3.13
strain factor
D
g
dimensionless factor used to transform a deflection value into a strain value
4 Principle
Each of several cut lengths of pipe is supported horizontally and loaded throughout its length to
compress it diametrically to achieve a desired level of strain. The force application surfaces are either
bearing plates or beam bars.
The pipe is immersed in water at a given temperature for a period of time during which the force remains
constant and the increasing vertical deflection is measured at intervals until failure (see 3.9) occurs.
The relative vertical deflection at failure [ultimate relative vertical deflection, y /d (see 3.6)] is
u, wet m
converted into a bending strain at failure (ultimate bending strain, ε , in percent), either calculated
u, wet
using Formula (1) or determined from a strain-deflection calibration curve (see 10.3).
The strain may also be measured directly by the use of waterproofed strain gauges.
The following strain calculations assume that the neutral axis is at the pipe wall midpoint. For pipe
wall constructions that produce an altered neutral axis position, it is necessary to evaluate results by
substituting 2ȳ for the wall thickness e where ȳ is the distance from the appropriate pipe surface to the
neutral axis. The neutral axis position shall be determined using an appropriate method, e.g. calculation
or use of strain gauge couples.
y
e
u,wet
ε =×D ××100 (1)
u,wetg
d d
m m
where for crown or invert failures:
D is calculated using Formula (2)
...