ISO 10468:2003

INTERNATIONAL ISO
STANDARD 10468
First edition
2003-12-01


Glass-reinforced thermosetting plastics
(GRP) pipes — Determination of the
long-term specific ring creep stiffness
under wet conditions and calculation of
the wet creep factor
Tubes en plastiques thermodurcissables renforcés de verre (PRV) —
Détermination de la rigidité annulaire spécifique à long terme en fluage
en conditions mouillées et calcul du facteur de fluage mouillé




Reference number
ISO 10468:2003(E)
©
ISO 2003

---------------------- Page: 1 ----------------------
ISO 10468:2003(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.


©  ISO 2003
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland

ii © ISO 2003 — All rights reserved

---------------------- Page: 2 ----------------------
ISO 10468:2003(E)
Contents Page
Foreword. iv
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 1
4 Principle. 4
5 Apparatus. 4
5.1 Compressive loading machine . 4
5.2 Force application surfaces. 4
5.3 Water container. 5
5.4 Measuring devices. 5
6 Test piece. 5
7 Number of test pieces. 6
8 Determination of the dimensions of the test pieces . 6
8.1 Length. 6
8.2 Wall thickness. 7
8.3 Mean diameter. 7
9 Conditioning. 7
10 Procedure. 7
11 Calculation. 8
11.1 Extrapolation of the deflection data. 8
11.2 Calculation of the long-term specific ring creep stiffness under wet conditions for
position 1 . 8
11.3 Calculation of the wet creep factor . 8
12 Test report. 8
Annex A (informative) Equal increments of lg(time in h) . 10

© ISO 2003 — All rights reserved iii

---------------------- Page: 3 ----------------------
ISO 10468:2003(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 10468 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.

iv © ISO 2003 — All rights reserved

---------------------- Page: 4 ----------------------
INTERNATIONAL STANDARD ISO 10468:2003(E)

Glass-reinforced thermosetting plastics (GRP) pipes —
Determination of the long-term specific ring creep stiffness
under wet conditions and calculation of the wet creep factor
1 Scope
This International Standard specifies a method for determining both the long-term specific ring creep stiffness
and the wet creep factor for glass-reinforced thermosetting plastics (GRP) pipes.
2 Normative references
The following referenced documents are indispensable for the application 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 7685:1998, Plastics piping systems — Glass-reinforced thermosetting plastics (GRP) pipes —
Determination of initial specific ring stiffness
ISO 10928:1997, 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.
3.1
vertical compressive force
F
vertical force, expressed in newtons, applied to a horizontal pipe to cause a vertical deflection
3.2
specific ring stiffness
S
physical characteristic of a pipe, expressed in newtons per square metre, that is a measure of the resistance
to ring deflection per metre length under external load and is defined by Equation (1):
E× I
S= (1)
3
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
4
power per metre (m /m), i.e.
3
e
I= (2)
12
© ISO 2003 — All rights reserved 1

---------------------- Page: 5 ----------------------
ISO 10468:2003(E)
e being the wall thickness of the pipe, in metres;
d is the mean diameter of the pipe, in metres (see 3.3).
m
3.3
mean diameter
d
m
diameter, expressed in metres, of the circle corresponding with the middle of the pipe wall cross-section and
given by either of the following equations:
dd=+e (3)
mi
dd=−e (4)
me
where
d is the internal diameter, in metres;
i
d is the external diameter, in metres;
e
e is the wall thickness of the pipe, in metres.
3.4
initial specific ring stiffness
S
0
value of S, expressed in newtons per square metre, determined by testing in accordance with ISO 7685
3.5
long-term specific ring creep stiffness at position 1
S
x, 1, creep, wet
value of S, expressed in newtons per square metre, at a reference position, position 1 (see 10.2), at x years,
obtained by extrapolation of long-term stiffness measurements at a constant force under wet conditions
(see 3.2 and 10.2)
3.6
calculated long-term specific ring creep stiffness under wet conditions
S
x, creep, wet
calculated value of S, expressed in newtons per square metre, at x years obtained using Equation (5):
SS=×α (5)
xx, creep, wet 0 , creep, wet
where
x is the elapsed time, in years, specified in the referring standard;
α is the wet creep factor (see 3.7);
x, creep, wet
S is the initial specific ring stiffness, in newtons per square metre.
0
3.7
wet creep factor
α
x, creep, wet
ratio of the long-term specific ring creep stiffness to the initial specific ring stiffness, both at a reference
position, position 1 (see 10.2), and given by Equation (6):
S
x,1, creep,wet
α = (6)
x, creep, wet
S
0, 1
2 © ISO 2003 — All rights reserved

---------------------- Page: 6 ----------------------
ISO 10468:2003(E)
where
S is the initial specific ring stiffness at position 1, in newtons per square metre, determined
0, 1
in accordance with ISO 7685;
S is the long-term specific ring creep stiffness at position 1, in newtons per square metre.
x, 1, creep, wet
3.8
vertical deflection
y
vertical change in diameter of a pipe in a horizontal position, expressed in metres, in response to a vertical
compressive force (see 3.1)
3.9
long-term vertical deflection
y
x, 1, wet
value of the vertical deflection y, expressed in metres, at the reference position, position 1 (see 10.2), at
x years under wet conditions
3.10
deflection coefficient
f
dimensionless factor which takes into account general second-order theory as applied to deflection and is
given by Equation (7):
−5
fy=+1860 2 500× /d×10 (7)
()
1m

where
y is the long-term vertical deflection at position 1, in metres;
1
d is the mean diameter (see 3.3) of the pipe, in metres.
m
3.11
calculated strain
ε
calc, 1
strain on the inner surface at the crown and invert of a pipe at the reference position, position 1, given in
percent by Equation (8):
e y
1
4,28×× ×100
dd
mm
ε = (8)
calc,1
2

y
1
1+

2× d
m
where
y is the vertical deflection at position 1, in metres;
1
d is the mean diameter of the pipe (see 3.3), in metres;
m
e is the wall thickness of the pipe, in metres.
© ISO 2003 — All rights reserved 3

---------------------- Page: 7 ----------------------
ISO 10468:2003(E)
4 Principle
A cut length of pipe supported horizontally is loaded throughout its length to compress it diametrically to a
prescribed level of strain calculated using Equation 8. 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 vertical deflection is measured at intervals. The long-term specific ring creep stiffness is
estimated by extrapolation.
The wet creep factor is then determined from the long-term specific ring creep stiffness and the initial specific
ring stiffness of the same test piece. The declared wet creep factor is the average of the results from two test
pieces.
NOTE It is assumed that values for the following test parameters will be set by the standard making reference to this
International Standard:
a) the method for measuring the initial specific ring stiffness, i.e. method A or B of ISO 7685:1998 (see 3.4);
...