ISO 1288-2:2016

DRAFT INTERNATIONAL STANDARD
ISO/DIS 1288-2
ISO/TC 160/SC 2 Secretariat: ANSI
Voting begins on: Voting terminates on:
2014-01-09 2014-06-09
Glass in building — Determination of the bending strength
of glass —
Part 2:
Coaxial double-ring test on flat specimens with large test
surface areas
Verre dans la construction — Détermination de la résistance du verre à la flexion —
Partie 2: Essais avec doubles anneaux concentriques sur éprouvettes planes, avec de grandes surfaces de
sollicitation
ICS: 81.040.20
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formal vote in CEN.
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THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
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ISO/DIS 1288-2:2013(E)
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 SUPPORTING DOCUMENTATION. ISO 2013

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ISO/DIS 1288-2:2013(E)

Copyright notice
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ii © ISO 2013 – All rights reserved

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FDIS 1288-2
Contents
Foreword
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols (and abbreviated terms) . 2
5 Principle of test method . 3
6 Apparatus . 3
6.1 Testing machine . 3
6.2 Loading device . 6
6.3 Measuring instruments . 6
7 Sample . 6
7.1 Shape and dimensions of the specimens . 6
7.2 Sampling and preparation of specimens . 7
7.3 Number of specimens . 7
8 Procedure . 7
8.1 Temperature . 7
8.2 Humidity . 7
8.3 Thickness measurement . 7
8.4 Base plate . 8
8.5 Positioning of specimen and loading ring . 8
8.6 Load application . 8
8.7 Loading rate . 8
8.8 Location of the origin . 9
8.9 Assessment of residual stresses . 9
9 Evaluation . 9
9.1 Limitation of the evaluation . 9
9.2 Calculation of bending strength . 9
10 Test report . 11
Annex A (informative) Example of a device for keeping the gas pressure, p, in line with the piston
force, F . 13
Bibliography . 16

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FDIS 1288-2
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 3.
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 part of ISO 1288 may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 1288-2 was prepared by Technical Committee ISO/TC 160, Glass in building,
Subcommittee SC 2, Use considerations
ISO 1288 consists of the following parts, under the general title Glass in building — Determination of the bending
strength of glass:
 Part 1: Fundamentals of testing glass
 Part 2: Coaxial double ring test on flat specimens with large test surface areas
 Part 3: Test with specimen supported at two points (four point bending)
 Part 4: Testing of channel shaped glass
 Part 5: Coaxial double ring test on flat specimens with small test surface areas
This Standard has been based on EN 1288-2 Glass in building - Determination of the bending strength of glass" -
Part 2 : Coaxial double ring test on flat specimens with large test surface areas prepared by Technical Committee
CEN/TC 129 "Glass in building"/WG8 "Mechanical Strength".
According to the CEN/CENELEC Internal Regulations, the national standards organisations of the following
countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,
France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden,
Switzerland and the United Kingdom.

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FDIS prEN/ISO 1288-2

Glass in building — Determination of the bending strength of
glass — Part 2: Coaxial double ring test on flat specimens with
large test surface areas
1 Scope
This International Standard specifies a method for determining the bending strength of glass for use in buildings,
excluding the effects of the edges.
The limitations of this part of this International Standard are described in ISO 1288-1.
ISO 1288-1 should be read in conjunction with this part of this International Standard.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this part of ISO 1288. For dated references, subsequent amendments to, or revisions of, any of these publications
do not apply. However, parties to agreements based on this part of ISO 1288 are encouraged to investigate the
possibility of applying the most recent editions of the normative documents indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain
registers of currently valid International Standards.
ISO 1288-1, Glass in building - Determination of the bending strength of glass - Part 1 : Fundamentals of
ISO 16293-1: Glass in building – Basic soda lime silicate glass products – Part 1: Definitions and general physical
and mechanical properties
ISO 48, Rubber, vulcanised or thermoplastic - Determination of hardness (hardness between 10 IRHD and 100
IRHD)
3 Terms and definitions
For the purposes of this part of ISO 1288, the following terms and definitions apply.
3.1
bending stress
the tensile bending stress induced in the surface of a specimen
NOTE For testing purposes, the bending stress should be uniform over a specified part of the surface.
3.2
effective bending stress
a weighted average of the tensile bending stresses, calculated by applying a factor to take into account
non-uniformity of the stress field
3.3
bending strength
the tensile bending stress or effective bending stress which leads to breakage of the specimen
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FDIS 1288-2
3.4
equivalent bending strength
the apparent bending strength of patterned glass, for which the irregularities in the thickness do not allow precise
calculation of the bending stress
4 Symbols (and abbreviated terms)
2
A Effective surface area of quasi-uniform stress m
E
Modulus of elasticity (Young's modulus) of the specimen. Pa
NOTE for soda lime silicate glass (see EN 572-1) a value of 70 GPa is used.
F
Piston force N
F Piston force upon breakage, "breaking force" N
max
F Force transmitted by the loading ring to the specimen, "ring load" N
ring
h Thickness or average thickness of specimen m
L Side length of the square specimens m
Poisson number of specimen
µ
NOTE for soda lime silicate glass (see EN 572-1) a value of 0,23 is used.
p Gas pressure on the surface area defined by the loading ring Pa
p(F) Nominal gas pressure as a function of the piston force Pa
p (F ) Nominal gas pressure upon breakage Pa
max max
r
Location co-ordinate m
r Radius of loading ring m
1
r Radius of supporting ring m
2
r Average specimen radius (for evaluation) m
3m
Stress Pa
σ
Bending strength Pa
σ
bB
Equivalent bending strength Pa
σ
beqB
t Time s
Rate at which piston force rises N/s
∆F/∆t

F*,p*,σ* Non-dimensional quantities corresponding to F, p and σ (see equations (1) to (5))
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FDIS 1288-2
5 Principle of test method
The square specimen, of side length, L, and having virtually plain parallel surfaces, is placed loosely on a
supporting ring (a circular ring with a radius r ). The specimen is subjected to a load, F , by means of a loading
2 ring
ring (radius r ), which is arranged concentrically to the supporting ring. In addition, the area, A, defined by the
1
loading ring 0 < r < r is placed under gas pressure, p, which has a specific relationship with the ring load, F
1 ring
(see figure 1).
When the specimen is subjected to the ring load and the associated gas pressure, depending upon the dimensions
r , r , L, and h, a radial tensile stress field, which is sufficiently homogeneous for the test purpose, is developed on
1 2
the convexly bent surface over the area defined by the loading ring (see [1], [2], [3] of annex B). The tangential
tensile stress is equal to the radial tensile stress at the central point (r=0) of the specimen, but decreases as the
radius, r, increases.
Outside the loading ring, the radial and tangential stresses fall sharply towards the edge of the specimen, so that
the risk of breakage outside the loading ring is low. On the edge of the specimen itself, the radial stress is zero and
the tangential stress is a compressive stress, this being the case on both the concavely and the convexly bent
sides of the specimen.  The edge of the specimen is thus always under tangential compressive stress (see ISO
1288-1).
By increasing the force, F, and the gas pressure, p, the tensile stress in the central part of the specimen is
increased at a constant rate (see (6.1b)) until breakage, so the origin of the break can be expected to occur in the
surface area subjected to maximum tensile stress within the loading ring.
NOTE With the test apparatus as shown in figure 1, a force, pA, acts against the piston force, F, due to the gas pressure,
p. The force transferred by the loading ring is F = F - pA. Thus a distinction should be made between the piston force and
ring
the ring load.
The bending strength, σ , or equivalent bending strength, σ , is calculated from the maximum value, F , of
bB beqB max
the piston force, measured at the time of breakage, and the thickness, h, of the specimen, taking into account the
prescribed dimensions of the specimen and various characteristic material values. This assumes that the gas
pressure, p, follows the piston force, F, according to the nominal function p(F), (see figure 3).
6 Apparatus
6.1 Testing machine
The bending test shall be carried out using a suitable bending testing machine, which shall incorporate the
following features:
a) The stressing of the specimen shall be capable of being applied from zero up to a maximum value in a manner
which minimizes shock and is stepless;
b) The stressing device shall be capable of the specified rate of stressing;
c) The testing machine shall incorporate a load measuring device with a limit of error of ± 2,0 % within the
measuring range.
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FDIS 1288-2

r
1
p
F
1
2
h
r
3
2
L/2
1: Loading ring
2: Specimen
3: Supporting ring
Figure 1 — Basic diagram of test apparatus
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FDIS 1288-2
p
F
4
5
6
1
8
7
3
7
2
9
r
r
1
2
L/2


1 Specimen
(1)
2 Rigid base plate, preferably made of steel, with supporting ring (radius r ).
2
3 Rubber profile, adapted to the supporting ring, 3 mm thick, with a hardness (40 ± 10) IRHD (in accordance with
ISO 48).
(1)
4 Rigid loading ring (radius r ), preferably made of steel.
1
5 Force transmitting component, with a ball mechanism to ensure the force is centred in the loading ring.
6 Rubber profile, adapted to the loading ring, 3 mm thick with a hardness (40 ± 10) IRHD (in accordance with
(2)
ISO 48).
(3)
7 Adjustment jaws for centring the specimen.
8 Contact circle of the loading ring
9 Contact circle of the supporting ring
NOTE 1 The radius of curvature of the bearing surface of the ring is 5 mm.
NOTE 2 In the case of specimens which are patterned on the loading ring side, a sponge rubber profile approximately 5 mm
thick should also be used to ensure an adequate seal for the gas pressure.
NOTE 3 The jaws are removed before the bending test is started, in order that the edge of the specimen is not clamped.
Figure 2 — Loading device
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FDIS 1288-2
6.2 Loading device
6.2.1 Ring load
The ring load shal
...