SIST EN 61773:1999
(Main)Overhead lines - Testing of foundations for structures
Overhead lines - Testing of foundations for structures
Is applicable to the testing procedures for foundations of overhead line structures.
Freileitungen - Prüfung von Gründungen für Bauwerke
Lignes aériennes - Essais de fondations des supports
Est applicable aux procédures d'essais pour les fondations des supports de lignes aériennes.
Nadzemni vodi - Preskusi temeljev za nosilne konstrukcije (IEC 1773:1996)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 61773:1999
01-november-1999
Nadzemni vodi - Preskusi temeljev za nosilne konstrukcije (IEC 1773:1996)
Overhead lines - Testing of foundations for structures
Freileitungen - Prüfung von Gründungen für Bauwerke
Lignes aériennes - Essais de fondations des supports
Ta slovenski standard je istoveten z: EN 61773:1996
ICS:
29.240.20 Daljnovodi Power transmission and
distribution lines
SIST EN 61773:1999 en,fr
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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NORME
CEI
INTERNATIONALE
IEC
1773
INTERNATIONAL
Première édition
STANDARD
First edition
1996-11
Lignes aériennes –
Essais de fondations des supports
Overhead lines –
Testing of foundations for structures
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For price, see current catalogue
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1773 © IEC:1996 − 3 −
CONTENTS
Page
FOREWORD . 7
Clause
1 Scope and object. 9
2 Normative references . 9
3 Definitions . 11
4 Categories of tests . 11
4.1 Design tests . 11
4.2 Proof tests. 13
5 Geotechnical data. 15
5.1 General . 15
5.2 Soil investigation results . 15
5.3 Geotechnical design parameters . 15
5.4 Soil conditions during foundation installation . 15
6 Foundation installation. 17
6.1 General . 17
6.2 Variations on foundations for design tests . 17
6.3 Installation techniques for foundations subject to design testing. 17
6.4 Installation records . 19
6.5 Minimum period of time required between installation and testing . 19
7 Test equipment. 21
7.1 Load application . 21
7.2 Test loading arrangements. 23
7.3 Reference beam – Design tests . 25
7.4 Displacement measurement devices – Design tests. 25
7.5 Displacement measurement devices – Proof tests . 27
7.6 Calibration of measuring instruments . 27
8 Test procedure . 41
8.1 Number of tests . 41
8.2 Testing of pile groups . 41
8.3 Loading procedure. 43
8.4 Test recording . 45
9 Test evaluation. 47
9.1 General . 47
9.2 Design tests . 47
9.3 Proof tests. 49
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1773 © IEC:1996 − 5 −
Clause Page
10 Acceptance criteria . 49
10.1 General. 49
10.2 Design tests . 49
10.3 Proof tests. 51
11 Test report . 51
Annexes
A Bibliography . 53
B Soil investigations. 55
C Comments on clear horizontal distance between reaction supports
and test foundation. 61
D Formats for records of installation and testing . 67
E Guidance notes for graphical determination of foundation uplift or
compression capacity . 77
F Glossary of terms and explanations . 87
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1773 © IEC:1996 − 7 −
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OVERHEAD LINES –
TESTING OF FOUNDATIONS FOR STRUCTURES
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization
comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to
promote international co-operation on all questions concerning standardization in the electrical and electronic
fields. To this end and in addition to other activities, the IEC publishes International Standards. Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt
with may participate in this preparatory work. International, governmental and non-governmental organizations
liaising with the IEC also participate in this preparation. The IEC collaborates closely with the International
Organization for Standardization (ISO) in accordance with conditions determined by agreement between the
two organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the
form of standards, technical reports or guides and they are accepted by the National Committees in that
sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the
subject of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 1773 has been prepared by IEC technical committee 11: Overhead
lines.
The text of this standard is based on the following documents:
FDIS Report on voting
11/111/FDIS 11/117/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
Annexes A, B, C, D, E and F are for information only.
The contents of the corrigendum of March 1997 have been included in this copy.
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1773 © IEC:1996 − 9 −
OVERHEAD LINES –
TESTING OF FOUNDATIONS FOR STRUCTURES
1 Scope and object
This International Standard is applicable to the testing procedures for foundations of overhead
line structures. This standard distinguishes between:
a) foundations predominantly loaded by axial forces, either in uplift or compression, acting in
the direction of the foundation central axis. This applies to foundations of rigid lattice towers
with typical individual footings, that is concrete pad and chimney foundations, steel grillages,
concrete piers, piles and grouted anchors. Guy (stay) foundations are included when they
are tested in line with their true guy inclinations;
b) foundations predominantly loaded by lateral forces, overturning moments, or a
combination of both. This applies to single poles with typical compact foundations, for
example monoblock foundations, concrete slabs, concrete piers, piles and poles directly
embedded in the ground. It may also apply to H-frame structure foundations for which the
predominant loads are lateral forces, overturning moments, or a combination of both;
c) foundations loaded by a combination of forces mentioned under a) and b).
Tests on reduced scale or model foundations are not included. However, they may be useful for
design purposes.
Dynamic foundation testing is excluded from the scope of this document.
The object of this standard is to provide procedures which apply to the investigation of the load-
carrying capacity and/or the load response (deflection or rotation) of the total foundation as an
interaction between the foundation and the surrounding soil and/or rock. The mechanical
strength of the structural components is not within the object of this standard. However, in the
case of grouted anchors, the failure of structural components, for example the bond between
anchor rod and grout, may predominate.
2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this International Standard. At the time of publication, the editions
indicated were valid. All normative documents are subject to revision, and parties to
agreements based on this International Standard are encouraged to investigate the possibility
of applying the most recent editions of the normative documents indicated below. Members of
IEC and ISO maintain registers of currently valid International Standards.
IEC 50(466): 1990, International Electrotechnical Vocabulary (IEV) – Chapter 466: Overhead
lines
IEC 826: 1991, Loading and strength of overhead transmission lines
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1773 © IEC:1996 − 11 −
3 Definitions
For the purpose of this International Standard, the following definitions apply. The definitions
listed below supplement those given in IEC 50(466).
3.1 characteristic strength: The value guaranteed in appropriate standards. This value is
also called the guaranteed strength, the minimum strength, the minimum failing load or the
nominal strength and usually corresponds to an exclusion limit, from 2 % to 5 %, with 10 %
being, in practice, the upper limit (IEC 826, 1.2.1).
3.2 damage or serviceability limit load: The load corresponding to the strength limit of the
foundation, which, if exceeded, will lead to damage and noticeable deformation or reduction in
strength of the supported structure. The damage load is normally related to displacement
criteria and may also be known as the serviceability limit load.
NOTE – When applying this standard to testing foundations which are designed using deterministic loading
criteria, reference to this term may be necessary.
3.3 design load: The limit load or factored working load or the load derived with respect to a
specific return period of a climatical event, for which the foundation has been designed.
3.4 failure load: The maximum load which can be applied during testing. It is also known as
the limit state failure load and is usually associated with displacements leading to failure of the
structure.
3.5 maximum proof load: The maximum load applied to the foundation tested during a proof
test.
3.6 test report: Final document summarizing the results of investigations and foundation
tests.
3.7 working load: The maximum load likely to be experienced by the foundation under
normal working conditions, during the life of the line, with no overload factors included.
NOTE – The term working load does not apply to limit states design methods and is not compatible with
IEC 826. However, when applying this standard to testing foundations which are designed using deterministic
loading criteria, reference to this term may be necessary.
4 Categories of tests
With respect to the purpose of the test, the level of investigation and the method of execution,
this standard refers to two categories of tests:
a) design tests;
b) proof tests.
4.1 Design tests
Design tests are normally carried out on specially installed foundations, with one or more of the
following objectives:
a) to verify design parameters or methodologies;
b) to verify construction procedures;
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1773 © IEC:1996 − 13 −
c) to establish geotechnical design parameters and/or a design methodology for a specific
application;
d) to verify compliance of foundation design with specifications;
e) to determine the average failure load and coefficient of variation of the design type in
specified soil conditions.
Tests according to c) and/or d) are also known as type tests.
4.1.1 Full scale tests
Design tests should preferably be carried out with full scale units. When tests are carried out to
verify design parameters, the test foundation shall be as identical as possible to those
proposed for production (see 6.1).
Design tests are carried out to at least the design load or to failure, especially when testing
according to 4.1 c) and/or 4.1 d), using limit state design. Limitations of displacements,
deflection or rotation under load shall be considered where applicable. The level of
instrumentation and of investigation should be appropriate for the purpose of the test.
4.1.2 Reduced scale tests
In the case of large dimension foundations, it might be impractical to undertake design tests on
a full size foundation. Design tests on smaller dimension test foundations may be considered,
subject to the following conditions:
a) the test foundation is installed using the same techniques and materials as the production
foundation;
b) where necessary, the test foundation is instrumented in such a manner that the base and
shaft resistances can be derived separately;
c) for foundation types where the capacity is determined by lateral friction, the ratio of the
test foundation lateral dimensions to the production foundation lateral dimensions is not less
than 0,5. The depths should be equal.
Evaluation of reduced scale tests shall be carried out with great caution, unless the load
capacity is based entirely on skin friction (for example piles, caissons or grouted anchors).
Great care shall be taken with area/depth ratios and their absolute values.
4.2 Proof tests
These are intended for use during the installation of production foundations to act as a check
on the quality of the installation, on the materials being used, and on the absence of any major
variations in the assumed geotechnical design parameters. Proof tests may also be carried out
on foundations installed in heterogeneous soil conditions where a wide variation in the
foundation load-resistance capacity may be expected. Consistency, speed, economy and
effectiveness are the key considerations.
Proof tests are taken to a specific percentage of the design load (usually 60 % to 75 %), as
stipulated in the contract, but may not exceed the serviceability limit load. Limitations of the
displacement shall be considered. The level of instrumentation and investigation may be low,
but the reliability of the equipment and procedure shall be high.
Dynamic testing of piles after suitable calibration of the test equipment with design tests may
also be used for proof testing.
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1773 © IEC:1996 − 15 −
Typically, proof tests are carried out on foundations installed for structures of a specific line.
The foundations shall be fully serviceable after successfully passing the tests.
5 Geotechnical data
5.1 General
An initial soil investigation should be completed prior to the selection of a design test site. A
preconstruction soil investigation may be eliminated, either where the geotechnical parameters
are based on data derived during the actual installation (for example rock anchors), or where
proof tests are used to check installation criteria. However, in this case records should be kept
of previous soil investigations and of any assumptions made prior to or during the construction
of the foundations.
Procedures for detailed soil investigations are beyond the scope of this standard. However,
some general criteria, basic requirements and methods are included in annex B. This standard
provides only general criteria for soil investigations of test sites. For details, reference should
be made to the appropriate international or national standards and/or to recognized codes of
practice (for example [1]* ).
5.2 Soil investigation results
The results of the soil investigation and any subsequent laboratory testing shall be accurately
recorded, together with a sketch map of the site showing all the pertinent physical and
geological features.
5.3 Geotechnical design parameters
The geotechnical parameters used in the design of the foundations being tested, together with
the method used to calculate these values, either from laboratory tests or from empirical
considerations, shall be recorded.
5.4 Soil conditions during foundation installation
During the installation of any test foundation, the following information shall be recorded:
a) visual description, including weathering, discontinuities, etc. of each soil/rock stratum and
corresponding soil/rock classification;
b) ground water level;
c) any local soil/rock phenomena experienced during construction, for example side
instability, bottom heave, water ingress, etc.;
d) relevant meteorological data.
If the foundations are backfilled, the physical and geotechnical properties of the backfill should
be established by using field and/or laboratory tests. Details of the method used for backfilling
and compaction should be recorded.
_________
* Figures in square brackets refer to the bibliography given in annex A.
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1773 © IEC:1996 − 17 −
6 Foundation installation
6.1 General
Proof tests are conducted on production foundations. Therefore, there should be no difference
between the foundations tested and those not subjected to tests. Design tests are generally
carried out on specially installed foundations which shall be constructed using the specified
materials, to dimensions as close as possible to those required by the design.
6.2 Variations on foundations for design tests
For design tests, the following variations may be considered:
a) The connection (for example the stub or reinforcing steel) between the foundation and
the test apparatus may require modifications to ensure adequate strength when, and if, the
foundation is stressed to loads approaching or in excess of its design load. In this case, the
connection should have a minimum strength of 1,5 times the maximum test load during the
design test. Any such modification shall not intrinsically alter the designed behaviour of the
foundation in the ground, for example the lateral stiffness of long, slender columns.
b) Due to the hip slope of the leg, production foundations might not be loaded vertically.
However, the effect of inclined loading on the foundation capacity is low when the true leg
slope is limited. Therefore, in order to ease foundation testing, the foundation may be
modified so that its test axis is vertical, and the loads may be applied vertically where the
maximum true hip slope is less than 20 % (one horizontal to five vertical, see figure 1).
True vertical
Hip slope
True horizontal
Tower leg
Figure 1 – Leg slope (hip slope) for towers
with the shape of a regular frustum or truncated cone
6.3 Installation techniques for foundations subject to design testing
It is essential that all items which will affect the strength of the test foundations, for example
method of construction and compaction of fill material, shall be equivalent to those used for the
production foundations.
The techniques used for installation of the test foundations, should, where possible, be as close
as is practical to those which are intended to be used on the production foundation.
Diagonal
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1773 © IEC:1996 − 19 −
If the foundation is set so that its top is some distance below ground level, for example a pile or
an anchor set into the base of a buried cap, but the test foundation is extended to the ground
surface for ease of testing, then the extended portion of the foundation shall be sleeved, or
other precautions taken, to reduce the interaction between foundation and soil over the
extended portion.
6.4 Installation records
In the case of foundations for design testing, all relevant details of foundation size, construction
and installation shall be recorded. These records shall contain details relating both to design
requirements for the foundation and to the actual data for the as-built test foundation (typical
record formats are given in annex D).
Full details of soil conditions, description of excavation walls, quality, quantity, and method of
backfilling, compaction, etc., as required in 5.4, shall be recorded.
All details shall also be accurately recorded on an appropriate sketch.
For proof testing of production foundations, it is recommended that the record formats given in
annex D be used. These formats may be simplified, depending on the type of foundation and
test.
6.5 Minimum period of time required between installation and testing
A sufficient period of time shall elapse between the installation of the foundation and the
beginning of testing, to ensure adequate strength of concrete or grout, and to permit
reasonable relaxation of the strength-related properties of the soil, such as dissipation of pore
pressures.
Minimum time periods between installation and testing are:
Days
– steel grillage (from completion of backfill) 1
– concrete components of a foundation (see note) − reinforced 14
− unreinforced 28
– grouted anchors (see note) (after grouting, depending on grout strength) 7 to 14
– prefabricated piles driven in non-cohesive or free-draining soils
(after driving) 7
– prefabricated piles driven in cohesive soils (after driving) 21
– concrete piles augered or drilled and cast in situ 14
NOTE – A shorter time may be allowed if the concrete/grout sample strength tests have reached a value of not
less than twice the maximum bearing stress to be imposed during the test. Testing of stressed anchors may be
performed immediately after tensioning.
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1773 © IEC:1996 − 21 −
7 Test equipment
7.1 Load application
The load application mechanism shall be able to mobilize the foundation capacity, or overcome
the deflection design criteria, or both. Loading arrangements should, if possible, apply axial and
shear loads simultaneously where lateral loading is likely to have a significant influence on
foundation capacity.
Loads may be applied by a hydraulic jack, a winch system, or another loading mechanism, as
required. Motorized pumps should only be used preferably when automatic logging of
foundation movement is available. The ability to maintain load can lead to sudden and rapid
failure with little warning. If using motorized pumps or loading devices, a suitable control
system shall be used to avoid over-riding the load envisaged.
If loads are applied by hydraulic jack, the jack shall have a stroke able to mobilize the
foundation capacity, or overcome the deflection design criteria, or both. If the jack is unable to
produce such movement, the test procedure shall allow for adjustments of the loading system.
The hydraulic jack shall have a reasonably safe capacity, that is not less than 25 % but
preferably 50 % in excess of the expected maximum test load for design tests, and 10 % to
25 % respectively for proof tests.
Both the jack and the hydraulic pressure gauge shall be calibrated as a single unit, together
with a record of the pressure applied to the jack, and an independent measurement of the load.
Any winch or other mechanism used to apply load shall have a reasonably safe capacity, using
the same guidelines as for a hydraulic jack. For ropes under tension, their ultimate tensile
strength (UTS) shall be not less than three times the maximum load.
The loads applied to the test foundation may be measured by load cells, by the pressure gauge
on a calibrated hydraulic jack, by dynamometers installed on the winch line, or by another
acceptable apparatus. For design tests, a back-up system is recommended, for example load
cells and pressure gauge. Accuracy of measurement shall be within 5 % (preferably 1 %) of the
maximum test load. It is recommended that the load measuring device be installed as close as
possible to the load application point.
All equipment operating under hydraulic pressure including the hydraulic jack shall be capable
of withstanding, without leaking, a pressure of a minimum of 1,5 times, but preferably 2,0 times,
the equivalent maximum load expected in the test.
The loading mechanism (bearing plates, struts or blocks, etc.) shall possess an adequate
structural stiffness, and a minimum ultimate design capacity equivalent to 1,5 times the
maximum applied test load.
All test equipment shall be installed in such a manner that no individual or cumulative
component failure can cause a hazard to any person working on the site. All works shall be
conducted in accordance with the appropriate safety codes and national standards.
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1773 © IEC:1996 − 23 −
7.2 Test loading arrangements
7.2.1 Axially-loaded foundations
Test loads can be applied by the following means:
– test loading beam and supports (see figure 3);
– fulcrum beam arrangement (see figure 4);
– A-frame (see figure 5);
– hydraulically operated crane (uplift tests).
In the case of compression tests, the reaction can be transferred to the subsoil by tension piles
or ground anchors.
The minimum clear distance (L) between reaction supports (see figure 3) should be chosen
carefully to prevent any influence on the behaviour of the foundation. This distance should be
increased if advisable due to the expected failure mode, and if suitable test equipment is
available. Suggested minimum distances for proof tests (see figure 2 for meaning of symbols)
are given by:
a) pad and chimney, grillages, concrete block foundations, or buried anchors:
L = e + 0,7 × a (m)
where
e is the width of foundation in metres;
a is the depth of foundation in metres;
L is the distance between nearest points of reaction supports.
b) for concrete piers, driven piles, drilled and grouted piles, or helix anchors:
L = 3 × e (m) or 2 (m), whichever is greater.
In the case of design tests, it is advisable to increase these distances. Annex C discusses basic
considerations for establishing minimum clear distances between reaction supports.
7.2.2 Laterally loaded foundations, foundations under overturning moments
Lateral test loads can be applied directly to foundations by the following means:
– hydraulic jack and reaction foundation (see figures 6 a and 6 b);
– hydraulic
...
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