The design of the lifting inserts for a specific concrete product should be documented in the precaster's technical documentation. Normally this will be part of the general design of the product, and the result shown on the production drawings. The following should be included:
description of the relevant concrete product, provided by the precaster;
description of the lifting insert, e.g. type, size, length and corresponding key;
location of the inserts in the product;
characteristic concrete compressive strength at time of lifting;
minimum edge distance and spacing;
assumed Factory Production Control requirements (including crack control);
installation instruction for the inserts and the supplementary reinforcement;
assumptions for lifting operations used in design, e.g. dynamic factors, loading angles, form friction and adhesion provided by the precaster (see Section 7);
safety concept used in design (see Annex A);
handling instructions.
11 Lifting and handling instructions
The following information should be available at the precast plant and on site for each type of precast element:
lifting keys to be used;
weight of the precast element;
permitted suspension points; if necessary balancing yoke;
permitted storage points;
allowable inclination of lifting wires;
placing and support of stacks;
maximum stacking height;
temporary supports or stabilising measures , if required;
any measures for protection, if necessary (this does not have anything to do with lifting and handling, except to prevent ice forming in lifting recesses);
allowable orientation of the element during handling.
In certain cases it might be necessary additionally to include a description of the required compensation devices (see Fig. 5.1), the transport and erection procedures and to indicate the centre of gravity.
Annex A
(informative)
Provisions for testing of inserts for specific lifting and handling
situations
A.1 Objectives
A.1.1 General
The design process for a specific lifting application can often be based on calculation models as described in this report. In some cases, however, the precaster may need to verify the load capacity of inserts used under various conditions by testing. Depending on the situation, the objectives of the test programme may vary. The aim, however, is to obtain a sound and uniform basis for the design.
This Annex describes the planning, execution and evaluation of such test programs to support design of inserts. The annex is not intended to cover the full testing program needed to support a declaration valid for a range of applications.
A.1.2 Types of objectives
The objective of these tests is to provide reliable information on the resistance properties of a particular insert for a limited area of application. The insert might be produced by a precaster for his own use or it might be an insert as part of a system.
The testing program limited to the special application may intend to confirm an existing design model, it may intend to develop a special design procedure or it may intend to determine a resistance value for the insert. Prior know-ledge should be used as far as possible, but the effect of prior knowledge depends on the circumstances.
Testing conditions should reflect the conditions within the intended range of application and this should be documented.
A.2 Specification of test specimen
A.2.1 Areas of application
A lifting insert should be tested depending on the field of its application. For example, a distinction between lifting of slabs and pipes on one side and walls and linear concrete elements such as beams and columns on the other side is generally appropriate.
The test conditions should consider:
direction of loading of the insert (tension, shear or in combination);
dimensions of the concrete member;
concrete strength at the age of lifting;
reinforcement.
A.2.2 Design of test specimen
Depending on the area of application, typical test specimen may be arranged as shown in Table A.1 and Figures A.1 to A.3.
In addition the steel resistance should be tested (if included in the calculation model).
Table A.1 — Typical test specimen simulating different areas of application Type of loading
Application of inserts in
Tension Combined tension and shear Shear
Walls and linear elements Figure A.3 Figure A.3 Figures A.3 or A. 4 Slabs and pipes Figure A.1 or
Figure A.2
Figure A.1 Figure A.4
Figure A.1 — Example of a test set-up for inserts under tension load and combined tension and shear load
Key
1 Jack 2 Pipe 3 Insert
Figure A.2 — Example of a test set-up for inserts under tension load in a pipe
a) b)
Key
1 Polystyrene 2 Edge distance
a) b) Figure A.4 — Examples of transverse shear test set-ups
A.2.3 Age of concrete specimen at testing
The specimen should be representative for the concrete product, i.e. cured and kept as the product and tested such that properties can be established for the relevant lifting situations. The precise history of the specimen should be known i.e. age, production, curing method, storage, etc.
Typically testing is performed at early age of the concrete. It should be noted that the tensile strength of the concrete develops slower than the compressive strength during the first days of hardening. Furthermore, it should be considered that temperatures due to heat of hydration may yield strength development of the test specimen different from that of the corresponding cubes or cylinders stored together with the specimen. A.2.4 Specification of inserts
The testing samples should be representative of the production of the manufacturer as applied to the precast concrete element.
The lifting inserts should be installed in accordance with the intended use.
The lifting inserts to be tested should be unambiguously identified by comparison with relevant specifications and drawings.
A.3 Loading conditions
A.3.1 Load and support conditions
After the concrete specimen has been installed, the lifting insert should be connected to the test rig by means of the lifting key intended for use in practice. If the lifting insert is part of a lifting system, the lifting insert should be tested with the appropriate lifting key. In other cases the smallest high strength hook intended to be used should be used in the tests.
The test rig should be placed such that an unrestricted concrete failure is possible. The clearance ls between
insert and support of the test set-up on the specimen to avoid an influence on the concrete break-out resistance should be at least:
in case of inserts under tension loading in general the clearance between outer perimeter of the insert and support of the test set-up ls ≥1,5⋅hef ;
in case of inserts under tension loading where other than concrete break-out failures are to be studied, the distance between support and insert may be reduced to a value of half of the insert length and the directly connected rebars;
in case of transverse shear loading ls ≥1,5⋅h , Figure A.4.b.
In a combined tension and shear test the load may be applied by either one jack acting at the specified angle to the lifting insert axis or by two jacks under servo control applying simultaneously an axial tension load and a shear load, respectively. During the test the intended angle of load application should be kept constant with a tolerance of ± 2 degrees.
A.3.2 Loading history
The insert should be loaded to failure unless the resistance of the insert is determined by attributes. The load shall be applied to the specimen according to the following procedure:
Speed of loading shall not exceed 10% of expected ultimate load per minute. In case of manual recording of test data the time includes actual time used to increase the load from one level to the next and the time spent at each load level to record displacements and to make other observations;
The loading history should start with one loading-unloading step to a small load value (5% of expected ultimate load to settle the set-up);
The loading history shall contain 5 loading-unloading sequences to service load level each sequence consisting of 5 load steps (if the stiffness or permanent deflections are part of the objectives).
A.4 Measurements
Tests should be carried out using measuring equipment for load and displacement having traceable calibration.
The load application equipment should be designed to avoid sudden increase in load especially at the beginning of the test. The measuring error of load and displacement should not exceed 3 % of measured values at ultimate load in each test.
Displacements should be recorded continuously (e.g. by means of displacement electrical transducers) with a measuring error not greater than 0,1 mm.
The displacements of the insert relative to the concrete surface at a distance of > 1.5 lain case of tension
loading and > 1,5c1 in case of shear loading from the insert should be measured in the direction of the load
application.
A.5 Test programs
A.5.1 General
The need for testing arises when prior knowledge is insufficient. It means that the need may vary from almost nothing to infinity depending on the situation. And it means that there may be more than one good solution to a given problem.
Prior knowledge may be hard core evidence like original results of earlier traceable tests. It may be state-of-the-art evaluations of test results from other sources (like the present report or design recommendations from suppliers of inserts). It may even be experience from previous successful use of an
insert. From a statistical point of view the use of these various types of prior knowledge is not necessarily unambiguous and thus the need for testing is always debatable. Furthermore, it may well be more economical to compensate for uncertain design rules by over-sizing the inserts instead of doing more testing. The following recommendations should therefore be considered as guide lines for good practice rather than legal minimum requirements.
A.5.2 Tests to verify prior knowledge
The precaster will often have a certain prior knowledge about the resistance properties of an insert to be used in a certain application. The aim of testing is to fill in the remaining gaps. The typical situations would be in a range between the following two examples:
The validity of an earlier initial type testing (ITT) is to be checked. Strong prior knowledge can be claimed and the rules given in EN 1990, Annex D.8.4 may be used requiring only a few tests;
The precaster intends to use a “home made” insert for a limited range of applications. The insert may or may not be covered by the type descriptions in clause 8. For the initial type testing (ITT) the precaster assumes that the load capacity of the insert within the application range may be calculated according to a certain calculation model. Tests are then used to verify that the assumed calculation model can be used or how the model may be improved. EN 1990, Annex D.8.2 describes the procedure and an example on the use of the procedure is given in TR 14862:2004.
The term “prior knowledge” is by nature a flexible concept. Furthermore, some of the descriptions given in EN 1990 may be interpretable so that different designers may reach different results from these procedures. It is therefore important that a clear and fair limitation on the range of applicability of the resulting calculation model is given.
A.5.3 Tests utilising no prior knowledge
A.5.3.1 Determination of properties for one insert used for specific applications
This possibility may be used successfully for ITT when an insert is to be used in a very narrow range of applications. A number of tests may be used to determine the mean value and the deviation of the resistance. The characteristic resistance may then be found using ordinary statistical methods as described in EN 1990, Annex D.7.2. Prior knowledge is not needed in this case:
The tests may be performed for only the most unfavourable situation within the range of applications in order to obtain a characteristic resistance that may then be used for the whole range;
Tests may also be performed for several situations which each represent the most unfavourable case of a group of situations within the range of applications;
In any case the testing should cover at least the most unfavourable combination of the intended lifting and handling conditions, e.g. lowest concrete strength or loading direction with the lowest expected ultimate resistance.
The method may utilise prior knowledge on the coefficient of variation, but if a larger range of applications should be covered, it would often be more economical to develop a design model according to clause A.5.2.
A.6 Assessment of the test results
A.6.1 Characteristic resistance
The evaluation of the test results should follow the procedures given in EN 1990, Annex D. The characteristic resistance is defined as the 5 %-fractile of the ultimate loads measured in a test series at a confidence level
of 75 %. In general, a normal distribution and an unknown standard deviation of the population should be assumed.
The aim of testing is normally to obtain an estimate for the characteristic resistance. The assessment will be different, however, depending on the testing program chosen in clause A.5. If a program according to A.5.2 is chosen, the result is a calculation model which predicts the characteristic resistance for a (limited) range of situations. If no prior knowledge is used the result will be a number (clause A.5.3.1) valid for one insert in one application.
A.6.2 Verification of a calculation model
A.6.2.1 Strong prior knowledge
If a calculation model is known from previous tests (including an upper bound value for the coefficient of variation) a few more tests may be used to estimate the characteristic resistance, Rk. According to EN 1990,
Annex D.8.4 the following estimate may be used, provided that each additional test result deviates less than 10 % from the mean value of the additional results:
∑
= k i k R n R η∑
∑
≤ ⋅ − i i i n R n R R 1 0,1 1 whereRi are the individual test results;
n is the number of tests and;
ηk can be taken from the following table:
Reduction factor ηηηηk
Coefficient of
variation For 1 test For 2 or 3 tests
0,05 0,80 0,90 0,11 0,70 0,80 0,17 0,60 0,70
A.6.2.2 Modification of calculation model
When testing is used to verify a calculation model the test result to be assessed is the ratio between measured and calculated values (using measured values of all parameters entering the calculation model). Ideally, this ratio should be 1,0. If the scatter on this ratio is large or even systematic the model should be modified so that the scatter is reduced. Details about the assessment may be found in EN 1990, Annex D.8.2 and in TR 14862:2004.
A.6.3 Determination of a single property
If the test program does not utilise prior knowledge (test program according to clause A.5.3.1), the test results to be evaluated are the measured values. Rules for the evaluation are given in EN 1990, Annex D.7.2. A normal distribution and an unknown standard deviation of the population may normally be assumed.
A.7 Test report
The report should include enough information to make it possible to repeat the tests. At least the following information should be available:
A.7.1 General information
Description and type of insert.
Insert identification (dimensions, materials, coating, production method).
Name and address of manufacturer.
Name and address of test laboratory.
Date of tests.
Name of person responsible for test.
Type of test (e.g. tension, shear, oblique tension, short-term or repeated load test).
Number of tests.
Test rigs, illustrated by sketches or photographs.
Particulars concerning support of test rig on the test member. A.7.2 Test members
Composition of concrete. Properties of fresh concrete (consistency, density).
Date of manufacture.
Dimensions of control specimens, and/or cores (if applicable) measured value of compression strength at the time of testing (individual results and average value).
Dimensions of test member.
Nature and positioning of any reinforcement.
Direction of casting, if horizontally or vertically. A.7.3 Installation of the insert
Information on the positioning of the insert (e.g. placed on the uncast face or cast face of the test member).
Distances of inserts from edges of test member and between adjacent inserts.
Tools employed for insert installation.
Depth of anchorage.
Quality and type of screws and nuts employed.
A.7.4 Measured values
Parameters of load application (e.g. rate of increase of load, size of load increase steps, etc.).
Displacements measured as a function of the applied load.
Any special observations concerning application of the load.
Ultimate load.
Cause(s) of rupture or failure.
Radius (maximum radius, minimum radius) and height of a concrete cone produced in the test (where applicable).
A.8 Evaluation report
The evaluated data should be reported and as a minimum requirement, the report should include at least the following information:
complete product identification, explicit installation instructions, and design data;
description of types of lifting inserts fasteners;
constituent materials of the lifting inserts;
Annex B
(informative)
Information to be given by the insert supplier
B.1 Information on the content of an operational manual
B.1.1 General technical introduction The introduction should contain the following:
a) Short description of the lifting anchor system and its components including the connection between key and lifting inserts.
b) Description of the use of the lifting system with regard to:
Storage;
assembly in formwork;
lifting and handling precast units; c) General specification:
corrosion behaviour;
type of marking and signing the system; d) General field of application:
range of concrete unit types;
load directions; e) Restrictions;
f) Compliance with Directive 98/37/EC, (Machinery Directive);
g) Short summary of the design method and assumptions used in design. B.1.2 Documentation of the lifting anchor
a) Available types, dimensions and sizes and their marking in figures and tables b) Materials
c) Information on which keys can be used, e.g. colour code for threaded systems d) The characteristic resistance of the lifting anchor itself
f) Load table, dependent of the type of key used, showing at least the insert load capacity for the minimum concrete strength in different directions
g) Required supplementary reinforcement, shape, amount, diameter, length, depending on the lifting conditions
h) Minimum dimensions of the concrete elements, spacing between anchors, edge distance, panel thickness, concrete cover
i) Analysis and hints of risk and danger j) Restrictions
k) Declaration of conformity for CE marking B.1.3 Documentation of the lifting key
The operation instruction has to fulfil the European Machinery Directive 98/37/EC. The following information should be given:
a) Available types and their marking b) Marking with identification of:
producer;
type and/or size;
maximum working load e.g. colour code for threaded systems;
fabrication number;
year of production;
c) Dimensions and sizes in figures and tables d) Materials
e) Admissible fields of application
f) Information on which inserts can be connected g) Restrictions in use and storage
h) Analysis and hints of risk and danger i) Possible consequences of misbehaviour j) Maximum working load in allowed directions k) Description of first time usage inspection l) Removal of the lifting device
lifetime definition;
description of checking;
criteria for bringing the key out of service;
necessary measure tables;
allowed and forbidden repair or maintenance work; m) Declaration of conformity for CE marking
B.1.4 Documentation of accessories a) Available types and their marking
b) Dimensions and sizes in figures and tables c) Materials
d) Description of typical application of all accessory components
for assembly/fixing anchors to formwork;
for marking and signing the system;
closing of openings;
cleaning threads;
e) Analysis and hints of risk and danger f) Restrictions
Bibliography
[1] Design of fastenings for use in concrete, CEN TS 2).
[2] Eligehausen, R.; Mallée, R.; Silva, J.F.: “Anchorage in Concrete Construction”, Ernst & Sohn, Berlin, 2006.
[3] Directive 98/37/EC, of the European Parliament and of the Council of 22 June 1998 on the approximation of the laws of the Member States relating to machinery, Official Journal of the European Communities, L 207, Vol. 41, July 1998.
2) under preparation in TC 250/SC 2
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