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BSIConcrete Elements

ICS 91.100.30Design and Use of Inserts for Lifting andHandling of Precast PUBLISHED DOCUMENT PD CEN/TR 15728:2008

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BSIThis Published Document was published under the authority of the Standards Policy and Strategy Committee on 31 October 2008

BSI 2008

ISBN 978 0 580 60274 0Amendments/corrigenda issued since publication

Date Comments008

National foreword

This Published Document is the UK implementation of CEN/TR 15728:2008. The UK participation in its preparation was entrusted to Technical Committee B/524, Precast concrete products.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.

TECHNICAL REPORTRAPPORT TECHNIQUETECHNISCHER BERICHT

CEN/TR 15728

May 2008

ICS 91.100.30

English Version

Design and Use of Inserts for Lifting and Handling of PrecastConcrete - Elements

Conception et utilisation d'inserts pour le levage et lamanutention du bton prfabriqu - lments

Bemessung und Verwendung von Transportankern frBetonfertigteile

This Technical Report was approved by CEN on 2 March 2008. It has been drawn up by the Technical Committee CEN/TC 229.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATIONC O M I T E U R O P E N D E N O R M A LI S A T I O NEUR OP IS C HES KOM ITEE FR NOR M UNG

Management Centre: rue de Stassart, 36 B-1050 Brussels

2008 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.

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Contents Page

Foreword..............................................................................................................................................................3

1 Scope ......................................................................................................................................................4 1.1 Scope / General......................................................................................................................................4 1.2 Types of inserts for lifting and handling .............................................................................................4 1.3 Minimum dimensions ............................................................................................................................4 2 Normative references ............................................................................................................................5 3 Definitions and symbols .......................................................................................................................5 3.1 Definitions ..............................................................................................................................................5 3.2 Symbols ..................................................................................................................................................7 4 General design principles.....................................................................................................................8 4.1 General principles..................................................................................................................................8 4.2 Partial factors .........................................................................................................................................8 5 Actions on inserts..................................................................................................................................9 5.1 Actions....................................................................................................................................................9 5.2 Effect of lifting procedures on load directions...................................................................................9 5.3 Actions from adhesion and form friction ..........................................................................................11 5.4 Dynamic actions ..................................................................................................................................12 6 Choice of inserts..................................................................................................................................12 7 Use of Suppliers recommendations .................................................................................................13 8 Use of CEN/TC 229 recommendations for typical user situations .................................................14 8.1 General conditions ..............................................................................................................................14 8.2 Types of inserts covered ....................................................................................................................17 8.3 Lifting of walls and linear elements ...................................................................................................21 8.4 Lifting of slabs and pipes ...................................................................................................................32 9 Precaster use of testing ......................................................................................................................36 10 Recommended technical documentation .........................................................................................36 10.1 General..................................................................................................................................................36 10.2 Properties of inserts ............................................................................................................................36 10.3 Design of specific lifting application .................................................................................................37 11 Lifting and handling instructions.......................................................................................................37 Annex A (informative) Provisions for testing of inserts for specific lifting and handling situations .....39 Annex B (informative) Information to be given by the insert supplier.......................................................48 Bibliography ......................................................................................................................................................51

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Foreword

This document (CEN/TR 15728:2008) has been prepared by Technical Committee CEN/TC 229 Precast concrete products, the secretariat of which is held by AFNOR.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.

To ensure the performance of the precast concrete products, lifting and handling should be taken into account in the design of the product.

Inserts are used for lifting and handling of precast elements. They should meet an appropriate degree of reliability. They should sustain all actions and influences likely to occur during execution and use.

This Technical Report deals with all lifting inserts cast into precast concrete elements i.e. lifting parts developed and produced at the precasting plant as well as lifting inserts as part of a system supplied by a manufacturer of lifting systems. The intent of this document is to give information to precast product designers.

The failure of inserts for lifting and handling could cause risk to human life and/or lead to considerable economic consequences. Therefore inserts for lifting and handling should be selected and installed properly by skilled personnel.

This Technical Report based on current practices gives recommendations for correct choice and design of lifting inserts according to the lifting capacity of their part embedded in the concrete. It is based on EN 1992-1-1 (Eurocode 2) and on published suppliers data.

In the Technical Report numerical values for partial safety factors are recommended as basic values that provide an acceptable level of reliability. They have been selected assuming that an appropriate level of workmanship and of quality management (Factory Production Control) applies. They may be applied in the absence of national regulations.

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1 Scope

1.1 Scope / General

This Technical Report provides recommendations for the choice and use of cast-in steel lifting inserts, hereafter called 'inserts' for the handling of precast concrete elements. They are intended for use only during transient situations for lifting and handling, and not for the service life of the structure. The choice of insert is made according to the lifting capacity of their part embedded in the concrete, or may be limited by the capacity of the insert itself and the corresponding key declared by the insert manufacturer. The report covers commonly used applications (walls/beams/columns and solid slabs and pipes) and the range of these applications is further limited to prevent other types of failure than concrete breakout failure (cone failure), failure of supplementary reinforcement or failure in the steel insert. A basic supposition is that the concrete is demonstrably uncracked during all lifting situations.

The limitation in scope is used to obtain simple design models. Further information may be found in [1].

The recommended safety levels are intended for short-term-handling and transient situations.

This Technical Report applies only to precast concrete elements made of normal weight concrete and manufactured in a factory environment and under a factory production control (FPC) system (in accordance with EN 13369:2004, clause 6.3) covering the insert embedment.

This Technical Report does not cover :

The design of the insert itself (for inserts manufactured by insert suppliers).

The lifting key that hooks on to the embedded lifting insert as a component between the insert and the lifting machinery (crane, excavator), nor its compliance with the embedded insert. These components, when brought to the market separately, are covered by the Machinery Directive (98/37/EC).

Lifting inserts for permanent and repeated use.

This report is not an interpretation of the Machinery Directive.

1.2 Types of inserts for lifting and handling

This Technical Report applies to the embedment of lifting inserts made by the precaster for his own use as well as lifting inserts forming part of lifting systems brought to the market by a lifting system supplier, see tables 8.3 and 8.6. Devices made by the precaster may consist of smooth bars, prestressing strands and steel wire ropes. The system devices may be e.g. internal threaded inserts, flat steel inserts and headed inserts.

Lifting loops of ribbed bars are not covered, nor wire ropes of less than 6 mm.

1.3 Minimum dimensions

This Technical Report applies in general to inserts with a minimum nominal diameter of 6 mm or the corresponding cross section. In general, the minimum anchorage depth should be la = 40 mm.

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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.

EN 1990:2002, Eurocode Basis of structural design.

EN 1992-1-1:2004, Eurocode 2: Design of concrete structures Part 1-1 : General rules and rules for buildings.

EN 10025-2:2004, Hot rolled products of structural steels Part 2: Technical delivery conditions for non-alloy structural steels.

EN 10138-3, Prestressing steels Part 3 : Strand 1).

EN 12385-4:2002, Steel wire ropes Safety Part 4 : Stranded ropes for general lifting applications.

EN 13369:2004, Common rules for precast concrete products.

EN 13414-1:2003, Steel wire rope slings Safety Part 1 : Slings for general lifting service.

CEN/TR 14862:2004, Precast concrete products Full-scale testing requirements in standards on precast concrete products.

3 Definitions and symbols

For the purposes of this document, the following terms, definitions and symbols apply.

3.1 Definitions

3.1.1 concrete breakout failure concrete cone separated from the base material by loading the insert

3.1.2 concrete breakout resistance the resistance corresponding to a concrete cone surrounding the insert or group of inserts separating from the member

3.1.3 edge distance the distance from the edge of the concrete surface to the centre of the nearest insert

1) Presently under preparation

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3.1.4 anchorage length for cast-in headed insert bolts and splayed inserts, the anchorage length, la , is illustrated in Figure 1

sLasLa ++= )(25,1l sLasLa ++= 85,0)(25,1l

Figure 1 Examples of anchorage length for different types of inserts

3.1.5 embedment depth distance from the concrete surface to the farthest point of insert, measured perpendicular to the concrete surface

3.1.6 factory Production Control (FPC) a quality system satisfying the requirements in EN 13369, clause 6.3

3.1.7 headed insert a steel insert with a head for anchorage installed before placing concrete

3.1.8 insert a steel unit cast into concrete and used for lifting of precast elements

3.1.9 insert loading axial, shear or combined - Loads applied to the insert

3.1.10 insert resistance load capacity (characteristic value) of the part of the insert embedded in the concrete (different from maximum working load of the insert see 3.1.13). In this report, the wording characteristic resistance is sometimes used

3.1.11 lifting key lifting tool to couple to the embedded insert

3.1.12 lifting system system of lifting key and appropriate insert

3.1.13 maximum working load maximum load guaranteed by the supplier before steel failure, reduced by application of the relevant safety coefficient and marked on a lifting key or system (from Directive 98/37/EC, 4.1.1)

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3.1.14 precaster producer of precast concrete elements in a factory environment

3.1.15 pullout failure a failure mode in which the insert pulls out of the concrete without a steel failure and without a concrete breakout failure

3.1.16 side-face blow-out resistance the resistance of inserts with deeper embedment but thinner side cover corresponding to concrete spalling on the side face around the embedded head while no major breakout occurs at the top concrete surface

3.1.17 insert steel failure failure mode characterised by fracture of one of the steel insert parts

3.1.18 minimum reinforcement reinforcement required by EN 1992-1-1 or in national annex (Nationally Determined Parameter)

3.1.19 supplementary reinforcement reinforcement designed to resist the full load in case of a concrete failure

3.1.20 complementary reinforcement reinforcement provided to avoid brittle failure

3.1.21 supplier manufacturer of lifting inserts brought to the market or its authorized distributor

3.2 Symbols

3.2.1 Action and resistance

Ed design value of actions acting on a single insert

NRk characteristic value of resistance of a single insert

NRd design value of resistance of a single insert

qadh adhesion

dyn dynamic coefficient

G partial factor for dead load

Q partial factor for live load

c partial factor for concrete

s partial factor for steel

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3.2.2 Concrete and steel

fck characteristic compressive strength of concrete (strength class) measured on cylinders (150 x 300) mm

fyk characteristic steel yield strength or steel proof strength respectively

fuk characteristic steel ultimate tensile strength

As stressed cross section of steel

3.2.3 Inserts

Notation and symbols frequently used in this technical report are given below. Further particular notation and symbols are given in the text.

c edge distance from the axis of an insert

d diameter of insert bolt or thread diameter

dh diameter of insert head (headed inserts)

ds diameter of reinforcing bar

la anchorage length (Figure 1)

4 General design principles

4.1 General principles

The inserts load capacity for lifting and handling should be calculated and/or tested according to the principles and design models given in this document. Embedment conditions for lifting and handling, which do not conform to these principles or design models, should be tested according to the recommendations given in Annex A and evaluated in accordance with EN 1990.

Actions should be obtained from the relevant parts of EN 1991-1 where applicable.

4.2 Partial factors

4.2.1 Partial factors for actions

In the absence of National provisions the following factors are recommended:

G = 1,15 (partial factor for dead load) ;

Q = 1,5 (partial factor for live load, i.e. adhesion, friction and dynamic actions).

4.2.2 Partial factors for resistance

In the absence of National provisions the partial factors given in Tables 1 and 2 are recommended.

Recommended values of the partial factors s for characteristic resistance of steel based on characteristic ultimate values (Ruk, fuk) are given in Table 1. For solid steel loops, steel wire ropes and prestressing strands the partial factor s is based on the characteristic resistance of the loop including effects of the lifting hook.

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Recommended values of the partial factor c for failures in the load transfer between the insert and the concrete are given in Table 2. These values assume that an FPC system is used to control that concrete is uncracked in the vicinity of the insert.

Table 1 Partial factors s for steel failure

Type of insert 8.0//800 ukykuk ffandmmNf 8.0//800 >> ukykuk fformmNf

Solid steel lifting systems Max(1,5; 1,2 fuk/fyk) 1,7

Solid steel (smooth bars) lifting loops*) 2,0 -

Steel wire ropes - 1,8

Prestressing strands - 1,8 *) The material for smooth bar lifting loops should be at least equivalent to S235J2+N.

Table 2 Partial factors c for concrete failure

Loading in Certified FPC

Tension 1,5

Shear, combined tension and shear 1,5

5 Actions on inserts

5.1 Actions

The forces acting on an insert should be calculated for all relevant loading situations taking into account the product properties, the position of the inserts, condition of the form, lifting equipment, number and length of the ropes, chains or straps and the static system. In some cases it might be necessary to take into account the deformations of the precast element during lifting and handling.

5.2 Effect of lifting procedures on load directions

Inserts for lifting and handling may be subjected to loads acting in different directions during operation. As examples information on slabs and wall elements are given.

The lifting equipment should allow statically determinate load distribution to the inserts (see Figure 2). To ensure that all inserts carry their required part of the load, sliding or rolling couplings between the lifting wires or chains should be used when there are more than two lifting points. In a statically indeterminate system the load distribution on the inserts depends in most cases on the unknown stiffness of the ropes and the position of the insert (see Figure 3). Therefore only the statically determinate part of a system should be used in calculating the actions on the inserts.

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a) b)

Figure 2 Examples of handling equipment for slabs

Figure 3 Statically indeterminate system, only two inserts loaded

Figure 4 Example of statically determinate lifting of a slab and resolution of forces

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Depending on the equipment used during lifting the inserts may be subjected to combined parallel and transverse shear load (Figure 5a), combined tension and parallel shear loads (Figure 5b), transverse shear loads (Figure 5c) or axial tensile loads (Figure 5d).

a) b) c) d)

Key a) Combined parallel and transverse shear load b) Combined tension and parallel shear load c) Transverse shear load d) Axial load

Figure 5 Examples of loads on lifting inserts for walls

Shear loads acting on inserts may be assumed to act without a lever arm, if the design of the inserts and its key avoids significant concrete crushing in front of the insert during loading. If this condition is not satisfied the lever arm should be taken as the actual distance between the shear force and the concrete surface plus half the nominal diameter of the insert.

5.3 Actions from adhesion and form friction

Adhesion and form friction will occur when the precast element is removed from the formwork. The values should be taken from National provisions. In the absence of National provisions the values for the combined effect of adhesion and form friction qadh given in Table 3 may be considered. General values for form friction are difficult to assess and friction should be avoided as far as possible.

For some types of uneven form surfaces (structured matrixes, reliefs, structured timber etc.) the forces may be much larger than given in the table, and should be considered separately. The forces may be zero if the concrete does not come in contact with the form at all, for example if the concrete is poured on a layer of bricks that has been laid out on the form bottom. Large vertical form surfaces may create extensive friction forces due to undulations in the form. Prestressed components will usually have a camber caused by the prestressing force, and will therefore have lower friction against the vertical sides of the form.

Table 3 Examples of values of qadh

Formwork and condition qadh *)

Oiled steel mould, oiled plastic coated plywood 1 kN/m2

Varnished wooden mould with planed boards 2 kN/m2

Oiled rough wooden mould 3 kN/m2 *) The area to be used in the calculations is the total contact area between the concrete and the form.

The actions, Ed, for demoulding situations should be determined from:

fadhQGd AqGE +=

with

G = weight of the precast concrete element ;

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Af = form area in contact with concrete ;

G and Q are partial safety factors for permanent and variable actions respectively.

5.4 Dynamic actions

During lifting and handling the precast elements and the lifting devices are subjected to dynamic actions. The magnitude of the dynamic actions depends on the type of lifting machinery. Dynamic effects should be taken into account by the dynamic coefficient dyn given in National regulations. In the absence of National Regulations the values of Table 4 may be considered. Other dynamic influences than covered by Table 4 should be based on special provisions or engineering judgement.

Table 4 Influence of dynamic actions on site

Dynamic influences Dynamic coefficient (dyn)

Tower crane and portal crane 1,2 x)

Mobile crane 1,4 x)

Lifting and moving on flat terrain 2 2,5

Lifting and moving on rough terrain 3 4

x) In precasting factories and if special provisions are made at the building site lower values may be appropriate.

The actions, Ed, for lifting situations should be determined from Equation (5.3):

GGE QdynGd += )1(

6 Choice of inserts

Having determined the actions on the insert for all relevant load combinations the task remains to choose an appropriate insert and relevant reinforcement.

The insert load capacity depends on the field of application. The designer has three options in choosing the appropriate lifting arrangement :

1) The recommendations given by the insert suppliers may be used directly. This option is further described in clause 7;

2) The design charts provided in clause 8 may be used;

3) Tests may be carried out specific to the intended application as outlined in clause 9.

Figure 6 indicates which option could be appropriate in a given situation.

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7 Use of Suppliers recommendations

The commercially available lifting systems are usually designed and optimised for defined fields of application, in some cases based on results from proprietary test programs. Catalogue material from the supplier often describes corresponding design methods. These methods may be used provided that one of the following conditions is satisfied :

1) The method is certified by an accredited third party in accordance with a relevant ETAG;

2) The method is certified by an accredited third party in accordance with a CEN product standard;

3) The method is certified by an accredited third party based on tests according to Annex A;

4) The method is given by national provisions.

The suppliers declaration of the product should state the method chosen. If the supplier cannot satisfy either of these conditions, or if the intended application falls outside the range of validity for the design methods recommended by the supplier, the designer should choose one of the options in clause 8 or clause 9.

Information given by the supplier should conform to Annex B.

NOTE Suppliers catalogues may disclaim the responsibility for the use of the data. Consequently, such catalogues should not be used as a recommendation.

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Key 1) The application of the insert is fully within the limits stated in the catalogue of an insert supplier or manufacturer. These limits include weight, concrete strength, edge distance, dimensions of the concrete member, local reinforcement and mode of lifting. 2) To verify the design model of chapter 8 for a certain type of insert it might be necessary to perform tests according to Annex A. The reinforcement provided to transfer loads from the insert into the element should be designed according to National provisions. Reinforcement for other purposes such as flexural or shear capacity of the precast element in use would not normally be considered in this. 3) Specific testing is intended to justify the capacity in a particular situation. As an example, this might include inserts for tunnel segments or bridge beams. It does not provide information for a wide range of applications.

Figure 6 Flow chart for the design of lifting inserts

8 Use of CEN/TC 229 recommendations for typical user situations

8.1 General conditions

For most common applications, present practice and available general information concerning the load capacity of inserts can be combined into a design model. This model is described in further details in sections 8.3 8.4. The

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model is not universally applicable. Limitations on the range of validity are used to exclude situations where other types of failure than concrete breakout failure (cone failure), failure of supplementary reinforcement or steel failure in the insert can occur. Within the indicated limited range of validity the model yields results that are very close to present practice. The limitations on the range of applicability are the following:

1) Field of application

The most common fields of application are:

a) walls and other linear elements (such as beams and columns), where the insert is typically long compared to the edge distance (the smallest distance from the insert to a concrete surface parallel to the insert) and where the concrete in the vicinity of the insert is uncracked.

b) slabs and pipes, where the edge distance is large while the possible length of the insert is limited by the thickness of the element and where the concrete in the vicinity of the insert is uncracked. This section covers the use of some common types of inserts in these two situations, cp tables 7 and 10.

2) Reinforcement is provided in the region of the insert, either as complementary reinforcement or as supplementary reinforcement.

Minimum reinforcement is typically provided according to EN 1992-1-1. Although provided for other reasons the reinforcement may also act as a safeguard against failure in case cracking should unexpectedly take place in the concrete around the insert. If minimum reinforcement is not provided complementary reinforcement should be provided. If the minimum reinforcement is left out the risk of accidental cracking and brittle failure might be unacceptable.

The presence of complementary reinforcement also makes it possible to postpone the development of a breakout failure so that the capacity of the insert becomes somewhat larger than in unreinforced concrete, see e.g. ref. [2].

Supplementary reinforcement is designed specifically to transfer the full load on the insert to the concrete element as a whole. The suggested models for design of the supplementary reinforcement are in accordance with the rules given in EN 1992-1-1.

3) Minimum characteristic strength of concrete.

Where no other indication of minimum concrete compressive strength is given, it is assumed that the concrete strength (at the time of lifting) is at least 15 MPa measured on cubes, side length 150 mm (or 12 MPa measured on cylinders).

4) Factory Production Control (FPC).

It is assumed that the precaster applies a Factory Production Control system according to the requirements in EN 13369, clause 6. It is furthermore assumed that the inspection scheme for finished product inspection includes a check that no harmful cracking has occurred in the neighbourhood of the inserts at the time of delivery.

5) No extrapolation of design graphs.

The validity of the calculation model outside the range covered by the graphs is not sufficiently known and therefore the graphs should not be extrapolated.

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6) Safety factors.

To facilitate the use of nationally determined partial factors the capacity values given in this chapter could be used as characteristic values.

Figure 7 Type a) inserts. Headed bolts and spread anchors

Headed bolts and spread anchors transfer axial load to the concrete through mechanical interlock at the built-in end while shear load is transferred more or less directly between the recessed lifting key and the concrete at the top end.

Figure 8 Type b) inserts. Anchors with additional rebar

These inserts maintain the possibility of shear transfer directly from the lifting key to the concrete, while the axial load is transferred to the concrete through a separate reinforcement bar to be threaded into a hole in the insert.

Figure 9 Type c) inserts. Anchor systems with threaded sockets

These inserts may utilize a simpler, threaded key to transfer the load to the insert. The axial load is transferred to the concrete through a bonded rebar either in the form of a separate bar threaded into a hole or as a built in rebar (e.g. waved anchors) included in the system. The corresponding key may or may not be suitable for transfer of shear forces.

Figure 10 Type d) inserts

These inserts are short versions of type a) inserts possibly with an extended bearing area at the built-in end of the insert. They are intended for use in slabs and pipes to sustain axial load and shear load.

Figure 11 Type e) inserts. Similar to type a)

Inserts intended for use in slabs and pipes with short embedment lengths and large bearing areas that are also suited for supporting the necessary minimum reinforcement. Axial load as well as shear load may be accommodated.

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Figure 12 Type f) inserts. Plate sockets

A threaded socket mounted on a plate providing a bearing area for axial load. The corresponding keys are usually not suited for transfer of shear, but special options exist.

8.2 Types of inserts covered

8.2.1 Commercially available inserts

Many types of inserts are commercially available as illustrated in Figure 7 12.

All these standard lifting systems consist of an insert embedded in the concrete element and a matching unit (key) that connects to the insert (Figure 7). The crane hook or hook of a lifting sling attaches to the key. The combination of components from different systems is prohibited.

Threaded lifting devices and corresponding keys should be marked with a colour corresponding to their diameter. The colours given in Table 5 are recommended.

Table 5 Recommended colour identification codes of lifting systems for threaded lifting systems

Diameter Colour

Rd 12 orange

Rd 16 red

Rd 20 light-green

Rd 24 dark-grey

Rd 30 dark-green

Rd 36 light-blue

Rd 42 silver-grey

Rd 52 yellow

For other than threaded systems, the following method of marking is possible.

The marking consists of a System ID and an Insert ID (Table 6). It should be fixed directly to the cast-in part and the lifting key.

Table 6 Marking of insert and key

System ID Insert ID

Producer System Specification

Lifting key P S

Insert P S X

The System-ID consists of the identification of the producer P (minimum two letters or logo) and the producers name for the system S.

In many cases different types of cast-in-inserts belong to the same system. Therefore the insert has to be marked with an Insert-ID containing additional information such as the specification by the supplier X and the length of the anchor Y. It should be visible after pouring the concrete. It is recommended to mark the insert directly with its length or to use a length identification code (capital letter or colour).

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8.2.2 Inserts made by the precaster

In addition to the commercially available inserts the precasters may produce their own lifting loops from smooth bars, prestressing strands or steel wire ropes. Necessary information on the handling of the element, e.g. lifting hook dimensions, shall be given in erection specifications.

Lifting loops should only be used if the lifting angle is approximately the same in all lifting and handling situations. Furthermore, the lifting angle should be kept within the limits indicated in Figure 14.

Figure 13 Lifting loops made of smooth bar, strand or steel wire rope (Type g) inserts)

Examples of the inserts are shown in Figure 13 and they should conform to the following specifications:

Smooth bars

The material for smooth bar lifting loops should be at least equivalent to EN 10025-2, S235J2+N. During operation the minimum bending diameter of the smooth bar should not be less than 5 bar diameters. The size of the lifting hook may require a larger bending diameter.

Strands

The shape of the strands may be adapted to the various types of elements. Prestressing strands that have been deformed before shaping should not be used. Bending of the strands during stocking or turning of elements should be avoided.

The bending diameter of the strand loop (illustrated by the curvature of the sleeve in Figure 13) should be equal to or less than twice the diameter of the lifting hook (the diameter is 2s in the figure in Table 8). The bending diameter of the strand loop must be larger than the diameter of the lifting hook. The strand diameter should not exceed 13 mm and the bending radius should be at least 50 mm.

Bundling of maximum four strands may be used only when provided with a steel sleeve bent together with the strands, see Figure 13.

To take into account effects of lifting hook diameter and different load distribution to the strands within a bundle, capacity reduction factors are given in Tables 8 and 9.

Steel wire ropes

Only steel wire ropes, which comply with EN 12385-4 and 13414-1 should be used.

Steel and fibre cores are allowed. The rope grade should be 1770 N/mm2 or 1960 N/mm2. However, in calculations only a value of 1770 N/mm2 should be considered.

To ensure sufficient flexibility of a rope the steel wire ropes should consist at least of the following number of wires:

d = 6 mm: 42 wires minimum d 14 mm: 114 wires d > 14 mm: 200 wires

The bending diameter of the steel wire rope should not be less than 2 rope diameters.

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To ensure sufficient bond steel wire ropes must be cleaned. The ends of the lifting loop made of a steel wire rope should be ferrule-secured or split. Split ends should not be taken into account in the design, but a ferrule-secured end will provide some extra anchorage.

The loading angle, , (angle between the direction of the force and the axis of the insert) should not exceed 30, (see Figure 14). The effect from on the distribution of the force to the legs of the loop should be considered.

a)

b)

Figure 14 Loading angle for lifting loops

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Table 7 Design summary for inserts under inclined tensile loading in walls and linear elements

Anchor type

Walls and linear elements

a)

b)

c)

g)

Basic steel capacity Choose an insert with sufficient steel resistance based on supplier declaration

Choose an insert and associated rebar both with sufficient steel resistance based on supplier declaration, see Figure 21

Choose an insert with sufficient steel resistance based on supplier declaration

Choose an insert with sufficient steel resistance based on supplier declaration

Wall thickness Prevent blow-out failure by using Figure 16 Ensure that wall thickness is sufficient to obtain normal anchorage conditions: wall thickness larger than 7 times bar diameter (straight bars) or 11 times bar diameter (other than straight bars). If smaller thickness: the embedment length shall be increased.

Amount of complementary reinforcement Prevent brittle failure due to concrete cracking, see Figure 17

Anchorage Anchorage length, see Figure 1

Anchorage length for axial load Determine required anchorage length corresponding to concrete cone capacity from Figure 18.

Determine required anchorage length for bent rebar, see Figure 22.

Determine required anchorage length for hooked rebar, Figure 22. Check that necessary anchorage length determined from Figure 17 is smaller

Determine required anchorage length for strand or hooked bar, Figure 22.

Supplementary hairpin reinforcement (replaces complementary reinforcement)

If concrete cone capacity is too small or if shear load component: determine required reinforcement to carry the whole anchor load, see Figure 19, 20 and 22

None for tension None for tension None for tension

Supplementary diagonal pull reinforcement, see Figure 23

Choose reinforcement arrangement and amount

Choose reinforcement arrangement and amount

Choose reinforcement arrangement and amount

Not used. Insert to be tilted according to load direction

Capacity reduction due to shear in wall plane

20% for loading angle 300

21

The choice of an appropriate insert for a wall application would typically involve:

Selection of an insert, suitable for the load direction and with sufficient resistance of the insert itself;

Checking that the concrete wall thickness is sufficient;

Checking that the available reinforcement can prevent brittle failure;

Determination of the required anchorage length for the insert;

Checking the need for supplementary reinforcement around the insert;

Compensation for the possible reduction in capacity due to shear load component.

These items are summarised in Table 7 and further dealt with in the following sections.

8.3.1 Basic steel capacity

All commercially available inserts should be marketed together with a declaration stating the expected characteristic resistance of the insert corresponding to a failure in the steel. The value should cover the transfer of load from the key or lifting hook to the insert and any type of possible failure within the insert itself (e.g. welding). The value may be given as a combination of the maximum working load and a safety factor.

For type g) inserts (usually produced by the precaster) the precaster should evaluate the available characteristic resistance with due respect to the key or lifting hook to be used. An estimate can be made by ordinary vectorial addition of the resistance in the two legs.

For lifting loops made of strands the influence of the lifting hook and the bundling of strands with a sleeve should be taken into account by the factors k1 and k2:

ukssRk fAkkN = 21,

The reduction factors k1 and k2 to consider the influence of the diameter of the lifting hook and bundled strands are given in Table 8 and 9.

In the case when a steel sleeve is used for a single strand loop, factor k1 may be increased by 25%, however k1 1,0.

Table 8 Influence of the lifting hook, capacity reduction factors for lifting loops made of strands

Diameter 2s [mm] k1

25 or 60 0,65 50 0,8

75 0,9

Table 9 Reduction factors for lifting loops made of bundled strands

Number of strands 2 3 4

k2 0,90 0,85 0,75

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The thickness of the wall shall be sufficient to avoid failure modes that cannot be counteracted effectively by reinforcement.

Type a) inserts

For type a) inserts a side-face blow-out failure may occur at the built-in end of the insert, see Figure 15.

Figure 15 Side face blow-out failure

The risk of a blow-out failure depends primarily on the anchor force, the concrete strength and the edge distance. The strength may be found from the following expression, [1]:

ckhRk fddcN = )(44,11 22 [N]

For inserts with a head diameter, dh [mm], larger than 2,4 times the shaft diameter, d [mm], (dh 2,4d) this may on the safe side be replaced by

ckkefcRk fhkN =

43 [N]

where c [mm] is the edge distance, fck [N/mm2] is the concrete strength and

The curves given in Figure 16 are based on this latter expression assuming that the insert is placed in the middle of the wall. If not, the wall thickness should be assumed to be twice the smallest edge distance. The diagram also assumes that partial safety factors for steel and concrete are the same. If the partial safety factor to be used is smaller for steel than for concrete (blow-out), the next higher insert dimension may be required.

Type b), c) or g) inserts

The other insert types transfer their load to the concrete primarily by bond stresses. The anchorage length necessary to develop the full resistance of the insert depends on the concrete cover when this cover is small.

The wall thickness needed to make the anchorage length independent of the thickness is taken from EN 1992-1-1, clause 8.4.4. For ordinary rebars the wall thickness should be at least 7 times the bar diameter for straight bars and 11 times the bar diameter for other than straight bars. See also clause 8.3.4.

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Key Y Characteristic axial resistance, kN X Wall thickness, mm Blow-out failure --- Insert steel failure

Figure 16 Required wall thickness to avoid side-face blow-out failure for inserts of type a) with dh > 2,4 d and fuk = 500 Mpa

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According to EN 1992-1-1 most wall elements will have minimum mesh reinforcement (one or two layers). Minimum reinforcement is presently a Nationally Determined Parameter. Beams and other linear elements will also normally have minimum shear reinforcement in the region of the insert. In case of unexpected cracking of the concrete around the insert this reinforcement already provided will often be sufficient as complementary reinforcement to avoid accidental failure, although the unexpected cracking may render the element unsuited for its purpose. It should be checked, however, that the design load can be carried by the complementary reinforcement without yielding (partial resistance factor, s = 1).

s

cyksRk fAN

=

The reinforcement As should be positioned within a maximum distance from the insert of 0,75 la, and proper anchorage lengths should be provided on both sides of the potential crack. For small embedment depths these requirements may not be easily satisfied. Alternatively, a few extra hairpins may be placed next to the insert with maximum distance between hairpins = 50 mm. The graphs in Figure 17 may be used to determine the required amount of reinforcement (either hairpins or mesh reinforcement) for a given characteristic insert resistance and anchorage length (for c = 1,5).

Key Y Characteristic insert resistance, kN X Anchorage length, mm 1 Mesh 2 Hairpins

Figure 17 Complementary reinforcement required to ensure ductile failure (fyk=400 MPa, accidental design situation, c = 1,5 and s = 1,0)

The rebars used with inserts of type b) and c) are usually so long that a cone failure is very unlikely (anchorage failure, see 8.3.4, or steel failure is likely). A check of the complementary reinforcement is therefore not required in these cases.

8.3.4 Anchorage length for axial load

The insert should have sufficient anchorage length, so that the full load on the anchor can be transferred to the concrete. Insufficient anchorage length is likely to result in a cone failure for anchors of type a) while the other types are more likely to be pulled out of the concrete (anchorage failure).

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The anchorage length, la [mm], required to develop a certain force, Nrk, for type a) inserts may be determined based on the following calculation model for fck [N/mm2]:

ckkacRk fkN = 43 l [N]

11

2

+=a

c kckl

where

7,11,616,0

75,1

4

3

2

1

=

=

=

=

kkkk

Although the calculation model does not explicitly refer to reinforcement it should not be used unless the minimum reinforcement described in 8.3.3 is provided. Furthermore the range of validity is limited to la 350 mm and NRk 300 kN. The head diameter should be dh > 2,4d to avoid a pull-out failure.

The calculation model yields up to 20% higher results than a similar model given in ref [1] for inserts in unreinforced concrete. The difference is due to the effect of the complementary reinforcement. As described in ref [2] the breakout failure is initiated at working load level by a crack formed at the head of the insert. This crack increases in length as the load is increased. The presence of complementary reinforcement will slow down the propagation of the crack and lead to a breakout failure at a higher load level.

Results from the calculation model are given in diagrams in Figure 18. A required characteristic insert resistance and an available wall thickness determines the required anchorage length for the insert (the insert should of course have the required steel strength). The region to the left of the curved lines in the diagrams signify a possible failure by side-face blow-out which means that the wall thickness is not sufficient, see Figure 16.

If the application is outside the range of validity for Figure 18 or if the required anchorage length for some reason cannot be accommodated a supplementary reinforcement should be used.

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Key Y Characteristic axial resistance with complementary, kN X Wall thickness, mm 1 Possible Blow-out see Figure 16

Figure 18 Required anchorage length corresponding to concrete cone failure for type a) inserts with dh>2,4d, when complementary reinforcement is provided. For inserts with yield strength higher than

600 MPa dh 2,5d is needed for fck = 15 MPa.

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counteracted by this reinforcement close to the insert. The hairpins serve as a load distributor within the concrete member. In case of splitting of the concrete the crack width is kept small.

Key 1 Insert stirrup

Figure 19 Supplementary reinforcement for insufficient anchorage lengths

The amount of hairpin reinforcement is given by the diagram in Figure 20. The diagram is based on the assumption that the whole anchor force should be transferred to the element through the hairpin reinforcement (no concrete contribution). It also means that the complementary reinforcement defined above to prevent a brittle failure is not needed when the supplementary hairpins are provided.

yk

sds f

NA

=

The hairpins should be located as close as possible to the insert, and they should at least be located within a distance from the insert of no more than 75% of the length of the insert. The hairpins should be properly anchored on both sides of the potential cone failure surface. The anchorage length for the open ends of the hairpins can be found from diagram in Figure 22. The anchorage of the closed ends of the hairpins should be checked with accepted methods of calculation and the use of sound engineering judgement. The length of the hairpins should be the sum of the anchorage length of the open end and the length of the insert. The anchorage of the closed ends of the hairpins needs not to be checked if the insert embedment depth is more than 300 mm and the maximum distance between the hairpins is 50 mm.

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Key Y Characteristic axial resistance with supplementary reinforcement, kN X Number of double-leg stirrup 1 Stirrups reinforcement

Figure 20 Supplementary reinforcement, 2-leg stirrups anchored on both sides of potential crack, see Figure 19

Type b), c) and g) inserts

The required anchorage length for anchors of type b), c) and g) is determined on the basis of EN 1992-1-1, clause 8.4.2 and clause 8.10.2. Results are given in Figure 22 for rebars and strands assuming good bond conditions. If good bond conditions cannot be expected the anchorage lengths should be increased by 40 %.

For some inserts of type c) the length of the insert may be sufficiently short to facilitate a cone failure. In such cases a supplementary reinforcement can be used as for type a) inserts. Otherwise, no improvement in axial load capacity is obtained by supplementary reinforcement.

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Key Y Characteristic axial resistance, kN X Bar diameter, mm 1 Single bent rebar

Figure 21 Supplementary reinforcement, single bent bar, type b) inserts

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Key Y Anchorage length/bar diameter X Concrete strength, fck, Mpa 1 Strands 2 Anchorage ULS 3 Rebars, diameter = d 4 Straight bar 5 Straight/hooked bar 6 Hooked bar

Figure 22 Anchorage lengths for bonded reinforcement with diameter = d and cover = cd for good bond conditions. If bond conditions are not good, the anchorage length values should be multiplied by 1,4.

8.3.5 Effects of shear load in the plane of the wall

A shear component of the insert force will introduce two possible negative effects on the insert capacity: a shear failure in the anchor itself and a failure in the concrete due to the contact pressure between the top of the insert and the concrete.

Both these effects may be counteracted by the design of the insert and its corresponding key. Type a) and b) inserts typically have keys transmitting the shear component of the anchor load directly to the concrete, thus introducing very limited shear stresses in the anchor steel. The capacity of anchor type c) will be reduced as a consequence of the shear stresses in the steel. Anchor types g) may be mounted with an inclination, so that the direction of the force on the insert may be kept within the limits indicated in Figure 14.

Type a) and b) inserts

If the lifting angle becomes larger than 30 type a) inserts should be supplied with the hairpin reinforcement described in 8.3.4, so that reliance on complementary reinforcement only is not accepted. Furthermore, the shear force transfer to the concrete calls for supplementary reinforcement, consisting of horizontal hairpins (angled pull links), see Figure 23. The hairpins surround the insert close to the top surface and as they are intended to take up the shear load on the insert, they should point in the opposite direction of the load. The amount of supplementary reinforcement should be sufficient to resist the whole shear load component in tension.

If these reinforcement requirements are met, type a) and b) inserts can be expected to have a reduction in tensile load capacity of 20 % of the tension load capacity for loading angles between 30 and 60.

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Key 1 Mesh reinforcement Q 2 Edge reinforcement 3 Length of slot-in link L1 4 Slot-in link (positioned as closely to anchor as possible) 5 Angled pull reinforcement as close as possible to recess 6 Additional reinforcement for pull

Figure 23 Supplementary reinforcement for combined axial and shear load

Type c) inserts.

For type c) inserts a suitable key must be used to obtain any shear resistance and even then the shear resistance of the insert itself cannot be greater than about 50 % of the insert steel resistance in tension. If supplementary reinforcement is provided according to the same rules as for type a) and b) inserts, the reduction of the insert tension load capacity can be expected to be 30 % for loading angles between 300 and 450.

Type g) inserts

The load direction should be kept within 30, see Figure 14. Furthermore the opening angle should not exceed 60. It should be recalled that the insert might be placed with the axis at an angle to the surface of the wall top.

The reduction in insert load capacity can be expected to be 15 % per 10 loading angle.

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The choice of inserts to be loaded with a transversal shear force component, see Figure 5c), is rather complicated, mainly because the local stresses introduced by the transfer of load from the insert to the concrete are augmented by the global stresses from bending moments in the wall. Generally, the transversal shear should be kept as small as possible, the edge distance should be as large as possible and supplementary tilting reinforcement should be provided, e.g. according to Figure 24. Further information may be found in [1].

Key 1 Additional reinforcement 2 Radial reinforcement 3 Transverse pull

Figure 24 Examples of lifting inserts in a wall with supplementary tilting reinforcement for transverse shear load transfer

8.4 Lifting of slabs and pipes

Since the thickness of the slab or pipe wall is the limiting factor, the relevant types of inserts are short and provided with some sort of head, plate or similar anchorage device designed to activate as large a concrete cone as possible. Some of the insert types and their corresponding keys are designed to transfer shear components of the insert load directly to the concrete, see also 8.2.1.

A summary of the items to be dealt with is given in Table 10.

8.4.1 Minimum edge distances

The full insert load capacity is obtained only if the edge distances are large enough to allow the cone to develop fully and independently of the edge distance. This is likely to be the case if the edge distance is at least 1,5 times the length of the insert. Smaller edge distances will reduce the load capacity.

8.4.2 Complementary reinforcement in slabs and pipes

Since the function in many cases is based on the cone resistance it is essential that a complementary reinforcement be provided to avoid brittle failure. Figure 25 illustrates a possible arrangement with the reinforcement on top of the insert head. The figure shows the amount of reinforcement needed to obtain ductile failure for a certain needed tensile resistance of the insert. The required anchorage length is dealt with in section 8.4.3.

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Key Y Characteristic axial resistance, kN X Diameter of complementary rebars in slabs, mm

Figure 25 Arrangement of complementary reinforcement in slabs and pipes for fyk=500 MPa. Required length of rebars is app. 30 50 times bar diameter (highest value for larger diameter)

The insert may in some cases be placed so that the main reinforcement in the slab or pipe can provide the same function. In that case a separate complementary reinforcement is not needed.

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Table 10 Design summary for inserts under inclined tensile loading in slabs and pipes

Anchor type

Slabs and pipes

d)

e)

f)

Distance to edge Edge distance at least 1,5 times length of insert

Complementary reinforcement See Figure 25

Replaced by supplementary reinforcement

Anchorage length Anchorage length la see Figure 1

Anchorage length la see Figure 1.

Required anchorage length Determine required anchorage length corresponding to concrete cone capacity from Figure 26

Determine required anchorage length corresponding to concrete cone capacity from Figure 26

Supplementary reinforcement None None See Figure 27

Capacity reduction due to shear component

20% for loading angle 30

35

8.4.3 Anchorage length for axial load

Assuming that the reinforcement requirements in section 8.3.4 are satisfied, the necessary anchorage length to obtain a given capacity for type d) and e) inserts can be found from Figure 26. The curves correspond to a cone failure according to the calculation model given in section 8.3.4., assuming that edge distance is larger than 1,5 times anchorage length. Again the complementary reinforcement delay the crack development compared to an unreinforced situation which explains an increased strength compared to values in ref [1]. It should be noted that the same range of validity as given in section 8.3.4 apply (i.e. NRk < 300 kN).

Key Y Characteristic resistance with complementary reinforcement, kN X Anchorage length, mm

Figure 26 Anchorage length needed in slabs and pipes to obtain required characteristic resistance. Edge distances larger than 1,5 times anchorage length

For very short anchors (typically type g) inserts with embedment length smaller than 75 mm in shallow slabs reliance on the cone resistance should not be used. Instead a reinforcement designed to carry the whole anchor load should be arranged according to Figure 27.

Key 1 Main reinforcement (surface)

Figure 27 Supplementary reinforcement is needed in slabs for very short inserts

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8.4.4 Effects of shear load

The applications dealt with in clause 8.4 will not have shear loads pointing towards the edge.

For anchor types that are used with a key designed to transfer shear forces directly to the concrete, the load capacities given in section 8.4.3 for tension loads can be used for a loading angle smaller than 45.

For other types of anchors the load capacity should be reduced by 30% for loading angles between 30 and 45.

9 Precaster use of testing

The precaster may need to do testing in three situations that are different from a statistical point of view, because the extent of prior knowledge is different. EN 1990 provides the basis when the statistical data are taken from identified and sufficiently homogeneous populations and a sufficient number of observations are available.

In the first case the precaster wants to check that a design based on supplier information or on the recommendations in chapter 8 is valid for a specific application. Strong prior knowledge can be assumed and that may reduce the necessary testing program to 2-5 tests. EN 1990, Annex D.8.4 provides the basis as described in Annex A.5.2 and A.6.2.1.

In the second case the precaster wants to verify a design that may be outside the range for which available information is valid. The insert to be applied may be new or it may be used outside the stipulated limits. In this case the necessary testing program is likely to be somewhat larger, because the strength of prior knowledge is somewhat debatable. EN 1990, Annex D.8.2 provides the basis as described in Annex A.5.2 and A.6.2.2.

In the third case the precaster wants to utilise an insert for which no prior knowledge is available. The necessary testing program is likely to be large. EN 1990, Annex D.7.2 provides the basis as described in Annex A.5.3 and A.6.3.

10 Recommended technical documentation

10.1 General

The precaster should make sure, that the choice and design of the lifting arrangement is documented. The documentation should include:

Technical information on the properties of the inserts;

Technical documentation related to the design of the specific lifting application;

Lifting and handling instructions.

10.2 Properties of inserts

The following technical information should be available for any kind of insert, whether produced by the precaster or delivered by a supplier (see Annex B):

General description of the lifting system, including material properties, sketches main dimensions, main uses, instructions for use, limits of use, etc.;

Lifting and handling operations assumed in design;

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The design method and suggested design values:

when design values are determined by calculation, verification of the validity of the design method for the insert dimensions and that the design method covers the assumed lifting and handling situations;

when the design values are determined by testing, verification that the test method represents the lifting conditions in practice;

when the design values are determined by testing or calculation assisted by testing, both verifications mentioned above and the evaluation of the test results;

safety concept used in design.

NOTE For lifting systems put on the market by a lifting systems supplier contractual information should be available e.g. in brochures. Only contractual documents should be used (often commercial brochures are not contractual). For other lifting inserts the information should be available as part of the precaster's technical documentation.

10.3 Design of specific lifting application

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;

required number of suspension points;

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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.

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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;

arrangement of insert(s) within concrete member (distance between inserts, edge distance, etc.);

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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

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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

Figure A.3 Examples of test set-ups for inserts under tension load and shear load in a wall

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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 efs hl 5,1 ;

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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 hls 5,1 , 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 la in 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

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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

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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:

= ikk RnR

iii RnRnR 11,01 where

Ri are the individual test results;

n is the number of tests and;

k can be taken from the following table:

Reduction factor kCoefficient 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.

NOTE The number of tests should be large enough to establish a stable coefficient of variation of the ultimate load.

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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.

Length of thread engagement (where applicable).

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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 con