Design Guide

Unilift Locking KlawConcrete Lifting Systems

Unicon Systems is a division of Ancon Building Products.

When Unicon Systems joined Ancon, it created a unique business with thecustomer in mind. We now offer an unrivalled service to the precast concreteindustry of Australia. The combined technical and commercial strengths of thebusinesses, together with an extensive product range and nationwide operations,enable us to provide a customer-focused service that is second to none.

Ancon is part of the Engineered Accessories division of CRH plc, an internationalbuilding materials group with operations in over 35 countries and 80,000employees. Our product portfolio of lifting, fixing and anchoring technologiesincludes market leading brands from across the CRH network.

Ancon sales and technical support is available nationwide to offeradvice, process orders and provide a one-to-one service. Chooseyour location to identify your nearest regional sales office.

Sydney Tel: 1300 304 320 Fax: +61 (0) 2 9675 3390

Brisbane Tel: 1300 304 320 Fax: +61 (0) 7 3395 6693

Melbourne Tel: 1300 304 320 Fax: +61 (0) 3 9311 1777

Perth Tel: 1300 304 320 Fax: +61 (0) 8 9453 2300

Email: technical@ancon.com.auWeb: www.ancon.com.au

Service and Support

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Unilift concrete lifting systemsfor the precast industry.

Contents

Unilift Systems 4

Locking Klaws 6

Cone (foot) Anchors 8

Reo (eye) Anchors 9

Standard Recess Formers 10

Limit State Design of Concrete 11

Serviceability Limit States 12

Designing Concrete Lifting Anchors with AS3850:2003 14

Concrete Strength Limit State 17

Design for Concrete Strength 20

FAQ: Contribution of Panel Reinforcing Steel 21

Concrete working load limit 22

Design of Hanger bars for Reo (eye) Anchors 27

FAQ: Hanger bars 28

FAQ: Lifting loops 29

Rigging Guide 31

3

Performance

Ensure you have read and understood this manual before designingwith Unilift Systems.

• Use Unilift Systems strictly in accordance with Ancon’s recommendations

• Do not modify any lifting component by welding or other means

• If in doubt contact our sales engineers who will be pleased to assist you

• For best results always specify genuine Unilift components

Unilift S

ystems

Locking

Klaw

sC

one (fo

ot) A

nchors

Reo

(eye) Ancho

rsS

tandard

Recess Fo

rmers

Perfo

rmance

BenefitsVersatile• Systems to suit all applications

• Standardised load range groups of1.3, 2.5, 5, 10, 20 and 32 tonnesWorking Load Limit (WLL)

• Fast, efficient handling of products in thefactory, during transport and on the job-site

Safe• Engineered for safety. Anchor WLL includes

a factor of 3 against ultimate failure

• Components of different load groups are notinterchangeable

• Anchors and Locking Klaws are clearly markedwith their performance (WLL)

• Locking Klaws safely and securely lock ontothe anchor head

Easy to use• Simple and quick to install

• One click connection

• Easy to train operators in use and thenminimal supervision required.

Efficient and Economical• Standardised components reduce costs

• Quick connections save labour and crane time

• Recessed anchors avoid remedial work

• Efficient stacking with less product damage

Dependable Quality• Designed and tested to meet or exceed the

requirements of AS3850: 2003 and OSH NZCode of Practice ISBN 0-477-03658-9May 2002

• Recessed anchors resist damage in handlingand transport

• Nothing to clog or jam

• Anchors are Hot-Dip Galvanised for superiorcorrosion resistance

Trusted• Well known, proven technology

• Engineered and tested for safety

• Backed by Ancon experience andcomprehensive technical support

How is Unilift used?• Specify the optimum Unilift system according to

the loads, type of panel, and handling methods

• Choose a recess former to suit the casting method

• Insert Unilift anchors into the recess formers

• Attach the recess with the anchor to the mould

• Cast and cure the panel to the minimum strengthrequired for lifting (normally 15MPa)

• Remove the moulds and recess formers to exposethe anchor head

• Attach the Unilift Locking Klaw by rotating the Klawand locking it over the anchor head

• Hoist slowly, removing the panel from the castingbed and avoiding impacts

AnchorForged anchor set below theconcrete surface

RecessFormed in the concrete by arecess former to permitattachment of the Locking Klawto the Anchor head.

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Unilift SystemsUnilift - the quickest, safest, most economical systems for liftingand handling a wide variety of precast concrete products,particularly for civil engineering applications.

Locking KlawSafety clutch which locksto the anchor head

Cone AnchorClassic spherical headed, forgedfoot anchor - the first choice formost applications.

Locking KlawAncon’s unique safety clutch.Safer, stronger, faster, lighter.

Reo AnchorEye anchor used with hanger barif concrete is too weak for coneanchors.

System Components

5

Rubber FormerFlexible former suitable for mostsituations.

Steel Recess with rubber ringIdeal for production precastingand permanent mouldattachment.

Articulated Steel RecessRobust former for rigid anchorconnection in productionprecasting.

Plastic recessOne-trip recess.

Colletted Steel RecessRigid anchor connection forsevere conditions e.g.pipemaking.

Tilt-up SetsFor site casting, e.g. tilt-upanchors with support chairs.

Also available:

Special products to meet individual applications, available on request.

Unilift S

ystems

They meet the requirements of AS3850: 2003 and arecompatible and interchangeable with standard clutches for1.3t to 32t WLL anchor systems.

Locking Klaws (LK) improve safety, performance andflexibility in all situations.

LK Technologies fix the design flaws which have causedfailures of other clutches.

CentriLok• Unique ‘well’ in the curved lifting lips locates the

anchor in its optimum, central position at the rear ofthe slot!

• Under load, the Klaw locks and resists rotationtoward the disconnected position, locking the ‘tail’.

• The side of the well traps the anchor head andlocks the Klaw at its position of maximum strengthand safety.

• Safe for use in hanger applications (upside down).

• The locked Klaw protects against dangerousdisconnections where there is a risk of fouling, acommon problem when lowering precast drainageproducts in confined spaces (e.g. loweringproducts into trenches or past formwork).

Taperwall• Reinforced side walls. The unique ‘tapered

cantilever’ increases the strength when turning andside lifting.

• Lighter but stronger - more efficient metaldistribution.

• Higher WLLs for 1LK and 2LK compensates forsling angles.

• Designed to fit spherical and ‘reduced’ recesses.

FlushTail• Tail has clearance to the concrete surface.

• Less concrete damage when lifting toward the tail.

Compact-8• Lightweight and efficient figure-8 chain link design.

• Additional clearance when side lifting.

• Round links do not damage lifting hooks, links etc.

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Locking Klaws

Safer, faster, lighter, strongerclutches for all spherical headlifting anchors

These clutches are used for lifting a wide range of precast concrete products for building andcivil engineering including panels, pipes, pits, manholes, box culverts, road barriers, bridgebeams, planks, sound walls, culverts etc.

Anchor in central positionat rear of slot

Figure-8 shaped chain link designUnique well

1LK 2LK 5LK 10LK 20LK 50LKL 170 215 270 365 515 780W 66 85 110 145 210 270Ch 44 59 62 83 103 160Cw 40 52 70 90 130 160Sw 33 42 57 73 110 155SI 72 88 113 144 195 235ø 56 68 88 112 152 195S 11 16 22 31 43 55Smax 13 18 25 32 46 58

Nominal Dimensions, Working Load Limits

Locking Klaws solve these critical problems, caused by traditional clutch designs

WLL t0° slingangle 2 3 5 10 20 50Annual Proof 24 36 60 120 240 590Load kNWLL t60° sling 1.7 2.6 4.3 8.6 17.2 43angleNominal 1.3 2.5 5 10 20 32-45WLL anchor

7

W

Sw SI

Ch

L

Ø

S, Smax

Anchor loses support from the rear of the sphere andthe load spreads the lips of the clutch.

Side loading worsens theproblem.

Standard clutch spheres rotate underload because nothing traps the anchor.

Spread lips cause pull-offfailure and shearing ofanchor heads.

And in severe cases, theside of the clutch bendsand breaks.

Typical example of astandard clutch with lipsspread by the anchormoving around the slot.This clutch is at the pointof failing.

Locking

Klaw

s

Cw

Cone (foot) Anchors

Classic spherical headed,forged foot anchor - the firstchoice for most applications

• Hot dip galvanised, forged, high impact strengthconstruction steel

• Genuine Unilift anchors are stamped with ‘U’on the head.

• Anchor Strength WLL and length stamped on thehead of the anchor

H S FWLL (mm) (mm) (mm)1.3 19 10 252.5 26 14 355.0 36 20 5010.0 47 28 7020.0 70 39 9832.0 88 50 135

Standard Anchor Length L (mm)WLL 35 45 55 65 75 85 95 120 1501.3 CA01035 CA01045 CA01055 CA01065 - CA01085 - CA01120 -2.5 - - CA02055 - CA02075 CA02085 - CA02120 -5.0 - - - - CA05075 - CA05095 CA05120 CA0515010.0 - - - - - - - - CA1015020.0 - - - - - - - - -32.0 - - - - - - - - -

Standard Anchor Length L (mm)WLL 170 240 280 340 500 700 960 12001.3 - CA01240 - - - - - -2.5 CA02170 - CA02280 - - - - -5.0 CA05170 CA05240 - CA05340 - - CA05960 -10.0 - - - CA10340 - - - -20.0 - - - CA20340 CA20500 - - -32.0 - - - - - CA32700 - CA321200

S

F

L

H

Part Codes and Anchor LengthsOther sizes are available for special order

8

Anchor Dimensions

Co

ne (foo

t) Ancho

rs

Reo (eye) Anchors

Eye Anchor used with hangerbar if concrete is too weak forcone anchors.

• Hot dip galvanised, forged, high impact strengthconstruction steel.

• Genuine Unilift anchors are stamped with ‘U’ on the head.

• Anchor Strength WLL and length stamped on the head of the anchor.

• Ideal for thin panels and other applications where the concrete shear cone developed bythe anchor is insufficient to provide the working load limit of the anchor (e.g. low strengthconcrete).

• A hanger bar, also known as a tension bar, is threaded through the hole in the anchor andembedded deep in the concrete. See below for the appropriate hanger detail.

Standard Anchor Length L (mm)WLL 50 65 90 120 180 250 3001.3 RA01050 RA01065 - - - - -2.5 - RA02065 RA02090 - - - -5.0 - - - RA05120 - - -10.0 - - - - RA10180 - -20.0 - - - - - RA20250 -32.0 - - - - - - RA32300

Hanger / Tension HL Cut Hanger / Tension Bar LengthWLL H L S Bar Dia D for 15MPa (AS3600 60mm cover)1.3 19 65 10 R8 7002.5 26 90 14 N10 8705.0 36 120 20 N16 102010.0 47 180 28 N20 152020.0 70 250 39 N28 276032.0 88 300 50 N40 5300

L

H

To suitD

D

S

HL

9

Part Codes and Dimensions

Part Codes and Dimensions

Reo

(eye) Ancho

rs

Standard Recess Formers

Used to accurately and reliably set the anchor into its recess inthe concrete product. Recess formers are non-interchangeablebetween load groups, minimising errors. Available in a variety oftypes to meet the demands of different applications.

Semi-Spherical Rubber Recess

• Hard oil resistant, yet flexible, rubber

• For attachment to steel and timber forms or floats

Size 1.3 2.5 5 10 20 32Diameter (mm) 60 74 94 118 160 214Part Code RRF01 RRF02 RRF05 RRF10 RRF20 RRF32

Steel Recess with Rubber Retaining Ring

• Economical recess for production precasting

• Long service life

• Uses a replaceable rubber retaining ring

• May be attached directly to the mould

• Available also with magnetic attachment

Size 1.3 2.5 5Diameter (mm) 60 74 94Recess Part Code SRF01 SRF02 SRF05Ring Part Code RR01 RR02 RR05

Articulating Steel Recess Former

• Similar in action to the semi-spherical rubber recessbut manufactured from steel

• Long service life for production precasting

Size 1.3 2.5 5Diameter (mm) 60 74 94Part Code SRF01A SRF02A SRF05A

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Stand

ard R

ecess Form

ers

Limit State Design ofConcrete Lifting SystemsThe designer must analyse all limit states and failure mechanisms.

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Strength Limit StatesAnchor strength:

Will some part of the anchor or other component(e.g. hanger bar) on which the anchor depends for itsload carrying capacity fail?

Concrete strength:

Will the concrete crack or fail?

What are the consequences of cracking?

If the concrete cracks does this cause completefailure (pull-out) of the anchor or is pull-out preventedby a secondary anchoring attachment (e.g. hangerbar)?

Design for anchor strength• If the anchor is to be used without a hanger bar,

select an anchor which has a WLL as specified tomeet or exceed the factored anchor load.

• If the anchor is to be used with a hanger bar, checkthe WLL of the anchor and the WLL of the hangerbar (AS3850: 2003 and AS3600) is sufficient tomeet or exceed the factored anchor load.

Design for concrete strength• Well embedded anchors transfer the applied loads

to the concrete. If the applied load exceeds theconcrete flexural, tensile or shear strength concretecracking will occur.

• If cracking results in complete anchor pull-out, thisdefines the concrete strength ultimate limit state.

• A designer may choose to reinforce the anchorand/or concrete to control cracking and retain theanchor, preventing pull-out e.g. with a hanger bar.Serviceability may then limit the design.

There are no Australian standards which provide theWLL for inserts in concrete, and no standard methodfor calculation of the tensile and shear capacities ofthin concrete panels. These must be determined fromtests. In this regard AS3850: 2003 says:

2.2 WORKING LOAD LIMIT (WLL)

The WLL shall be derived from one of thefollowing, as appropriate:

(a) The relevant Australian Standard.

(b) By dividing jRu, obtained from the relevantAustralian Standard, by the limit state factor (LSF)

(c) By dividing the multiple of the mean value of thetest results (x) (see Appendix A of AS3850: 2003)and the capacity reduction factor (j), by the limitstate factor (LSF) and the sampling factor, ks.

Check the WLL of the concrete for its(compressive) strength at the time of lifting for eachlifting situation (e.g. edge lifting from the mould,edge lifting while suspended, face lifting, handlingin the factory and storage, loading and unloadingon transport, erection).

For well embedded anchors of given embedmentdepth, panel thickness, concrete tensile, flexural andcompressive strengths, the concrete strength limitstate (and therefore WLL) is independent of theanchor itself - it is a function of the load applied to theconcrete.

In Australia, the limit state design of concrete liftingsystems for precast concrete elements is governedby the Australian Standard AS3850:2003.

Perfo

rmance

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Welding and welding embrittlementWhilst Unilift anchors are manufactured from steelswhich are readily weldable, there are issues with zinccontamination, localised hardening (e.g. uncontrolledheat inputs), joint design, undercutting etc.

Welding of Unilift components or indeed anytype of lifting anchors is not recommended.

Strain age embrittlementUnilift anchors are forged from alloy steels andmetallurgical condition insensitive to SAE.

Corrosion limit stateUnilift anchors are hot dip galvanised (coatingthickness >50 micron) to provide resistance toatmospheric corrosion in most environments. Longterm exposure to marine environments can beexpected to result in eventual corrosive attack andpossible rust staining of the concrete.

Impact strength limit state -anchor toughness and resilienceLifting anchors are subject to high load concentration,possible impact loads and extreme environmentalconditions (temperatures, corrosion etc), requiringmaterials of high toughness. This has beenrecognised in AS3850: 2003 which specifiesminimum toughness properties. Unilift anchors areforged from high toughness alloy steel (DIN 1.0570)with impact strength exceeding the requirements ofAS3850: 2003.

Fatigue and multiple lifting limit statesThe WLL of Unilift anchors is ~60% of the 40,000cycle fatigue limit for these steels and so fatigue is nota significant issue. On the other hand, mechanicaldamage, loss of metal, notching or corrosion pittingreduce both impact and fatigue strength.

General guidelines• Undamaged anchors can be considered safe for

multiple lifting for at least 100 lifts over at leastthe half-life of the galvanised coating from thecorrosion table on page 13.

• Where anchors are designed for intentional long-term multiple lifting, the design factor should beincreased from 2.5 to 5 to account for additionalwear and tear.NB: Standards require a design factor of 5 forlifting equipment intended for long term multiplere-lifting operations to compensate for wear inservice.

• Check for wear, mechanical or corrosion damagebefore attempting to lift with anchors after longterm exposure which may have sufferedcorrosion or other damage.

Serviceability Limit States

The strength limit state is not the only consideration andnot always the limiting factor.

Serviceability limit states also control the selection of materials.

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Typical AV Long TermAS/NZS Environmental corrosion rate AV Long Term Typical

ISO 9223 2312 External of steel corrosion rate Service life -category corrosivity Interior micron/year of Zinc 42 micron coatingC1 Very low Alpine < 0.1 < 0.1 >50 years

Dry interiorsC2 Low Arid/rural/urban 0.1 - 1.5 0.1 - 1.7 40-50 years

Interiors with occasionalcondensation

C3 Medium Coastal50 metres to 1 km inland from

sheltered seas or 1 km to 10-50 kmfrom surf beaches depending upon - - 14-40 years

prevailing winds andtypography.

Industrial e.g. dairies,food processing etc

C4 High Sea-shore calm - - 7-14 yearsSwimming pools

C5 Very high Sea-shore surf and offshore - - 5-7 years

Is minor concrete cracking/spallingacceptable?High Finish Building Panels

Minor flexural cracking may be tolerable andcontrolled by reinforcing detailing to close the cracksto permissible crack widths. Generally severecracking and spalling is not permissible and wouldrequire expensive patching and repair in the factory orin-situ.

Where a high finish is required, typically visible andexterior walls, un-cracked design and systems whichminimise cracking (e.g. EdjPro) should be specified.

Panels and precast elements for civil and generalapplications

In some cases minor cracking and spalling may notbe a significant issue for the intended application e.g.pits, bridge planks, bunker walls for gravel storage,lids etc. Cracked and spalled products give theimpression of “poor quality”. Reputablemanufacturers, proud of their products seek tominimise cracking and damage around the anchorpoints of their otherwise well finished, high qualityproducts.

Where thin products are to be lifted from their edges,Unilift and similar systems can lead to damagearound the recess and in these cases the UniconEdjPro system offers users a superior performancewith a unique recess, anchor and clutch designdeveloped to eliminate cracking for Perfect Panels.

* Source: Galvanisers Association of Australia

Stainless steel anchors are available for aggressive environments.

The service life of Unilift galvanised anchor coatings depends on the environment in which it is used.

Perfo

rmance

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Designing Concrete Lifting Anchorswith AS3850:2003

Historical Note:Prior to the adoption of AS3850 in 1990, safe working loads for concrete lifting anchors were calculated usinga factor of 3 between the working load and the minimum ultimate strength of the anchor.

The AS3850 code committee chose to reduce this (Design Factor) from 3 to 2.5 for the Working Load Limit ofanchors and applied a mandatory Load Factor of 1.2 (essentially a dynamic load factor) to the static load,thereby retaining the overall minimum factor of 3 (1.2 x 2.5 = 3.0).

High impact loads - e.g. travel over rough ground“Bouncing” whilst suspended can generate loads up to 5 times the static load at the anchor point. Where thistype of loading cannot be avoided e.g. transporting pipe components with a backhoe, then increased dynamicfactors must be applied when factoring the load to ensure that the anchors, locking klaws, chains attachmentsand lifting equipment are capable of withstanding these impact overloads.

e.g. Rectangular panel 10 x 2.5 metres x 150 mm thick, normal weight concrete (density 2.4)

Weight in tonnes: = 10 x 2.5 x 0.150 x 2.4 = 9 tonnes

Volume x Density

Calculate the weight of the object

Select the Load Factor

Calculate the factored load

Weight x Load Factor

Calculate the total factored load

Design Lifting Condition Load Factor AS3850: 2003 RequirementLifting from smooth, oiled steel moulds and 1.2 1.2casting beds, handling and erection with a craneLifting from concrete casting beds, 1.5 1.5e.g. site-cast tilt upLifting deep ribbed panels or objects where high suction 2 -and adhesion loads can be generatedLifting from moulds without removable side forms 3 -Travelling over rough ground whilst suspended 4-5 -

Design guide for load factors, reference AS3850: 2003, Clause 3.5.2Note: AS3850: 2003 always requires a minimum load factor of 1.2!

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Calculate the loads applied to the lifting system during lifting from the mould; and alsowhen suspended during handling and panel erection.Note! When a panel is supported on one edge and tilted from the horizontal position to the vertical, half of thepanel weight may be used for the calculation of loads prior to final lift off. After lift off the full weight of the panelmust be used for the calculation of factored loads.

Select the number of lifting pointsDetermine the minimum (normally 2 points) or required number of lifting points to ensure that the stresses fromlifting do not exceed the strength of the object being lifted. e.g. a long thin panel lifted from its edge willnormally require multiple lifting points so that the flexural stresses do not exceed the panel strength.

Select the method of rigging and apply a ‘sling factor’ if requiredNB: 1LK and 2LK Locking Klaws have increased WLLs (2t and 3t respectively) to enable these to be used atfull nominal anchor capacity (1.3t and 2.5t) at sling angles up to 60° an advantage for slinging many smallelements.

a

Factored anchor load =

(factored load / number of anchors) x sling angle factor

Check the factored load at each anchor

Factored clutch load =

(factored load / number of anchors) x sling angle factor

Check the factored load in the clutch and sling components

Included angle a Sling Angle Factorbetween the slings0° 130° 1.0460° 1.1690° 1.42120° 2

Perfo

rmance

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Designing Concrete Lifting Anchors with AS3850:2003

Check whether the factored load exceeds the WLLof the concreteCase 1: Cone anchor - uncracked concrete design

Is the concrete strong enough to support the WLL without cracking the concrete?

• Check the WLL of the concrete - WLLc (fRuc /2.5), either by reference to thetables in this manual or by calculation.

• Consider a longer cone anchor or increase the concrete strength at the timeof lift.

WLLct = fRuc / 2.5

Case 2: Reo (eye) anchor – cracked concrete design

If the concrete cracks at a load less than the WLL x 2.5

• Use a Reo anchor with correctly designed and detailed hanger bar.The limit state is controlled by hanger bar failure Ruh.

WLLt = fsRuh / 2.5

AS3850:2003 does not provide full design methods for lifting inserts.

Refer: the following extracts:

1.5 Use of Limit States Design

Tilt-up panels shall be designed for all phases of their design life, from casting to their service in the final structure.Where these aspects are covered by AS3600, the design shall be carried out using limit states design (LSD)procedures.

C1.5 Limit states design at this stage is under investigation and the committee is not in a position to recommendlimit state procedures for insert design and erection stresses in panels.

C2.2 The WLL of a system will need to be assessed by a suitably experienced and competent person. It should benoted that the manufacturer of a device cannot determine the WLL of the device for each and everyconfiguration that may be involved in a given system.

3.5.4 Design of panels for manufacture and erectionPanels may be designed

(a) to be uncracked; or

(b) assuming they are cracked, in accordance with reinforced concrete design methods.When designing a panel on the basis of cracked sections, that is, using the assumptions of reinforcedconcrete design, sufficient reinforcement shall be used to provide the necessary design capacity. The designershall ensure that the assumptions for effective depth are consistent with the reinforcement detailing.

C3.5.4 Generally, panels will be designed for erection assuming they are uncracked and for the appropriate loads inthe completed structure on the basis of reinforced concrete design. Cracks in panels, which occur duringlifting, are difficult to repair and/or camouflage and therefore tilt-up panels are usually designed to remainuncracked during the erection process. In panels with large openings, designers need to make a judgementas to the position of reinforcement in the panel adjacent to the opening.

If the factored anchor load......exceeds the WLL of the Locking Klaw = Increase the number of lifting points or:

Select a higher WLL Klaw and anchor group

...exceeds the WLL of the anchor strength = Increase the number of lifting points or:Select a higher WLL anchor group

...exceeds the WLLc for concrete strength = Select an eye anchor with hanger bar

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Concrete Strength Limit State: Ruc

For a Cone anchor the concrete failureload is dependent on:• compressive strength f'c of the concrete• depth of embedment h of the anchor in

the concrete• distance a from the anchor to any edge

or face• the spacing c between anchors

The geometry of Cone anchors efficiently transfersthe full load from the foot of the anchor to theconcrete. The anchor length defines the embedmentdepth (plus the set down from the surface).

When the load causes concrete failure, it does so bya ‘shear cone’ being pulled from the concrete with adepth equal to the embedment depth of the anchor.The strength limit state of the concrete is proportionalto the area of shear cone.

The fully developed shear cone has a diameter of approximately 6h. Where anchors are placed closer to anedge than a < 3h or with a spacing c < 6h between anchors, the area of the shear cone is reduced and so thepull-out capacity of the concrete is proportionally reduced. In thin panels where the edge distances to the facesare small, the shape of the shear cone is changed to that of a ‘pie’ shape.

‘Zipper’ failureSometimes, in thin panels and short edge distances, when multiple anchors are embedded along a topedge of a thin panel, the failure surfaces link up and splits the concrete to each face and edge so that astrip of concrete equal to the embedment depth is ‘zippered’ away from the rest of the panel.

h

Embedment depth

3h a

c

Centre spacing

Edge distance

Concrete cone failure

Perfo

rmance

18

Concrete Strength Limit State: Ruc

Prediction of Cone Anchor Failure and Ruc for design

Where Ruc (kN), h (mm), f'c (Mpa):

• Embedment greater than 120mm:Use the Haeussler equation to predict cone failure:

fRuc = kc . h2. f'c0.67

kc = 9.72 x 10-4

• Embedment less than 120mm:Use the ACI CCD equation (better fit from tests less than 100mm):

fRuc = knc . h1.5. f'c0.5

knc = 1.55 x 10-2

Reduction factors for edge distancesA simple and effective method for calculation of the reduction of conic areas comes from the realisation that afull cone is developed at a diameter of 6h at an angle of ~30° and that the concrete strength limit state Ruc isdirectly proportional to the area of the pull-out cone.

From trigonometry, the fully developed shear cone has a conic surface proportional to the hypotenuse of atriangle with sides h and 3h and since by Pythagoras' theorem the length of the hypotenuse (conic surface)varies by the square root of the two sides of the triangle, the ratio of the reduced area is as follows:

for a = edge distanceh = embedment depth so that

Reduced Conic Area a √sin(30. a/h)

Note when a = 3h this reduces to sin90° = 1

Ruc-reduced = Ruc . √sin(30. a/h)

This power equation may be extended to cater for anchors placed close to an edge and/or at anchor spacingsless than 6h (3h + 3h).

Ancon can assist designers to calculate Ruc for more complex anchor placements than the tables in this designguide cater for. The program includes the calculation of Ruc- reduced according to the geometry and strength ofthe product to be lifted.

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Concrete Strength Limit State: Ruc

Other types of failure

Very short anchorsAdhesion failure - where the force required to breakthe bond between the concrete and the anchorresults in anchor pull-out without a cone.

Long anchors in the tops of columnsHorizontal splitting failure – where the force requiredto provoke splitting to each surface is less than todevelop a shear cone. This is similar to “zipper” failureand most commonly seen where long anchors areplaced in small piles.

Long anchors in thin panelsSide Blowout failure - where the embedment depthfrom the surface of the panel to the foot of the anchorcontrols cone failure.

Perfo

rmance

20

Design for Concrete Strength

Factored concrete strength limit state:

fcRuc = 0.6 Ruc

WLL for concrete strength limit state:

WLLc = fcRuc / 2.5

From AS3850:20031. The factored ultimate load f Ruc is the predicted failure load of the concrete when it cracks and can no

longer support the load. It includes the capacity reduction factor fc = 0.6 for concrete.

This is defined as follows in Appendix A of AS3850: 2003

f Ru = x/ks . . A4.6

where

f Ru = strength limit state capacity

x = mean value of test data (Paragraph A4.4)

ks = sampling factor, Table A2 = 1.3 (more than 5 tests)

and

WLL = f Ru /2.5

NB!

i) The concrete will crack at Ruc. At this load a cone anchor (foot anchor) will pull-out.

ii) If an eye anchor is used with a hanger bar then after cracking the load is transferred to the hanger.If the hanger is not strong enough it will fail by shearing at the connection point (hole in the anchor) ortensile failure of the bar or pull-out from the concrete.

iii) If the hanger has been correctly designed (see section on hanger bar design) then this shall becapable of providing an ultimate failure load not less that 2.5 times the WLL of the hanger bar or theWLL of the anchor, whichever is the lower.

2. If the design anchor load is less than the WLL of the concrete then the anchor can be used withoutadditional reinforcing or panel cracking. Shear reinforcing over the anchor and recess can assist incontrolling cracking where serviceability requires.

3. The factored ultimate load (f Ru) for edge shear (loading toward the edge) is the load at which the paneledge is predicted to crack, regardless of whether a shear bar is present. If a shear bar is present it shouldcontrol the crack and minimise the risk of spalling. Ancon recommends sufficient anchors be installed sothat the design anchor load is less than f Ru or some spalling may occur.

21

FAQ: Contribution of panel reinforcing steel

Contrary to a popular misconception, thepresence of reinforcing steel in the panel cannotbe assumed to increase the failure strength!

Steel designed to elastically control cracking forshrinkage and in-place loads does not necessarilyincrease the failure load sufficiently to meet therequirements for lifting!

The purpose of reinforcing an anchor against ultimatefailure is quite different from adding steel to controlcracking in normal concrete design.

• The limit state for crack control steel is the elasticlimit i.e. steel yield.

• The limit state for lifting anchor reinforcement issteel failure i.e. breaking load, divided by a designfactor of 2.5.

Lifting loads are not expected to exceed the designWLL and most don't! However higher loads canoccur accidentally and for this reason the designfactor is required. The most likely accidentaloverloads are impact loads.

Concrete subjected to impact loads tends to failexplosively; whilst the same load applied slowly maynot lead to more than cracking, the additional forcesgenerated within the concrete from impact causespalling, delamination and loss of bond andconfinement of the reinforcing steel. If the impact loadis sufficient to exceed both the WLL and cone failurestrength concrete, then the reinforcing steel must becapable of resisting the factored lifting load. After theconcrete has cracked only fully confined steel iscapable of reinforcing the concrete in the anchoragezone.

Additional steel may be designed to specificallytransfer lifting loads but in doing so it becomes part ofthe lifting system and must be designed to AS3850:2003 accordingly.

Designers must ensure that effective shear reinforcingsteel (e.g. closely spaced stirrups) encloses theconcrete in the anchorage zone and the steel towhich the loads are to be transferred to preventspalling, loss of bond and anchorage.

If it is necessary to reinforce the cracking in andaround the anchor zone, the area of steel required totransfer the lifting load must be designed to meet therequirements of AS3850: 2003 i.e. f Ru / 2.5 ≥ S*and development, confinement etc accordingto AS3600.

Can the failure strength be improved by the panel reinforcing steel?

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22

Concrete working load limitWLLc design tables

The design tables provide WLLc for the failure of theconcrete (concrete strength limit state).

1. WLLc is calculated for products with shrinkagereinforcing. As the presence of unconfinedreinforcing makes no difference to the WLLc theeffect of other steel must be disregarded unless ithas been specifically designed for lifting and hasbeen detailed accordingly.

2. WLLc in these tables includes the design factor of2.5 required by AS3850: 2003.

3. Where the factored load exceeds the WLLc eyeanchors must be used with a hanger bar designedin accordance with AS3850: 2003 and AS3600(see tables).

4. If the factored shear load toward a free edgeexceeds the ultimate shear capacity, the edge islikely to fail. Initial cracking may commence fromabout 50% of the ultimate capacity. Ancon doesnot recommend Unilift systems for edge lifting thinproducts toward a face because compression of

the concrete by the clutch may cause edgecracking and spalling. Ancon EdjPro systems havebeen specifically designed for this type of liftingand offer solutions for the production of PerfectPanels.

5. ‘Shear bar’ reinforcing over the recess may helpcontrol, but cannot prevent cracking!

6. When panels are rotated about a supporting edge(e.g. from mould), with hanger bars fitted toanchors to prevent them pulling out, shearcracking does not limit the anchor WLL but couldresult in panel damage. Loads should be limited tothe ultimate edge shear capacity of the concreteand/or shear bars used to control cracking.

7. Ancon recommends a minimum concretecompressive strength f´c=15MPa at time of lifting.

Ancon has expressed the values for the WLLs intonnes force (rather than kN) to avoid confusionbecause most lifting equipment is specified inAustralia for WLL in tonnes.

Preferred length and short Cone anchorsSpecial care must be taken when designing with foot anchors shorter than the “preferred lengths” shown in thetable below for each load range which have been designed to develop the WLL of the anchor when placed atthe minimum edge distance in concrete of at least 10MPa.

Load GroupWLL t 1.3 2.5 5 10 20 32PreferredAnchor 120 170 240 340 500 700Length (mm)Part Code CA01120 CA02170 CA05240 CA10340 CA20500 CA32700

23

Concrete Strength WLLc of anchors with minimum edge distance a≥3h and spacing s≥6h

Embedment Min Edge Min Anchor WLLc = ФRuc / 2.5 tonnes Forcemm Distance Spacing 10MPa 15MPa 20MPa 30MPa 40MPa30 90 180 0.33 0.40 0.46 0.57 0.6635 105 210 0.41 0.51 0.59 0.72 0.8340 120 240 0.51 0.62 0.72 0.88 1.0145 135 270 0.60 0.74 0.85 1.05 1.2150 150 300 0.71 0.87 1.00 1.23 1.4155 165 330 0.82 1.00 1.15 1.41 1.6360 180 360 0.93 1.14 1.31 1.61 1.8665 195 390 1.05 1.28 1.48 1.82 2.1070 210 420 1.17 1.44 1.66 2.03 2.3475 225 450 1.30 1.59 1.84 2.25 2.6080 240 480 1.43 1.75 2.02 2.48 2.8685 255 510 1.57 1.92 2.22 2.72 3.1490 270 540 1.71 2.09 2.42 2.96 3.4295 285 570 1.85 2.27 2.62 3.21 3.70100 300 600 2.00 2.45 2.83 3.47 4.00105 315 630 2.15 2.64 3.04 3.73 4.31110 330 660 2.31 2.83 3.26 4.00 4.62115 345 690 2.47 3.02 3.49 4.27 4.93120 360 720 2.67 3.51 4.25 5.58 6.76125 375 750 2.90 3.80 4.61 6.05 7.34130 390 780 3.14 4.12 4.99 6.55 7.94135 405 810 3.38 4.44 5.38 7.06 8.56140 420 840 3.64 4.77 5.79 7.59 9.21145 435 870 3.90 5.12 6.21 8.15 9.88150 450 900 4.18 5.48 6.64 8.72 10.57160 480 960 4.75 6.23 7.56 9.92 12.03170 510 1020 5.36 7.04 8.53 11.20 13.58185 555 1110 6.35 8.33 10.11 13.26 16.08190 570 1140 6.70 8.79 10.66 13.99 16.96240 720 1440 10.69 14.03 17.01 22.32 27.06280 840 1680 14.55 19.09 23.15 30.37 36.83340 1020 2040 21.45 28.15 34.13 44.79 54.31400 1200 2400 29.69 38.96 47.24 61.99 75.17500 1500 3000 46.39 60.88 73.82 96.86 117.45700 2100 4200 90.93 119.32 144.68 189.84 230.20

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24

Concrete working load limit WLLc design tables

Concrete Strength WLLc for preferred length anchors when the anchor is placed closerto one edge, less than the critical edge distance: a1 < 3h, and the remaining edgedistances exceed the critical edge distance: a2, a3, a4 ≥ 3h

Effective EdgeAnchor WLL Embedment Distance WLLc = ФRuc / 2.5 tonnes ForceLength mm hef mm a 10MPa 15MPa 20MPa 30MPa 40MPa1.3 x 120 125 30 1.03 1.35 1.63 2.14 2.60

40 1.18 1.55 1.88 2.47 3.0050 1.32 1.73 2.10 2.76 3.35

2.5 x 170 177 40 2.00 2.62 3.18 4.17 5.0650 2.23 2.93 3.55 4.66 5.6575 2.73 3.58 4.34 5.69 6.90

5 x 240 250 50 3.75 4.92 5.97 7.83 9.4975 4.59 6.02 7.30 9.58 11.61100 5.29 6.94 8.41 11.04 13.39

10 x 340 350 75 7.61 9.98 12.10 15.88 19.26100 8.78 11.52 13.96 18.32 22.22150 10.72 14.07 17.06 22.39 27.15

20 x 500 510 100 15.45 20.28 24.59 32.26 39.12150 18.90 24.81 30.08 39.47 47.86200 21.80 28.60 34.68 45.50 55.17

32 x 700 710 100 25.39 33.32 40.40 53.01 64.28200 35.86 47.06 57.06 74.87 90.78250 40.05 52.56 63.73 83.62 101.40

Bolded values: Concrete WLLc exceeds the nominal WLL of the anchor steel.

a2 ≥ 3ha1 < 3h

WLL Concrete Tension

a3 ≥ 3h a4 ≥ 3h

25

Concrete working load limit WLLc design tables

Concrete Strength WLLc for preferred length anchors placed in the centre of thin panelwhen the panel thickness t < 6h (a1, a2 < 3h) and the remaining edge distances exceedthe critical edge distance: a3, a4 ≥ 3h

Effective PanelAnchor WLL Embedment Thickness WLLc = ФRuc / 2.5 tonnes ForceLength mm hef mm t = 2a 10MPa 15MPa 20MPa 30MPa 40MPa1.3 x 120 120 60 0.38 0.50 0.60 0.79 0.96

80 0.50 0.66 0.80 1.05 1.27100 0.63 0.82 1.00 1.31 1.59

2.5 x 170 177 80 0.69 0.90 1.09 1.43 1.74100 0.86 1.12 1.36 1.79 2.17150 1.28 1.68 2.04 2.67 3.24

5 x 240 250 100 1.21 1.59 1.93 2.53 3.07150 1.81 2.38 2.89 3.79 4.59200 2.41 3.16 3.84 5.03 6.10

10 x 340 350 150 2.55 3.34 4.05 5.31 6.44200 3.39 4.45 5.39 7.07 8.58300 5.06 6.64 8.05 10.56 12.81

20 x 500 510 200 4.95 6.49 7.87 10.33 12.52300 7.40 9.72 11.78 15.46 18.74400 9.84 12.91 15.66 20.55 24.91

32 x 700 710 200 6.89 9.04 10.97 14.39 17.45400 13.75 18.04 21.87 28.70 34.80500 17.15 22.50 27.29 35.80 43.41

Bolded values: Concrete WLLc exceeds the nominal WLL of the anchor steel.

a3 ≥ 3h

a4 ≥ 3h

WLL Concrete Tension

a1, a2 = t/2 < 3h

t

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26

Concrete working load limit WLLc design tables

Concrete Shear Strength WLLc.shear for anchors loaded toward a free edge

fRuc.shear and WLLc.shear = ФRuc.shear / 2.5 tonnes ForceEdge

Anchor WLL Distance 10MPa 15MPa 20MPa 30MPa 40MPaLength mm a fRuc.s WLLc.s fRuc.s WLLc.s fRuc.s WLLc.s fRuc.s WLLc.s fRuc.s WLLc.s

1.3 x 120 50 0.36 0.14 0.44 0.17 0.50 0.20 0.62 0.25 0.71 0.2875 0.66 0.27 0.81 0.33 0.94 0.38 1.15 0.46 1.33 0.53100 0.97 0.39 1.19 0.48 1.38 0.55 1.69 0.67 1.95 0.78300 3.45 1.38 4.22 1.69 4.87 1.95 5.97 2.39 6.89 2.76

2.5 x 170 75 0.85 0.34 1.05 0.42 1.21 0.48 1.48 0.59 1.71 0.68100 1.29 0.52 1.58 0.63 1.83 0.73 2.24 0.90 2.58 1.03125 1.73 0.69 2.12 0.85 2.45 0.98 3.00 1.20 3.46 1.38400 6.54 2.62 8.01 3.21 9.25 3.70 11.33 4.53 13.08 5.23

5 x 240 100 1.65 0.66 2.02 0.81 2.33 0.93 2.86 1.14 3.30 1.32125 2.27 0.91 2.78 1.11 3.21 1.28 3.93 1.57 4.54 1.81150 2.89 1.15 3.53 1.41 4.08 1.63 5.00 2.00 5.77 2.31540 12.53 5.01 15.34 6.14 17.72 7.09 21.70 8.68 25.05 10.02

10 x 340 150 3.75 1.50 4.59 1.84 5.30 2.12 6.49 2.60 7.49 3.00175 4.61 1.84 5.65 2.26 6.52 2.61 7.99 3.20 9.22 3.69200 5.48 2.19 6.71 2.68 7.75 3.10 9.49 3.79 10.95 4.38770 25.20 10.08 30.87 12.35 35.64 14.26 43.65 17.46 50.41 20.16

20 x 500 200 7.23 2.89 8.86 3.54 10.23 4.09 12.53 5.01 14.47 5.79300 12.28 4.91 15.03 6.01 17.36 6.94 21.26 8.50 24.55 9.82400 17.32 6.93 21.21 8.48 24.49 9.80 30.00 12.00 34.64 13.85

1050 50.09 20.04 61.35 24.54 70.84 28.34 86.77 34.71 100.19 40.0832 x 700 500 29.69 11.88 36.36 14.54 41.99 16.79 51.42 20.57 59.38 23.75

1250 82.34 32.94 100.85 40.34 116.45 46.58 142.62 57.05 164.68 65.87

a

WLL Concrete Tension

Where the edge distance is substantially less than 3hcare must be exercised in selecting anchor systemsto avoid cracking and spalling of the panel edge.

• Ancon recommends EdjPro systems, specificallydesigned for edge lifting thin panels, for theproduction of Perfect Panels.

The following table shows that the full working loadlimit of preferred length anchors is not supported bythe shear capacity of the concrete when loadedtoward the free edge until the edge distanceapproaches 3h.

• Typically, minor cracking commences from about50% of the limit state strength fRuc.s.

• ‘Shear bar’ reinforcing may help control crackingbut shear bars cannot prevent cracking!

27

Design of Hanger barsfor Reo (eye) anchors

AS3850: 2003 requires hanger bars (being part of the anchor system) be designed as follows:

Clause 2.2 Working Load Limit (WLL)The WLL shall be derived from one of the following, as appropriate:

(a) The relevant Australian Standard.(b) By dividing f Ru, obtained from the relevant Australian Standard, by the limit state factor (LSF).(c) By dividing the multiple of the mean value of the test results (x) (see Appendix A of AS3850: 2003) and the

capacity reduction factor (f), by the limit state factor (LSF) and the sampling factor, ks.

Note: option (a and b) are determinative because (c) is not appropriate. It is not possible to guarantee that thestrength of the bar which is used for testing is the same as, or representative of, every bar delivered for makingthe hanger bars in practice. The characteristic strength of reinforcing bars specified in AS4671 and AS3600should be used in the design of hanger bars made from standard grade reinforcing steels.

Example:500N grade hanger bars. AS4671 specifies an ultimate/yield strength ration of 1.08 (minimum).

ultimate strength in tension Ru = Ab x 1.08 x 500 N= Ab x 1.08 x 500 / 1000 (kN)= 0.54 x AAb (kN)

where Ab = cross sectional area of the barNow the WLL of lifting inserts (including the hanger reinforcing bar which is part of the anchor)

WLL = f Ru /LSF ...... Cl. 2.2 (b) AS3850: 2003fs = 0.8 ...... table 2.3 (a) (i) AS3600

LSF = 2.5...... Cl 2.4.2 AS3850: 2003Therefore

WLL = 0.8 x 0.54 x Ab / 2.5 = 0.173 x Ab (kN)Since a hanger bar has 2 legs in tension, the capacity of the bar in tension is double this force:

Ru = 2 x Ab x 0.54 / 9.8 (tonnes Force)WLLhanger bar = 2 x Ab x 0.173 / 9.8 (tonnes Force)

The following table shows the calculated loads and development lengths according to the requirements ofAS4671, AS3850: 2003 and AS3600 for a hanger bar with two legs centrally located with a minimum of 60mmcover either side.The recommended hanger bar lengths shown in this table have been calculatedconservatively, for concrete compressive strength f'c =10MPa. This is to provide effective hanger reinforcementwhen demoulding. Shorter lengths may be used at higher concrete strengths.

RuHanger Area Total Ultimate Tensile Strength WLL Tension Limit Statedb Ab Area for 2 legs AS3850: 2003 f*Ru / 2.5Rebar Area 2 x Ab tonnes Force tonnes ForceN12 113 226 12.45 4.0N16 201 402 22.15 7.1N20 314 628 34.60 11.1

The development length of the hanger bar is calculated from AS3600 to develop Ru.

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FAQ: Hanger bars

28

Why use a hanger bar?Thin concrete panels cannot support a high loadwhen they are lifted by their edges. If the concretewere to crack, a pie shaped segment including theanchor would be torn from the panel.

A hanger bar is a reinforcing bar which improves theload capacity of the anchor beyond the load at whichthe concrete would otherwise fail.

What is a hanger bar?A reinforcing bar bent in an inverted V shape which ispassed through a hole in the anchor. The lifting load istherefore transferred by the hanger bar, deep into theconcrete panel.

✓When are hanger bars required?When the concrete cracking load is less than 2.5 times the required WLL.

• Hanger bars are always required for edgelift anchors of any type in 150mm thick panels when the AnchorLifting Load is greater than about 2.3tonnes. This is because most panels are lifted from the mould when theconcrete is only 10-15MPa.

• At 10MPa, the cracking strength is only 5.7tonnes which provides a 2.3tonne Working Load Limit(including the Design Factor of 2.5 required by AS3850: 2003).

Will a horizontal bar e.g. edge trimmerwork?NO!

Horizontal bars do not transfer vertical load they“zipper” out of the edge.

Does panel mesh improve the liftingload?NO!

Panel mesh is only designed for shrinkage forces.It must NEVER be relied upon to improve the liftingload capacity of anchors in panels!

Can the lifting load be improved by theother panel reinforcing bars?Maybe, but ONLY if that reinforcing steel has beenespecially designed to accept the lifting load!

This is NOT normal! Normal panel reinforcing steel isonly designed for in-service structural loads. It mustNEVER be relied upon to improve the lifting loadcapacity of anchors in panels.

✗

✗

✗

29

FAQ: Lifting Loops

What is the problem with lifting loops?Lifting loops of smooth round bars can be made ofsteels which meet lifting code requirements BUT theyhave significant disadvantages compared to Uniliftsystems. In the end they cost more.

• Every loop must be engineered and installationsupervised to control quality

• Bending the steel results in internal stresses whichcan sensitise the material to strain ageembrittlement after heating – e.g. galvanising orhigh environmental temperatures

• “Kinking” occurs unless lifted with a pin diameter atleast 6 times the loop steel diameter, degradingstrength, ductility and toughness.

• They are only suitable for straight lifts. Angled liftingcreates stress points and damage.

• There is no visual confirmation of the WLL of theloop nor indication to users of lifting restrictions/requirements – e.g. minimum pin diameter.

• Loops are exposed to mechanical damage, preventeasy stacking, slow production and increase cranecosts in the factory and on site.

Why are lifting loops made of reinforcingsteels not suitable - or allowed?Just because a loop is designed to be strong enoughdoes not mean it is safe to lift with! Reinforcingmaterials do not have the required properties for liftingand combined with the disadvantages of exposedloops projecting from precast products they present ahigh risk of failure.

Do they meet the requirements of standards andconstruction codes? No!

• AS3850:2003 – specifically excluded - Cl. 2.4.1.Properties do not meet Cl. 2.4.2.

• National code of Practice, Precast. Feb 2008: -Cl. 5.1.4 – prohibited.

What about design rules?

There are none. Since they are not supported bystandards there are no rules for design.

What makes reinforcing steels unsuitablefor lifting?Fitness for purpose

Steels for lifting inserts are required to be both ductileand tough and to meet the impact strength ofAS3850: 2003 they need at least 12% uniformelongation and typically exhibit 20% or more.

Reinforcing steels are designed to be fit for onepurpose: concrete reinforcing! They excel as uni-axialstrength elements subject to continuous loadingwithin their elastic range.They are steels of lowductility, without specified impact properties becauseconcrete reinforcing requires no more. They aredivided into three principal classes:

• Hot rolled “N” class bars which have sufficientductility (5%) to enable them to be bent (but notre-bent) to shape and to provide moment re-distribution capacity when required.

• Hot rolled or drawn “L” class wires which can bebent but have insufficient ductility (1.5%) formoment re-distribution.

• Hard drawn, high carbon wires and strands forprestressing and never intended to be bent. Thesehave anisotropic properties in the drawn direction ofhigh tensile strength (~1800MPa) but low ductility3.5%. They are notch sensitive making themsusceptible to localised embrittlement fromcorrosion pitting, mechanical damage or martensitichardening from metal abrasion or localised heating(e.g. weld spatter).

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Prestressing strands and cables aresometimes engineered for heavy lifting sowhy are they particularly unsuitable forlifting loops?Lifting with cables made of straight lengths of strandcan be safe. This is quite different to a loop! Strand isspun from seven large diameter, hard drawn, stiff, lowductility spring wires. They are ideal tension membersbut not designed to resist shear or bending loads.

When a loop of strand is bent over a small diameter(e.g. around a hook or shackle with a radius of lessthan about six times the strand diameter), the wirestend to “birdcage” and separate. The strand nolonger functions as a whole but as a collection ofindividual wires, each with a different loop diameter(because of the unravelled helix). Not only is there anincrease in the stress in the wires because of beinglooped but since some wires are now longer thanothers, the loads are concentrated in the shorterwires.

"Bunching" strands cannot increase carrying capacitybecause the shortest strands and wires take the loadfirst. In order for load re-distribution to occur, theseshort wires must plastically deform before the otherscan accept their full share of the load. Howeverprestressing wires have low ductility and are designednot to deform significantly before they break and soreliance on load re-distribution must be consideredvery hazardous.

Some have suggested that load equalisation can beachieved by covering the strands with a sleeve (e.g. asteel pipe). This is not possible. The sleeve deformsbut the load is only transferred to the shortest strandor wire within the sleeve. Crumpling of the tube alsocauses stress concentrations. Worse, wire breaks arehidden from view and failure can occur withoutwarning.

There are other OHS hazards with PC strands andwires; removal by cut-off saw or gas cutting causesthe strands to violently fly apart and or "flick" theoperator with (hot) splinters of hardened steel and orbroken saw blade pieces; corrosion and mechanicaldamage have severe implications as these materialsare easily embrittled by notches and corrosion pitting.

31

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Rigging Guide

Regulatory RequirementsAS3850: 2003 and the National Code of Practice for Precast and Tiltup Construction require that riggingsystems be designed to distribute loads equally between all anchors in precast components. If loads are notequally distributed, damage or failure can occur to the precast components, the rigging components or both.

Rigging Geometry affects the loads in the rigging equipment and the precast components being lifted.Common rigging errors can result in loads of twice the design loads. A common mistake is to lift acomponent designed with four equally loaded points with four fixed length slings attached to a ring or hook.The small variations in the lengths of the rigging result in the load in this case only being shared by two of theslings, resulting in double the load applied to the anchors and the concrete surrounding the anchor. Whenlifting thin precast panels this has been the cause of many failures.

Rigging with multiples of three lifting points (except for the special case shown) is not recommended by codes.

T T

P=4T

T T

T T

P=2T

T

2T 2T 2T

P=6T

TT

T

P=3T

c.g.

Rigging Diagrams for Equalised LoadingCorrect rigging for equalised anchor loading

2 points

4 points

2 fixed lengthEqual loads in each

3 pointsOnly for special cases!

Special Case! 3 fixed legslings equally distributed

around the centre of gravity

2 sheaved slingsEqual loads in each

Flat lift - equalised

Flat lift - equalised Flat lift - equalised

c.g.

Always ensure that the centre ofgravity (centroid) of the objectbeing lifted lies below the centreof lift of the lifting anchors toavoid instability and topplingduring lifting.

Flat lift - equalised

T T

P=2T

P=2

P=4T

T T T T

2T2T

Rigging Guide

Recommended Rigging Configurations when Facelifting with Unilift QwikTilt systems

Minimum 2D Minimum 3C + DMinimumC + 300mm

D

C

D

2 x 1 2 x 2 4 x 2

2 x 4

Minimum 4.5D or4.5E whichever isthe greater

Minimum 3D

D

E

Minimum 3D

4 x 2

The maximum slingangle q should bespecified in thelifting design.

Sheave Sheave

Sheave Sheave

2 point edge lifting:For tilting up panels by their long edge, e.g.from the casting bed. For typical 150mmthick panels less than 5 metres long.

Preferred 4 point equalised edge lifting:With load equalising beam and sheaved slings.For typical 150mm thick panels5 - 10 metres long.

Non-preferred 4 point equalised edge-lifting:With sheaved slings

Recommended Rigging Configurations when Edge-lifting panels with EdjPro systems

32

q

33

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Transporting in the factory, handling and erection by top-lifting from the edge

2 point 4 point

Main Winch:Connect two standard EdjPro clutches or EdjPro Hammerlock clutches to the EdjPro top-lift erection anchors.

Auxiliary Winch:Connect an EdjPro clutch with locking ring arm away from the point of lift to the ‘spin-up’, or ‘tail-lift’ EdjProanchor which is located at approximately ¼ of the long edge.

Standard EdjPro clutches EdjPro Hammerlock clutches

Mid-air Panel Rotation ‘Spin-up’ and Erection using EdjPro anchors and clutches

Spin-upEdjPro Anchor

AuxiliaryWinch

MainWinch

Top-liftEdjPro Anchors

Turn the panel bytransferring the load tothe main hoist.

Remove the spin-up clutch.Hoist the panel into position anddisconnect the top lift clutches,preferably with the aid of anelevated work platform.

Rigging Guide

34

Many accidents and failures have occurred with these rigging configurations because of the difficulty ofensuring that the loads are evenly distributed.

Flat lifting with three points is possible when they areequi-distant from the centre of gravity.

TT

T

c.g.

Special Case! 3 fixed leg slings equallydistributed around the centre of gravity

This can be OK but it is generally safer forstability to lift with 4 fixed leg slings anddesign for sharing the load on 2 of the4 points.

T

2T

T

T

2T 2T 2T

P=6TEqual Load

P=4TCentral AnchorDouble Loaded

P=2T P=2T

T T TT

0

0 TT

0

0

0

0

4 point rigging with fixed length slings developsunequal loads i.e. load is shared on two slings only

Flat lift4 x fixed slingsno equaliser

4 equal length slings unequalloads. Panel tries to bend toequalise the loads.This overstresses the panelcausing cracking.

T T

2T

T T0 0 0 0

Fixed leg slings can lead to indeterminate loading

Rigging diagrams showing unequal loading

Rigging with multiples of 3 slings isparticularly difficult and not recommended

35

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NOTES

© Ancon Building Products 2012

The construction applications and details provided in this literatureare indicative only. In every case, project working details should beentrusted to appropriately qualified and experienced persons.

Whilst every care has been exercised in the preparation of thisdocument to ensure that any advice, recommendations orinformation is accurate, no liability or responsibility of any kind isaccepted in respect of Ancon Building Products.

With a policy of continuous product development Ancon BuildingProducts reserves the right to modify product design andspecification without due notice.

These products are available from:

Masonry Support Systems

Windposts and Lintels

Wall Ties and Restraint Fixings

Channel and Bolt Fixings

Tension and Compression Systems

Stainless Steel Fabrications

Flooring and Formed Sections

Shear Load Connectors

Stainless Steel Reinforcement

Reinforcing Bar Couplers

Reinforcement Continuity Systems

Punching Shear Reinforcement

Precast Concrete Accessories

Ancon Building Products7-9 Second AvenueSunshineMelbourneVIC 3020AustraliaTel: 1300 304 320Fax: +61 (0) 3 9311 1777

Ancon Building Products82 Chisholm CrescentKewdalePerthWA 6105AustraliaTel: 1300 304 320Fax: +61 (0) 8 9453 2300

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Overseas Offices:

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