Simply better connected.

Hilti. Outperform. Outlast.

Hilti solutions for

post-installed rebar connections

Simply better connected.

Hilti. Outperform. Outlast.

Hilti solutions for

post-installed rebar connections

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More than 100,000 satisfied customers benefit every year from our 25 years of experience in this field.

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Hilti solutions for

post-installed rebar connections

Simply qualified.By Konrad Bergmeister.

The corresponding building codes are applied to the design of rein-forced concrete structures. These codes, however, don’t cover the use of post-installed reinforce-ment. Approvals and regula-tions therefore have a significant role to play in filling this gap.

These approvals prequalify inject-able adhesive mortar systems for use in post-installing rebar connections designed in accordance with existing building codes. A good example of this is the European Technical Approval (ETA) for rebar which allows the design of post-installed rebar connections in concrete using approved products in accordance with Eurocode 2 (EC 2).

Approvals are necessaryDesign engineers can thus now adhere to the familiar rules laid down in these obligatory building codes when design-ing post-installed rebar connections. This is greatly facilitated by use of products with the relevant approval (in Europe, for example, ETA approval). These approvals are necessary to confirm the suitability of an injectable adhesive mortar system regarding its compliance with existing building codes and its ability to meet the design require-ments for the structure concerned.The correct tools and accessories as well as technical expertise are essen-tial where concrete connections are to be made using post-installed rebar. This includes rebar detection devices,

dependable drilling machines, suit-ably matched cleaning and injection accessories, comprehensive instruc-tions and documentation of the pro-cesses and, last but by no means least, proper training of the applicable personnel. This is necessary to ensure high reliability of the fastening solution over the entire life of the structure.

Design engineers should rely on manufacturers or suppliers that provide complete system solutions, including suitable injectable adhesive mortars, for the post-installation of rebar connections in conformance with regulations – systems that have been approved for this application.

Prof. Dr.-Ing. Dr. Konrad Bergmeister is Head of the Department of Civil En-gineering and Natural Hazards at the University of Life Science and Natural Resources in Vienna, Austria, including the Institute of Structural Engineering that he headed previously. He has over 20 years of experience in the field of structural engineering and design and has led many major infrastructure projects. The main topics of his research work are faste-ning systems, structural analysis, monitoring and maintenance.

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Simply works better than cast-in.by Jakob Kunz

Typical definition of bond strength for cast-in according to codes.

Post-installed reinforcement works at least as well as cast-in rebars. This has been proven by the comprehensive testing required for European Techni-cal Approvals for post-installed reinforcement connections. Con-sequently, the design process is straightforward and in accordance with structural concrete codes (Eurocode 2) for post-installed overlap splices, reinforcement anchorage at simple supports and connections of columns mainly loaded in compression.

Only straight bars can be post-installed in cured concrete, but cast-in rein-forcement often uses hooks to reduce anchorage length or bends to divert forces. Hilti has thus invested in exten-sive research to find solutions that allow post-installed reinforcement to be used in situations where standard structural concrete detailing would

require hooks or bends. A revolution-ary new design method has now been developed on the basis of this research.

Hilti HIT Rebar Design MethodAccording to structural concrete build-ing codes, the bond strength of cast-in bars is limited, even where depth of concrete cover is considerable. Accord-ingly, in some zones such as in walls where anchorage depth is often limited, welded transverse reinforcement or hooks are used to compensate for the reduction in available anchorage depth. The Hilti Rebar Design Method also makes it possible to reduce anchor-age length while maintaining the high bond strength needed to replace hooks or welded transverse reinforcement.

Better results through more detailed researchResearch has shown that the bond strength of bars anchored with Hilti adhesive mortars is higher than that of

cast-in-place bars, provided there is adequate concrete cover1. The Hilti HIT Rebar Design Method takes advan-tage of this increased bond strength in order to achieve anchorage length reductions of up to 50% compared to the figures given in building codes.

Frame node connections with straight barsAccording to standard reinforcement design concepts, bends are required at moment-resisting connections. Working together with the Technical University of Munich and the American University of Beirut, Hilti has carried out theoretical and laboratory research in order to propose an adequate strut-and-tie model that takes the specific characteristics of frame node connec-tions with straight bars2 into account.

Connection of members under tensionWhere a connection is made between concrete members under predominant

Typical bond strength of Hilti adhesive depending on cover.

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Strut-and-tie modeling of frame node connections for straight (post-installed) and bent (standard cast-in) bars.

tension, the principles of anchor design should be applied3. As a specialist in anchoring to concrete, Hilti is well qualified to provide the appropriate solutions. Factors such as the pos-sibility of concrete cone breakout must be given special consideration.

Post-installed reinforcement for shear loadsThanks to many years of research, Hilti is also in an excellent position to provide solutions for post-installed shear interface reinforcement4 for concrete overlays or post-installed punching shear reinforcement5.

References1) Kunz, J., Muenger F.: Splitting and Bond Failure

of Post-Installed Rebar Splices and Anchorings. Bond in Concrete. fib, Budapest, 20 to 22 Novem-ber 2002.

2) Hamad, B.S., Al-Hammoud, R., Kunz, J.: Evaluati-on of Bond Strength of Bonded-In or Post-Instal-led Reinforcement. ACI Structural Journal, V. 103, No. 2, March–April 2006.

3) Design of Bonded Anchors. EOTA Technical Re-port TR 029. European Organisation for Technical Approvals, June 2007.

4) Randk, N.: Untersuchungen zur Kräfteübertragung zwischen Alt- und Neubeton bei unterschiedlicher Fugenrauhigkeit. University of Innsbruck, Austria, 1997 (Thesis in German).

5) Fernandez Ruiz, M., Muttoni, A., Kunz, J.: Strengthening of Flat Slabs Against Punching Shear Using Post-Installed Shear Reinforcement. ACI Structural Journal, V. 107, No. 4, July–August 2010.

Dr. Jakob Kunz is Scientific Consultant for the Hilti Anchor Business Unit. He gained his doctorate at the ETH (Swiss Federal Institute of Technology) in Zurich and Lausanne and has been with Hilti as a research engineer, project manager and chief scientific officer since 1989. Dr. Jakob Kunz specializes in the fields of fastening technology and reinforced concrete design. He is a member of fib, IABSE, ACI and SIA 179

Hilti HIT Rebar Design Method. Bond strength depends on concrete cover. Where cover is limited, splitting is the controlling fac-tor and the red and grey lines therefore show more or less linear functions. Where cover is sufficient, pull-out begins to become the controlling factor. With Hilti adhesives, the cover limit is usually higher than that specified for cast-in in concrete building codes (fbd=bond strength, c=cover, ∅=bar diameter).

post-installed cast-in

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Connections made in the great majority of standard applications, such as in walls, slabs, beams, foundations or supporting col-umns can be designed using the Hilti HIT post-installed rebar sys-tem. The system’s versatility gives design engineers the flexibility they need to come up with the opti-mum solutions and specifications.

The task is further simplified by PROFIS Rebar 2.0, a software tool developed by Hilti that lets users design rebar connections according to the Hilti HIT Rebar Design Method or in accordance with the latest Eurocode guidelines.

Simply better designed.PROFIS Rebar 2.0 makes design-ing post-installed rebar connections

easier than ever before. All that has to be entered is the information about loads and geometry – this clever PC application then guides the user to the optimum solution. The results can be exported in the form of a report contain-ing the details needed for installation of the connections on the jobsite.PROFIS Rebar 2.0 optimizes the solu-tion provided by taking all aspects of the latest Hilti adhesive mortars and techniques into account. This cuts installation cost dramatically. In certain situations, embedment depth can be reduced by as much as 50%, result-ing in a large saving in drilling and adhesive mortar cost. The Hilti HIT Rebar Design Method thus makes much more efficient use of the prod-ucts employed and optimizes overall costs all the way from the specifica-tion stage to the final installation.

The current version of Hilti PROFIS Rebar 2.0 can be downloaded from www.hilti.com/rebar.

Simply better connected.with Hilti PROFIS Rebar 2.0

The advantages of Hilti PROFIS Rebar 2.0• New design method that optimizes connections by reducing embedment depth• All relevant technical data and installation instructions can be printed

out in the form of detailed, clearly-structured reports• Totally reliable calculation models thanks to Hilti’s vast know-how and experience

7*The availability of services may vary from country to country. Please contact Hilti in your area for further information.

Simply more support.Hilti services for engineers.Technical adviceHilti’s qualified engineers and techni-cians provide consulting, support and advice free of charge. They’ll be pleased to answer any question on the subject of post-installed rebar con-nections – on the phone, at your office or on site as per your convenience.

Anchor Fastening Technology ManualThis technical manual provides a wealth of information and practical examples of post-installed rebar connections as well as all the technical data for the Hilti HIT system for your easy reference.

User training*By providing special training, Hilti ensures that rebar installation person-nel know how to use the HIT system in accordance with the proper pro-cedures so that post-installed rebar connections can be made correctly.

Pull-out testsHilti offers the possibility of carry-ing out on-site rebar pull-out tests to validate expected loads.

Rebar analysisThe Hilti PS 200 Ferroscan System provides information about exist-ing reinforcement by determining its position, diameter and depth of cover-age without the need for destructive procedures such as removal of con-crete. Hilti PROFIS Ferroscan software simplifies the job of analyzing the data obtained. For more information please refer to www.hilti.com/ferroscan.

Specification text examplesExamples of specification texts suitable for use in contract ten-ders can be downloaded free of charge from www.hilti.com/rebar.

The Hilti PROFIS Ferroscan software shows the position coverage and size of transverse and longitudinal reinforcement clearly.

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Simply the best solution: concrete + concrete = Hilti HIT system.

The outperforming HIT The extra-reliable HIT The Clean-Tech HIT

Hilti HIT-RE 500 Hilti HIT-HY 150 MAX Hilti HIT-CT 1

Bond strength ◾◾◾◾◾◾◾◾◾◾ ◾◾◾◾◾◾◾◾◽◽ ◾◾◾◾◾◾◽◽◽◽Permissible rebar diameter range 8 – 40 mm 8 – 25 mm 8 – 25 mmMaximum embedment depth 3.2 m 2 m –Temperature of base material -5°C / 40°C -10°C / 40°C -10°C / 40°CWorking time 4 h / 12 min 3 h / 2 min 1.5 h / 2 minCuring time 72 h / 4 h 12 h / 30 min 12 h / 30 minSuitable for water-filled holes and underwater use

◾ ◽ ◽

Drilling method: hammer drilling ◾ ◾ ◾Drilling method: diamond drilling ◾ ◽ ◽European Technical Approval (ETA) ETA-08/0105

(only from 5 to 40°C)ETA-08/2020 –

Fire resistance tested and approved ◾ ◾ ◾Label-free ◽ ◽ ◾

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Simply approved.The Hilti HIT system for professional installations.

Hilti HIT-RE 500, HIT-HY 150 MAX and HIT-CT 1 injectable mortars have been awardedETA approval for use in post-installed rebar connections. The stringent approval require-ments qualify the mortars for use in applications where con-nections are designed in accor-dance with Eurocode 2 (EC 2).

No matter which Hilti HIT injectable mortar a design engineer selects, the reliability of its bonding characteristics or its compliance with building codes is never in doubt because the system has been prequalified through approval. Current design methods in accordance with the applicable building codes, in this case EC 2, can be applied.

Simply reliable and safe.Hilti HIT injectable adhesive mortars have been free of toxic substances for years. Hilti HIT-HY 150 MAX and HIT-RE 500 thus does not contain any styrene. Hilti is now taking this philoso-phy a step further with the introduction of HIT-CT 1, the first totally clean inject-able adhesive mortar. This new formula, entirely free of hazardous compounds,

Town Town business city development, Vienna. With its gross floor area of about 130,000 m2, Town Town is a major business development in the city of Vienna. The 31,000 m2 ground area for this project was created by placing a concrete deck over a subway line. This involved connecting pre-cast concrete slabs to pre-stressed, pre-cast beams using special internally threaded sleeves. Hilti HIT-RE 500 was used on site to set 4,000 of these internally threaded anchors with 20 mm reinforcing rods at a depth of about 50 cm. The most important criteria for specification of this rebar connection method by STRABAG, the Austrian construction giant, were its tested fire resistance and its ability to take up high loads at a very shallow anchorage depth. The con-nections were designed in accordance with Eurocode 2 using the Hilti PROFIS Rebar software.

Use of these accessories

is demonstrated during

Hilti HIT training for instal-

lation personnel.

makes waste management easier, cuts disposal costs and contributes to health-ier working conditions. Thanks to the en-tirely new level of safety it brings to the installation procedure, warning symbols on the package are no longer required.

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Why is it important not only to specify mortar

but the overall application? Post-installed rebar

connections typically have signifi cant embedment

lengths. The equipment used must therefore allow

drilling to be carried out accurately, avoiding cross-

ing with neighboring holes. If dust remains on the

walls of the holes drilled, bond strength as specifi ed

cannot be achieved. The holes must therefore be

properly cleaned along their entire length using a

steel brush fi tted to an electric drill.

Injection without creation of air pockets and bubbles

is possible only when it’s done from the bottom of

the hole and when mixer extensions and “piston”

plugs are used. Air bubbles may cause pressure

to build up when the rebar is inserted into the

adhesive. This pressure can become so high that

the adhesive is squirted out of the hole towards the

worker, causing a hazard. Air can also inhibit proper

curing of the adhesive and, last but not least, the

presence of air impedes bonding, reducing the ef-

fective bonding length.

What does a European Technical Rebar Approval

attest to an adhesive? The product has passed

a number of acceptance tests proving that the

behavior of post-installed rebar connections is at

least comparable to that of cast-in-place rebar

connections (comparable load transfer with a com-

parable load-displacement behavior) under various

conditions.

Hilti HIT is used to post-install about 35,000 km of rebar every year.

Hilti solutions for

post-installed rebar connections

Which conditions are assessed for a European

Technical Rebar Approval? Bond strength in differ-

ent grades of concrete, substandard hole cleaning,

wet concrete, sustained load and temperature influ-

ence, freeze-thaw conditions, different installation

directions, maximum embedment depth, avoidance

of air bubbles during injection, durability (corrosion,

chemical attack).

The acceptance tests don’t include fire or

fatigue loads. Can loads of this kind be taken

up by post-installed reinforcement? It’s true that

the adhesive forms a layer between the concrete

and rebar, which may result in cast-in-place and

post-installed rebar connections having significantly

different characteristics under such conditions. Hilti

has performed specific research on these loading

conditions and can provide corresponding design

recommendations.

What’s the main difference between cast-in-

place and post-installed reinforcement? While

detailing of cast-in-place reinforcement often

requires bends or hooks or welded-on transverse

reinforcement, post-installed reinforcement is limited

to straight bar ends because only straight holes can

be drilled.

What’s the advantage of the Hilti HIT Rebar De-

sign Method for post-installed anchorage where

depth is limited, e.g. when connecting a slab

to a wall? With cast-in reinforcement, anchorage

length can be reduced by using hooks or welded

transverse reinforcement, which is not possible

with post-installed reinforcement. Hilti adhesives,

however, usually provide higher bond strength than

that specified in building codes for cast-in-place

reinforcement. Since such applications have a large

concrete cover, the designer can take advantage of

the high bond strength of the adhesive by reducing

the anchorage length significantly.

How can moment-resisting connections be

designed for post-installed reinforcement?

Such connections normally require bends in the

connecting reinforcement. The Hilti HIT Rebar

Design Method includes a strut-and-tie model for

the design of moment-resisting connections with

post-installed straight bars anchored using Hilti ad-

hesives. Laboratory tests have proven this model to

be correct and it has been assessed by independent

experts.

How can concrete members under tension be

connected using post-installed rebars? Rein-

forcement in such members is usually hooked back

by bending it around the perpendicular reinforce-

ment in the base member which, again, isn’t pos-

sible with post-installed reinforcement. As a highly

experienced specialist in the field of anchoring to

concrete, Hilti is well qualified to provide recommen-

dations on how these principles should be used to

connect such members. It should be noted that due

Do you still have questions about rebar installation?Get in touch with Hilti.Our qualified and experienced account managers, field engineers and custo-mer service representatives are at your service. Anytime. For more information, please visit www.hilti.com/rebar

to the possibility of concrete cone breakout failure,

the design of connections of this kind must take

brittle failure mode into account as it is done in Hilti

PROFIS Rebar 2.0

Can the post-installation technology also be

used for shear reinforcement? Although this topic

is still under research, Hilti already offers well-

proven solutions for post-installed shear interface

reinforcement and for post-installed punching shear

reinforcement. Please ask Hilti Technical Service for

details.

Hilti solutions for

post-installed rebar connections

Design

The latest version of Hilti PROFIS Rebar puts post-installed re-bar connection design and the calculation of overlap and an-chorage lengths at your fingertips.

Drilling

Drill faster and more safely with Hilti combihammers and ex-tra-rugged Hilti hammer drill bits or with Hilti high-performance diamond coring systems.

Cutting

Hilti angle grinders featuring Smart Power and fitted with Hilti AC-D cutting discs are ideal for cutting rebars to length. Alter-natively, Hilti cordless reciprocating saws provide total mobility.

Detection

Hilti detectors such as the PS 35 indicate the position of rein-forcing bars and their concrete cover.

Cleaning

Hilti HIT Profi Rebar sets keep all the required cleaning acces-sories conveniently at hand.

Setting

Make a quick, easy, professional job of post-installed rebar connections – with Hilti HIT injectable mortars and efficient Hilti dispensers.

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Hilti Corporation I 9494 Schaan I Liechtenstein I P +423-234 2111 I F +423-234 2965 I www.hilti.comHilti. Outperform. Outlast.

Everything you need for fast, easy and reliable post-installed rebar.