Appendix 1 Rebar Design

5 Appendix 1

10.1 Rebar fastening application 287

10.1.1 Post-fix system advantages 287

10.1.2 Application examples 287

10.2 Product Information Hilti HIT-HY150 Rebar 290

10.2.1 The injection system 290

10.2.2 Adhesive bond 290

10.2.3 Installation 291

10.3 Rebar Fastening Design Concept 293

10.3.1 Scope 293

10.3.2 Symbols 294

10.3.3 Fastening design 297

10.3.4 Detailing provisions 301

10.3.5 Transmissible forces 305

10.4 Examples of applications 306

10.4.1 Wall connection 306

10.4.2 Wall extension 307

10.4.3 Installation of an intermediate floor 308

10.4.4 Installation of steps between landings 310

10.5 Test reports, Supplementary information 311

10.5.1 Relevant reports 311

10.5.2 Test results: Pull-out tests on rebars 311

10.5.3 Test results: Full scale beam test 313

286

5

Rebar fastening design

287

10.1.1 Post-fix system advantages

With the use of the Hilti HIT-HY150 injection system it is possible to connect new concrete to existing structures with maximumconfidence and flexibility.

➥ design flexibility

➥ formwork simplification

➥ reliable like cast in

➥ defined load characteristics

➥ simple, high confidence application

➥ horizontal, vertical and overhead applications

10.1.2 Application examples

Floor slab connection

• Intermediate floor slabs

• Structural alterations, renovation works

• Reinstate temporary openings, e.g. tower cranes,debris removal

✓ simplification of wall formwork

✓ flexibility of construction methods

✓ unobstructed temporary openings

✓ reduced risk of reinforcement damage

Wall and beam connections

• Construction joints

• Structural extension

• Horizontal starter bars

✓ reinforcement continuity

✓ simplified fixing and stripping of formwork

✓ unobstructed joint preparation

✓ small drill hole dimensions

10 Appendix 1

10.1 Rebar fastening application


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5

Vertical connections

• New columns, piers• Structural enhancement• Pile caps

✔ accurate location

✔ no complex reinforcement fixing

✔ unobstructed site access

Major structural repair

• Bridge parapet renovation• Structural upgrading• Concrete remedial works

✔ reduced concrete removal

✔ avoid reinforcement welding or similar connections

✔ overhead installation

Structural connections

• Staircases• Counterforts• Manholes• Corbels

✔ accurate location of starter bars

✔ allows for complex details

✔ simplified wall formwork and joint

preparation

✔ odour free for confined space working


289

Retaining walls

• Diaphragm walls• Contiguous walls• Curtain walls

✔ easy application

✔ small diameter drill holes

✔ connection of deformed bars

✔ moisture tolerant solution

Concrete overlay

• Bridge deck renovation• Structural bonding across composite

interfaces• Structural upgrading of slabs and beams

✔ rapid serial application

✔ small hole dimensions

✔ quick curing

Cantilever connections

• Balcony• Access platforms• Landings

✔ negligible displacement

✔ deformed bar fixing

✔ high confidence like cast in

✔ short rebar exposure avoids rust staining


290

5

10.2 Product Information Hilti HIT-HY150 Rebar

10.2.1 The injection system

The Hilti HIT-HY150 injection system is designed to be safe and simple inapplication resulting in high quality reinforcement fixings.

Its components:

Dispenser MD2000:Manual dispenser.Ergonomic design.Consistent performance.

Foil pack:330ml of two-component adhesive.Opens automatically.Reliable mixing.

Cassette as «refillable cartridge»:Stability in use.Storage function.Reduces waste.

10.2.2 Adhesive bond

Hilti HIT-HY 150 adhesive is a hybrid system consisting of organic and inorganic binding agents.

The polymerisation reaction of the resin component ensures good bon-ding and a rapid curing injection system with good handling characteri-stics.

The cementitious reaction improves stiffness and bonding, especially athigher temperatures.

The combined action of the two components results in negligible materialshrinkage.

The result is a very strong bond between rebar and concrete similar tothat of cast in situ reinforcement.

The hybrid mortar contains no styrene and is virtually odourless.

Organicagents

Cementitousagents

Stronghybrid bond

+

➙

Dispensers MD 2000 for foil pack P 5000 HY for jumbo cartridges

Foil pack: Jumbo cartridge:(330 ml) (1100 ml)

BD 2000 for foil pack


291

10.2.3 Installation

The holes shall be drilled with arotary percussive drill to ensureadequate hole surface roughn-ess. Diamond core drills shallnot be used without subse-quent surface roughening. Ho-les shall be dry at the time ofanchor installation.

Used foil packs can be stored inthe cassette for up to fourweeks. To restart, just changethe mixer nozzle.Reject material from first triggerpull.

Start injecting from the bottomof the hole to ensure completefilling. Some mortar shouldoverflow upon inserting the reb-ar to show complete filling.

Allow for complete curing befo-re applying any load.

To transfer shear loads the surfa-ce of the existing concreteshould be roughened.

Prepare hole

Prepare HIT system

Injecteand insert rebar

Allow to cure

Roughen surface for shear loading

32 3x

3x

1

1

2MD 2000

3

4 5 6

8

MD 2000MD 2000

7 9

121110

Drill hole Brush out hole Blow out hole

Put foil pack Screw mixer Put this into holder onto foil pack assembly into

MD 2000 dispenser.

Inject into hole Unlock Insert rebardispenser

Straighten rebar Allow to cure Concrete.


292

5

The curing time is dependent on temperature:

Foil pack temperature between 5 °C and 40 °C!

The correct drill diameter is important for the perfomance of the adhesivebond as well as for the economy of the application.

The necessary injection volume can be calculated to fill the space bet-ween rebar and hole wall plus enough safety measure to allow for toodeep drilling, cavities in the base material, overflow etc.

Rule of thumb: fill hole 2/3 full

Calculated Volume [ml]: V[ml] = lb,inst � (D2-�2)/1000volume:

Volume [trigger V[MD] = lb,inst � (D2-�2)/8000pulls MD2000]:

Curing time

Drill diameter

Injection volume

Base material Gelling time Curing time temperature tgel tcure

-5 °C 90 min 6 h

0 °C 45 min 3 h

5 °C 25 min 1,5 h

20 °C 6 min 50 min

30 °C 4 min 40 min

40 °C 2 min 30 min

Nominal Maximumrebar diameter recommended hole

diameter

� D

8 mm 12 mm

10 mm 14 mm

12 mm 16 mm

14 mm 18 mm

16 mm 22 mm

20 mm 28 mm

25 mm 32 mm


293

10.3 Rebar Fastening Design Concept

10.3.1 Scope

The design method presented here is based on Eurocode 2: ENV 1992-1-1 «Design of concrete structures, Part1, General rules and rules for buil-dings» [5]

Consequently, it only applies to reinforced concrete. In the case of non-reinforced concrete, – or if the reinforcement is not known – the anchortheory in the fastening technology manual must be used.

Rebar connections in reinforced and non-reinforced concrete set up a dif-ferent flow of forces:

In non-reinforced concrete, the tensileforce, N, is transmitted to the concreteby the connection rebar. The forcewhich can be transmitted depends onthe size of the cone of concrete whichwould break away with the rebar andwhich is influenced by the effectiveanchorage length, edge distance andspacing.

In the case of reinforced concrete, theedge distance and spacing are not ofprimary importance because the ten-sile force is transmitted by theconnection rebars to the cast-in reb-ars via the concrete bond betweenthem.

General rule:

The performance characteristics of rebar fastenings with Hilti HIT-HY150correspond to those of cast-in rebars. All construction rules set up in Eu-rocode 2 apply; in particular, the transmission of the anchoring forcesinto the connecting building components must be ensured in accor-dance with the principles of reinforced concrete construction (e.g.transverse reinforcement, concrete cover etc.).

Design concept based on Eurocode 2

Anchor design

Rebar fasteningdesign

Spacing

Z Z

Anc

hora

gele

ngth

Edgedistance

Z Z

Z Z

N N

N N

N N


294

5

10.3.2 Symbols

The following symbols are used in this manual in accordance with Euro-code 2:

� [mm] Nominal diameter of ribbed rebar

D [mm] Hole diameter

lb [mm] Basic anchorage length

lb, inst [mm] Installed anchorage length

lb, min [mm] Minimum anchorage length

e [mm] Distance between reinforcing bar and connection rebar

fyk [N/mm2] Characteristic yield stress of rebar

This is the stress below which 5% of the strength rea-dings obtained for the rebar at 2‰ permanent defor-mation fall.

Typical stress-straindiagram of reinforcingsteel (EC2: ENV 1992-1-1, Fig. 3.2)

Typical distribution ofstrength readings with5%-fractile as charac-teristic value.

designation

steel strength

yield strength

characteristic value

ft

εu0.2%

fy

ε

σ

95%5%

Num

ber

of r

ead

ings

fyk fy

lb, inst

e

ø

D


295

(EC2: ENV 1992-1-1, Table 3.1) cylinder cube

Concrete classification asper Eurocode Concrete strength fck fck,cube

classes [N/mm2] [N/mm2]

C 16/20 16 20

C 20/25 20 25

C 25/30 25 30

C 30/37 30 37

C 35/45 35 45

→ →

�S Partial safety factor for rebar

This takes account of the difference between thestrength of the test specimens and that of rebars in-stalled with the usual care.

(EC2: ENV 1992-1-1 Table 2.3)

fck [N/mm2] Characteristic compressive cylinder strength of con-crete at 28 days.

fck is the cylinder compres-sive strength below which5% of all strength readingsobtained with the givenconcrete fall.

The classification of concrete e.g. C 20/25, refers tothe characteristic cylinder/cube compressive strengthof concrete as defined in section 7.3.1.1 of ENV 206.

Safety factor steel

Concrete strength

Characteristic value

Fundamental combination �S = 1.15

Accidental combination �S = 1.00(except earthquakes)

fcfck

95%5%

Num

ber

of r

ead

ings

Rebar designations used in various countries are ba-sed on national standards:

Other steel classifications

Country Standard Designation fyk=

Europe EC2

A ÖN BSt 550 550

CH SIA S 500 500

D DIN BSt 500 500

F NFP FE 500 500

GB BS FY460 460


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5

�c Partial safety factor for concrete

This takes account of the difference between thestrength of test cylinders and that of concrete placedon site with the usual care.

(EC2: ENV 1992-1-1, Table 2.3)

�b Partial safety factor for Hilti HIT-HY 150 adhesive

This takes account of the difference between thestrength of the test specimens and that of adhesiveplaced on site with the usual care.

�b is taken equal to �c. Additional partial safety factors

are included in the characteristic value.

(EC2: ENV 1992-1-1, Table 2.3)

�Q, �G Partial safety factor for actions (loads)

This allows for uncertainties in loads and load combi-nations.

ENV 1992-1-1, Table 2.2

Safety factor concrete

Safety factor adhesivebond

Safety factor load

Fundamental combination �c = 1.5

Accidental combination �c = 1.3(except earthquakes)

Fundamental combination �b = 1.5

Accidental combination �b = 1.3(except earthquakes)

Permanent Variableactions actions

Favourable effect �G = 1.00 �Q = 0.00

Unfavourable effect �G = 1.35 �Q = 1.50

There are other concrete classifications according tonational standards. Some other designations for aC20/25 concrete include:

Other concrete classificationsCountry Standard Designation

Europe EC2 C20/25

A ÖN B4200 B300

CH SIA 162 B30/20

D DIN 1045 B25

F NFP 18400 B250

GB BS1881 C25P


297

10.3.3 Fastening design

The working principle of a design is best understood by reviewing thepossible failure modes and setting down corresponding limits to utilisation.

The design load of a connection rebar is:

10.3.3.1 Limit to Rebar Utilisation Ryd

The design tensile force, Ryd, at which therebar steel is fully utilised, results from theproduct of the steel cross-sectional area ti-mes the characteristic strength of the steeldivided by the partial safety factor.

Design value of rebar strength:

This value is crucial when the installed anchorage length is greater thanthe basic anchorage length. (See 3.3.4)

10.3.3.2 Limit to Adhesive Bond Utilisation Rbd

The force which can be taken up in the sur-face of the bond between rebar and adhesi-ve increases linearly with the anchoragelength, but only with the square root of therebar diameter.

Design value of adhesive strength:

Doubling the diameter only results in a 40%increase of the bond strength.

Failure modes

Design load

Steel failure

Adhesive bond failure

Ry

Ryd = 1/4 � � 2 � � � fyk /�s

[N] [mm] [N/mm2]

Rd = MIN {Ryd; Rbd; Rcd} > Sd

Rbd = 25� � � lb,inst � �––� /�b

[N] [mm] [mm]

Rb


298

The equation allows for theperformance of the adhesive.

It was determined by Profes-sor Marti of the Swiss Fe-deral Institute of Technology(ETH), Zurich based on a re-view of comprehensive testdata [1].

This value is crucial when the installed anchorage length is smaller thanthe basic anchorage length (see 10.3.3.4) and the class of concrete is hig-her than C 25/30.

10.3.3.3 Limit to Concrete Bond Utilisation Rcd

The force which can be taken up in the bondinterface between mortar and hole wall in-creases linearly with anchorage depth, butonly with the square root of the characteri-stic concrete strength times the hole dia-meter.

Design value of bond betweenHilti HIT-HY 150 and concrete

Maximum hole diameter D, see Appendix 3

Concrete failure

Rcd = 4.5� � � lb,inst � �fck �D/�c

[N] [mm] [N/mm2] [mm]

Rc

lb = 3d

d = 12mmd = 16mmd = 20mmd = 25mm

τ bm

•d

010 2

25

50

75

δε [mm]

Maximum hole diameter D, see Appendix 2

5


299

1/4 � �2 �� fyk/�s <_ 4.5�� lb,inst ��fck�D/�c

lb,inst >_ �2 � fyk� �c/(18 ��fck�D��s)

The equation allows for the performanceof the bond interface.It was determined by Professor Marti ofthe Swiss Federal Institute of Technology(ETH), Zurich, based on a review of com-prehensive test data [1].

On principle, the partial safety factorwould have to be ��b ��c. Since, how-ever, �b = �c, the formula can be simplified.

Test arrangement

This value is crucial when the installed anchorage length is smaller thanthe basic anchorage length (see 10.3.3.4) and the class of concrete doesnot exceed C 25/30.

10.3.3.4 Basic anchorage length

If this length is exceeded, the steel is fully utilised.

The basic anchorage length is derived by setting

Ryd <_ Rbd

(rebar strength <_ adhesivebond strength)

and

Ryd <_ Rcd

(rebar strength <_concrete bond strength)

As a result, the basic anchorage length is obtained as the maximum valueof the two limiting anchorage lengths:

lb = MAX � �3/2 � fyk� �b/(100 ��s); �2 � fyk ��c/(18 ��fck�D��s)�

[mm] [mm] [N/mm2] [mm] [N/mm2] [N/mm2] [mm]

Basic anchorage length

1/4 � �2 �� fyk/�s <_ 25�� lb,inst ��––� /�b

lb,inst >_ �3/2 � fyk� �b/(100 ��s)


300

5

If it is assumed that D = 1.2 ��

the limit results at fck = 26 N/mm2

Consequently, up to and including C 25/30, it is the grade of concretewhich is crucial, but from C 30/37 it is the grade of Hilti HIT-HY 150 adhe-sive that is decisive.

Schematic presentation of limits to utilisation:

Limits for fasteningloads

lb, min Basic anchoragelength lb

Concrete class fck, fck,cube

Anchoragelength lb,inst

C 45/55

C 40/50

C 35/45

C 30/37

C 25/30

C 20/25

C 16/20

C 12/15

Rb

Ry

Ryd = 1/4 x ø2 x π x fyk / γs[N] [mm] [N/mm2]

Rbd = 25 x π x lb, inst x ø / γb[N] [mm] [mm]

Rcd = 4.5 x π x lb, inst x fck x D / γc[N] [mm] [N/mm2] [mm]

Rebar crucialConcrete crucial

Hilti HIT-HY 150 crucial

Rc

Basic anchorage length for various rebar diameters, classes of concreteand grades of steel:

�s = 1.15; �c = �b = 1.5

The limit at which the grade of adhesive or grade of concrete is crucial, isobtained from

Rbd = Rcd 25�� lb��/�b = 4.5 �� lb��fck �D/�c

fck = (25/4.5)2 ��/D

Concrete Rebar � [mm]: 8 10 12 14 16 20 25class fyk = D [mm]: 12 14 16 18 22 28 32

Influence of steel:C20/25 450 Ib [cm]: 14 20 27 34 40 56 81C20/25 500 Ib [cm]: 15 22 30 38 45 62 90C20/25 550 Ib [cm]: 17 24 33 42 49 68 99

Influence of concrete:C16/20 500 Ib [cm]: 17 25 33 42 50 69 101C20/25 500 Ib [cm]: 15 22 30 38 45 62 90C25/30 500 Ib [cm]: 15 21 28 35 42 59 82

Influence of

. . . steel grade

. . . concrete class


301

10.3.4 Detailing Provisions

Basically, a rebar set with HIT HY150 can be considered like a cast-in reb-ar. The basic anchorage length of section 10.3.3.4 corresponds to the ba-sic anchorage length of Eurocode 2. The detailing provisions of Euroco-de 2, some of which are quoted in the following paragraphs, shall be ap-plied to the basic anchorage length of section 10.3.3.4. The rebars setwith HIT HY150 shall be disposed according to the same rules as cast-inrebars would.

10.3.4.1 Minimum Anchorage Length

To ensure that the force acting on the connection rebar is transmitted tothe cast-in rebar, the following lengths must exceed those given in Euro-code 2:

For anchorages in tension:EC2: ENV 1992-1-1 formula (5.5):

lb,min = MAX (0.3 lb[mm]; 10 � � [mm]; 100 [mm])

For anchorages in compression:EC2: ENV 1992-1-1 formula (5.6)

lb,min = MAX (0.6 lb[mm]; 10� � [mm]; 100 [mm])

Column connection10.3.4.2 Splice Length(EC2: ENV 1992-1-1 formula 5.7 and 5.8)

When rebars in tension or compression are lapped, increased splittingforces occur. In order to take up these splitting forces, the anchoragelength lb,inst, defined by sections 10.3.3.1 to 10.3.3.3, must be multipliedby a factor �, which is given in the following table.

lsplice = �*lb,inst

The splice length must exceed the minimum lengths given in the same ta-ble.

Minimum anchoragelength

Anchorages intension

Anchorages in compression

DeckenanschlussFloor connection


302

5

10.3.4.3 Distance between cast-in rebars and new rebars

Cast-in rebars and the nearest rebars may touch at length of overlap(EC2: ENV 1992-1-1, 5.2.1.1 (5)).

If the clear space between the connection rebars and the nearest cast-inrebar is . . .

e > 4 ��

the overlap must be increased by an amounte - 4 �� (cf. example 4.2)

The minimum distance between cast-in rebars and farther away connec-tion rebars should be:

a >_ MAX (2� � [mm] ; 20 [mm])

Splices

Rebar spacing

. . . to nearest rebar

. . . to farther awayrebar

l b, m

in

eab

% of spliced bars < 30 % > 30 %

bar spacing a G 10 Ø G 10 Ø < 10 Ø < 10 Ø

edge distance b G 5 Ø < 5 Ø G 5 Ø < 5 Ø

� = 1.0 1.4 2.0

0.3 lb 0.42lb 0.6 lblb,min,sp = MAX 15 Ø MAX 15 Ø MAX 15 Ø

200mm 200mm 200mm{ {

( )

{application:

typical typicalslab beam


303

10.3.4.4 Poor Bond Conditions

All previously given values apply to good bond conditions.

Poor bond conditions may for exam-ple occur because the concrete be-neath the cast-in rebar sinks.Rebars fastened with Hilti HIT-HY150always have good bond conditions.An increase in anchorage length by afactor 1.4 can be necessary to ensurethe transfer of the load to other (possi-bly poorly bonded) cast in rebars.

Bond conditions according to EC2: ENV 1992-1-1, Fig. 5.1:

Bond conditions are also considered as good if rebars are embedded ver-tically or at an angle of max. 45° to the vertical.

10.3.4.5 Limit State of Cracking

According to EC2: ENV 1992-1-1:4.4.2.1 (6), the maximum design crackwidth must be limited to 0.3 mm for exposure classes 2–4:

Class 2: humid environment with or without frost

Class 3: additionally with de-icing salts

Class 4: and sea water environment.

Bond conditions

Crack width limits

Surface of concrete

RebarSinkingof concrete

h 250mm h 250mm

Direction of concreting

h 600mm

h Good bond h/2 Good bond

Poor bond

Good bond

300mm Poor bond


304

5

According to EC2: ENV 1992-1-1: 5.2.4 P(1), the crack width must be ve-rified at the end of the splice of the rebars. Cracks hardly occur in the spli-ce zone itself because of the greater amount of reinforcement i.e. cast-inrebars plus connection rebars.

Pull out tests showthat at the level ofthe recommendedvalues (Fs) the dis-placement is typical-ly below 0.1mm [1].

From this observa-tion and other ex-perimental eviden-ce it can be con-cluded that crackwidth limits are met.

10.3.4.6 Green Concrete

If the rebar connection is to be loaded before the concrete reaches its 28-days compressive strength, the actual strength readingsshould be used with the given formulae. However, special attentionshould be given to concrete creep.

3.4. Transmissible forces

According to the given formulae and good bond conditions, the followingvalues result depending on the load level and the installed anchoragelength

Displacement clearly below 0.3 mm

0 0.4 0.8 1.2Slip at loaded end of rebar [mm]

Rm (Short term)

Rk (Short term)

Rk (Long term)

Rd

Fsd

FsRecommendedload range

Ten

sile

load

[kN

] ExperimentTheory

Displacement at loaded end of rebar [mm]


305

10.3.5.2 Level of Recommended Loads

If the design values are divided by the partial safety factor for actions (lo-ads), the recommended loads are obtained. For the sake of simplicity, �G

= �Q = 1.5 in this table.

Rebar dia. Hole dia. Design value of connection force Basic� D Rd length

Ib

[mm] [mm] [kN] [mm]

8 12 14.6 17.5 20.4 21.9 21.9 21.9 21.9 21.9 21.9 21.9 21.9 21.9 21.9 21.9 150

10 14 15.8 18.9 22.1 25.2 28.4 31.5 34.1 34.1 34.1 34.1 34.1 34.1 34.1 34.1 217

12 16 20.2 23.6 27.0 30.3 33.7 37.1 40.5 43.8 47.2 49.2 49.2 49.2 49.2 292

14 18 25.0 28.6 32.2 35.8 39.3 42.9 46.5 50.1 53.6 66.9 66.9 66.9 374

16 22 31.6 35.6 39.5 43.5 47.4 51.4 55.4 59.3 79.1 87.4 87.4 442

20 28 minimum 44.6 49.1 53.5 58.0 62.4 66.9 89.2 112 134 612

25 32 anchorage length 62.0 66.8 71.5 95.4 119 143 895

Anchorage length [mm]: 100 120 140 160 180 200 220 240 260 280 300 400 500 600

Concrete C20/25: fck = 20 N/mm2; minimum anchorage length for lapped rebars (see 10.3.3.5)

Steel: fyk = 500 N/mm2 minimum anchorage length for connection

Rebar dia. Hole dia. Recommended value of connection force Basic� D Frec length

Ib

[mm] [mm] [kN] [mm]

8 12 9.7 11.7 13.6 14.6 14.6 14.6 14.6 14.6 14.6 14.6 14.6 14.6 14.6 14.6 150

10 14 10.5 12.6 14.7 16.8 18.9 21.0 22.8 22.8 22.8 22.8 22.8 22.8 22.8 22.8 217

12 16 13.5 15.7 18.0 20.2 22.5 24.7 27.0 29.2 31.5 32.8 32.8 32.8 32.8 292

14 18 16.7 19.1 21.5 23.8 26.2 28.6 31.0 33.4 35.8 44.6 44.6 44.6 374

16 22 21.1 23.7 26.4 29.0 31.6 34.3 36.9 39.5 52.7 58.3 58.3 442

20 28 minimum 29.7 32.7 35.7 38.7 41.6 44.6 59.5 74.3 89.2 612

25 32 anchorage length 41.3 44.5 47.7 63.6 79.5 95.4 895

Anchorage length [mm]: 100 120 140 160 180 200 220 240 260 280 300 400 500 600

Concrete C20/25: fck = 20 N/mm2; minimum anchorage length for lapped rebars (see 10.3.3.5)

Steel: fyk = 500 N/mm2 minimum anchorage length for connection

10.3.5.1 Level of Design Value

10.3.5 Transmissible Forces

According to the given formulae and good bond conditions, the followingvalues result depending on the load level and the installed anchoragelength.


306

5

10.4 Examples of applications

The following examples show the large variety of possibilities to solve problems by making rebar connectionswith Hilti HIT HY-150 adhesive.

10.4.1 Wall connection

According to the design calculation, the verti-cally compressed new wall is dimensioned as follows:

Concrete class C 20/25fck = 20 N/mm2

Steel grade fyk = 500 N/mm2

Wall thickness: 18 cmVertical: � 10/20 cm both

sidesHorizontal: � 8/25 cm both

sides

Floor connection: � 10 mm/20 cm both sidestable 10.3.4.1 hole depth = lb = 217 mm

D = 14 mm

Alternative 1: � 12 mm /20 cm both sidesas per 10.3.5.1 Rd = Rd (� 10) = 34.1 kN

at lb,inst = 20 cmRd (�12) = 33.7 kN ˜ 34.1 kNlb,inst > lb,min = MAX (0.6�292; 10�12; 100)

= 175 mm

Alternative 2: � 14 mm/20 cm both sidesas per 10.3.5.1 Rd = Rd (� 10) = 34.1 kN

at lb,inst = 19 cmRd(�14) = 34.0 kN ~ 34.1 kN

but lb,inst < lb,min = MAX (0.6�374; 10�14; 100)= 224 mm

If compressive forces are being transmitted, a reduction of the hole depth when using rebars of larger diameter can only be achieved to a moderate extent due to the limitations of the minimum an-chorage length.

Existing wall

2 x ø8/25cm

2 x ø10/20cmExisting floor

New wall

18cm


307

Side wall connection: � 8mm/25 cm both sidestable 10.3.5.1 hole depth =lb = 15 cm

D = 12 mm

Alternative 1: � 10 mm /25 cm both sidestable 10.3.5.1 Rd = Rd (� 8) = 21.9 kN

at lb,inst = 14 cmRd (� 10) = 22.1 kN > 21.9 kNlb,inst > lb,min = MAX (0.3�217; 10�10;100)

= 100 mm

Alternative 2: � 12 mm/25 cm both sidesas per 10.4.1 Rd = Rd (� 8) = 21.9 kN

at lb,inst = 13 cm10.3.5.1 interpolated Rd (� 12) = 21.9 kN = 21.9 kN

lb,inst > lb,min = MAX (0.3*292; 10�12; 100)= 120

It is simple to vary the hole depth by using the tables.

10.4.2 Wall extension

The existing wall is reinforced by �

8mm/25cm rebars and shall be exten-ded by a new wall with the followingcharacteristics:

Concrete class C 20/25fck = 20 N/mm2

Steel grade fyk = 500 N/mm2

Wall thickness: 20 cmHorizontal rebars: � 8/25 cm

both sides

Lap connection: � 8mm /25 cm both sidestable 10.5.1 hole depth = lb = 15 cm

D = 12 mm

Owing to the � 8mm/25 cm rebars already cast in the wall to be connected, nothing is gained by rebars of larger diameter because the force acting on the connection must be transmitted to thecast-in reinforcement via the overlap.

Existing wall

ø8/25cm

New wall


308

5

If the position of the existing reinforcement is not known it is advisable to assume the worst case regardingthe proximity of the nearest cast-in rebar. If this can be e > 4�� = 32mm, the anchorage length must be ac-cordingly increased.

max e = 250/2 =125 mmextension as per 10.3.4.3 lb,inst = 150+(125-32) = 243 mm

Instead of a hole depth of 15 cm, it must be 24 cm to ensure that the forces are transmitted from the connec-tion rebar to the cast-in rebar. It is therefore recommended that the rebar position is measured using the Fer-roscan instrument.

Connections to and extensions of columns etc. can also be designed in the same way as wall connectionsand wall extensions.

10.4.3 Installation of an intermediate floor

Details:Span length L = 4.3 mSlab thickness h = 16 cmConcrete cover c = 2 cmEffective depth d = 13 cmConcrete classC 20/25 fck = 20 N/mm2

Grade of steel fyk = 500 N/mm2

Loading:Live load Q = 2.00 kN/m2

Partial safety factor for variable actions �Q = 1.50Q��Q = 3.00 kN/m2

Dead weight = 4.00 kN/m2

Intermediate walls = 1.00 kN/m2

Floor build-up = 1.50 kN/m2

Permanent loads G = 6.50 kN/m2

Partial safety factor for permanent actions �G = 1.35G��G = 8.78 kN/m2

ø10/14cm

d h

2d d

L

MMd


309

Bending moment M at mid-span

M = (Q ��Q + G��G) � L2/8 = 27.2 kNm/m

Required cross-sectional area of reinforcement from the design programme

As,requ = 5.31 cm2/m

→ implemented � 10 mm/14 cm (As,provided = 5.61cm2/m)

This mid-span reinforcement determined by the design calculation and shown in the reinforcement drawingis anchored in the walls using connection rebars having the same diameter and spacing.Therefore, only the minimum anchorage depth is required according to the rules for rebars at supports.

Connection: � 10mm/14 cm located belowfrom 10.3.4.1 lb,min = MAX {0.3�217; 10�10; 100}

= 100mmhole depth = lb,min = 10 cmD = 14 mm

The connection surfaces must be roughened to take up the shear force.

Alternative: Instead of extending the mid-span reinforcement, the minimum required connection force in the support area is determined andanchored. A truss model with an inclination of 45° is assumed

Loading: 3 d away from the support because the tensile force set up before the rebar lap has to be transmitted

Md = (Q��Q + G��G)�(L–3 �d)�3�d/2= 11.78�(4.3–0.39)�0.39 / 2= 9.0 kNm/m

Vd = (Q��Q + G��G)�L/2 �(1–3d / (0,5 L)) = 20.7 kNZrequ = Md / (0.9 d) + Vd /2 = 97.6 kN/m

selected: same rebar spacing as for large-area reinforcement e = 14 cm

Zrequ/rebar = Zrequ �e = 97.6 �0.14 = 13.7 kN

as per 3.4.1: � 8mm /14 cm located belowlb,inst = 10 cmRd,inst = 14.6 kN > Zrequ/rebar = 13.7 kN

Using detailed calculation, � 8 mm rebars instead of � 10mm can be used for anchoring. This demontratesthat it is worthwhile to perform a design calculation.


310

5

Loading at mid-span

M = (Q��Q + G��G) x L2/8 = 43.9 kNm/m

Required cross-sectional area of reinforcement from the design programme

As,requ = 8.20 cm2/m

→ implemented � 12 mm/13 cm (As,provided = 8.70 cm2/m)

In the landings, rebars � 12 mm/13 cm are cast in as well. Step connection: � 12mm/13 cm located belowtable 10.3.5.1 Basic anchorage length lb = 29 cmsplice factor: � = 1.4 (a > 10 � )

Hole depth = lb, inst = 29 �1.4 = 40 cmD = 16 mm

The connection surfaces must be roughened to take up the shear force.

10.4.4 Installation of steps between landings

Details:Step height h(ST) = 18 cmStep width w(ST) = 28 cmGradient� = arctan (h(ST)/b(ST)) = 32.74°Distance betweensupports L = 4.88 mSlab thickness h = 18 cmConcrete cover c = 2 cmEffective depth d = 15 cmConcrete classC 20/25 fck = 20 N/mm2

Grade of steel fyk = 500 N/mm2

Loading:Live load Q = 3.00 kN/m2

Partial safety factor for variable actions �Q = 1.50Q��Q = 4.50 kN/m2

Dead weight of steps= 25�(h(ST)/2 + h/cos �) / 100 = 7.60 kN/m2

Dead weight of landing= 25�h / 100 +1.5 = 6.00 kN/m2

→ The dead weight of the stepsis used throughout the entirelength, i.e. G = 7.60 kN/m2

Partial safety factor forpermanent actions �G = 1.35

G��G = 10.26 kN/m2

h(ST)

12012 120 128 x 28 = 224

L = 488

ø12/13

h = 18

ø12/13


311

10.5 Test reports, Supplementary information

10.5.1 Relevant reports

[1] Marti, P., «Verankerung von Betonstahl mit Hilti HIT-HY150 (Anchoring Concrete Reinforcement usingHilti HIT-HY150)», Report no. 93.327-1, December 17th., 1993, 13pp.

[2] Höhere Technische Lehr- und Versuchsanstalt Rankweil (Higher Technical Teaching and Testing Institu-te, Rankweil, Austria), «Tragverhalten bei zentrischem Zug: Bewehrung BSt 500 mit Hilti HIT-HY150 inBeton eingemörtelt (Loadbearing behaviour under tensile load: Rebars BSt 500 anchored in concreteusing Hilti HIT-HY150 adhesive)», Report no. 311/94, September 1994.

[3] SOCOTEC, «Cahier des charges d’emploi et de mise en œuvre du système de scellement à base derésine; HIT HY 150 pour l’ancrage d’armatures pour béton armé»Cahier des charges accepté par SOCOTEC sous le n°: BX 1032 (Juin 1994).

[4] Hilti AG, «Fastening Technology Manual», 1993.[5] CEN: European Committee for Standardization, «ENV 1992-1-1 Eurocode 2: Design of Concrete Struc-

tures – Part 1: General rules and rules for buildings», 1991For national application refer to the national standard adopting the above European standard and tothe relevant National Application Document.

10.5.2 Test results: Pull-out tests on rebars

As described in the test report from HTL Rankweil [2], pull out tests have been made with the following setupand results:

Test setup:

Concrete: fck = 35,40,20 N/mm2

Rebars: fyk = 500 N/mm2

Drilling: Hammer drillCleaning: Brushing and BlowingSpacing: Sufficient spacing and edge distanceLoading: Tensile loading to failureSample: Diameters 8,10,12,14,16,20,25

Embedment 5�� , 10�� , 15�� , lbThree samples each


312

5

0

25

50

75

100

125

150

175

200

225

0 2 4 6 8 10 12 14 16 18 20Displacement [mm\

Ten

sile

load

[kN

\

} lb,inst = lb = 612mm}lb,inst=15�� = 300mm

lb,inst=10�� = 200mm

lb,inst= 5�� = 100mm

Load/displacement curves for � 20 mm rebars

Test results:

Rebar dia. Drill dia. Anchorage length� [mm] D [mm] 5�� 10�� 15�� Ib

8 12 8.9 17.8 25.1 25.114.2 P 16.3 P 31.1 P 31.9 S16.5 P 31.0 P 31.2 P 26.7 P8.7 P 29.8 P 31.8 S 30.0 P

10 14 12.4 24.8 37.3 39.321.0 P 40.0 P 47.1 S 47.3 S21.9 P 38.6 P 47.0 S 48.1 S24.7 P 46.6 P 50.0 S 48.7 S

12 16 16.3 32.6 49.0 56.529.5 P 56.9 P 69.7 S 72.5 S29.2 P 65.5 P 69.9 S 69.8 S24.5 P 60.7 P 71.2 S 69.7 S

14 18 20.6 41.1 61.7 77.037.8 P 90.6 P 97.8 S 97.1 S39.6 P 87.2 P 98.3 S 97.7 S38.5 P 92.3 P 98.2 S 97.4 S

16 22 25.1 50.3 75.4 100.558.7 P 109.1 S 138.1 S 138.8 S47.5 P 83.4 S 136.6 S 139.2 S49.7 S 106.5 S 138.7 S 142.2 S

20 28 35.1 70.2 105.4 157.165.7 C 116.6 P 202.0 P 211.1 P78.9 P 160.8 P 208.6 P 211.5 S67.7 C 135.5 P 205.0 P 205.2 P

25 32 49.1 98.2 134.1 245.4138.7 P 276.0 P 275.3 C 341.8 P123.7 P 217.6 C 300.1 C 328.2 C119.4 P 285.7 P 257.0 C 312.0 P

RkFult, ModeFult, ModeFult, Mode

Rk: Theoretical ultimate load (characteristic load with � = 1.0)Fult: Actual ultimate load Mode: failure mode, where P = pull out

S = steel failureC = concrete failure

fult, Modefult, Modefult, Mode


313

10.5.3 Test results: Full scale beam test

In order to demonstrate that the characteristics of Hilti HIT-HY150 rebarfastenings are similar to cast-in solutions the following test was underta-ken [2]:

A concrete beam (40cmx25cmx475cm) is cut through at one third of itslength. Reinforcement bars of equivalent dimensions (twice � 22 mm be-low and twice � 14 mm on top) are installed alongside the original rein-forcement using Hilti HIT; thus the beam is rejoined.

The beam is then supported at the end points while a test load is appliedat the two third-points (the re-fastened and the original one). Bending ofthe beam is measured below these two points to compare the performan-ce of the reattached side to the original side.

As can be seen on the diagram thereattached side bends in about thesame way as the original side.

The performance of the Hilti HIT fastening indeed con-forms to a cast-in rebar.

The measured bending moment atfailure of this beam (69.18 kNm)corresponds well to the calculatedmoment (68.10 kNm)

70

60

50

40

30

20

10

00 5 10 15 20 25 30

Bending [mm]

Load

F [k

N]

original

reattached

1.5 m 1.5 m 1.5 m

25 cm

40 cm

2 rebars ø 22 mm, lb = 68 cm

2 rebars ø 14 mm, lb = 35 cm

F/2F/2

Documents

Appendix 1 Rebar Design