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1. IntroductionThe structural design and thus the production of structural elements made of reinforced concrete isbased on forces and loads current in codes of the time. However, during the service life of a structure,various circumstances may require that the service loads are changed due to:

• Modification of the structure• Aging of the construction materials• Deterioration of the concrete caused by reinforcement corrosion• Earthquake design requirements; fire design changes• Upgrading of building codes relating to load bearing capacity or service loads etc.

The consideration of the actual loads resisted by a structure is a necessary prerequisite for the devel-opment of a comprehensive rehabilitation concept. Basically, the methods available for the structuralstrengthening of structural elements made of reinforced concrete are as follows:

• Application of cast or sprayed concrete with additional reinforcement• Placing of additional reinforcement in slots cut in the concrete• External post-tensioning• Installation of supports or additional bearing members• Steel plate bonding to increase shear or flexural capacity.

An alternative to these traditional methods of strengthening is the use of Fibre Reinforced Polymer (FRP)composites.

2. Selection of the S&P FRP systemThe basic fibres used for the FRP composites are imbedded in a matrix and applied as reinforcing ele-ments to an existing structural member. For flexural enhancement, prefabricated FRP composites (S&PLaminates CFK) are used. As prefabricated laminates are not suitable for confinement or shear en-hancement situations, sheets made of different types of basic fibres are offered for manual laminationon the job site.

Different types of FRP composites:

Fibre direction Fibre arrangement Typical application

S&P C Sheet uni-directional ——— stretched increase in stiffness

S&P A Sheet uni-directional ——— stretched special applications

S&P G Sheet bi-directional ~~~~ undulating increase in ductility

S&P Laminate CFK uni-directional ——— stretched increase in stiffness(partly prestressed)

In both the S&P C Sheets and the S&P Laminates CFK, the fibres are stretched. However, due to manualapplication, the C Sheet becomes slightly wave like in form. As a consequence, these products aresuited for absorbing tensile forces at a minimum elongation. Both sheets and laminates are preferredfor use in the increasing of flexural capacity of a structural element. Carbon fibres with a high modulusof elasticity are used in their production. This modulus of elasticity is the decisive parameter whencomparing the various types of carbon fibre sheets and CFK laminates.

In the bi-directional S&P sheets the fibres are arranged in the form of waves due to the weaving processused in their production. As a result, the absorption of tensile forces takes place at a higher elongationthan with the carbon sheets. Bi-directional sheets are ideally suited for increasing the ductility of a struc-tural element and are often used in the seismic upgrading of concrete structures. Glass fibres with amodulus of elasticity of 70,000 N/mm2 are used in these applications. The selection of normal E-glassor alkali-resistant AR-glass depends on the application. Since strains during load transfer into thecontact substrate are relatively high, the stresses in the substrate are distributed by the formation ofmicro-cracks and are thus locally relieved. Thus, glass sheets are able to be applied to substrates witha low inherent tensile strength.

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S&P glass sheets are suited for the strengthening of historic buildings or the increasing of shear capacityof walls made of bricks or masonry. On the other hand, for the application of S&P C Sheets andS&P A Sheets an inherent substrate tensile strength of >1.0 N/mm2 is required. In the case of prefabri-cated S&P Laminates CFK, the load transfer into the substrate is concentrated and thus strengtheningwith these laminates requires substrates with an inherent tensile strength >1.5 N/mm2.

Demands on the substrate:

Product Inherent tensile strength

S&P C Sheet / S&P A Sheet >1.0 N/mm2

S&P G Sheet approx. 0.2 N/mm2

S&P Laminate CFK >1.5 N/mm2

Testing of the bond (tensile) strength of the bearing Roughening of the surface by sandblasting or grinding.substrate.

In order to ensure the load transfer from the S&P FRP system to the substrate, the surface must beroughened by sandblasting or grinding.

3. Types of fibres for S&P FRP systems

Type of fibre Modulus Tensileof elasticity strength

GPa N/mm2

Carbon 240 - 640 2,500 - 4,000Aramid 124 3,000 - 4,000Glass 65 - 70 1,700 - 3,000Polyester 12 - 15 2,000 - 3,000(Steel 210 250 - 550)

S&P Reinforcement manufactures custom-mode sheets of either a single fibre type or of fibre combina-tions (hybrids). The advantages and disadvantages of the various fibres are as follows:

Car

bon

Gla

ss

PES

2500

2000

1500

1000

500

0 5 10 15

Ara

mid

e

Steel

3

E- glass: Uncoated E-glass corrodes in alkaline environments. Since the coating may be subjectedto damage near its edges during the application, E-glass should only be applied in non-alkaline areas (reinforcement of asphalt) or where it is completely embedded in the epoxyresin matrix. E-glass sheets should not be used for strengthening of concrete in combina-tion with a water vapour permeable matrix.

AR-glass: Alkali-resistant glass is suited to confinement reinforcement for concrete elements (in-crease in ductility) in combination with an epoxy resin matrix and a water vapour perme-able matrix.

An intensive research program has been carried out with the S&P AR Glass. During 28 days the glasswas stored in the substances listed below and then examined:

Saturated solutions of calcium hydroxide:10% potassium hydroxide10% sodium hydroxide

Acids: Chlorides:5% acetic acid 10% calcium chloride10% hydrochloric acid 10% sodium chloride10% nitric acid 10% potassium chloride

Nitrates: Sulphates:10% calcium nitrate 10% calcium sulphate10% potassium nitrate 10% sodium sulphate10% sodium nitrate 10% potassium sulphate10% ammonium nitrate

View of S&P AR Glass in the scanningelectron microscope, after storage

The S&P AR Glass was resistant against all acids, salts and alkalis examined in the test. After a storageof 28 days none of the samples showed any weight reduction. No surface modification and thus noattack was observed in the scanning electron microscope. The S&P AR Glass is highly alkali-resistant(resistance against 100% caustic soda).

Aramid: Aramid is a very tough material. Aramid sheets are used, as an example, for the manu-facture of bullet-proof vests. For structural elements this extreme toughness providesbenefits for special applications such as the strengthening of rectangular columns.Because of the very high price of the A fibres, the S&P A Sheet (aramid sheet) is oftenreplaced by carbon or glass fibre products.

Upon request, S&P offers the S&P A Sheet 120 (Types A and B). The products are uni-directional fibre sheets of different weights. Several tests have been carried out witharamid sheets. For more information please ask the S&P engineering department.

Carbon fibres: Used as the basic fibres for reinforcement of concrete, carbon provides all the benefits:

• High modulus of elasticity (depending on fibre type)• Minimum coefficient of thermal expansion (approx. 50 times lower than steel)• Excellent fatigue properties• Excellent resistance to all types of chemical attack• Will not corrode• Freeze/thaw and de-icing salt resistance.

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4. S&P FRP glass fibre systems4.1 Seismic upgrading with S&P G Sheet 90/10 (Types A and B)

Load-bearing column after earthquake in San Francisco(USA)

In the analysis of a structure for seismic upgrading the structure as a whole is considered for ductility.Individual elements may have their ductility increased using S&P G Sheets 90/10 made of either E-glassor AR-glass. The performance of glass in ductility enhancement has been proven by large scalepush-pull (reverse cycle) tests. Only system approved epoxy may be used as a primer or for theimpregnation of the S&P G Sheet. Please contact S&P for detailed test reports.

4.2 Protection of structures subject to explosion hazardswith S&P G Sheet 50/50

The S&P G Sheet 50/50 has been speciallydeveloped for this field of application. The sheet,which has a 50% glass content in two orthogo-nal directions, can be applied in several layers.S&P offers also prefabricated GFK plates for thesame purpose. These are glued on to the struc-tural element with approved epoxy resin. Varioustest reports are available from S&P Reinforce-ment.

The S&P specialty products have been tested forspecial protective structural elements for NATO.

...... Reference column- - - Column wrapped with C Sheet (1kg/mm2)––– Column wrapped with G Sheet 90/10 (Types A and B) (4kg/mm2)

-5 -4 -3 -2 -1 0 1 2 3 4 5

-5 -4 -3 -2 -1 0 1 2 3 4 5

PullPush

Drift Ratio ∆/L (%)

Late

ral l

oad

Deflection

Explosion

S&P G Sheet AR2-directional

Actuator

Lateralload

200/200 mmcolumn

2000

mm

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4.3 Repairs to historic buildings with S&P G Sheet 50/50

The woven S&P G Sheet 50/50 is suited for the reinforcement of historic buildings and for applying tosubstrates with a low inherent tensile strength (brickwork/natural stone). The high toughness of the S&PG Sheet 50/50 ensures the load transfer from the sheet to the substrate by the formation of micro-cracks. Aspects of building physics in relation to the moisture conditions of the structure should betaken into account in each individual case.

5. S&P FRP carbon fibre systemsBoth uni-directional S&P C Sheets and S&P Laminates CFK can almost be considered as homo-geneous. Since C fibres are linear-elastic and subject to brittle fracture, FRP laminates loaded in thefibre direction are also linear-brittle/elastic. If the fibre volume and the mechanical values of the com-ponents are known, some properties of FRP in the fibre direction can be estimated from a compositecalculation; the low contribution of the matrix in practice can be neglected.

5.1 Mechanical long-term properties

Creep strengthThe creep strength of CFRP is far superior to that of other fibre composites. This has been proven in alarge number of tests. In a creep test conducted on CFRP rods in a saline solution under alternatingload, no failure was registered in the rods up to a continuous stress level of 70% of their short-timetensile strength after 10,000 hours. A creep strength of 79% of the short-time tensile strength is extra-polated for CFRP rods for a period of 50 years.

When CFRP is used as reinforcement, the continuous tensile stress under service loading can beexpected to be a maximum of 20% of the short-time tensile strength. At this level, no loss of strengthof relevance in dimensioning occurs as a result of continuous stress situations.

Fatigue strengthFRP made of C fibres (CFRP) has a very high fatigue strength. In Japanese tests conducted with maxi-mum stresses of less than 87.5% of the short-time tensile strength and amplitudes of up to 1,000N/mm2, more than 4 · 106 load cycles were attained. No fatigue failure and, in the subsequent tensiletest, no reduction in tensile strength was established on CFRP rods embedded in concrete after 4 · 105

load cycles with an oscillation range of 0.05 - 0.5 fc and a frequency of 0.5 Hz.

When CFK plates are used as reinforcement, the maximum stress which can be expected in service willnot exceed 20% of the short-time tensile strength and hence it is not the fatigue strength of the CFKmaterial which governs the design, but always the reinforcing or prestressing steel.

Combinationof adhesives S&P Sheet

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Creep and relaxationCreep and relaxation are expressions of the viscoelastic behaviour of a material. With fibre composites,it is possible to distinguish between axial creep in the composite cross section and interlaminar creep.Both types of creep are negligible in CFK laminates under continuous stress conditions which occurwhen used in strengthening applications.

Under continuous loads which exist in the service state, carbon fibres themselves do not display ameasurable creep deformation or stress loss as a result of relaxation. In contrast, the epoxy resin matrixis a visco-elastic material and is linear-elastic up to a strain of εM = ±20%. Hence, creep failure will notoccur when strains are less than the yield strain of the reinforcing steel (which is not permitted to creepin the service state).

The ratio of the Young’s Moduli Ef/Em = ±30 and the matrix volume component of vM = ±30% meansthat the tensile force carried by the matrix is only some 0.5% of the total tensile force. Force rearrange-ments of the fibres as a result of matrix creep can thus be neglected. There is seen to be virtually nocorrelation between time and strength for UD laminates which have continuous fibres and which areloaded in a direction parallel to the fibres.

Relaxation tests conducted on CFRP rods over a period of 3,000 hours with a starting stress level of70% of the static short-time tensile strength produced relaxation losses of less than 2%. Relaxationlosses of 2 to 3% were extrapolated from the logarithmic profile of the creep curve over time for a dura-tion of 50 years and the above stress level.

To sum up, it can be stated that UD-CFRP plates bonded with epoxy resin do not undergo significantcreep or relaxation when subjected to the types of low creep generating continuous loading which resultfrom their application to elements which are already subject to dead loads.

5.2 Physical and chemical material properties

DurabilityCFRP exhibits very good resistance to all the chemical attacks of relevance to construction applica-tions. This has been proven by a large number of tests. Creep tests on CFRP rods under permanentstress levels of 5 to 75% of the short-time tensile strength and temperatures of 21°C - 80°C, which wereexposed to simulated concrete pore liquids at pH = 10 - 13.5 over a period of three months, did notreveal any reduction in interlaminar shear strength.

Component tests on prestressed concrete beams, reinforced with CFRP rods prestressed to 40% oftheir short-time tensile strength, which were immersed in alkaline solutions for 81 days at pH =12.5 - 13, did not show any strength reduction. Parallel tests on bare CFRP rods that were exposed tothe same solutions at 60°C likewise failed to show any negative influence on the mechanical properties,from the immersion.

Thermal propertiesThe measured coefficient of linear thermal expansion for the two S&P plate types in the longitudinal andtransverse direction are set out in the following table.

Plate type αT; longit. [10-6K-1] αT; transv. [10-6K-1]

S&P 150/2000 ±0 30

S&P 200/2000 ±0 20

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The coefficient of thermal expansion in the transverse direction is of no relevance for dimensioning. Thedifference between the coefficient of expansion of the S&P Laminate CFK plates in the longitudinaldirection and that of concrete, at αT = ±10 · 10-6K-1, could be expected to have a negative impact on thebond between the plate and the concrete in the event of major temperature fluctuations.

At EMPA, two series of beams were subjected to a static bending test following 100 freeze/thaw cyclesat between -25°C and 20°C and the results were compared to those of identically designed beams thathad not been exposed to the freeze/thaw cycles. The beams in one of the series displayed cracks priorto the freeze/thaw cycles on account of prior loading, while the beams in the other series had no cracks.The beams were saturated with water during the freeze cycles, which meant it was possible to studythe potential loosening of the composite structure as a result of freezing water, in addition to the poten-tial impact of any thermal incompatibility of the CFRP and the concrete. The results did not reveal anyreduction in flexural load bearing capacity, when compared to the reference beams.

A further concrete beam reinforced with a CFRP plate was cooled to -60°C without the plate becomingdetached from the concrete or any fibre buckling resulting from the induced compressive stresses.

The adhesive bond between a CFK plate and an aluminium substrate did not reveal any damage to thebond up to the minimum temperature of -133°C. The problem of thermal incompatibility is morepronounced with CFRP/aluminium composites than with CFRP/concrete composites on account of thealuminium’s high coefficient of expansion (αT,AL = 23.4 10-6K-1). Even though it was not possible to studypotential bond failure in this test, the test nonetheless showed that, under the temperature conditionsof relevance for construction purposes, no fibre or plate buckling has to be expected as a result offorced compressive stresses with standard-modulus CFRP plates.

According to the current state of knowledge, the dissimilar thermal expansion behaviour of CFRP platesand concrete in no way impairs the load carrying capacity of structural elements strengthened withCFRP plates. Nonetheless, in order to make provision for any potential uncertainty and knowledge gaps,it is recommended (in agreement with design guidelines contained in an existing CFRP plate approval),that the design value for the bond failure stress be reduced by 10% when major temperature fluctua-tions have to be taken into account. This recommended reduction is based on approximate estimates.

Fire behaviourCarbon fibres have high heat resistance. The glass transition point of the matrix resin is TGM = 100 -130°C. The load carrying capacity of the composite system is determined by the adhesive which has aglass transition point of TGK = ±47°C. This temperature will be attained after just a few minutes of a stan-dard fire.

With reinforcement levels of η ≤ γv ≤ 1.75 below the safety level for the structural element in thereinforced state, element safety will not fall below γresidual = 1.0 in the event of plate failure. The fireresistance period will then be conditioned by the reinforced concrete component, i.e. by the cover onthe concrete. The fire resistance period can be increased by a fire protection cladding.

With reinforcement levels ηB, of γv < η ≤2, the structural element safety in the event of plate failure willfall to γresidual = γv/η <1.0. The fire protection cladding must thus prevent the layer of adhesive from heatingup to TGK over the desired fire resistance period. This should be verified in each individual case.

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6. Manual lamination at the job sitewith S&P C Sheet

UD carbon sheets are used as confinement reinforcement for load bearing elements or as external shearreinforcement for beams. As the influence of the matrix is negligible in terms of strength, only the fibreproperties (not the properties of the composite) and the theoretical fibre cross section are used fordesign purposes.

The theoretical fibre thickness for design of a UD carbon sheet layer is determined as follows:

Due to the application process, the site lamination does not always produce an optimum fibre ar-rangement. There is also a risk of damage to the fibres while they are being rolled on to the surface. Itis therefore recommended that the E-modulus used for the fibres be reduced by a safety factor [S].

Recommended safety factor [S]:1.2 UD stretched products1.5 woven products

The value of strain used in design should not be greater than 50% of the ultimate strain and it alsodepends on the individual case at the strengthening (Shear/Confinement/Flexural)

Recommended design values for strain of C fibre sheets:• Shear reinforcement Limiting design strain = 0.2-0.3%

• Confinement reinforcementof load-bearing structures

Limiting design strain = 0.4-0.6%

• Flexural reinforcement Limiting design strain = 0.6-0.8%

The selection of the ideal carbon fibre for the production of a sheet is based on the following criteria:

Carbon fibre type: Modulus of elasticity 640,000 N/mm2 (Safety factor S = 1.2)Ultimate strain 0.4%Limiting design strain 0.2%Field of application: Shear reinforcement S&P C Sheet 640

S&P C-Sheet

Theoretical fibrethickness for design =

weight of C fibre

density of C fibre

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Properties of S&P C Sheet 640 for external shear strengthening

Weight Theoretical Modulus Ultimatethickness of elasticity elongation

400 gr./m2 0.190 mm 640,000 N/mm2 0.4%

Width of S&P C Sheet Shear force (0.2%) for design (1 layer)

150 mm 30 · 103 N each side

300 mm 60 · 103 N each side

Carbon fibre type: Modulus of elasticity 240,000 N/mm2 (safety factor S = 1.2)Ultimate strain 1.55%Limiting design strain 0.4-0.6%Field of application: Confinementreinforcement of load-bearing structures S&P C Sheet 240(Replacing of corroded stirrups)

Properties of S&P C Sheet 240 for confinement reinforcement

Weight Theoretical thickness Modulus Ultimate(C fibres only) of elasticity strain

200 gr./m2 0.117 mm 240,000 N/mm2 1.55%

300 gr./m2 0.176 mm 240,000 N/mm2 1.55%

Width of carbon (1 layer of sheet) Tensile force (0.6%) for design (1 layer)

200 gr./m2 weight 300 gr./m2 weight

300 mm 42 · 103 N 63 · 103 N

1000 mm 140 · 103 N 210 · 103 N

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6.1 Aspects of building physics to consider in site application

A STRUCTURE MUST BE PERMEABLE TO WATER VAPOUR FROM THE INSIDE

TO THE OUTSIDE.

VITRUVIUS De-bonding of a coatingRoman architect and engineer, approx. 50 B.C. due to vapour pressure.

When total surface wrapping of concrete is intended, aspects of building physics must be considered.30-50% of the surface of the element should remain water vapour permeable. A total surface coveragewith an epoxy matrix is therefore not suitable. In such cases, the element is only partially wrapped. Asan alternative, the matrix can be varied as follows:

Anchoring area of the sheet: Epoxy matrix => System approvedWater vapour permeable area of the sheet: PU or acrylic matrix adhesives

Calculation of the water vapour permeability of the coating

Sd = µ H2O · layer thickness [m] < 4 m

Sd: Resistance of the coating against water vapour transmissionµH2O: Water vapour transmission rate of the coating

As is the case with thin coatings, aspects of building physics must be checked when intending to fullywrap with fibre composites. The type of matrix used is the limiting factor relating to water vapour trans-mission.

FRP matrix µH2O Shear modulus

Epoxy matrix 1,000,000 >3,000 N/mm2

PU or acrylic matrix 400 - 3,000 50 - 500 N/mm2

In areas where the fibre composites are subject to load transfer (anchoring and lap zones), it is alwaysnecessary to apply an epoxy matrix with a high shear modulus. In the water vapour permeable zonesof the fibre composite, however, a PU or acrylic matrix is used to protect the C fibres.

When using FRP for reinforcement, it is essential that aspects of building physics be consideredin each individual case.

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Example A

Example B

A total surface coverage using C sheets and anepoxy matrix to the underside of the box girdersoffit is possible. Water vapour permeability intothe inside of the box girder is assured.

Example C

• Epoxy adhesive • PU or acrylic adhesive(anchoring/lap (water vapourarea) permeable area)

Due to the use of different matrices, 50% of theelement's surface remain open to water vapourtransmission.

A total coverage for flexural reinforcement usingS&P C Sheets is not recommended. Reinforce-ment using S&P Laminates CFK, allowing watervapour transmission between the laminates, is abetter solution.

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6.2 Special adhesives for site application of FRP sheet systems

Standard adhesives System approved standard adhesives may only be applied to substrates witha moisture content of <4%. In addition, the dew point must be measuredduring the application; the temperature must be at least 3°C above the dewpoint.

Special adhesives System approved special adhesives are required for substrates with a highmoisture content. In order to ensure an optimum load transfer from the FRPto the substrate, a system approved primer must be brushed into the sub-strate.

PU or acrylic matrix These adhesives are not suitable for load transfer areas and must not beapplied to lap areas of C sheets. The vapour permeable adhesives serve as aprotection of the C fibre.

Note: Special adhesives for underwater applications of S&P Sheets (off-shoreworks) are available from S&P.

The application guidelines of the system approved primer and the impregnation epoxy must be fol-lowed in each case. These guidelines must be ordered from the supplier of the reinforcing system.Recommended Health and Safety measures for the use of epoxies must be observed. The S&P FRPreinforcing systems may only be applied in combination with system approved adhesives. In the caseof non-compliance, all product liabilities are declined.

7. Strengthening of load bearing elements withS&P C Sheet 240

7.1 Replacing of corroded reinforcement by using FRP

In the case of traditional concrete repair, also the corroded steel reinforcement is replaced by FRP. Thus,the original safety factor of the constructional element is guaranteed after the repair.

Concept:

• Remove all spalled concrete.

• If the chloride content of the concrete exceeds the approved limit, apply a corrosion inhibitor.

• Repair with cementitious repair mortar.

• New: The corroded reinforcement may be replaced with FRP.

• Finally, coat the structural element.

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Replacement of corroded flexural reinforcement withS&P Laminates CFK bonded into slots.

S&P Laminates CFK (type 10 mm/1.4 mm) are epoxy bonded into slots cut into the column to preventbuckling.

The corroded reinforcing stirrups are replaced by confinementreinforcement with S&P C Sheets 240.

In order to verify the reinforcing effect of the FRP confinement against compressive loading, varioustests were conducted by internationally recognized testing institutes on behalf of S&P Reinforcement.

Slot-appliedS&P Laminate CFK

Slot-appliedS&P Laminate CFK

Epoxyadhesive

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7.2 Large scale tests on FRP reinforced circular columns

At the Technical University of Gent (Belgium)large scale tests were carried out on circularcolumns of height 2.0m and diameter 400mm, towhich different FRP systems had been applied.

FRP • S&P C Sheet 240 (stretched fibres)systems: • S&P C Sheet 640 (stretched fibres)

• Carbon/glass hybrid (undulating fibres)• Glass sheet (undulating fibres)

The increase in compressive strength obtainedfrom the FRP confinement was measured.

In order to achieve an identical increase in compressive strength, the following fibre quantities wererequired in the confinement direction:

• S&P C Sheet 240 (stretched fibres) 1.0 kg of C fibres• S&P C Sheet 640 (stretched fibres) 1.6 kg of C fibres• Carbon/glass hybrid (undulating fibres) 2 - 3 kg of fibres• Glass sheet (undulating fibres) ≈ 4.0 kg of G fibres (3.6 kg confinement, 0.4 kg vertical)

Since the consumption of epoxy adhesive increases in proportion to the fibre volume, the use of cheapglass fibres for confinement reinforcement is not economical.

The cost/benefit comparison shows that the confinement reinforcement of the load bearing column with the S&P C Sheet 240 is the most economical solution.

In an additional test series the columns were wrapped with S&P C Sheet. The approved adhesive wasapplied to the anchoring/lap areas only, and the remaining surface of the columns was left withoutadhesive (water vapour permeable). The increase in compressive strength of the columns with partialand with full surface adhesive application was more or less identical. The reinforcing effect of the watervapour permeable FRP confinement could thus be established.

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Large scale test on a column with confinement reinforcementof 5 layers of S&P C Sheet 240

Identical tests were carriedout on circular and rectangularcross sections.

increase ofthe compressivestrength 100%

Roundingof edges

R = 1 cm60%

R = 3 cm80%

In order to guaranteetwo confined cores, aline of horizontal bars,firmly attached to theexternal concrete sur-face on its both ends,

should cross the section of the column. The verti-cal spacement between these bars shall notexceed the diameter of the cores to be confined.

(D=150 mm)

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7.3 Design concept for the confinement of axiallyloaded columns

While the design of structures subject to bending moments is generally based on capacity design prin-ciples, where a high level of ductility is required of an element when it passes into the non-linear range,the strengthening of axially loaded columns by means of external confinement reinforcement producesa triaxial stress situation due to the fact that strains at right angles to the direction of loading are im-peded, thus allowing a substantial increase in the load carrying capacity of the column. Since thisincrease is proportional to the increase in transverse compressive strength, confining materials shouldtherefore exhibit a low ductility. Carbon fibres are very well suited for this application as they offer a highmodulus of elasticity and exhibit linear-elastic behaviour until failure, without yielding. Thus, whatappears to be a negative feature in the case of flexural strengthening, can be considered an advantagefor confinement.

The design concept is based on a circular column completely wrapped with S&P C Sheet. If an axialload N is applied to this column, a vertical stress σz is created. In addition, due to the fact that the strainat right angles to the longitudinal axis is impeded by the confinement reinforcement, a horizontal com-pressive stress σx is created which acts evenly from all sides (Fig. 1). The highest stress σx the C sheetcan carry, is calculated as follows:

fFRP: Tensile strength of the C fibre sheet [N/mm2]tFRP: Thickness of the C fibre sheet [mm]r: Radius of the column [mm]

Due to the confinement reinforcement, the con-crete of the column is exposed to a triaxial com-pressive stress condition. If the cross elongationof steel reinforced concrete columns is impededby means of steel clamps, the concrete com-pressive strength can be increased to a maxi-mum of:

fC FRP

= fc+ 4 · σ

x

Fig. 1: Longitudinal and cross section of a con-crete column exposed to a vertical load andcompletely wrapped with a C sheet.

The related longitudinal compressive strain εcc of the column can be expressed as:

Non-regular situations, especially those regarding columns with some of its longitudinal bars notstrongly tied by the internal stirrups should be carefully analysed, regarding, for example, what is estab-lished at the FIB Bulletin nr. 1. In this situation the S&P A Sheet 120 can be an interesting solution.

fFRP · tFRPσx =r

fC FRP: Concrete compressive strength afterFRP confinement [N/mm2]

fc: Uniaxial concrete compressive strength[N/mm2]

σx: Horizontal concrete compressive stressresulting from confinement reinforcementwith C fibres [N/mm2]

εcc = εco · [1+5{ fC FRP -1}]f

C

εco = f

c

60

17

Design table: FRP confinement of axially loaded columns

Exa

mp

le:

A c

ircul

ar c

olum

n Ø

300

mm

req

uire

s its

axi

al c

omp

ress

ive

stre

ss c

apac

ity in

crea

sed

fro

m4.

0 N

/mm

2to

7.0

N/m

m2(+

3.0

N/m

m2 ),

saf

ety

fact

or 1

.75:

Req

uire

d 4

σ x=

1.7

5 x

3.0

N/m

m2=

5.2

5 N

/mm

2

1 la

yer

of S

&P

C S

heet

240

(200

gr./

m2 )

= 4

N/m

m2=

> 2

laye

rs a

re r

equi

red

18

7.4 FRP confinement of axially loaded columns:Application guidelines

Slot-application of S&P Laminate CFK Rounding of edges R =1-3 cm

Checking of flatness (max. deviation 1 mm per 30 cm) Application of S&P C Sheet 240

Sanding of S&P C Sheet Mineral-based final coating

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8. Prefabricated FRP laminatesPrefabricated laminates are produced by the extrusion method. In a continuous process, the carbonfibres are soaked in epoxy resin and hardened through heating. For technical reasons, the extrusionmethod limits a maximum fibre content to approx. 70%. The elastic properties of a uni-directional layercan be calculated from the performance of the fibres and of the matrix. Since the modulus of elasticityand the tensile strength of the matrix can be neglected for the calculation of the laminate properties,the values are approx. 70% of the values of the carbon fibre. The S&P laminates are manufactured bya new method. For the production of S&P hybrid laminates various types of carbon fibres with differentmoduli of elasticity and different tensile strengths are used. Normally, the modulus of elasticity of ahybrid laminate does not have a linear progression. Carbon fibres with a high modulus of elasticity anda low ultimate elongation will break sooner than fibres with a low modulus of elasticity. In the hybrid,however, the C fibres with a higher elongation are prestressed during the production procedure. Thisproduces a linear progressive modulus of elasticity in the laminate. Due to this hybrid technology, inex-pensive C fibres with a low modulus of elasticity can be used.

While the design for manual on-site lamination is based on the theoretical fibre cross section and theparameters of the fibres only, the design for application of prefabricated CFK laminates is based on thecross section and the parameters of the composite.

The production of the S&P Laminates CFK is subject to a strict quality control procedure in accordancewith ISO 9001. Thus, the properties of the laminates are guaranteed by the manufacturer.

Properties S&P Laminate 150/2000 S&P Laminate 200/2000S&P Laminates CFK

Modulus of elasticity165,000 N/mm2 205,000 N/mm2

for design

Ultimate tensile strength 2,700 - 3,000 N/mm2 2,400 - 2,600 N/mm2

Special laminates with a modulus of elasticity of 300,000 N/mm2 can be custom-made to the specificrequirements of a project. However, the application is often not economical because of their low effec-tive tensile strength (~1,200 N/mm2). For the laminates with a modulus of elasticity equivalent to steel,calculation rules for steel plate bonding are used. Due to the higher utilization of the tensile strength,this type of laminate is normally the most economical alternative.

S&P Laminate CFK

Thicknessof laminate

20

Detachment of the laminate

Concrete

Steel

Concrete

Steel

min. ε(elongation of the laminate)

Concrete

Steel

max. ε(elongation of the laminate)

8.1 Design for flexural strengthening usingS&P Laminates CFK

The bonding of an additional external S&P Laminate CFK on to the tensile stress zone of a structuralelement subject to bending is carried out with a system approved epoxy resin. Thus, a reinforced con-crete structure is produced with an elastic-plastic (steel reinforcement) and a perfectly elastic tensileelement (S&P Laminate CFK). Models for the calculation of the load bearing capacity of the compositestructure and of the anchor lengths were found by means of bond tests.

Related bond failure forces of all bond tests on CFK laminates, depending on the anchor length (TUBraunschweig, Germany)

The existing design model for the bond strength of reinforcements glued on to concrete is based on thenon-linear mechanics of brittle fracture and is suited for any type of elastic laminate material. The appli-cability of the existing models was established during the bond tests carried out to obtain the approvalfor S&P Laminates CFK in several countries.

8.2 Approved elongation limit for design

Cracks in the exposed area of the concrete are necessary for the steel reinforcement to absorb thebending stresses. A high allowable elongation limit of the laminate permits large depth cracks. With alow allowable laminate elongation the crack depth remains minimal. Large crack depths lead to adetachment of the CFK laminates due to shear forces caused by displacements.

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21

Beam tests have demonstrated that the detach-ment of the laminate depends on the elasticelongation as well as on the plastic steel elon-gation. Failure of the internal reinforcement wasinitiated at an elongation of the CFK laminate ofapprox. 0.65% which corresponds to 5.7 timesthe yielding point of the internal steel. Failure ofthe structure occurred at an elongation of theS&P laminate of approx. 1.3%.

Measured plate tensile forces from local strains:

Theoretical and measured plate tensile forces in slab

The approved maximum elongation limit for designof S&P Laminates should therefore be restricted to 0.6 - 0.8%.

Recommended tensile strength of the S&P Laminate for design:

Elongation limit for S&P Laminate 200/2000 S&P Laminate 150/2000flexural design (E = 205,000 N/mm2) (E = 165,000 N/mm2)

0.6% 1200 N/mm2 1000 N/mm2

0.8% 1600 N/mm2 1300 N/mm2

In addition, it must be checked that the internal reinforcement of the structural element will notundergo plastic deformation in the service state. In practice, the tensile strength for design of theS&P Laminate CFK will often be restricted by the elongation limit of the internal reinforcement (DIN0.5%, Euro Standard 1.0%).

The following diagram shows the procedure for dimensioning of the flexural strength with S&P Lami-nates CFK.

22

8.3 Procedure for design of flexural strength (diagram)

A Reinforcing factor V

B Design rules

η

η: Strengthening factorMv: Moment ultimate stress state (after strengthening)Mo: Moment ultimate stress state (before strengthening)

According toGerman approval

23

C Check of spacing

D Development length (anchor length)

24

8.4 Flexural strengthening with S&P Laminates CFK:Application guidelines

Delivery of S&P Laminates CFK Cutting of S&P Laminates CFK

Application of adhesive to laminate Pressing on of laminate

• Standard epoxy Moisture content substrate <4%• Special adhesive for wet substrate Moisture content substrate >4%• Special adhesive for low temperature Application up to -20°C• Special adhesives for underwater applications Upon request

Box girder soffit reinforced with S&P Laminates CFK

25

9. Design software “flexural/shear”for S&P FRP systemsPeter Onken, Wiebke vom Berg, Dirk Matzdorff; bow ingenieure, Braunschweig

9.1. General Introduction

S&P Lamella is an analysis program for reinforced concrete slabs and beams that have to be strengt-hened with S&P FRP laminates to resist uniaxial bending. The program can be used both as a designtool for strengthening beams and slabs and as an analysis tool for checking existing designs. The pro-gram provides the user with the appropriate FRP laminates, internal forces and performs the necessarycalculations for proving that a given design satisfies the requirements of a specific job.

The program was developed in Microsoft Visual Basic 6.0 for Windows '95, Windows '98 and Windo-ws NT operating systems. The program is windows-based both for input and output. The analysisresults can be printed directly by a standard windows printer. Routines for automatic installation anddeinstallation will be provided on the compact disc. The program is adjustable to different country con-figurations.

9.2. Analytical Basis

The program S&P Lamella has been developed for different national code systems as British Stan-dard BS 8110, American Concrete Institute ACI 318 and Eurocode 2. For calculations following theACI code system, the program supports the European metric system as well as the American imperialsystem (psi). Additionally the program is based on the analytical approach of the German GeneralApproval for the Strengthening of Reinforced Concrete Members by Externally Bonded CFRP lamina-tes and also on the guidelines in the Rules for the Strengthening of Reinforced Concrete Members viaExternal Bonding of Unidirectional Carbon Fiber Reinforced Polymer laminates, Draft Sept. 1998.

The prevailing national code can be chosen by the user at the start of the program as shown in theopening window (fig. 1).

Internal forces for the existing systemto be strengthened must be determinedinitially by the user in a hand calculati-on or with the help, for example, of aseparate structural analysis program.The design for unstrengthened andstrengthened systems is performed ite-ratively by finding the internal forceequilibrium of the concrete cross-section. Plane sections are assumedto remain plane and the constitutivemodels for concrete and steel corre-spond to non-linear stress-strain rela-tionships in accordance with the na-tional codes. Concrete is assumed tohave no tensile strength.

9.3. Safety Concept

The program is following the safety concept of the different national standards according to the codechosen in the opening window. The safety concept of the provided national codes is based on partialsafety factors for ultimate limit states, i.e. on one side the partial safety factors for actions or loads onbuilding structures and on the other side the partial safety factors for materials. In the special case ofthe ACI 318 the partial safety factor on the material side is expressed by a reduction factor. The follo-wing table gives an overview.

Fig. 1 Opening window of the program

26

Table 1: Partial safety factors for EC2, BS ACI

Loads materials

Code dead loads live loads concrete reinforcement

γG γQ γC γS

Eurocode 2 1,35 1,5 1,5 1,15

BS 8110 1,4 1,6 1,5 1,15

ACI 318 1,4 1,7 1 / 0,9

9.4. Program SequenceAt the beginning of the calculations the user has to enter thesectional area of the concrete structure, the existing reinfor-cement and the material properties of the concrete structure.Furthermore it is necessary to choose the desired type ofCFRP strip (high or low modulus of elasticity) before startingthe calculations.The user then specifies the characteristic bending momentpresent in the reinforced concrete section at the time justprior to strengthening, i.e. what moment, MSk0, acts on thesection at the time when the lamellas are bonded in place.Commonly this will be the dead load moment. This inputdefines the initial state of strain in the section. Next, theexpected moment demand after strengthening MSdL must bespecified, which is corresponding to design loads. Thisprocedure is shown schematically in figure 2.

The program calculates the design resistance of theunstrengthened section MRd0 and in dependence of theexpected design moment MSdf the degree of strengthening η.Furthermore the program provides the required cross-sectional area for the FRP laminates Af req for the strengthenedsection. Figure 3 depicts the superposition of the initial strainand additional demand in the strengthened state. The strainsare assumed to have linear distribution.

After dimensioning the cross-sectional area ofthe external bonded FRP laminates additionalwindows provide the user with the ability tocontrol the strain profiles for the ultimate limitstate (ULS) and service limit state (SLS). Furthermore in additional proofs the programperforms a bonding check for the anchorage ofthe FRP laminates and shear strength check ofthe strengthened structure. If necessary, thelevel of required externally bonded FRP sheetswill be determined to increase the shear capa-city.

Fig. 2 Load cases before / duringand after strengthening theconcrete structure

The program calculates the necessarycross-sectional area of the CFRP stripsfor the ultimate limit state of thestrengthened structure under the follo-wing condition

MRdf > MSdf

where MRdf indicates the design resi-stance (internal moment) of the strengt-hened section and MSdf indicates thedesign action or load of the streng-thened structure.

The serviceability check of the strengthened system is not provided by the program. In every case where it is neces-sary the serviceability, like the control of crack width and the deflection of structure has to be checked by the user.

Fig. 3 Superposition of the initial strain and addi-tional strain after strengthening

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9.5. Input data9.5.1 General

To enter the input data for the calculations the program supports the user by a special card file system.The card files are sorted in different blocks like geometry, reinforcement, material properties and loadactions as depicted in figure 1. According to the different national codes the input fields for the materi-al properties are containing some default values. In some special cases default values can only bechanged by the provided enable key-button in the menu. These values may not be conform to theregulations of the national codes. For quick changes the program allows to enter input data in any cardfile in spite of the sequence of the card files. Special graphic elements in every card file will support theuser to identify the required input data.

9.5.2 Geometry

The program supports the calculation of 3different section types: slabs, rectangularbeams and T-beams. After entering thedimensions of the concrete section it hasto be considered if the calculations willperform for positive and negativemoments, i.e. a moment of span or amoment at support. The input card file forthe geometry of the concrete section isdepicted in figure 4.

9.5.3 Rebars

The next card file contains the parametersof reinforcement. The program allows theinput of 2 layers of rebars on the tensionside and also includes possibility ofcompression rebars. The input card file forreinforcement is depicted in figure 5.

9.5.4 Steel –Material Properties

The card file steel contains details of thereinforcement material properties for thetension layer, compression layer and stir-rups. According to the different nationalcodes the input data fields for the materialproperties are containing default values.The reinforcement steel is assumed to beelastic-perfectly plastic as depicted infigure 6. The modulus of elasticity, themaximum steel strain and the partialsafety factor for reinforcement can bechanged if necessary by a special enablekey-button.Fig. 6 Steel input card file

Fig. 5 Rebars input card file (T-beam)

Fig. 4 Geometry input card file (T-beam)

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9.5.5 Concrete – Material PropertiesIn accordance to the CEB Model Code 90concrete is assumed to have parabolicstress-strain characteristics up to a pointwhere it is assumed to behave perfectlyplastic, as shown in figure 7. The maximumstrain for concrete subjected to uniaxialcompression is limited as stated in theprevailing national codes. Also the concre-te classes and the partial safety factor forconcrete are classified to these codes. Thespecial enable button can be used tochange the default values.

9.5.6 FRP – Material PropertiesAfter entering the data of the concretestructure it is necessary to choose the de-sired type of FRP laminates. There are twotypes of FRP laminates available: S&P150/2000 and S&P 200/2000. The FRPlaminates are assumed to behave linearelastically (figure 8). The modulus of elasti-city will be chosen according to type oflaminates. The strain limit states for thelaminates are set according to the GermanGeneral Approval for the Strengthening ofReinforced Concrete Members by Exter-nally Bonded CFRP laminates:

Fig. 8 FRP input card file εF max = 5 fsyk/Es

εF max = 0.0065 for S&P CFRP Strips 150/2000

εF max = 0.0075 for S&P CFRP Strips 200/2000

9.5.7 LoadBefore starting the calculation the designvalues for load actions have to be spe-cified. First of all the user must check thebending moment at time of strengtheningMSk0 (Fig. 1) which is assumed to be a cha-racteristic value. This bending moment isneeded to evaluate the initial state of strainin the unstrengthened structure. For thecalculation of the necessary cross-sectio-nal area for the laminates the input of thedesign moment after strengthening MSdf isrequired. The input value MSdf must includethe partial safety factors for combination ofaction. Next the characteristic moment afterstrengthening MSkf is needed for the calcu-lation of strain profile under service stateconditions (SLS). This value can be enteredexactly by the user or calculated from theprogram with an average load safety factor.The default value may be changed by theuser. The input card file for the load isdepicted in figure 9.

Fig. 9 Load input card file

Fig. 7 Concrete input card file

41

9.6. Analytical Procedure and Dimensioning

After entering the required data the calcu-lations will be started by the calc button.The very exact iterative solution procedure,the use of non-linear material properties forboth concrete and steel and the possibilityto include the effects of compressionrebars enable an especially economicalallocation of FRP laminates. The necessarycross-sectional area for the strips will bedetermined by satisfying the equilibriumconditions for the internal forces (ΣH = 0,ΣM = 0) through varying the state of theinternal strain distribution. An opening window (dimensioning card fileas shown in figure 10) provides the userwith the ability to choose the cross-sectionof FRP laminates and the number of lami-nates or especially for slabs the distancebetween the laminates. If the providedcross-sectional area of the laminatesexceeds the required value the programconducts the proof: MRdf > MSdf. and thefollowing card files will be enabled. Furtherthe program is giving the degree of streng-thening h which indicates the ratio betweenthe resistance of the strengthened section(MSdf) and the resistance of the unstreng-thened section (MRd0).

Additional windows allow the control of thestrain profiles for the ultimate limit state(ULS) and the service limit state (SLS).

Fig. 10 Dimensioning output window

Fig. 11 Strain output window (ULS)

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9.7. Additional Proofs9.7.1 Bonding Check

The proof of bonding strength is performedaccording to regulations of the GermanGeneral Approval for the Strengthening ofReinforced Concrete Members by Extern-ally Bonded CFRP laminates as a functionof the substrate strength and the end pointof the laminates. Therefore the beginning ofthe loaded portion of laminates (in tension)can be pinpointed depending on localmoment distribution and also dependingon staggered reinforcement. The proof thatthe bond strength is greater than the bondtensile force in the theoretical ultimatemoment will be performed in a specific out-put window. Recommendations for thebonding length are given by the program.

9.7.2 Shear DesignThe shear strength calculation is performedaccording to the rules of the different natio-nal codes. The existing stirrups are takeninto account. The magnitude of demandwill determine whether or not shear reinfor-cement is required. If necessary, the level ofrequired externally bonded strap binder isdetermined either for steel material or byusing S&P C Sheets 640. The program isgiven recommendations for the anchoringof the required strap binder.

9.8. Other FeaturesIn addition to purely technical functions, the program offers the possibility to enter project and positionnumbers as well as descriptions. Data blocks can be loaded or saved as needed. The program alsoenables the user to input a letterhead that then appears at the top of every page of output. Input data,analysis results and strain profiles can be printed by a standard windows printer.

Fig. 12 Bonding output window

Fig. 13 Shear output window

43

Sampel using S&P design software

Moment at time ofCross-section FRP strengthening

Moment due to service(after FRP strengthening)

Moment due to design loads(after FRP strengthening)

The code for the access tothe S&P Design Software isreplaced every year. Please

ask S&P or our regionalrepresentative for the new

valid code.

44

S&P Lamella– bending tension reinforcing with CFK Lamella –

45

46

47

10. External shear reinforcement using FRPOften when using CFK laminates for flexural strengthening, it is necessary to increase the shear capa-city. This can be achieved by using S&P C Sheets 640.

Shear force (V) must be resisted by the concrete (Vc), by the internal stirrups (Vs) and by the glued-onS&P C sheet 640 (Vf).

V = Vc+ Vs + Vf

Usually in the International Codes Shear, V is controlled by a limit called Vr, that depends on the cross-section area. Assuming that V < Vr, two situations may be distinguished:

Situation 1: The existing internal shear reinforcement (plus concrete) is not sufficient to absorb theshear force:

Vf = V – Vc –Vs

In this case, the S&P C Sheets 640 must be anchored in the compression zone.

The S&P C Sheet 640 is anchored in the web,150 mm above the neutral axis. According tosome International Standards, encapsulation ofthe stirrups in the compression zone is required.

Slots are cut into the plate in order to allow com-plete wrapping with S&P C Sheet 640 strips.

48

Situation 2: The existing internal shear stirrups (plus concrete) are sufficient to absorb the shear force.

V < Vs + Vc

In this case, the S&P C Sheet 640 must be dimensioned to transfer the shear force from below (fromthe flexural strengthening) up to the stirrups, in order to guarantee the complete compliance to the trussmodel (strut and tie).

So, the S&P C Sheet 640 doesn’t need to go up to the compression zone, but only to have a length thatguarantees the overlapping with the stirrups beyond the centroid of the flexural reinforcement.

The S&P design software automatically calculates the cross section of stirrups made of steel or S&P CSheet 640. These additional external shear stirrups can be replaced by external shear reinforcementwith S&P C Sheets 640.

The maximum strain when S&P C Sheet 640is used in shear applications shall not exceed 0.2-0.3 %,

in order to be compatible with elongation ofthe internal stirrups.

100

mm

existing stirrups (shear reinforcement)

existing flexural reinforcement

flexural strengthening with S&P laminates CFK

shear compatibility with S&P Sheet C 640

49

Technical data of S&P C Sheets 640 (external shear reinforcement)

Weight Theoretical Elastic modulus Breaking elongationthickness of C fibres

400 gr/m2 0.190 mm 640´000 N/mm2 0.4%

Width of S&P C Sheet 640 Shear force absorption for design Potential replacing of (0.2%), 1 layer application ST37 stirrups according

to the design software150 mm 30 · 103 N per side 140 mm2 (beam width 1 m)

300 mm 60 · 103 N per side 280 mm2 (beam width 1 m)

During a test series at Potsdam Technical University, the strengthening effect of FRP strips used toincrease the resistance to shear forces of reinforced concrete structures was established.

11. Slot application of S&P Laminates CFKThe S&P Laminate CFK 10/1.4 with a width of 10 mm and a thickness of 1.4 mm is specially designedto be bonded into slots in concrete or timber structures. A concrete saw is used to cut slots approx. 3mm wide and 10-15 mm deep into the substrate. The slots are filled with the system approved epoxyadhesive, and the S&P Laminates are pressed on edge into the adhesive.

The performance of slot-applied laminates has been tested at the Technical University in Munich. Thetest results positively proved that a good and uniform bond exists between the laminate and the con-crete. Furthermore, the high tensile strength of the laminate fibres was fully utilized prior to shear fail-ure between laminate and surface.

11.1 Bond tests

Tests: Comparison of slot-applied and surface-applied CFK laminates by means of bond strengthtests.

50

The illustration shows the relative displacement in the static tensile strength test.

Strength-displacement ratios of CFK laminates bonded into slots versusCFK laminates bonded on to the surface (anchor length 25 cm)

The illustration clearly shows the considerably more ductile behaviour of the slot-applied laminate.

The bond performance of the S&P Laminate corresponds to that of deformed reinforcing steel encasedin concrete. However, the stiffness of the bond in the lower load range is higher than with surface-applied CFK.

At an anchor length of 25 cm, the slot-applied laminateprovided three times the tensile strength of the surface-applied

laminate with the same cross section.

These test results confirm those numerous investigations which have shown that the bond performanceof reinforcement glued on to the surface is very brittle. The potential relative displacements up to fail-ure in the bonding area between the CFK laminate and the concrete are within a range of below 0.3 mm,while the potential displacements of deformed bars encased in concrete are in the range of 1 mm. Thus,the bond of encased reinforcement is clearly more ductile. This leads to a redistribution of forcesbetween the surface-applied CFK laminate and the encased deformed steel. Therefore, this type ofbond provides only a relatively low load transfer into the laminate. In addition, this load transfer is highlydependent on the concrete quality and, particularly, on the substrate bond strength.

The bond provided by slot-bonded CFK laminates has aconsiderably higher load canying capacity. Within the range ofworking loads, the bond performance is higher and, within the

range of failure loads, far more ductile compared tosurface-applied laminates.

51

11.2 Flexural tests on beams

Three point load tests with a span of 2.5 m were carried out on various reinforced concrete beams.

Each sample was either reinforced by a surface-applied CFK laminate 50/1.2 or by two slot-appliedCFK laminates 25/1.2.

– On test beams A1 and B1 failure occurred due to debonding of the CFK laminate.

– On test beam A2 failure occurred due to tensile fracture of the slot-applied laminate.

– On test beam B2, with a low shear reinforcement made of steel, shear failure occurred in the concrete.

The load-deflection curves of test beams A1 and A2 are shown in the illustration:

Interpretation of results from test beams A

At equal stiffnesses, the breaking load was morethan doubled using the slot-applied laminate.This is due to the high utilization of the tensilestrength of the CFK laminate.

The load-deflection curves of test beams B1 and B2 are shown in the illustration:

Interpretation of results from test beams B

The load-deflection curves are almost identicalexcept that the slot-applied CFK laminateexhibited a substantially higher breaking load.

CFK Laminate

Beam sections

52

11.3 Benefits of slot-applied laminates

– The improved utilization of the laminate permits higher loads to be applied and laminate cross sec-tions to be reduced.

– The quality of the substrate (tensile strength of the surface) is less important. Slot-applied laminatescan also transfer loads into substrates with a low bearing capacity (brickwork, masonry).

– The slot application is more economical than levelling and roughening required for surface-appliedlaminates.

– The slot-applied laminate is protected against mechanical damage. Better performance is achievedin the event of a fire, thus reducing the cost of fire protection measures.

11.4 Anchoring at the ends of the laminates

The S&P design software automatically calculates the required anchor length. In case of anchoring thelaminates in a compression zone, no mechanical aid is needed. In the case of steep moment curves,under tension zone, the anchor length of the S&P laminate as indicated by the S&P design software isoften insufficient. In this situation, two alternatives for anchoring at the laminate ends are available.

A) Strengthening of slabsThe forces are transferred from the laminate into the sub-strate through a stainless steel plate fixed with 4 - 6 steelbolts.

Tests demonstrate that with this type of anchoring the ten-sile force transferred from the laminate into the substratecan be doubled.

B) Strengthening of beamsThe ends of the S&P Laminate CFK are wrapped with the S&P C Sheet 640. Thus, the forces aretransferred into the web of the beam. Tests on bending beams, with and without confinement rein-forcement of the laminate ends, have been carried out at the University of Lisbon.

Testing arrangement

The test results show that due to the confine-ment reinforcement of the beam at the ends ofthe laminates, the bending moment can beincreased by approx. 20%.

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12. Seismic retrofittingStrengthening is often a necessary measure to overcome an unsatisfactory deficient situation or wherea new code requires the structure – or a part of it – to be modified to achieve new requirements.

For a structure to remain elastic under seismic action, typically associated with a 10% exceedance in50 years, it has to be designed for lateral forces with magnitude in the order of 50% or more of its weight.As it will cost a lot of money, seismic design codes allow, as design philosophy, the development of sig-nificant inelastic response since the inherent deformations do not endanger the integrity of the individualmembers and of the structure as a whole.

Recent earthquakes in urban areas have repeatedly demonstrated the vulnerability of older structuresto seismic deformation, not only the traditional masonry ones but also those made with reinforcedconcrete, particularly regarding the column - beam connection, showing deficient shear strength, lowflexural ductility, insufficient lap splice length of the longitudinal bars and, very often, inadequate seismicdetailing, as well as, furthermore, in many cases, very bad original design, with insufficient flexural ca-pacity.

Failure modes

For a good design of the seismic strengthening of an existing structure it is necessary to understandthe seismic actions and the typical failure modes that can be observed under its load / deformationinput. Regarding reinforced concrete frames, these modes could be summerized as follows:

• The most critical mode of failure is the column shearfailure – see picture – where inclined cracking leads tothe concrete cover spalling and to the rupture – oropening – of the stirrups. To prevent this brittle failure,the columns need to have guaranteed shear capacityboth in its ends – potential plastic hinge regions, whereconcrete shear capacity can degrade with increasingductility demands – and in the column center portion,between flexural plastic and/or existing built-in columnhinge.

• Another mode consists of a confinement failure of the plastichinge region, where subsequent to flexural cracking, coverconcrete crushing and spalling, buckling of the longitudinalreinforcement or compression failure of concrete initiates pla-stic hinge deterioration, usually limited to shorter regions in thecolumn. It can also happen that the column fails to the debon-ding of the lap splices of the longitudinal reinforcement. Theassociated flexural capacity degradation can occur rapidly atlow flexural ductilities in cases where short lap splices are pre-sent and little confinement is provided.

54

• Regarding the horizontal elements, failure can alsooccur due to shear, near the plastic hinge regions,but also as a consequence of deficient flexuralcapacity, both on the top and bottom of the beams.

Methodology of strengthening

Many researchers have shown that a better confinement of concrete on the potential plastic hinge re-gions increases significantly the failure strain of concrete and therefore the overall ductility. The perform-ance of the S&P G Sheet 90/10 in ductility enhancement has been proven by push-pull tests (chap. 4.1).For this reason, retrofit methods typically utilise schemes for increasing the confining forces either inthe potential plastic hinge regions or over the entire columns or beams span.

Advanced composites have shown to be technically just as effective as, and more economical than,conventional steel jacketing.

As a result of the confinement provided by the composite belts – either glass and carbon fibre epoxyimpregnated sheets - wrap, concrete will fall at higher strains. The lateral pressure exerted by the com-posite will increase the compressive strength of concrete in both the core and shell regions, resultingin higher axial as well as lateral load carrying capacity. The lateral confinement guaranteed by the wrapwill also provide additional support against buckling of the longitudinal bars.

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S&P G Sheet 90/10 A

Round column D = 100 – 300 mm

1 – 3 layers of S&P G Sheet 90/10 A are required to achieve the maximumdisplacement level.

Square columnD = 100 – 300 mm(The edges must be rounded)

S&P G Sheet 90/10 B

Round column D = 300 – 600 mm

2 – 3 layers of S&P G Sheet 90/10 B are required to achieve the maximumdisplacement level.

Square columnD = 300 – 600 mm(The edges must be rounded)

The S&P engineering team will assist you with more information on static design.

Strengthening of masonry

Masonry structures or the masonry pieces of some constructions typically show cross crackingbetween overtures or rigid elements as a consequence of seismic actions.

57

First strengthening concept

Regarding masonry wall strengthening is usually done by the application of S&P Laminates CFK, as-suming x or + cross styles, depending on each case. Care must be taken in detailing the intersectionof the strips.

The method was developed at EMPA, Switzerland, to upgrade masonry buildings in seismicly en-dangered areas using FRP material.

CFK laminates are bonded diagonally to the shear walls. Both ends of each laminate must be anchoredinto the existing concrete slab. In practice a slot is cut into the concrete slab. The slot is filled with asystem approved epoxy paste and the laminate is placed into it.

At EMPA Switzerland shear walls 3.60 x 2.00 m were subsequently loaded cyclically in the horizontaldirection at the upper edge of the walls. The earthquake resistance could be increased with the CFKlaminates strengthened walls by a factor of over 4.

Picture and diagram: Dissertation ETH Nr. 10672, G. Schwegler”Verstärken von Mauerwerken mit Faserverbundwerkstoffen”.

Second strengthening concept

The masonry can be strengthened with the S&P G Sheet 50/50. The bi-directional glass woven mustbe applied to the full surface only on one side of the masonry. If the product is not anchored into theadjoining concrete slabs, the earthquake resistance can only be increased minimally.

The best solution is a combination of the first and the second method. Thanks to the S&P G Sheet 50/50 the cracks can be distributed uniformly over the masonry surface. The earthquakeresistance of the masonry wall can be increased. Thanks to the release of the CFK laminates and dueto the end anchoring into the concrete slabs, the system ductility can be increased.

Design should consider the possibilities offailure in each member as well as in thestructure, as a whole, applying appropriate localand global criteria. In any case, strengtheningmust be considered both for the resistance –shear and flexural (bending and axial inter-action) capacities – and ductility considerations.A coefficient considering the non-monolithicbehaviour γn = 0,9 must be adopted, and it mustbe guaranteed that the effects of cyclic loads aswell as the formation of plastic hinges areaddressed.

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13. Prestressing System S&P laminate CFKS&P has developed a prestressing system for S&P Laminates CFK and has applied for a patent. Thesystem is exclusively used by a world-wide network of specialized applicators.

� Fixed anchoring:(A steel plate is fastened to the concretesuface by means of heavy-duty anchors).

The S&P laminate CFK is glue-appliedbetween the steel plate and the con-crete surface.

� Mobile anchoring:(The S&P laminate CFK is glued betweentwo steel plates, held together by means ofscrews.).

After the final setting of the adhesive ofplate (3) the mobile anchorage (plate 2)is removed (cut off).

� Prestressing system:(The prestressing kit is fastened to a steelplate applied to the concrete surface bymeans of anchors).

The S&P laminate CFK is applied tothe concrete by adhesive, finally set-ting after the prestressing process.

During a test series carried out at the University of Freiburg (Switzerland) the behaviour of a concreteslab reinforced with untensioned and prestressed S&P Laminates CFK was investigated. The followingis a summary of the breaking tests performed on the Laminate Type 80/1.2. For a detailed report plea-se contact S&P or the system applicator.

13.1 Testing Arrangement

Steel FRP Prestressing Prestressing Prestressinglongitud. vertical 0/00 stress (N/mm2) force (kN)

Reference LC1 6 Ø 12 (Ø8 s=150) 0 0 0 0

LC5 6 Ø 12 (Ø8 s=150) 0 0 0

LC2 6 Ø 12 (Ø8 s=150) 4.0 640 2x61 = 122

LC4 6 Ø 12 (Ø8 s=150) 6.0 960 2x92 = 184

2 S&P laminateCFK 150/2000,

Typ 80/1.2

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13.2 Test results

Under working load the test specimens whichwere reinforced with prestressed S&P LaminatesCFK exhibited a high reduction in the deflectionand the crack widths. Due to the overriding nor-mal force the concrete cross sections remain inthe unbroken condition I, up to and above themaximum working loads.The failure condition shows a high increase inthe breaking load, at substantially higher deflec-tion levels compared to LC5 specimens. Sam-ples with untensioned CFK laminates show anincrease in the breaking resistance of 32%, whileprestressed CFK laminates raised the breakingresistance by 82% at a prestress of 4‰ and by93% at a prestress of 6‰. The breaking elonga-tion measured on the prestressed S&P Lamina-tes CFK was practically increased by a factorcorresponding to the respective prestressingforce.

Research by University of Fribourg, CH

Table: Failure load/Failure moment

S&P laminate CFK Concrete slabs Failure load Failure moment Failure moment(kN) (kNm) (%)

– LC1 Reference 16.4 82.6 100

2 x 80/1.2 LC5 FRP 24.0 109.4 132

2 x 80/1.2 LP2 FRP 40/00 35.3 150.1 182

2 x 80/1.2 LP4 FRP 60/00 37.9 159.4 193

13.3 Conclusion

Prestressing of the S&P LaminatesCFK has a very positive influenceon the behaviour of strengthenedreinforced concrete structures.Deflection and crack formationunder working load are reduced.The breaking moment is substanti-ally increased.

With the lightweight S&P prestres-sing kits it is possible to prestressthe S&P Laminates CFK to an elon-gation of 6‰. The system has been specially developed for the strengthening of reinforced large-span concrete slabs.

There is a high potential of applications in bridge construction:• Post-reinforcement of overloaded elements• External prestressing of bridges with corroded internal prestressing cables• Repairs to connection joints

40.0

35.0

30.0

25.0

20.0

15.0

10.0

5.0

00.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0 180.0 200.0

Deflection (mm)

Load

(kN

)

LP4 FRP 0.60 /00

LP2 FRP 0.40 /00

LC5 FRP

LC1 RC

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14. Outlook for the application of S&P Laminates CFK in timber construction

It is a well-known fact that strength and stiffness of glue-laminated timber girders vary considerably.This is due to the different tensile strengths of the individual layers. For this reason, the allowable flex-ural strength of glue-laminated girders is reduced. Tests were carried out by Wiesbaden TechnicalUniversity (Germany) to evaluate the reinforcement of glue-laminated girders with S&P Laminates CFK.

To this end, three series of glue-laminated girders with different height/length ratios, with and withoutS&P Laminates CFK, were produced and compared. The S&P Laminate CFK 200/2000 was applied be-tween the support points only, not outside.

Height/length ratio and reinforcement level of girder series A to C

The objective of the tests was to bridge weakpoints in the glue-laminated girders, such asdovetail joints and knots, with S&P LaminatesCFK. The high modulus of elasticity of the lami-nate was used to increase the flexural strengthof the glue-laminated girder/S&P Laminate com-posite.Thus, the cross section of the timber girder canbe reduced to obtain the identical flexuralstrength.

14.1 Flexural tests / Arrangement of beams

The tests were carried out using a 1,000 kNbending test machine. To avoid tilting, thebeams were laterally fixed to the support andthe loading points.

Static system and loading device:

Loading cycleThis testing procedure basically consisted of a bearingsystem which was subjected to a defined loadingpattern during a defined period of time. The deforma-tions measured at given intervals were continuouslyregistered and recorded for subsequent evaluation.

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Arrangement of measuring points

The deflections on the loading points and at mid-span of the beam were measured by means of load-deformation detectors. The strain at mid-span of the beam across the entire cross section of the beamand the CFK laminate was measured using strain gauges.

Test results at breaking load

FAILURE PERIPHERAL STRAINin the timber section

Girder type Force Deflection Pressure Tension(kN) (mm) (mm/m) (mm/m)

A series

B 50 without CFK 168.7 56.4 -3 3.1

BC 50 with CFK 169.3 49.1 -2.55 2.4

Difference (%) 0.4 12.9 0.2 3.8

B series

B 30 without CFK 56.2 68.8 not measured 2.6

BC 30 with CFK 95.1 112.6 not measured 4.8

Difference (%) 69.2 63.7 n/a 84.6

C series

B 36 without CFK 38.3 119.3 -2.2 2.35

BC 36 with CFK 62.6 183.1 -3.82 3.4

Difference (%) 63.4 53.5 73.6 44.7

Summary

The examination of the loading of flexural beams up to rupture provided information on the load bear-ing capacity and the performance under loading of the composite structure in the plastic state. It wasfound that the increase of the load bearing capacity was substantial. In one of the tests the breakingload of the fibre reinforced girder could be raised by up to 93% compared to conventional glue-laminated girders. With a reinforcement level of 0.47%, this is a considerable increase.

62

A stress/strain diagram was made based on the strain measurement in the timber section and the lami-nate. The measurement of the strains in the composite cross section should indicate from which stresslevel the timber girder changes into the plastic state and also if the CFK laminate is utilized in its ultimatetensile strength range. In a second part of the investigation of this system, design concepts are definedand applied. The concepts should basically be designed to ensure that in the event of a failure of theCFK reinforcement the remaining cross section is able to absorb the assumed load with a safety factorof 1.1.

Stress/strain diagram:

Girder cross section, Strain line in the failure state, Stresses in the timber sectiondimensions w/h girder series B and C and the laminate

Both girder series with a higher height/length ratio (B and C series) displayed a very elastic deformationbehaviour in the compression zone. In the case of the A series with a lower height/length ratio, flexuralfailure of the timber could likewise be observed on the reference sample without fibre reinforcement.The fibre reinforced samples, by contrast, showed a different failure mechanism. As a result of the highload application, the girder cross section failed due to shear displacements: first in the support area andthen over the entire length of the girder. This means that the change in the failure mechanism wascaused by the reinforcement of the girder. In this case, it could be possible to further increase thebreaking load by means of external steel jackets.

Note:Currently, a further testing programme is in progress: In order to prevent shear displacements in thesupport area, additional S&P Laminates CFK are applied into slots on the outside of the glue-laminatedgirder.

14.2 Bond tests FRP application to timber

The BOKU University in Vienna has conducted tensile tests to examine the strengths of S&P LaminatesCFK applied to timber structures.

Samples for testing of the mean shear strengths

S&P Laminates CFK were glued in parallel to the fibres onto oneface of the timber beams, and the shear strengths [tm] of theapplied CFK laminates were measured. The following parame-ters were varied: adhesive, laminate surface (rough, smooth),application areas of the adhesive.

63

Adhesive Fm tm Type of failure(kN) [kN] (N/mm2)

Epoxy resin adhesive - type A 6,71 5,59Failure in timber, scarcely any adhesive failure

Epoxy resin adhesive - type E 6,75 5,63Failure in timber, scarcely any adhesive failure

Resorcinol-phenolic adhesive 5,00 4,12 Adhesive failure type C

Resorcinol-phenolic adhesive 3,56 2,97 Adhesive failure type D

Application of adhesive:

• Ambient temperature: 20°C• Relative humidity of air: 30%• Moisture content equilibrium of timber: approx. 7%

The suitability of the system approved epoxy adhesive on dried timber was established during thesetests.

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15. Fire protection measures for FRPstrengthened elements

When strengthening with laminates made of steel or CFK, one must consider that the heat resistanceof epoxy based adhesives is limited to temperatures between 60° and 80°C (140° and 180°F). In theevent of a fire, this leads to a premature failure of the laminate. Therefore, measures must be taken toprotect S&P Laminates CFK against premature failure.

In the event of a failure of the CFK laminate, the residualsafety factor S is decisive for the necessary measures for fire

protection. The S&P design software automatically outputs theresidual safety factor in the case of failure

of the S&P Laminate CFK.

Residual safety in the eventof laminate failure

S > 1.0 S < 1.0

Fire resistance ensuredby internal reinforcement

Additional protective measures forS&P Laminates CFK are required!

Conventional fire protection for internalreinforcement only

A DA

Example: Fire protection plates

Fire A = 100 mm A = 200 mmresistance (D) (D)

F 30 2 x 20 mm 2 x 20 mm

F 60 2 x 40 mm 2 x 30 mm

F 90 > 110 mm 2 x 40 mm

F 120 > 110 mm > 110 mm

S&P Laminate CFK

Please contact the S&P Technical Servicefor detailed documentation.

Fire protection plates

Fire protection plates

Concrete ceiling

65

16. Texts for specifications16.1 Flexural strengthening with S&P Laminates CFK

Item Text Unit

1 InstallationTransport (to and from) and supply of necessary Pappliances and materials for the reinforcing job.Additional site visits. Pcs.

2 ScaffoldingInstallation and supply of scaffolding, incl. required Pmeasures for dust protection during the construction phase.

3 Substrate preparationRemoval of cement skin by sandblasting, incl.cleaning with brush or vacuum cleaner.

Theoretical application surface + 20% excess:Laminate width 50 mm mLaminate width 80 mm mLaminate width 100 mm mLaminate width 120 mm m

4 Levelling of substrateRemoval of local excess profile and reprofiling of cavities and unevennesses in the application area with system approved levelling mortar.

Bill of quantities, based on actual consumptionLabour hSystem approved levelling mortar kg

4.1 If the substrate is poor, priming of the concrete surface is recommended. Priming with system approved primer. m2

5 S&P Laminates CFKDelivery and application of S&P Laminates CFK with system approved epoxyadhesive according to the application guidelines of the system supplier:

Elastic modulus CFK laminates: >200,000 N/mm2

Tensile strength at 0.8% elongation: >1,600-1,700 N/mm2

Elongation at break CFK laminates: <1.2%Product names: S&P Laminate CFK 200/2000

System approved adhesive

Type of laminate: Tensile force/laminate at 0.8% elongation:50 mm/1.4 mm 112 x 103 N m80 mm/1.4 mm 179 x 103 N m

100 mm/1.4 mm 224 x 103 N m120 mm/1.4 mm 269 x 103 N m

6 Reference samples laminateDelivery and application of reference samples of S&P Laminates CFK for subsequent bond strength testing. (Ideally, the reference areais added on to the application area.) Pcs.

6.1 Bond strength testTesting of bond strength of the S&P Laminate CFK to the substrateby means of test cores Ø 50 mm. Pcs.

6.2 Reference samples adhesiveDuring the application of the adhesive, two samples of the epoxy adhesive(prisms 40 x 40 x 160 mm) must be produced every day for subsequent quality control. Pcs.

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16.2 Reinforcement of load bearing columns with S&P C Sheet 240

Item Text Unit

1 InstallationTransport (to and from) and supply of necessary Pappliances and materials for the reinforcing job.Additional site visits. Pcs.

2 ScaffoldingInstallation and supply of scaffolding, incl. required Pmeasures for dust protection during the construction phase.

3 Slot-application of S&P Laminates CFKDelivery and application of the S&P Laminates CFK 10/1.4 minto slots cut into the substrate, according to S&P application guidelines. (slot depth 10-15 mm/slot width 3-5 mm)Product names S&P Laminate CFK 10/1.4

System approved adhesive

4 Substrate preparation prior to application of C Sheet Removal of cement skin by sandblasting or surface roughening, m2

incl. cleaning with brush or vacuum cleaner. All edges must be rounded to a minimum radius of 1-3 cm.

5 Levelling of substrateRemoval of local excess profile and reprofiling of cavities and unevennesses in the application area with system approved levelling mortar.Bill of quantities, based on actual consumptionLabour hSystem approved levelling mortar kg

6 Primer application• Anchoring/overlapping areas System approved epoxy primer m2

• Vapour permeable areas PU or acrylic paint

7 Application of S&P C Sheet 240 (200 gr./m2)Wrapping and simultaneous impregnation of column with S&P C Sheet 240, incl. lap areas of sheets of 150 mm in the fibre direction.

• Anchoring/lap areas System approved impregnation adhesive• Vapour permeable areas PU or acrylic paint 1 layer m2

2 layers m2

... layers m2

8 Final coatingApplication of water-vapour permeable coating of PU or m2

acrylic paint.

9 SandingSanding of final coating, or laminating resin respectively, m2

in the case of subsequent plaster application.

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16.3 External shear reinforcement with S&P C Sheet 640

Item Text Unit

1 InstallationTransport (to and from) and supply of necessary Pappliances and materials for the reinforcing job.Additional site visits. Pcs.

2 ScaffoldingInstallation and supply of scaffolding, incl. required Pmeasures for dust protection during the construction phase.

3 Substrate preparation prior to application of C Sheet Removal of cement skin by sandblasting or surface roughening, m2

incl. cleaning with brush or vacuum cleaner. All edges must be rounded to a minimum radius of 1-3 cm.

4 Levelling of substrateRemoval of local excess profile and reprofiling of cavities and unevennesses in the application area with system approved levelling mortar.

Bill of quantities, based on actual consumptionLabour hSystem approved levelling mortar kg

5 Primer applicationApplication of the system approved epoxy primer to the m2

application area.

6 Application of S&P C Sheet 640 (400 gr./m2)Wrapping and impregnation of the structural elementto be shear reinforced with S&P C Sheet 640.

Product names C sheet: S&P C Sheet 640 (400 gr./m2)System approved impregnation adhesive

Width 150 mm 1 layer m2

... layers m2

Width 300 mm 1 layer m2

... layers m2

7 Anchoring with steel platesApplication and anchoring of corrosion protected steel plates with two welded-on anchor bolts Ø 10 mm. Drilling of the holes and application of the anchor bolts with system approved adhesive to beincluded in the price per unit.

Anchor length in concrete: 150 mmDimensions steel plates: W = 150 mm / H = 150 mm Pcs.

W = 300 mm / H = 150 mm Pcs.

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16.4. Reinforcement with S&P G Sheet AR 50/50(Poor substrate / Historic buildings)

Item Text Unit

1 InstallationTransport (to and from) and supply of necessary Pappliances and materials for the reinforcing job.Additional site visits. Pcs.

2 ScaffoldingInstallation and supply of scaffolding, incl. required Pmeasures for dust protection during the construction phase.

3 Substrate preparation prior to application of G Sheet Removal of cement skin by sandblasting or surface roughening, m2

incl. cleaning with brush or vacuum cleaner. All edges must be rounded to a minimum radius of 1-3 cm.

4 Levelling of substrateRemoval of local excess profile and reprofiling of cavities and unevennesses in the application area with system approved levelling mortar.

Bill of quantities, based on actual consumptionLabour hSystem approved levelling mortar kg

5 PrimingApplication of system approved epoxy primer, if required m2

6 Application of S&P G Sheet AR 50/50Application of S&P G Sheet AR 50/50, incl. overlapping of the sheets in both directionsand simultaneous impregnation of the constructional element.

Impregnation with system approved impregnation adhesive1 layer m2

2 layers m2

… layers m2

16.5. Seismic retrofitting of colums(Item 1-5 equal as above)

Item Text Unit

6 Application of S&P G Sheet AR 90/10,Application of S&P G Sheet AR 90/10, incl. overlapping of the sheets in main directionand simultaneous impregnation of the constructional element.

Impregnation with system approved impregnation adhesive

S&P G Sheet 90/10 Type A 1 layer m2

2 layers m2

… layers m2

S&P G Sheet 90/10 Type B 1 layer m2

2 layers m2

… layers m2

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17. S&P FRP product overview

S&P Laminates CFK 150/2000 S&P Laminates CFK 200/2000

Modulus of elasticity Tensile strength at break Modulus of elasticity Tensile strength at break> 150 GPa 2500 N/mm2 > 200 GPa 2500 N/mm2

Width/thickness Tensile force at elongation Width/thickness Tensile force at elongationmm/mm of 0.6/0.8 % mm/mm of 0.6/0.8 %

50/1.2 58/77 x 103 N

50/1.4 67/90 x 103 N 50/1.4 84/112 x 103 N

80/1.2 92/123 x 103 N

80/1.4 108/143 x 103 N 80/1.4 134/179 x 103 N

100/1.2 115/154 x 103 N

100/1.4 134/179 x 103 N 100/1.4 168/224 x 103 N

120/1.4 201/269 x 103 N

* special dimensions upon requestDelivery in rolls of 150 m or ready-to-use(unroll set available upon request)

Levelling mortar: Adhesive:

Only approved systems Only approved systems

S&P G Sheet 90/10S&P C Sheet 240 S&P C Sheet 640 S&P A Sheet 120

or G Sheet 50/502-directional uni-directional uni-directional uni-directional

Modulus of elasticity (N/mm2) > 65’000 240’000 640’000 120’000

Tensile strength (N/mm2) > 1’700 3’800 2’650 2’900

Fibre density (kg/cm3) 2.6 1.7 2.1 1.45

Ultimate elongation (%) 2,8 1,55 0,4 2,5

Weight (gr./m2) different types 200 400 290available 300 420

Delivery in rollsWidth 680 mm Width 300 mm Width 300 mm Width 300 mmLenght 50 m Lenght 150 m or more Lenght 50 m or more Length 150 or more

Adhesives in the overlapping/anchoring zone: Upon request:

Primer and impregnation adhesive: Special adhesive for wet substrates

only approved systems Special adhesive for low temperaturesSpecial adhesive for underwater

applications

70

18. Literature

• Versuche zur Bestimmung der Werkstoffeigenschaften, der Verbundtragfähigkeit, des Entkoppe-lungsverhaltens von CFK-Lamellen sowie Biegeschubversuche an mit CFK-Lamellen verstärktenPlatten, Untersuchungsbericht Nr. 8524/5247 des Institutes für Baustoffe, Massivbau und Brand-schutz der TU Braunschweig vom 20.05.1998.

• Dolan. C.W., Leu, B.L., Hundley, A.: Creep rupture of fiber reinforced plastics in a concrete environ-ment. Proceedings of the Third International Symposium on Non-Metallic (FRP) reinforcement forConcrete Structures, Sapporo, October 1997, 2, 187 - 194.

• Ando, N., Matsukawa, H., Hattori, A., Mashima, M.: Experimental studies on the long – term tensileproperties of FRP-tendons. Proceedings of the Third International Symposium on Non-Metallic (FRP)reinforcement for Concrete Structures, Sapporo, October 1997, 2, 203 - 210.

• Uomoto, T., Nishimura, T., Ohga, H.: Static and fatigue strength of FRP rods for concrete reinforce-ment. Non-Metallic (FRP) reinforcement for Concrete Structures, Proceedings of the Second Inter-national RILEM Symposium (FRPCS-2), Gent, August 1995, 100-1070.

• Adini, R., Rahman, H., Benmokrane, B., Kobayashi, K: Effect of temperature and loading frequen-cy on the fatigue life of a CFRP-bar in concrete. Fiber Composites in Infrastructure, Proceedings ofthe Second International Conference on Composites in Infrastructure, ICCCI 98, Tucson, Jan. 1998,2, 203 – 210.

• Sheard, P., Clarke, J., Dill, M., Hamemrsley, G., Richardson, D.: Eurocrete – Taking account ofdurability for design of FRP reinforced concrete structures. Proceedings of the Third InternationalSymposium on Non-Metallic (FRP) reinforcement for Concrete Structures, Sapporo, October 1997, 2,75 – 82.

• Porter, M.L., Mehus, J., Young, K.A., O’Neil, E.F., Barnes, B.A.: Aging for fiber reinforcement inconcrete. Proceedings of the Third International Symposium on Non-Metallic (FRP) reinforcement forConcrete Structures, Sapporo, October 1997, 2, 59 - 66.

• Kaiser, H.: Bewehren von Stahlbeton mit kohlenstofffaserverstärkten Epoxidharzen. Dissertation Nr.8918, ETH Zürich, 1998.

• Terrasi, G.P., Kaiser, H.: CFK-Lamellen verstärkte Querschnitte bei Temperatursprüngen, nach-trägliches Verstärken von Bauwerken mit CFK-Lamellen, Referate und Beiträge zur EMPA/SIA-Studientagung vom 21. September 1995 in Zürich, Dokumentation SIA D 0128

• Terrasi, G.P.: Aluminium/CFK Hybride unter thermischer Beanspruchung. Diplomarbeit an der ETHZürich, Abt. für Werkstoffe.

• Vielhaber, Joh.: Versuchsreihe Verstärkung der Querkrafttragfähigkeit von Stahlbetonkonstruktionen,Fachhochschule Potsdam.

• Holzenkämpfer, P.: Ingenieurmodell des Verbunds geklebter Bewehrung für Betonbauteile. Disser-tation TU Braunschweig, 1994.

• Pichler, D.: Die Wirkung von Anpressdrücken auf die Verankerung von Klebelamellen. Dissertation,Universität Innsbruck Institut für Betonbau, 1993.

• Rostasy, F.S., Holzenkämpfer, P., Hankers, Ch.: Geklebte Bewehrung für die Verstärkung vonBetonbauteilen. Betonkalender 1996, Teil II, S. 547 – 638, Berlin: W. Ernst & Sohn, 1996.

• Verbundversuche an Doppellaschenkörpern mit CFK-Lamellen und Biegeversuche an mit CFK-Lamellen verstärkten Platten, Untersuchungsbericht Nr. 8511/8511 -Neu- des Institutes für Bau-stoffe, Massivbau und Brandschutz Braunschweig vom 05.11.1996.

• Täljsten, B.: Plate Bonding, Strengthening of existing concrete structures with epoxy bonded platesof steel or fibre reinforced plastics. Dissertation, Lulea University of Technology, Lulea, 1994.

• Fracture mechanics of Concrete Structures, From Theory to applications, Report of the TechnicalCommittee 90-FMA Fracture Mechanics to Concrete – Applications, Capman and Hall, London,New York, 1989, 188 – 190.

• Rostasy, F.S., Ranisch, E.-H.: Sanierung von Betontragwerken durch Ankleben von Faserverbund-werkstoffen. Forschungsbericht, Institut für Baustoffe, Massivbau und Brandschutz der TechnischenUniversität Braunschweig, Dezember 1994.

• Statische Belastungsversuche an mit CFK-Lamellen verstärkten Plattenbalken “Instandsetzung Für-stenlandbrücke”, EMPA-Bericht Nr. 165'432 vom 28.04.1997.

71

• Biege- und Schubtragverhalten eines mit geklebten CFK-Lamellen und Stahllaschenbügeln verstärk-ten Stahlbetonträgers, Untersuchungsbericht Nr. 8516/8516 Neu- des Instituts für Baustoffe, Massiv-bau und Brandschutz der Technischen Universität Braunschweig vom 13.05.1996.

• Tagung Kreative Ingenieurleistungen TU Darmstadt, BOKU Wien, Referate:Meier Urs, EMPA CH: Unidirektionale CFK Profile im konstruktiven IngenieurbauScherer Josef, S&P Reinforcement: Bewehrungsalternativen aus CFK in der BauwerkverstärkungLuggin Wilhelm, BOKU Wien: Verstärkung von Holzbauteilen mit geklebten CFK LamellenZilch Konrad, Blaschko Michael, TU München: Verstärkung mit eingeschlitzten CFK Lamellen

• Fachveranstaltung “Zusätzliche Beanspruchung für bestehende Bauwerke: Verstärken mitLamellen und durch Querschnittsvergrösserung”, TFB Wildegg/CH:Scherer Josef, S&P Reinforcement: Anwendungsmöglichkeiten von Faserverbundwerkstoffen in derBauwerkverstärkungBronner J., Tenax Fibers: Herstellverfahren / Technische Eigenschaften der KohlefaserHankers Ch. Dr., Torkret: Bemessungsbeispiel “Schubverstärkung mittels Stahlbügelnresp.Carbontücher”Ladner M. Prof., Hochschule Technik + Architektur: Bemessungsansätze für die Nachverstärkungvon Druckelementen mittels Faserverbundwerkstoffen

• Suter René, Hértier Christof: Rapport Nr. 6C-1999-02, Ecole d’ingénieurs et d’architectes deFribourg

• Forschungsergebnisse faserverstärktes Leimholz FH Wiesbaden, BOKU Wien• ACI Spring Convention March 14 – 19, 1999, Chicago:

Scherer Josef, S&P Reinforcement: Fiber reinforced polymer FRP systems for external strengtheningof concrete structures

• Taerwe L., Matthys S., Universiteit Gent: Inrijgen van Betonkolomnen met vezelcomposiet-laminaten.

• Allgemeine bauaufsichtliche Zulassung Deutschland-236.12-54 für S&P Lamellen CFK• Deutsches Institut für Bautechnik: Gutachten Nr. 98/0322

Ingenieurbüro Prof.Dr.Ing.Dr.Ing.E.h.F.S. Rostasy, Braunschweig• Bemessungsdiskette BOW Ingenieure, Braunschweig• Procédé “Carbone CFK”, Dossier SOTEL No EX 1443• T. Pauly and M.J.N. Priestly: Seismic design of reinforced concrete and masonry buildings• M.J.N. Priestly, F. Seible and G.M. Calvi: Seismic design and retrofit of bridges• Procédé “Carbone CFK”, Dossier SOTEC No. Ex 1443• G. Schwegler: Dissertation ETH Zürich CH 10672• T. Ripper, J. Scherer: "AVALIAÇÃO do DESEMPENHO de PLÁSTICOS ARMADOS com FOLHAS

UNIDIRECCIONAIS de FIBRAS de CARBONO como ELEMENTO de REFORÇO de VIGAS deBETÃO ARMADO", IBRACON 41st Congress, 1999, Salvador, Bahia, Brasil.

Patents:

S&P Reinforcement Company has applied world-wide for various patents in the field ofFRP reinforcement:

• Application of water vapour permeable FRP systems using a combination of adhesivesfor the reinforcement of constructional elements.

• Use of AR glass with FRP systems, for the reinforcement of constructional elements.

• Application of fast-setting adhesives in combination with CFK laminates, for thepost-reinforcement of load-relieved constructional elements.

• Application of special adhesives in combination with FRP systems onto wet substrates.

• Application of APS adhesives (up to -20˚C) in combination with CFK laminates.

• Production of prestressed CFK hybrids and application of these hybrids for the reinforcementof constructional elements.

• Prestressing system for CFK laminates.

• Anchoring elements.