STATE-OF-THE-ART: Strengthening Applications

TU1207 (2014) STATE-OF-THE-ART: Strengthening Applications, Working Group 3, COST Action TU1207 - Next Generation Design Guidelines for Composites in Construction

Disclaimer: this is a draft version. Both the table of contents and the content of the documents included below are subject to change. New sections will be added when addtional documents are made available.
Any comments or suggestions, please contact the chair or co-chair of Working Group 3

1. Bond

1.1 Experimental characterisation of bond between flexural EB FRP and concrete

A. Serbescu, M. Guadagnini and K. Pilakoutas

The strengthening potential of externally bonded FRP reinforcement (EBR) is already well established. However, the efficiency of FRP plate bonding systems is limited due to premature debonding, especially at the plate ends. Despite the large amount of research efforts, improving the accuracy of predictive models for debonding capacity continues to be a research challenge. The prediction ability of most of the available models relies on the accuracy of the bond-stress characteristics considered. These characteristics are normally determined by using experimental data from small-scale bond tests.

1.2 Bond problems in NSM systems

Antonio Bilotta, Francesca Ceroni and Emidio Nigro

In general, the bond behavior between the concrete and any external Fiber Reinforced Polymer (FRP) reinforcement influences the transfer of stresses between the reinforced member and strengthening. Then it affects the ultimate load carrying capacity of the FRP strengthened concrete members, as well as some serviceability aspects, such as crack width and crack spacing. In particular, the bond strength of a Near Surface Mounted (NSM) system made of FRP materials is directly related to the type of failure (at the bar-adhesive interface, at the adhesive-concrete interface, within the concrete, cohesive at the adhesive and in the FRP material). The overall bond strength is dependent on local bond strength and, thus, on the distribution of bond shear stresses along the interface. The local bond-slip behavior is affected by the following main parameters: materials’ mechanical properties, FRP reinforcement and grooves surface treatment, geometry of the strengthening system (bars or strips), grooves’ dimensions and depth of the FRP reinforcement in the groove. The shape ratio, k, namely the ratio between groove and FRP dimensions, also affects the failure mode of the strengthening system. In general, the local bond- slip behaviour and the bond strength are experimentally assessed by bond tests.


2. Flexural strengthening

2.1 Discontinous Bond in RC Beam Elements Externally Strengthened with CFRP

A. T. Gavriloska, M. Lazarevska

For a proper determination of the bearing capacity of the RC structure strengthened with externally added FRP reinforcement, a model has to be used, which can accurately describe the stresses in the bond layer. To evaluate the influence of the presence of such discontinuous zone upon overall response of the beam, a numerical assessment was proposed, where the bond between reinforced concrete beam and CFRP plate was modeled by a numerical displacement-based fiber model.

2.2 Modeling of Discontinous Bond in RC Beam Elements Externally Strengthened with CFRP

A. T. Gavriloska, M. Lazarevska

The effects of change in the environmental conditions, the increasing of the loads and the design of older structures, which may have been adequately compared with contemporary codes but are inadequate against the current codes, are all factors which contribute either for decreasing of the bearing capacity or structural safety of the construction. Non adequate performance of the reinforced concrete construction imposes the need for their repair and strengthening. In the recent years, typical retrofitting technique involves use of external bonded fibber reinforced polymer (FRP) plates. Failure behaviour of a plated beam can be very strongly influenced by the integrity of the bond between the plate and the concrete. One of the problems that can be encountered during the strengthening of reinforced concrete structures in the practice is inadequate execution of the bonding process. This may lead to weakening of the bond layer in some positions along the length of the plate, and to creating discontinuities within the bond layer.

2.3 Near Surface Mounted Reinforcement for Flexural Strengthening of RC Columns

Dionysios A. Bournas

Bournas and Triantafillou (2009) and Perrone et al. (2009) presented the results of full-scale experimental programmes which were aiming to provide a fundamental understanding of the behavior of reinforced concrete (RC) columns under simulated seismic loading, strengthened in flexure (of crucial importance in capacity design) with different types and configurations of near-surface mounted (NSM) reinforcing materials.


3. Shear and Torsion Strengthening

3.1 The Use of FRP Jackets as Shear Reinforcement

C. Chalioris, and C. Karagiannis

The effectiveness of the use of externally epoxy-bonded carbon FRP sheets as external transverse reinforcement to shear critical reinforced concrete beams with rectangular and T-shaped cross-section has been investigated in the experimental works of Karayannis & Chalioris (2003) and Chalioris (2003). The following FRP retrofits were examined: FRP sheets that (i) fully wrapped around the cross-section of rectangular beams along the entire shear span, (ii) fully wrapped around the cross-section and covered only a part of the shear span, (iii) U-jacketed T-beams along the entire shear span and (iv) U-jacketed T-beams along the entire shear span with FRP anchorage using bolted steel laminates.

3.2 FRP-EBR Repairs of RC Members in Torsion

C. Chalioris, and C. Karagiannis

The effectiveness of the use of externally epoxy-bonded carbon FRPs as external transverse reinforcement to under-reinforced concrete beams with rectangular and flanged cross-section under torsion has been experimentally evaluated in the work of Chalioris (2008). Three different FRP configurations were examined: (i) Fully and completely wrapped rectangular beams with continuous FRP sheets along the entire length and around the cross-section of the beam (full wrapping with sheets). (ii) Completely wrapped rectangular beams with discrete FRP strips around the crosssection of the beam (wrapping with strips). (iii) U-jacketed flanged beams with FRP sheets along the entire length of the beam that were bonded on the width and on both vertical sides of the web of the T-beam (U-jacketing with sheets).


4. Confinement

4.1 Use of Composites in Strengthening Reinforced Concrete Structures

I. Balafas, S.P. Tastani, S.J. Pantazopoulou

Concrete in compression cannot fail unless the material volume is free to expand laterally. When concrete is restraint laterally then failure is postponed and consequently strength and strain capacities are enhanced. This enhancement is a function of stiffness and strength and strain capacity of the restraint. The adequacy of FRPs as a lateral restraint material has been proved through experiments from early eighties. FRPs in the forms of jackets are wrapped laterally on the surface of concrete elements, restraining the natural tendency of concrete to expand and damage can be accumulated in the form of internal cracking. Initially, unreinforced cylindrical or prismatic specimens either wrapped with FRP jackets, or encased in FRP-tubes were studied in compression. Variables such as: the type of the composite, the orientation of fibers, the number of layers, the arrangement of wraps in strips, the cross sectional geometry of the specimen, the chamfering radius at the corners od specimens with orthogonal cross sections, the concrete quality and the mode of loading (monotonic or cyclic) were investigated. Later, the research was extended to include the confinement effectiveness in reinforced concrete members due to the need to retrofit existing brittle construction after the occurrence of significant earthquakes worldwide. For this reason, most of the experimental studies in this area focused into lightly reinforced columns with widely spaced stirrups.

4.2 Deterioration of FRP Jacket Effectiveness due to the Compaction of Low and Medium Strength Concrete

S.P. Tastani, I.Balafas, S. J. Pantazopoulou

When the FRP jackets are wrapped transversely on the lateral surface of a retrofitted concrete member they are able to develop passive confinement in response to lateral dilation of the encased concrete core. This dilation is owing to the longitudinal cracking that occurs in direction parallel to the compressive stresses (in axially loaded members or in the compression zone of structural members), as well as due to longitudinal cover splitting induced by rebar bond failure.

4.3 Deterioration of FRP Jacket Effectiveness Due to Reinforcement Buckling

S.P. Tastani, I.Balafas, S. J. Pantazopoulou

The efficacy of FRPs as confining reinforcement on r.c. members with longitudinal and insufficiently arranged transverse reinforcement (sparse and poor anchored) is compromised by the bar buckling that occurs in the unsupported length between successive stirrups. Bar buckling has serious consequences on the design for seismic upgrading: (i) If, confinement provided through FRP jacketing can totally prevent buckling of longitudinal bars regardless of magnitude of confining pressure then strengthening through FRP jackets of old-type r.c. members with sparse stirrups are totally safe regarding at least the developing strain ductility. (ii) If, on the contrary, the FRP jacket just postpones buckling to higher levels of axial deformation without eventually precluding it, then the several provisions for strengthening should be formulated so as the magnitude of the target compression strain plasticity be related with the design indices of the jacket (number of layers and material).

4.4 Recovery of Strength Mechanisms in Corrosion-Damaged Reinforced Concrete Through FRP Jacketing

S.P. Tastani, I.Balafas, S. J. Pantazopoulou

Corrosion of the reinforcement cage in concrete structures has manifold effects on strength, deformation capacity, and in the prevailing mode of failure through the following mechanisms:Reduction of the available steel area; Spalling of the concrete cover; Break-down of chemical adhesion between concrete and steel along the lateral bar surface; Reduced resistance to bar slip, owing to the cohesionless nature of rust and to attenuation of bar ribs; and Embrittlement of reinforcement. Whether it occurs in stirrup reinforcement or in the longitudinal bars, bar section loss and cover spalling have direct consequences on all strength mechanisms (flexure, shear, bond resistance and development capacity) as well as in the associated deformation capacities. A second level implication is the change in the relative magnitudes of available strengths in the individual response mechanisms, a factor that controls the hierarchy of failure that eventually limits seismic resistance.

4.5 Implications of Anchorage Bar Yield Penetration on the FRP Jacketing Effectiveness Before and After Repair

S. Tastani, G. Thermou, S. J. Pantazopoulou

In lightly-reinforced columns repaired through FRP-jacketing (i.e., jacketed after some extent of initial damage had been induced), the level of damage attained during the first loading –the latter is quantified by the attained longitudinal bar tensile axial strain, see Fig. 1a- appears to be critical for the post repair structural response and the associated FRP effectiveness. Irreversible damage of the bar-concrete interface and the associated loss of bond strength owing to extensive yield penetration into the anchorage during initial loading seems to limit the FRP-jacketing effectiveness as compared with the case where the element had attained an initial premature mode of failure, usually by shear, or by lap-splice splitting.

4.6 Lower Adequate FRP Confinement Limits for RC Columns

T.C. Rousakis, A.I. Karabinis

The contribution deals with columns of non-circular section having internal steel reinforcement according to modern design codes or old-type inadequate detailing. Columns with longitudinal bars which are critical to premature buckling are also included. The effect of slender bars on lower limit cases of strengthening through FRP confinement is examined. Plain concrete FRP confined columns and columns with bars adequately supported by transverse steel reinforcement are investigated for comparison. The columns under consideration were subjected to monotonic or cyclic axial compression. A significant variation in the behavior of FRP confined concrete comes up when bars are unstable, for a light external strengthening scheme as well as for monotonic or cyclic loading. The lower limits proposed by existing recommendations for adequate FRP confinement strengthening of columns are examined.

4.7 Effective Lateral Strain of FRP Confined Concrete – Load Originated Failure Criterion

T.C. Rousakis, A.I. Karabinis

Most empirical models on FRP confined concrete consider a constant confinement effectiveness coefficient k1 and an effective lateral strain at failure eje of the FRP jacket being lower than the one taken out from direct tension tests on cured FRP sheets. Average constant reduction factors are assumed for the tensile deformability of the jacket with respect to the material of the FRP. Design recommendations for strengthening with FRPs may follow more conservative approaches ending up with a global reduction factor for FRP jackets around 0.55 of deformability under direct tension eju. Different specific ultimate strain limits for different FRP materials may be taken into account in Eurocode 8 part 3 for seismic retrofit, for the satisfaction of target curvature ductility requirements.

4.8 Use of Composite Ropes in Confinement of Reinforced Concrete Members

T.C. Rousakis

Use of unbonded, non-impregnated fibers to confine concrete members may be an efficient technique to enhance both compressive strength and ultimate strain of concrete members. Triantafillou and Papanicolaou (2005), Triantafillou et al. 2006, in their study comparing FRP and TRM confinement, have also included spirally applied unbonded carbon fiber textile strips with end anchorages (resin impregnated). The strips were applied on a plain concrete column with square section and low corner radius of 15 mm. The efficiency of the method was similar to that of TRM technique in terms of strength and strain ductility for 4 layers. For lower confinement of 2 layers, the ultimate strain of confined columns was inferior. The results were remarkable considering the inherent brittleness of carbon fibers. Shimomura and Phong (2007) used rope reinforcements made of aramid or of vinylon fibers. In this study, real scale reinforced concrete columns have been wrapped externally with fiber rope reinforcements and presented upgraded shear resistance for higher horizontal top displacement under cyclic loading. Furthermore, aramid fiber ropes have been used as spiral internal shear reinforcement in real scale reinforced concrete beams.

4.9 The Effectiveness of FRP-Jacketing When Applied to Pre-Damaged RC Columns

G.E. Thermou, S.P. Tastani, S.J. Pantazopoulou

Review of previous experiments on brittle R.C. columns through FRP jacketing illustrates that the efficiency of FRP jacketing in strengthening applications is superior to that which is observed when jacketing is used as a repair means. Actually, performance of the repair appears to be related to the state of damage along the anchorage or lap splice of primary reinforcement sustained in the initial phase and whether these defects have been corrected or not, by additional measures such as concrete replacement in cases of cracked cover or by epoxy injections along the damaged anchorages, prior to FRP jacketing (Thermou and Pantazopoulou 2009). Surprisingly, this type of repair proves more effective in elements that have failed in a brittle manner rather than in cases that have undergone extensive yielding; the reason for that is that brittle failure along the member length occurs before the anchorage of the reinforcement has sustained excessive yield penetration, which cannot be avoided in ductile member behaviour (Thermou et al. 2011, Tastani et al. 2012, 2013). In order to trace the reasons why previously damaged R.C. members (such as columns) jacketed with FRP do not always perform as efficiently as in cases where jacketing was applied prior to damage accumulation, it is necessary to focus into the basic differences regarding the jacketing function in these two conditions. Emphasis should be placed on the effects of previous damage on the inelastic strain capacity of reinforcement which often depends on its anchorage conditions beyond the jacketed length.

4.10 Confinement of RC Columns with TRM Jackets

Dionysios Bournas, Thanasis Triantafillou

The upgrading of existing reinforced concrete (RC) structures through jacketing of columns has become a very popular technique in an increasingly large number of rehabilitation projects, both seismic and non-seismic. The use of fiber-reinforced polymers (FRP) has gained considerable popularity among all jacketing techniques, due to the favorable properties offered by these materials, namely high strength to weight ratio, corrosion resistance, ease and speed of application, and minimal change of geometry. Despite all these advantages, the FRP retrofitting technique has a few drawbacks, e.g. poor behavior at high temperatures; high costs; inapplicability on wet surfaces or at low temperatures; and difficulty to conduct post-earthquake assessment behind FRP jackets; these are mainly attributed to the organic epoxy resins used to bind the fibers. An interesting alternative to FRP materials are the so-called Textile-Reinforced Mortars (TRM). These new materials are made of textiles, that is fabric meshes made of long woven, knitted or even unwoven fiber rovings in at least two directions, impregnated with inorganic binders, such as cement-based mortars. In this State-of-the-art report the authors are summarizing recent experimental investigations on the use of TRM jackets as a means of confining poorly detailed old-type RC columns with deformed rebars, which suffer from limited deformation capacity under seismic loads due to either buckling of the longitudinal bars or bond failure at lap splice regions.


5. Strengthening of Beam-Column Joints

5.1 Experimental Report on FRP Repairs of Beam-Column Joints

C. Chalioris, and C. Karagiannis

A repair and strengthening technique of beam-column joints was examined in the experimental work of Karayannis & Sirkelis (2008). Epoxy resin injections were used to repair the damaged specimens in combination with externally bonded carbon FRP sheets that were used to wrap the joint body of external beam- column connections as a confining jacketing system. Carbon FRP sheets were also used to wrap the critical regions of the beam member of the examined subassemblages providing this way for confining of these regions and ensuring a good anchorage of the FRP sheets used for the jacketing of the joint body.


6. Prestressed Composite Reinforcement

6.1 Experimental Evaluation of Concrete Beams Prestressed by Composites

Miroslav Cerny

The results of statical tests of concrete beams in bending, strenghtened by prestressed carbon strips are presented. C-strip has been located on bottom of the beam and prestressed by 30 kN and 50 kN force. The tests have been focused on analysis of failure mechanisms of RC beams and comparison of loading capacity prestressed and nonprestressed RC beams strengthened by adhesive bonded C- strips.


7. Behaviour at Elevated Temperatures

7.1 Behaviour of FRP Rehabilitation Systems at Elevated Temperatures

Antonio Bilotta and Emidio Nigro

Fiber reinforced polymers (FRP) are composite materials successfully applied to repair and/or strengthen RC structures. For external strengthening of reinforced concrete (RC) structures, the FRP plates are easily bonded on concrete using adhesive, like epoxy resins, which ensure the transfer of forces between concrete and FRP. However, degradation of mechanical properties of composites (strength, stiffness and bond) due to high temperature (Dai et al., 2013; Nigro et al. 2012), moisture absorption (Jia et. al, 2005) and cycling loads (Nigro et al., 2011c; Dai et al., 2005) is a key aspect for a durable efficiency of composite materials.


8. Life Cycle Analysis

8.1 Economic Study on the Usage of FRPs with Concrete in Bridges

I. Balafas, C.J. Burgoyne

Steel corrosion in concrete bridges is currently the biggest threat to their durability. Globally, vast governmental budgets are spent so that bridge stocks remain in an acceptable condition. To solve the growing problem FRP materials have been proposed as an alternative concrete reinforcement. Even though extensive research has taken place in the last 30 years, their use has been limited to prototype structures. The construction industry hesitates to invest in these materials due to their high initial cost.


9. Composite Reinforcement and Design Guidelines

9.1 Fibre Reinforced Polymer Reinforcement Enters MC2010

Thanasis Triantafillou, Stijn Matthys

Most applications of fibre-reinforced polymers (FRP) deal with externally bonded reinforcement as a means to repair and strengthen damaged reinforced concrete (RC) structures or to retrofit RC structures in seismic regions. As internal reinforcement, FRP rebars or (more rarely) prestressing elements, are used in special projects, combining material strength and durability characteristics. Over the last years several national and international design guidelines have become available, specifically for the design and application of FRP strengthened or reinforced concrete structures. These efforts demonstrate clearly the interest in FRP as a novel reinforcing material for concrete construction. Hence, the time was there to introduce FRP reinforcement also in the new Model Code 2010 (MC2010). Main contributions to MC2010 relate to chapters 5.5 “Non-metallic reinforcement” and 6.2 “Bond of non-metallic reinforcement”. The material presented in these two chapters is further elaborated next.

9.2 Flowcharts for EBR Design According to fib Bulletin 14

A. Serbescu, M. Guadagnini and K. Pilakoutas

The following set of flowcharts summarizes the steps of a typical design process for strengthening RC beams with FRP materials, according to fib bulletin 14 (2001). Any FRP strengthening design should start by estimating the capacity of the existing RC beam and assessing the FRP strengthening feasibility (Flowchart 1). Depending on the strengthening target, the design can be governed by either ultimate (Flowchart 2) or serviceability limit state (Flowchart 3).

9.3 Italian Design Code Provisions - CNR DT200/R1: End/Intermediate Debonding of EBR

Antonio Bilotta, Francesca Ceroni and Emidio Nigro

Externally bonded (EB) Fiber-Reinforced-polymer (FRP) sheets and laminates are widely employed for enhancing the bending capacity of reinforced concrete (RC) beams (Teng et al. 2001). Although alternative systems are possibly available to connect the FRP strip to concrete members (Napoli et al., 2010; Bilotta et al., 2011), external bonding is still the most common technique. However, the adhesion between FRP and concrete substrate is an issue of concern and generally controls the ultimate capacity of RC beams. Particularly, intermediate debonding phenomenon which begins from a flexural or flexural-shear crack away from the ends of the FRP reinforcement (intermediate crack) throughout the FRP-concrete interface is one of the most common and peculiar failure modes observed in RC beams externally strengthened in bending by bonded FRP. On the other hand, the possible premature failure due to debonding can occur also at the end of the reinforcement (end debonding) before the intermediate debonding in case of absence of specific end anchoring systems. According to well-established mechanical models, end-debonding is basically due to the high interface shear stresses developing in the neighborhood of the FRP cut-off section as a result of the abrupt change in the transverse section of the strengthened beam (fib bulletin 14, 2001; ACI 440.2 R-08, 2008).

9.4 Comparison of the Existing Guidelines to Evaluate the Intermediate Crack Debonding in Externally Bonded FRP Reinforcement

E. Oller, A. Marí

Externally bonded (EB) fiber reinforced polymer (FRP) laminates have been already proved as an effective strengthening technique, specially in flexure and confinement, with applications worldwide. However, as observed in many experimental programs, flexural strengthening by EB FRP reinforcement is often limited by the laminate debonding before the appearance of a classical mode of failure (concrete in compression or FRP rupture). This laminate debonding usually occurs in the concrete, since it is the weakest material of the interphase concrete-adhesive-laminate. The debonding mechanism initiates along the span due to the existence of intermediate cracks (IC debonding) or at the plate end (PE debonding). The existing guidelines include some formulations to avoid this type of premature failures when designing the EBR.

9.5 Comparison of the Existing Guidelines to Evaluate the FRP Contribution in Shear Strengthened Beams

E. Oller, A. Marí, I. Rodríguez

Nowadays, there is a lack of worldwide consensus on the evaluation of the shear strength contribution of the externally bonded FRP reinforcement, in elements strengthened in shear through this technique. One of the main reasons might be the complexity of the resisting mechanisms, not only for the shear strengthening system but also for reinforced concrete. In addition, there is evidence of significant differences between the experimental results and theoretical predictions given by the existing guidelines. The correct evaluation of the FRP shear strength will allow us to design efficient strengthening solutions which ensure that the structure is capable to satisfy the existing requirements with the minimum cost of the intervention.


10. Databases and Empirical Modelling

10.1 Calibration of Design Formulas Based on Experimental Tests

Antonio Bilotta, Francesca Ceroni and Emidio Nigro

Although the assessment of models for bond strength for concrete elements externally strengthened with FRP materials (both NSM and EBR systems) has been widely dealt with by various researchers, the definition of safety factors to calculate design values is still an open item. Thus, in this section a general procedure to calibrate design formulas based on experimental results of different types of tests (i.e. bond shear tests, bending tests for assess flexural or shear strength of beams and slabs) is showed (Monti et al., 2009). The procedure was developed in according to the ‘design by testing’ procedure suggested in the European codes (EN1990). The procedure is not devoted to introduce new strength models, but to refine the existing strength models suggested in literature and codes based on a consistent statistical analysis of a continuously increasing amount of experimental results. Indeed, the procedure allows different corrective factors to be assessed, in order to predict both mean and characteristic values of the investigated bond strength according to a Limit State design approach.

10.2 Published Tests on Concrete Confined with FRP Jackets

I. Balafas, S.P. Tastani, S.J. Pantazopoulou

A unified database is assembled by merging several individual databases found in the literature (listed in the References). Criteria for inclusion of any given test is the requirement that lateral strains have been measured on the FRP jacket and reported during the test, at least up to the onset of failure. This strain measure is required so that lateral confining pressures, responsible for the strength and deformation capacity enhancement, may be estimated and considered explicitly in the exercise of calibration of the analytical models.

10.3 Upgraded Experimental Database for FRP Confined Concrete

T.C. Rousakis, N. Nistico, A.I. Karabinis

Current studies concerning statistical elaboration and review of existing experimental results in databases for confined concrete, usually include only the characteristic maximum bearing stress and corresponding strain values as well as the failure values. In cases of confined concrete members failure values may be defined at 20% or 15% drop of maximum load (when the post-peak load behaviour is degrading) or upon fracture of the FRP jacket. Existing international guides and codes provide semi-empirical relations to predict strength and strain at failure. Also, relations for the whole stress - axial strain curve are included. Fewer involve also prediction of the stress – lateral strain behaviour. Several existing recommendations include additional failure criteria related to lateral strain level or axial strain level in order to ensure the integrity of the columns or avoidance of shear failures among else. ACI 440.2R-08 and CNR-DT200 refer to 0.4% lateral strain as a limit value to avoid concrete shear failures. ACI 440.2R-08 also restricts the maximum compressive strain to 1% to prevent excessive cracking and the resulting loss of concrete integrity. Thus, design of FRP confined columns requires the estimation of stress and axial strain values at 0.4% lateral strain limit and stress at 1% axial strain, through reliable models.


11. Numerical Modelling

11.1 Numerical Model of FRP Strengthened Reinforced Concrete in Plane Stress State

V. Vitanov

The increased experimental research in the field of structural strengthening using FRP initiated attempts to simulate the behaviour of reinforced concrete strengthened with FRP composites using the finite element method. The majority of the numerical models of FRP strengthened RC members use element overlaying, where one-, two- or even three dimensional elements (solid or layered) that represent the FRP material are placed over the concrete elements, either with (Khomwan & Foster 2004; Wong & Vecchio 2003) or without (Kheyroddin & Naderpour 2008) interface elements which are used to model the adhesive material or the bond between the FRP and the concrete. An attempt to formulate a material model which will simplify the modeling of FRP strengthened reinforced concrete members (Vitanov 2012b) is presented here. The material model is implemented into ANSYS and tested using experimental data available in the literature.


12. Composite Reinforcement in the COST Countries

12.1 Strengthening of Civil Structures with FRP - State-of-the-Art Research in Switzerland

Masoud Motavalli, Christoph Czaderski, Julien Michels, Giovanni Terrasi, Thomas Keller, Anastasios P. Vassilopoulos, Christian Louter, D. Zwicky

In Switzerland, the following Institutes had worked and/or are working in the field. They are part of the Swiss Network. Empa; EPFL Lausanne; ETH Zurich; University of Applied Sciences; University of applied sciences (UAS) Fribourg. Furthermore, the following companies are part of the Swiss Network: Sika; S&P; FiReP

12.2 Externally Bonded FRP for the Strengthening of RC Structures (EBFRP). State of The Art in FRANCE

Emmanuel Ferrier, Marc Quiertant, S.Chataigner, K.Benzarti

This contribution gives an overview of the main result obtained in France on EBFRP applied on RC structures. Of course, it does not cover all researches done in this field since the 90’s in France, but covers the main outline and interesting points. This state of the art is divided into several parts: the academic or institutional research point of view, design issues, field applications and conclusion.