Falcon – A Multi-Disciplinary Effort to Promote FRP bridges in Sweden

Sweden has a long history in using fiber reinforced polymer (FRP) composites in marine, transportation and energy sectors. However, when it comes to application of composite materials to build bridge structures, it somewhat falls behind. Despite several advantages that FRP composites offer, such as high specific strength and stiffness, corrosion resistance and light-weight, their infrastructural applications in Sweden have not been fully understood and yet to be realized. The first efforts to use FRP composites for construction of pedestrian bridges started in 2011, however, due to lack of knowledge about the materials and design of composite structures among engineers, they were halted.\ua0 Falcon, a joint effort project with total budget of 640 k Euro funded by VINNOVA and co-funded by industrial consortium partners, aims at gathering together the relevant parties, consisting universities, research institutes, bridge designers, composite manufacturers and clients to realize the first FRP bridge in Sweden.\ua0 The main objectives of the project are to investigate and implement the best practice for FRP bridges and improve the procurement processes for bridge owners and thereby pave the way towards widespread infrastructural application of composites. This paper, presents some results of this project including legal hindrances and possible strategies to promote FRP as a construction material for future bridges

Experimental study of FRP-strengthened concrete beams with corroded reinforcement

Corrosion of steel reinforcement is the major cause of deterioration in reinforced concrete structures. Strengthening of concrete structures has been widely studied. However, most research was conducted on sound structures without considering the effects of corrosion. This paper presents an experimental study of the feasibility of using externally bonded FRP laminates combined with U-jackets, applied directly without repairing the deteriorated concrete cover, to strengthen beams with corroded reinforcement. Ten beams were tested in four-point bending. Two beams were not deteriorated and non-strengthened; these served as references. The other eight were pre-loaded to induce flexural cracks and then exposed to accelerated corrosion. Two of the deteriorated beams were not strengthened, three were strengthened with glass-FRP (GFRP) laminates and three with carbon-FRP (CFRP) plates on the beam soffits. On the six strengthened beams, CFRP U-jackets were installed along the span. Local corrosion levels were evaluated with a 3D-scanning technique. Pitting corrosion significantly reduced the load-carrying and deformation capacity of the deteriorated beams. Despite average corrosion levels of 20%, local corrosion levels up to 57% and corrosion-induced cracks up to 1.9\ua0mm wide, the FRP-strengthening method (applied directly to the beams without repairing the deteriorated concrete cover) was effective in upgrading the load-carrying capacity and flexural stiffness. The applied U-jackets effectively suppressed the delamination of the concrete cover and led to the rupture of GFRP laminates and a utilisation ratio of CFRP plates up to 64%. However, improvement in the deformation capacity was not noticeable; this requires further research

Innovative flexural strengthening of RC beams using self-anchored prestressed CFRP plates: Experimental and numerical investigations

This paper presents an innovative method of prestressing carbon fibre reinforced polymer (CFRP) plates used as externally bonded reinforcement for flexural strengthening of reinforced concrete (RC) beams. The proposed method aims to achieve self-anchorage of the prestressed CFRP plate and thus eliminate the need for conventional mechanical anchorage at its ends. Experimental tests of RC beams in four-point bending were conducted to investigate the strengthening efficiency of the self-anchored prestressed CFRP plate. The experimental results showed that using the self-anchored prestressed CFRP significantly improved the flexural performance of the strengthened beam in terms of bending stiffness, crack widths, and load-carrying capacity. The utilisation ratio of the prestressed CFRP plate reached 81% at its debonding. Numerical analyses using nonlinear finite element (FE) method were conducted to model the tested specimens. Based on the reliable simulation of flexural cracks and crack-induced CFRP debonding, parametric studies were conducted using FE analyses, in order to investigate the effect of prestressing levels and the CFRP plate\u27s stiffness on the flexural behaviour. Recommendations were then made for selecting a proper prestressing level and the mechanical properties of CFRP plates

Flexural strengthening of reinforced concrete beams using externally bonded FRP laminates prestressed with a new method

This paper presents a new method and a device for applying prestressed carbon fiber reinforced polymer (CFRP) laminates to flexural structural members without the need for mechanical anchorage of the laminates. An experimental test was conducted aiming to verify the feasibility of the stepwise prestressing method and investigate the flexural behavior of beams strengthened with passive (non-prestressed) CFRP and prestressed CFRP, respectively. Three RC beams with 4.2-meter-span were tested under four-point bending--one beam not strengthened as the control group, one with EB passive (non-prestressed) CFRP, and one with EB prestressed CFRP using the new prestressing technique. The strain values monitored during prestressing process demonstrated that a gradually decreasing prestressing force profile towards the CFRP ends was achieved by using this new prestressing method which eliminated the need for mechanical anchorage at laminate ends. The test results from four-point bending also revealed that using prestressed CFRP led to higher flexural stiffness, postponed yielding load, increased ultimate load bearing capacity, higher utilization of CFRP material tensile strength and reduced crack width

Innovative prestressing method for externally bonded CFRP laminates without mechanical anchorage

Strengthening of reinforced concrete (RC) structures by externally bonded carbon fiber reinforced polymer (CFRP) laminates has been widely accepted as an effective and cost-efficient method. It is well known that advantages offered by the bonded CFRP laminates can be further increased by prestressing the laminates prior to bonding. Mechanical anchors are essential, in this case, to prevent debonding since interfacial stress at areas close to the ends of the strengthening laminate is several times higher than the strength of the concrete substrate. Common anchorage solutions often consist of bolted metallic plates to clamp the prestressed CFRP laminate. Besides labor-intensive installation operation, the anchor plates are vulnerable to galvanic corrosion, which further complicates the inspection and increases the maintenance costs. There are also doubts about the long-term performance of such anchorage systems as it highly depends on the quality of the adhesive layer between the plate and laminate, and the level of pre-tension in clamping bolts. This paper presents the work conducted at Chalmers University of Technology on the development of an innovative prestressing method and a tool which allow for the application of prestressed CFRP laminates without mechanical anchors. The principles of the novel method and the prestressing system are explained. Experimental and numerical work carried out on an RC beam strengthened with this method is presented. Results indicate that CFRP laminates with high prestressing forces (approximately 30% of CFRP tensile strength) can be safely anchored without the need for mechanical anchors. Numerical results based on finite element analyses show that the proposed prestressing method can reduce the interfacial shear stresses in the CFRP-concrete adhesive joint below the bond strength with a reasonable safety margin

Fiber reinforced polymer culvert bridges—a feasibility study from structural and lcc points of view

Soil–steel composite bridges (SSCB) have become increasingly popular for short-span bridges as an alternative to concrete slab bridges mainly due to their low initial cost, rapid manufac-ture, simplified construction, and geometrical adaptability. SSCBs have a variety of applications and can be used over waterways or roadways. While conventional bridges tend to lose their load-carrying capacity due to degradation, SSCBs gain strength because of backfill soil consolidation. However, the load carrying capacity and integrity of such structures highly depends on the condition and load-carrying capacity of the steel arch element. A major drawback of SSCBs, especially those located on waterways or with poor drainage, is corrosion and subsequent loss of cross-sectional capacity. Unfortunately, the inspection of such bridges is not straightforward and any damage/collapse will be very costly to repair/replace. Fiber reinforced polymer (FRP) composites offer an attractive alternative to replace the steel in these types of bridges. FRP composites have significantly improved durability characteristics compared to steel, which will reduce maintenance costs and improve life-cycle costs (LLCs). This paper presents a new concept to use glass FRP as a construction material to construct soil–FRP composite bridges (SFCB). Various aspects of design and manufacturing are presented along with results and conclusions from a case study involving alternative bridge designs in steel and FRP composites

Forced Vibration Analysis of Laminated Composite Plates under the Action of a Moving Vehicle

This paper provides a finite element analysis of laminated composite plates under the action of a moving vehicle. The vehicle is modeled as a rigid body with four suspension systems, each consisting of a spring-dashpot. Overall, the vehicle possesses three degrees of freedom: vertical, rolling, and pitching motions. The equations of motion of the plate are deduced based on first-order shear deformation theory. Using the Euler-Lagrange equations, the system of coupled equations of motion is extracted and solved by using the Newmark time discretization scheme. The algorithm is validated through the comparison of both the free and forced vibration results provided by the present model and exact or numerical results reported in the literature. The effects are investigated of several system parameters on the dynamic response. &nbsp

Forced vibration analysis of laminated composite plates under the action of a moving vehicle

This paper provides a finite element analysis of laminated composite plates under the action of a moving vehicle. The vehicle is modeled as a rigid body with four suspension systems, each consisting of a springdashpot. Overall, the vehicle possesses three degrees of freedom: vertical, rolling, and pitching motions. The equations of motion of the plate are deduced based on first-order shear deformation theory. Using the EulerLagrange equations, the system of coupled equations of motion is extracted and solved by using the Newmark time discretization scheme. The algorithm is validated through the comparison of both the free and forced vibration results provided by the present model and exact or numerical results reported in the literature. The effects are investigated of several system parameters on the dynamic response

Analysis of adhesive joints used to bond FRP laminates to steel members – A numerical and experimental study

The strengthening of existing structures using bonded fiber reinforced polymer laminates has attracted agreat deal of attention in recent years. However, when compared with concrete structures, the applicationof this method for strengthening structural steel members is somewhat limited. This is mainly due tothe lack of an established design code for treating FRP-strengthened members. Issues such as the complexityof failure modes and the lack of knowledge of the force-transfer mechanism are obstacles thatcontribute to the difficulty associated with developing accurate design models. A few studies have underlinedthe need for new design approaches to strengthening steel members, since the existing designmethods are not accurate enough.The first step towards developing new design models is to study these adhesive joints. This paper dealswith analyses of adhesive joints used to bond CFRP laminates to steel substrates using a numerical andexperimental approach. A numerical study of joints has been made utilizing the FE method, while, in theexperimental part of the study, an optic measurement technique has been used. Different aspects of jointbehavior, such as strain distributions along the bond line and through the thickness of the adhesive layerand failure mechanisms are discussed