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Sudden brittle failure and FRP (fiber reinforced polymer) rebar slippage have been a problem for years with FRP rebar reinforced concrete. This motivated the research of using AGS grids/panel to reinforce concrete because of the mechanical interlocking between the concrete and the grid. Early research in the field of composite grid reinforcement of concrete was reported by,
"Sugita et al. (1992) of Japan, who worked with a New Fiber Composite Material for Reinforced Concrete (NEFMAC) grid made of either carbon fibers or a hybrid combination of carbon and glass fibers in a polymeric matrix. Its primary use is to reinforce concrete. The applications to date include reinforcement for tunnel lining, shotcrete reinforcement, LPG tanks, fender plates and precast curtain walls (none of which are primary structural components). Other types of commercial FRP grids include IMCO (molded grating), DURADEK (pultruded grating), SAFE-T-GRATE, KORDEK (rectangular grating), KORLOK (pultruded grating), and custom manufactured grids."
"The design of a reinforced concrete structure requires that flexural behavior be understood. The flexural behavior of a reinforced concrete beam can be characterized by its ultimate strength, failure mode, stiffness
(or amount of deflection), and predictability. Composite materials generally have a higher ultimate strength than steel, which allows for higher ultimate loads in composite-reinforced concrete. Sugita (1993) and Sugita et al. (1992) indicate that the Japanese have also explored the use of FRP-grid reinforcement for shotcrete applications. The prefabricated nature of the FRP grid lowers construction effort. The flexible nature of the grid that results from its lower stiffness permits easier placement on non-planar surfaces such as those found in tunnels. These researchers have also found that the higher flexibility of the FRP grid results in fewer voids in the shotcrete matrix that later require filling, further reducing construction costs. This may indicate a viable use for FRP reinforcement in constructing concrete elements with curved surfaces (e.g., domes, etc.)"
Banthia et al. (1995) compared the behavior of concrete slabs reinforced NEFMAC FRP grids with that of a slab reinforced with steel grid. The authors recommended that the steel design codes and procedures can be applied for FRP reinforced slabs as well. The research has shown that FRP grids used to reinforce concrete slabs have improved energy absorption capacity and the ultimate load carrying.
Rahman et al. (2000) evaluated the ultimate and the service load behavior of the bridge deck reinforced with carbon NEFMAC grid. The purpose of the work was to study the difficulty of construction, degradation due to cyclical loading, ultimate load carrying capacity, failure mode, and the behavior under service load. The authors found that the behavior under service load and the constructability to be satisfactory. Also, degradation due to cyclical loading, stress and deflection were found to be small while the ultimate load carrying capacity of the bridge deck was found to be exceptionally high.
Another study was conducted by Yost et al. (2001) using NEFMAC, and investigated the flexural performance of two dimensional FRP grids reinforced concrete beams subjected to four point monotonic loading. The authors tested 15 simply supported concrete beams reinforced with two dimensional FRP grids. The purpose of the study was to predict the deflection behavior, flexural strength and shear strength of FRP grid reinforced concrete beams using ACI 318 code. The results found that the flexural capacity of FRP grid reinforced beams can be accurately predicted using ACI 318-95 code. The study also concluded that grid configuration provides an effective load/force transfer mechanism, and the FRP grid tensile rapture was achieved without any deterioration in load/force transfer mechanics.
The interest in using AGS gratings and panels to reinforce concrete has continued in recent years (Berg et al., 2006, Zhang et al., 2004, Huang et al., 2002, Matthys and Taerwe, 2000, Smart and Jensen, 1997). Such panel/grid reinforcement enhances the energy absorption capacity, and the overall ductile nature of the member is improved, leading to an increase in the ultimate load carrying capacity of concrete slabs and beams. It is found that when the bay area/opening of grids is filled with concrete, the combined member derives its shear rigidity from the concrete filler and the concrete prevents the ribs (longitudinal and transverse bars) from buckling. FRP grid provides a mechanical anchorage within the concrete due to the interlocking between the cross rods, and hence no bond is necessary for proper load transfer between concrete and grid. Three dimensional FRP grids provide integrated axial, shear and flexural reinforcement. Also, the grid has the ability to cause a concrete member to have a pseudo-ductile failure profile. Two dimensional grids ensure adequate load/force transfer to develop the axial tensile strength of the longitudinal bar. At tensile rupture, no shear or bearing failure was found between the transverse bars and surrounding concrete, and also the grid nodes remained rigid.
The availability of various types of composite grids has created some problems for research in the area of composite grid reinforced concrete. There is not a well established basis for comparison among the different grids, as can be inferred from the work that has been done. For the most part, researchers have used the grids that were commercially available. This includes molded gratings, pultruded sections with mechanically attached cross-members, different volume fractions, different spacings and different fibers. Despite a few difficulties, the previous research has been fairly successful as a preliminary investigation. The researcher has shown that the fundamental principles used in the design of reinforced concrete structures are directly applicable in the design of composite reinforced concrete.
Ehab et al. (2005) recently tested the first bridge deck slab reinforced with GFRP (glass fiber reinforced polymer) bars constructed in Canada. There has been a rapid increase in using non-corrosive FRP reinforcing bars as an alternative to the steel reinforcement for bridge decks, especially those in harsh environments. A new two span bridge was built with a total length of 52.08 m, over two equal spans. The bridge deck was a 200 mm thick concrete slab. The deck measured over four spans of 2.70 m between bridge girders with an overhang of 1.40 m on either side of the deck. One full span of the bridge was totally reinforced with galvanized steel bars, while the other span was reinforced using glass fiber-reinforced polymer (GFRP) bars. The two span bridge decks were well instrumented at critical locations for strain data and internal temperature collection using fiber optic sensors. The bridge was inspected for service performance using calibrated truckloads as specified by the Canadian Highway Bridge Design Code.
Ehab et al. (2005) concluded that no obstacle during construction was encountered due to the use of the glass fiber reinforced polymer (GFRP) bars. The GFRP bars withstood all on- site placement and handling with no problems. The first year of service and during field testing, no cracks were found in the bridge deck slabs of either the GFRP or the steel reinforced spans. Due to truck loading, the measured tensile strains were in between 4-8 micro strain as the truckload moves over the gauge, and the maximum tensile strain values in concrete were very small when the truck was not over the gage. The obtained strains are well below cracking strain for concrete, which is in the range of 100-130 micro strain for normal weight concrete with a concrete elastic modulus of 25-29 GPa and compressive strength of 30-37 MPa. During the entire field test, the maximum tensile strain in glass FRP bars was 30 micro strain. This strain value is less than 0.2% of the ultimate strain of the GFRP material. After the deck slab develops a stable system of cracks, it is expected to see higher tensile strains in the bottom transverse glass FRP bars due to live load. The deflections obtained in the bridge deck slab were well below CHBDC allowable limits. The maximum measured deflection for the concrete slabs and girders never exceeded S/1350 (2 mm) and L/6510 (4 mm) respectively throughout testing. Recently proposed design approach by the MTQ that uses the obtained flexural design moments to find the required FRP reinforcement ratio based on satisfying a specific maximum stress limits and crack width, rather than transformation of steel bars to FRP bars based on strength and stiffness equivalences, leads to a significant reduction in the required amount of FRP reinforcement. However, the small measured strains under truck loads either in concrete or in GFRP bars when compared to the expected values according to the flexural design moments showed that the behavior of the deck under concentrated wheel loads behaves differently. After the deck develops a stable system of cracks, it is expected that the deck will develop an arching action between girders in the bridge. This kind of arching behavior will lead to more economical design. The obtained girder distribution factors are in good agreement with live load distribution factors provided by the AASHTO Load Resistance Factored Design Specifications (AASHTO 1998).
El-Ghandour et al. (2003) evaluated the punching shear behavior of FRP reinforced concrete flat slabs using a two phase experimental program. The tests were conducted with and without carbon FRP shear reinforcement in the slabs. In the first phase of the program, problems of crack localization and bond slip were identified. These problems were successfully eliminated by decreasing the flexural bar spacing in the second phase, and thus resulted in punching shear failure of the flat slabs. The authors concluded that carbon FRP shear reinforcement was found to be not so efficient in enhancing significantly the slab capacity because of its brittleness. Then a model is proposed and verified, which accurately predicts the punching shear strength of FRP RC slabs without shear reinforcement. For flat slabs with FRP shear reinforcement, it is concluded that the concrete shear resistance is reduced, but a maximum strain of 0.0045 is recommended for the reinforcement. Comparisons of the slab capacities with BS 8110, ACI 440-98 and ACI 318-95 punching shear capacity equations, modified to incorporate FRP shear reinforcement, show either conservative or overestimated results.
Karbhari, V.M et al. (2003) found that there is a lack of easily accessible, comprehensive and validated data base for the durability of FRP composite materials as related to civil infrastructure applications has been identified as a critical barrier to widespread acceptance of the composite materials by civil engineers and structural designers. This concern is emphasized because the structures of interest are primarily load carrying and are expected to remain in service life over extended periods of time without significant maintenance or inspection. These researchers presented a synopsis of a gap analysis study undertaken under the aegis of the Federal Highway Administration and the Civil Engineering Research Foundation to identify and prioritize critical gaps in durability data. The study focused on the use of FRP in bridge decks, external strengthening, internal reinforcement, seismic retrofit, structural profiles, and panels. Environments of interest are thermal effects (including freeze and thaw), alkalinity, moisture/solution, creep/relaxation, fatigue, fire, and ultraviolet exposure.
The authors Karbhari et al. (2003) worked on a gap analysis for different environmental conditions. They found that there is a substantial commonality of needs, which provides for the selection of research/data requirements that is important to the generic implementation of FRP composites in civil engineering infrastructure. These needs, in no particular order of priority because it is difficult to compare or transition the level of need within one environment to that in another environment, are as follows: (1) Assessment, collection, and appropriate documentation of available data in a form useable by the civil designer and/or engineer, (2) Testing under combined conditions of stress, temperature, moisture and solution at both the materials and structural levels are critical, (3) Testing over an extended 18-month time period. Since the tests were conducted over short time periods (less than 18 months), this can cause misleading results due to effects of fiber level degradation, slow inter-phase and post-cure, and can provide an erroneous level of comfort in some cases, (4) Characterization and assessment of the effects of under-cure and incomplete cure especially for ambient temperature cure systems are essential, (5) Development of appropriate gel coats, coatings and resin systems that would serve as protective layers for the bulk composite against external influences such as accidental damage and environmental conditions, and (6) Development of standardized conditions and solutions in laboratory studies that closely simulate actual field conditions.
Based on the results of the gap analysis conducted by the Karbhari et al., and on the overall results examined through discussions with experts in the area of durability, review of literature, results of discussions of the supplier and user panels, and subsequent discussions with members of the civil engineering industries and the FRP composites, a three pronged approach is recommended for future research activities in continuation of this study as described in the following: (1) Integrated Knowledge System acknowledging the current difficulty in accessing data and the possible loss of valuable data obtained in the previous isolated studies, it is recommended that an integrated knowledge system needs to be established at the earliest possible opportunity. This integrated knowledge system would serve as a repository for data in the area of durability that would be pertinent to civil engineering applications and in a form that is easy to access and of use by civil engineers, designers, and contractors. The integrated knowledge system would contain a number of data sets, which could either be used in an integrated manner or as single sets of reference to aid the design. (2) Establishment of Methodology: The present gap analysis exercise has provided a list of data needs related to environmental conditions and specific application areas. It is expected that the results of this present study will spur efforts to fill in areas identified as being high priority based on current availability and the importance of data. In order to ensure those efforts aimed at filling in gaps are not investigated in isolation and that appropriate protocols are used, it is recommended that appropriate protocols be established for data collection, testing, and validation. These protocols would provide a basis for collection and generation of future data cognizant with the eventual requirements of a structural design methodology. (3) Implementation of Plans for Field Assessment: It is well established that durability data obtained from laboratory experiments can differ substantially from field data. The determination of actual durability under field conditions over extended periods of time is required for the optimal design of FRP composites for use in civil engineering infrastructure. Hence, it is critical that steps be taken to collect data from field implementations on an ongoing basis. This data is invaluable to establish an appropriate durability based design factors, and also the opportunity of having new projects from which such data could be generated in a scientific manner should not be wasted.
Tavarez et al. (2003) focused on the use of explicit finite element analysis tools to predict the behavior of FRP grid reinforced concrete beams subjected to four point bending. Predictions were obtained from an explicit finite element software, LS-DYNA, widely used for the non-linear transient analysis of structures. The composite FRP grid was modeled in a discrete manner using shell and beam elements, and then connected to a concrete solid mesh. The load-deflection characteristics generated from the FE simulations show good correlation with the experimental data. Also, the authors developed a detailed finite element substructure model to further analyze the stress state of the main longitudinal reinforcement at ultimate loads. Based on this FE analysis, a procedure was proposed for the analysis of FRP grid reinforced concrete beams that accounts for different failure modes. A comparison of the proposed approach with the experimental data showed that the procedure provides a good lower bound for conservative predictions of load carrying capacity of the FRP grid reinforced concrete beams.
Tavarez et al. (2003) concluded the following from the explicit finite element results and comparison with experimental results. Failure in the FRP longitudinal bars occurred due to a uniform tensile stress and a non-uniform stress caused by localized rotations at large flexure-shear cracks. Therefore, this type of failure mode has to be accounted for in the design and analysis of FRP grid reinforced concrete beams, particularly those that exhibit significant flexure-shear cracking. The shear span for the medium and the long beam studied was sufficiently large enough, so that the stresses in the longitudinal bars were not considerably affected by shear damage in the beam specimen. Therefore, the particular failure mode obtained from the short beam model is only characteristic of beams with a low shear span to depth ratio. Moreover, based on the proposed analysis for such members, both the medium and the long beam could be designed by using conventional flexural theory since the critical shear value was never reached for these beam lengths. Numerical simulations can be used effectively to understand the complex phenomena and behavior found in the response of FRP grid reinforced concrete beams. Therefore, numerical simulations can be used as a complement to experimental testing to account for multiple failure modes in the design of FRP grid reinforced concrete beams, and the proposed method of analysis for FRP grid reinforced concrete beams considering multiple failure modes will under estimate the strength of the reinforced concrete beam, but it will aid a good lower bound for a conservative design. These design considerations will ensure that the FRP longitudinal bars will not fail catastrophically or prematurely, as a result of the development of large flexure-shear cracks in the beam, and thus the beam can develop a pseudo-ductile failure by concrete crushing, which is more desirable than a sudden FRP failure/rupture.
Bakis, C.E et al. (2002) conducted a survey using FRP composites for construction applications in civil engineering. Bakis et al. concluded that the amount of experience with different types of FRP construction materials varies in accordance with the perceived near term safety and economic benefits of the materials. For example, in case of externally attached reinforcements, the immediate safety and cost benefits are clear, and adoption of the FRP material by industry is widespread. In other cases where FRP composite materials are considered to be the primary load carrying components of structures, field application still maintains a research flavor while long term experience with the FRP material accumulates. A number of careful testing and monitoring programs of structures with primary FRP reinforcement have been set up around the world and should aid this experience base in the coming years. Codes and standards for FRP materials and their use in construction applications are either published or currently being written in the United States, Japan, Canada, and Europe. These official documents are typically similar in format to conventional codes and standards, which should ease their adoption by governing organizations and agencies. The most significant mechanical differences between conventional metallic materials and FRP composite materials are the lower stiffness, higher strength, and linear elastic behavior to failure of the former. Other differences such as the thermal expansion coefficient, heat and fire resistance, and moisture absorption need to be considered as well. The education and training of engineers, inspectors, construction workers, and owners of structures on the various relevant aspects of FRP technology and practice will be crucial in the successful application of FRP composite materials in construction. However, it should be emphasized that even with anticipated moderate decreases in the price of FRP composite materials, their use will be mainly restricted to those civil engineering applications where their unique properties are crucially required.
Matthys et al. (2000) evaluated the use of FRP grid reinforcement for concrete slabs, considering the behavior of the slabs under concentrated loading such as punching shear. From the performed analysis and the punching tests, a fairly strong interaction between flexural and shear effects was found for most of the tested slabs. For the FRP grid reinforced slabs with an increased slab depth or an increased reinforcement ratio, the punching shear strength was similar to or higher than the tested reference slabs reinforced with steel. For most slabs, slip of the bars took place resulting in higher deflections at failure. The calculation of the punching shear failure load according to empirical based models from different codes, modified mechanical model and an analytical model is developed.
Matthys et al. (2000) concluded that a fairly strong interaction between flexural and shear effects has been found from the tested specimens. However, in most slabs, a punching cone failure was observed. The bond between concrete and the grids was of considerable influence on the crack development and brittleness of the punching cone failure. For the FRP reinforced slabs with a similar flexural strength as the reference slabs reinforced with steel, the obtained punching stiffness and load in the cracked state were considerably less. However, for the FRP reinforced slabs with an increased slab depth or an increased reinforcement ratio, the behavior of the slabs was comparable to reference slabs reinforced with steel. The calculation of the mean punching failure load from the empirical based expressions such as most code equations, gives fairly good predictions, but with an underestimation for FRP reinforced slabs with low modulus of elasticity. The latter aspect was calculated by introducing the equivalent reinforcement ratio. Evaluation of the design punching shear capacity based on code equations, taking into account the modification, showed sufficient safety (mean global safety factor: 1.9-2.6) for all examined codes. Prediction based on code MC90 gives a mean global safety factor of 2.1 and the least scatter. A modified mechanical model by Hallgren (1996) shows good results in predicting the behavior of FRP and steel reinforced slabs. Another simplified model by Menetrey (1996) is largely dependent on the assumption of the core angle and underestimates the punching shear capacity considerably.
Dutta K.P. et al. (1998) discussed a new concept that FRP composite grid to reinforce concrete structural members. Prefabricated two and three dimensional FRP composite grid structures were investigated as a possible alternative to conventional one dimensional steel rods. Significant improvements in fiber volume fraction in isogrid and orthogrid systems were achieved by using laboratory investigations. Laboratory scale specimens showed excellent results under loading tests. Concurrent investigations showed that even though the FRP composite grid reinforced concrete is more flexible than the steel reinforced concrete, its post-failure deformations were pseudo-ductile, characterized by multiple low brittle failures before the onset of catastrophic failure. It was concluded that a combined composite-concrete reinforcement structure, with a higher volume of FRP fraction in the concrete, would substantially increase load capacity, stiffness and post failure concrete containment. These authors addressed not only the possible replacement of steel reinforcement with FRP composite grids, but also evaluated enhancement of the FRP composite application through load sharing with steel rods in a complementary fashion. Various manufacturing improvements such as the novel use of disposable toolings were explored.
The authors Dutta et al. (1998) from extensive research concluded that instead of simply replacing steel reinforcement with composite materials of the same type, the reinforcement method was proposed especially to make use of the grids unique properties. In this method, FRP grids were placed in the outermost layers of the structure, creating a concrete and grid sandwich. The concept was proven to be mechanically sound and economically feasible. It must be noted that the concept/work was brought to a conclusion before a demonstration model was developed, as had originally been proposed in the scope of work. Before developing any demonstration model, it is necessary that full-scale testing is done in the laboratory. This model demonstration and testing would have required additional time and resources that were not available before conclusion of the project. However, the work serves as a proof of concept for using FRP composite grid materials for reinforcing concrete members. The concept of FRP grid reinforced concrete has been shown to be both reliable and predictable. Based on experimental results, load-deflection behavior of FRP grid reinforced concrete is strictly a function of the mechanical properties of the concrete and the reinforcement. The load-transfer mechanism involved with FRP grid reinforced concrete is good enough to transfer internal stresses from the concrete to the reinforcement, and is possibly more reliable than relying on a shear transfer mechanism. There are encouraging results from the experimental work that tend to validate the initial proposed model built at Stanford University. Based on an examination of manufacturing methods, innovations will be required in material selection, processing, fabrication, and placement techniques. It is clear that a completed system as proposed by this examination could produce a concrete reinforcing methodology that would offer cost savings in field assembly such as placing and pouring, and simple design procedures while providing damage tolerance and durability.
Harris, H. G. et al. (1998) tested a new ductile hybrid FRP composite reinforcing bar for concrete members that were developed at Drexel University. This new hybrid FRP bar is unique and it has equivalent bilinear stress-strain characteristics, with a Young's modulus approach to that of steel reinforcement. It showed improved bonding characteristics through the direct introduction of ribs during the pultrusion process and in-line braiding used in its manufacture. When used as reinforcement in repaired or new concrete structures, it attains ductile nature similar to those of steel reinforcement and allows limit states design methodology. The new FRP composite bar, which fails in a gradual manner, has an equivalent bilinear stress-strain tensile curve with a definite yield point, with an ultimate strength higher than the yield strength, and with an ultimate failure strain between 2% and 3%. It has the distinct advantage of being noncorrosive, it is non-conductive, non-magnetic and light in weight, and has high strength. It can be tailored to strength levels that are compatible to current grades of pre-stressing tendons or steel reinforcing bars. This paper briefly describes the method of manufacturing and designing the new FRP composite bars. It compares experimental and the predicted stress-strain characteristics of the new FRP bars manufactured by a prototype pultrusion or braiding process, and also compares the behavior of these new FRP bars to steel bars in flexure. It investigates the implications of the bilinear stress-strain relationship of the reinforcement on the moment-curvature and load-deflection behavior of flexural members. Hence, it describes the ductile behavior of members reinforced with steel bars and with the new hybrid FRP bars.
The authors Harris et al. (1998) concluded that this new hybrid FRP reinforcement has unique bilinear stress-strain characteristics that facilitate its use in repaired or new concrete structures. It is light weight, non-corrosive as concrete reinforcement in aggressive environments, and has high strength. Feasibility of producing the new hybrid FRP reinforcement has been demonstrated with the laboratory production of 5 mm nominal diameter bars. Tensile tests showed consistent stress-strain properties. Beams having 1.2 m in length and with a 50 x 100 mm cross-section prepared with 5-mm ductile hybrid FRP reinforcing bars demonstrated the ability of the sections to undergo large in-elastic deformations. Moment-curvature and load-deflection relations showed the ability of the beam specimens tested and cycled from the post-cracked and post-yield load to achieve a ductile behavior with adequate bond strength similar to that of steel reinforcement bars. Limit-state design procedure is demonstrated with the new ductile hybrid FRP bars discussed in this paper. Ductility indexes calculated on the basis of curvatures, deflections and energy considerations of three hybrid FRP reinforced beams were found to be very similar to those of a reference steel reinforced beam.
Kumar, Sanjeev. V. et al. (1998) investigated the fatigue response of concrete bridge decks reinforced with FRP rebar. This fatigue response is important and critical to the long term endurance of this type of innovative structure. The fatigue tests were conducted on four concrete deck steel stringers to analyze the degradation of FRP reinforced bridge decks. An initial tensile stress of 2.27 MPa in the main FRP reinforcement, compressive of 3.1 MPa in the concrete deck top, and again a tensile of 24.8 MPa at the bottom flange of a steel stringer was applied for all specimens. During this research, the composite versus non-composite casting, the stringer stiffness and transverse post-tensioning using high-strength Dywidag steel rods were varied. The fatigue test results found that there was no loss of bond between FRP rebars and concrete in any of the test specimens. The major crack patterns were observed in the direction parallel to the stringers, i.e., flexural cracks in the concrete bridge deck spanning the steel stringers. Effective deck deflections at the center could be set as a measure of global deck degradation during fatigue, and this rate of degradation in bridge decks reinforced with FRP re-bars was found comparable to the bridge decks reinforced with steel re-bars.
Kumar, Sanjeev V. et al. (1998) concluded the rate of degradation in FRP reinforced bridge decks compared well with steel reinforced bridge decks in the fatigue crack propagation zone. The gradual stiffness degradation because of fatigue loads in concrete bridge decks prevailed until 80% of their total fatigue strength, and thereafter, a non-linear variation is found before failure (Hawkins 1974). The bridge decks reinforced with FRP rebars had a linear variation in stiffness degradation even after applying 2,000,000 fatigue cycles; thus, 2,000,000 fatigue cycles could be conservatively considered as 80% of the fatigue life of these bridge decks. Transverse post-tensioning in bridge deck 2 limited the increase of degradation by a factor of five when compared with bridge deck 3. However, a closer stringer spacing may be more economical and acceptable than transverse post-tensioning in the arresting loss of composite action or crack growth. Fatigue failure in concrete bridge decks is influenced by crack formation at the bottom of the bridge deck. It was concluded that 50% of the modulus of rupture of concrete could be the endurance limit of concrete under flexural fatigue (Hwan 1986). Hence, the span to depth ratios in the concrete slab should be maintained such that the extreme fiber tensile stress in the bridge deck is less than 50% of the modulus of rupture of concrete.
Schmeckpeper, Edwin R.; Goodspeed, Charles H. (1994) evaluated the suitability of FRP grids for use as a structural reinforcement in slab type concrete structures and highway bridge decks. The behavior of the FRP grid reinforced concrete beam was experimentally investigated. Two different types of FRP grids were used in the program; one with carbon fibers and another one with a mixture of carbon and E-Glass fibers. The mechanical properties of these two FRP grids were evaluated. For each of the two types of reinforcement, five concrete beams were tested until failure. The flexural behavior, as characterized by the load deflection response, was monitored throughout the beam tests. The results from the flexural tests on FRP reinforced concrete beams showed that the measured deflections, failure mode, and the ultimate loads were consistent with predictions.