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The state-of-the-art of fiber-reinforced polymer (FRP) composite stay-in-place (SIP) structural form systems for bridge decks is presented in this paper. This technique involves constructing a concrete deck whereby prefabricated FRP components act as both the permanent formwork and the bottom flexural reinforcement. The advantages and limitations of the technology are presented, along with the current progress of experimental and analytical investigations. Extensive laboratory investigation is presented covering numerous aspects of the system, including strength, fatigue, and environmental performance. A variety of system configurations are discussed. Examples of field applications are presented, along with evaluations of cost effectiveness and inspection considerations. The result of these investigations show that FRP SIP formwork systems can be both constructible and meet applicable code requirements for strength and serviceability. Preliminary cost assessments suggest that increases in material costs can be partially offset by savings in labor during installation. Finally, future research needs are identified.

This study presents a new method for predicting the strength of reinforcement-free bridge decks. The concept presented for the reinforcement-free bridge deck includes removing steel reinforcement, using compressive membrane action in the deck by tying concrete wide-flanged girders together, and introducing a polypropylene fiber to control shrinkage cracks. A modified strut-and-tie model (STM) that considers geometrical nonlinearity that can capture punching or flexural failure of the restrained bridge deck between the girders is proposed. The model provides a two-dimensional axisymmetric representation of the behavior of the reinforcement-free deck. Results from the proposed STM analysis method are compared to nonlinear finite element method (FEM) analysis results. Findings suggest that the proposed method is a practical and effective replacement for the time-consuming FEM analysis when the clear deck spans are 5ft or less.

Synopsis: The punching shear capacity of concrete slabs reinforced with threedimensional fiber-reinforced polymer (FRP) double-layer reinforcement cages composed of glass fiber-reinforced pultruded grating elements has been investigated using full-scale experimental tests and a number of different analytical models. Test specimens were full-scale prototype bridge deck slabs with varying end restraint and support conditions, differing dimensions, and two different FRP bar fiber lay-ups. The tests results were compared with the punching shear models in ACI 318, ACI 440, Eurocode 2, BS 8110, CEB-FIB MC90, JSCE, and a number of models proposed in the literature specifically for FRP reinforced slabs. Based on this investigation a new empirical model has been developed to predict the punching shear capacity of double layer grids having either restrained or simply supported edges and including an overlapping splice. The model is shown to give reasonably good predictions for both simply supported and restrained slabs.

This paper focuses on the use of explicit finite-element (FE) analysis tools to predict the behavior of fiber-reinforced polymer (FRP) composite grid reinforced concrete beams subjected to 4-point bending. Predictions were obtained using LS-DYNA, an explicit FE program widely used for the nonlinear transient analysis of structures. The composite grid was modeled in a discrete manner using beam and shell elements, connected to a concrete solid mesh. The load-deflection characteristics obtained from the simulations show good correlation with the experimental data. A detailed FE substructure model was also developed to further analyze the stress state of the main longitudinal reinforcement at ultimate conditions. Based on this analysis, a procedure was proposed for the analysis of composite grid reinforced concrete beams that accounts for different failure modes. A comparison of the proposed approach with experimental data indicated that the procedure provides a good lower bound for conservative predictions of load-carrying capacity.

Existing methods of flexural strengthening of reinforced concrete beams (RCBs) with fiber-reinforced polymer (FRP) strips require time-consuming and often difficult preparation to yield adequate bond strength between the FRP strip and the concrete substrate. This research presents a feasibility study of an alternative method of attaching FRP strips to RCBs. Off-the-shelf powder actuated fasteners are used to attach pultruded FRP strips to the concrete. Small-sized RCBs strengthened with this method were tested, and the results were compared with those from beams strengthened with conventional bonding methods and to results from control beams. Small-size RCBs strengthened using powder actuated fasteners achieved 65-70% of the increase in capacity of the beams strengthened using the conventional bonding method; however, the fastening method is extremely rapid and the failure modes of the beams strengthened by the fastening method were more ductile than those using the bonded method.

Results of tests of ten concrete beams reinforced with fiber-reinforced plastic grids fabricated from small pultruded profiles are presented. The beams were designed to investigate the behavior and performance of the grids when used to reinforce beams that develop significant flexural-strength cracking (a/d = 3). Different grids were designed to study the influence of the main bars, vertical bars and transverse bars (cross-rods) of the grid on the failure loads and failure modes. From the results of the testing it was concluded that pultruded grids can provide effective shear reinforcement, however, their design must account for failure of the main bars in the shear span. Overreinforced beams failed in a somewhat more ductile manner than underreinforced beams.

A research study on the effect of material degradation of fiber reinforced plastic (FRP) reinforcing bars on their bond strength and bond stiffness properties is reported in this paper. A convenient new embedded-rod test (ERT) specimen was developed and used in the study. The ERT specimen is recommended for future environmental degradation studies of FRP bars. The ERT specimen enables microscopic and mechanical tests to be performed on portions of the same FRP bar after it has been subjected to environmental conditioning while it is embedded in concrete. Photographs and scanning electron micrographs were used to investigate the nature of the degradation in the polyester and vinylester resin matrices and the E-glass fibers of smooth and deformed FRP bars. Pullout tests were used to investigate the bond strength and bond stiffness characteristics of the FRP bars. A descriptive model of the mechanism of the deterioration of the FRP material is proposed to relate the decreases in bond strengths and stiffnesses to the degradation of the materials in the FRP bars.

An experimental and analytical study was conducted to investigate the feasibility of developing three-dimensional fiber-reinforced plastic (FRP) grating cages to reinforce concrete members. Experimental FRP cages, fabricated from off-the-shelf commercially manufactured pultruded FRP profiles, were used to reinforce three concrete beams which were tested to failure. The performance of the FRP grating cage reinforced beams was compared with that of a control beam reinforced with conventional steel rebars. The results of the testing are given and a detailed analysis of the failure modes of the FRP reinforced beams is provided. A simplified analytical model is proposed to calculate the failure load of the beams. A truss model is used to predict deflection at failure. Predictions of the proposed models agree well with the experimental data. The construction practice potential of using the FRP grating cages is discussed. The pilot study indicates that the future development of FRP grating cages for concrete reinforcement would appear to be warranted.