Fiber Reinforced Polymer Bridge Decks Research Articles

Detection of subsurface defects in fiber reinforced polymer composite bridge decks using digital infrared thermography

Fiber reinforced polymer (FRP) bridge decks are rapidly emerging as potential alternatives to conventional reinforced concrete (RC) bridge decks. The FRP decks offer higher strength-to-weight ratios compared to RC decks. However, presence of subsurface defects such as debonds and delaminations formed during initial construction and in service can adversely affect the structural integrity and service performance of the FRP bridge decks. Hence, a field monitoring technique such as infrared thermography is required to evaluate the in situ condition of these FRP decks. This paper investigates the use of digital infrared thermography for subsurface defect detection in FRP bridge decks. Air-filled and water-filled debonds were inserted between the wearing surface and the underlying FRP deck in the laboratory. Simulated subsurface delaminations (of various sizes and thickness) were also created at the flange-to-flange junction between two FRP deck modules. The infrared technique was used to detect these embedded subsurface defects. Surface temperature–time curves were established for different sizes of delaminations and debonds. In addition, field study was conducted on a FRP bridge deck to detect debonds between the wearing surface and the underlying deck. The laboratory and field testing results show that infrared thermography is a potentially useful tool for defect detection in FRP composite bridge decks. The technique can possibly be used for several applications such as quality control during pultrusion of new decks (in factories), during field construction, and for field inspection of in-service decks.

An Autonomous Unmanned Ground Vehicle for Non-Destructive Testing of Fiber-Reinforced Polymer Bridge Decks

The use of fiber-reinforced polymer (FRP) composite bridge decks is increasing in many civil engineering applications because of its many useful properties. The traditional reinforced concrete bridge decks have steel reinforcing bars embedded in concrete. Because of the use of deicing salt on the bridges to melt snow and ice in winter, the reinforcing bars tend to corrode, thus reducing the life span of the reinforced concrete bridge decks by half (from about 50 yr to about 25 yr). The FRP composite decks are made of noncorrosive material and offer a higher strength-to-weight ratio as compared to the reinforced concrete decks. It is highly important that engineers know how to detect subsurface defects that can form in FRP decks, which may cause serious structural degradation and endanger structural integrity. Both infrared thermography (IRT) and ground penetrating radar (GPR) have shown promise in the field of non-destructive detection of defects. Instead of performing both analysis methods individually, it would be more cost effective for someone to conduct both IRT and GPR at the same time. Research at West Virginia University has produced an unmanned ground vehicle (UGV) that will acquire data from both GPR and IRT systems to create a combined defect map of the FRP bridge deck to better analyze the results. Thus, the proposed UGV enables rapid data acquisition from the FRP bridge deck in an automated and non-destructive fashion, which minimizes human error. The UGV also incorporates data analysis algorithms, which help in producing a detailed map showing the layout of defects on the bridge deck.

Simulations of structural behaviour of fibre-reinforced polymer bridge deck under thermal effects

Finite Element Method (FEM) has been employed to study the structural behaviour of two different Fibre Reinforced Polymer (FRP) bridge deck systems under thermal effects. Bridge system I is a hybrid FRP-concrete bridge superstructure, while bridge system II is an all FRP bridge deck on steel girder. Because the Coefficient of Thermal Expansion (CTE) of the FRP is higher than that of concrete, this study investigated the behaviour of bridge system I under different climatic conditions. This study describes the behaviour of bridge system II subjected to thermal loading from a truck fire incident combined with mechanical loading from the commercial trucks. Furthermore, fully coupled thermal-stress analyses were performed using FEM to determine the fire resistance limit. The paper illustrated that the thermal response of bridge system I would be significant under severe climatic conditions. Moreover, the thermal simulations showed that bridge system II is highly sensitive to the effect of elevated temperatures.

Theoretical and experimental analysis of FRP bridge deck under cold temperatures

The large temperature difference (~120°F) between the top and bottom of a fiber-reinforced polymer (FRP) bridge deck is attributed to low thermal conductivity of FRP materials and low thermal mass because of hollow core FRP decks. In this study, laboratory tests were conducted on glass FRP deck modules under low temperature gradient. A theoretical beam model was used to analyse the FRP deck-steel stringer system while closed form solutions (based on Macro Approach and Navier– Levy method) were derived using the plate bending theory for FRP deck modules. In addition, thermal stress evaluations from field test data were evaluated using theoretical models. The laboratory test data indicated that the FRP decks sag when they were subjected to negative temperature difference. Deflections and expansion of the deck top increased as the difference between the Ttop and Tbottom increased. Partial deck restraint, provided by steel stringers, resulted in partially induced stresses.

Construction, Inspection, and Maintenance of FRP Deck Panels

Composite materials are clearly having a major impact on how facilities are designed, constructed, and maintained. In order to enhance the application of fiber-reinforced composites in infrastructure renewal, it will be important to understand the constructability, maintainability, operability, and inspection issues related to the use of fiber-reinforced polymer (FRP) structural components. This paper identifies these issues as well as fabrication issues, construction methods, quality, man-hour requirements, cost and productivity issues, and the skill level required to install FRP bridge deck panels. The data required for this research were collected through two questionnaire studies, personal interviews with two manufacturers of FRP bridge deck panels (i.e., Hardcore Composites and Martin Marietta Composites), and candidate projects for FRP bridge deck construction.

Simulation-based determination of optimal life-cycle cost for FRP bridge deck panels

Fiber-reinforced polymer (FRP) composites are increasingly being used in civil infrastructure applications. FRP composites, however, are still relatively unknown to the practicing civil engineer and infrastructure systems planner. There are several unresolved issues to be considered in order to increase their application in construction of infrastructure. Recently, life-cycle cost analysis (LCCA) has been shown to identify how cost-effective FRP composites are compared with conventional materials [Hastak, Makarand and Daniel W. Halpin (2000). Assessment of life-cycle benefit–cost of composites in construction. Journal of Composites for Construction, ASCE, 4 (3) 103–111]. Although many models for estimation of life-cycle cost in FRP composites have been proposed, it remains difficult to predict the end of service life for new advanced materials. It is, therefore, important to assess the life-cycle costs of replacing conventional construction materials with advanced composites. This paper introduces an analytical model to determine optimal life-cycle cost under different discount factors (i.e., interest rates) and inflation rates. It presents a method to estimate the service life for FRP bridge deck panels. Monte Carlo simulation is used to account for uncertainty in those two parameters.

Durability of FRP Composite Bridge Deck Materials under Freeze-Thaw and Low Temperature Conditions

Fiber-reinforced polymer (FRP) composites, especially lightweight sandwich structures, are rapidly finding their way into civil infrastructure application. FRP composite panels are particularly attractive as bridge deck systems due to their high strength, low density, and durability, which are of importance to the bridge industry. Most of the vast amount of durability data for FRP has been generated for aerospace and automotive applications, which involve very different service conditions than civil infrastructure. For civil engineering applications, it is essential to examine the durability performance of FRP materials under weathering conditions. The ultimate goal of this research is to develop a reliable framework for durability assessment of FRP decks, including laboratory testing procedure and finite-element simulation capability. Such a framework should be applicable to all types of FRP deck construction. In this paper, specimens of typical FRP bridge deck skin materials are subjected to freeze-thaw cycling between 4.4 and –17.8°C in media of dry air, distilled water, and saltwater, and constant freeze at –17.8°C . The selected deck is used as an example for demonstration purposes. In addition, selected specimens are subjected to simultaneous environmental exposure conditions and sustained loading of 25% ultimate strain. It should be emphasized that most of the environmental conditions reported in the literature produce minor deterioration of a single composite property, and the assessment of such effect on this single property becomes unreliable because of a large property variation. Therefore, in this paper we use multiple mechanical properties as performance indices for damage evaluation. Based on findings from this work, it is concluded that freeze-thaw cycling between 4.4 and –17.8°C alone and up to 1,250 h and 625 cycles caused very insignificant or no change in the flexural strength, storage modulus, and loss factor of the FRP specimens conditioned in dry air, distilled water, and saltwater. Small reductions in storage modulus (about 1% or less) were observed when specimens were prestrained and subjected to 250 freeze-thaw cycles in distilled water and saltwater. Changes in flexural strength were statistically insignificant, since they were within the data scatter.

Life-cycle performance model for FRP bridge deck panels

Fiber-reinforced polymer (FRP) bridge deck panels have been used to replace deteriorated conventional bridge decks over the last few decades. However, there are still concerns on the overall long-term durability of FRP bridge deck panels under severe load and environmental conditions. In particular, FRP bridge deck panels are exposed to multiple environmental conditions (i.e. moisture, alkali environment, thermal, creep/relaxation, fatigue, ultraviolet exposure, and fire) during their service lifetime, which causes the synergistic degradation mechanism. Although some experimental research have been performed to determine the synergistic mechanism, none has considered the simultaneous impact of multiple load and environmental factors on the life cycle performance of an FRP bridge deck. Thus, it is important to model deterioration of FRP bridge deck panels to determine the synergistic mechanism and its impact on the service life. This article proposes the life-cycle performance model that is capable of predicting the structural deterioration of FRP bridge deck panels over time under the conditions discussed earlier. A complete description of the life-cycle performance model is presented along with a dataset obtained from experts in the field of FRP composite materials in order to illustrate the procedure and validate the logic of the theoretical model, as well as the feasibility of the results obtained.

FEA of Complex Bridge System with FRP Composite Deck

Innovative fiber-reinforced polymer (FRP) composite highway bridge deck systems are gradually gaining acceptance in replacing damaged/deteriorated concrete and timber decks. FRP bridge decks can be designed to meet the American Association of State Highway and Transportation Officials (AASHTO) HS-25 load requirements. Because a rather complex sub- and superstructure system is used to support the FRP deck, it is important to include the entire system in analyzing the deck behavior and performance. In this paper, we will present a finite-element analysis (FEA) that is able to consider the structural complexity of the entire bridge system and the material complexity of an FRP sandwich deck. The FEA is constructed using a two-step analysis approach. The first step is to analyze the global behavior of the entire bridge under the AASHTO HS-25 loading. The next step is to analyze the local behavior of the FRP deck with appropriate load and boundary conditions determined from the first step. For the latter, a layered FEA module is proposed to compute the internal stresses and deformations of the FRP sandwich deck. This approach produces predictions that are in good agreement with experimental measurements.

Dynamic Response of Three Fiber Reinforced Polymer Composite Bridges

Fiber reinforced polymer (FRP) composite bridge decks are gaining the attention of bridge owners because of their light self-weight, corrosion resistance, and ease of installation. Constructed Facilities Center at West Virginia University working with the Federal Highway Administration and West Virginia Department of Transportation has developed three different FRP decking systems and installed several FRP deck bridges in West Virginia. These FRP bridge decks are lighter in weight than comparable concrete systems and therefore their dynamic performance is equally as important as their static performance. In the current study dynamic tests were performed on three FRP deck bridges, namely, Katy Truss Bridge, Market Street Bridge, and Laurel Lick Bridge, in the state of West Virginia. The dynamic response parameters evaluated for the three bridges include dynamic load allowance (DLA) factors, natural frequencies, damping ratios, and deck accelerations caused by moving test trucks. It was found that the DLA f...

Critical Evaluation of Strain Measurements in Glass Fiber-Reinforced Polymer Bridge Decks

An experimental study of principal strains and deflections of glass fiber-reinforced polymer (GFRP) composite bridge deck systems is presented. The experimental results are shown to correlate well with those of an analytical model. While transverse strains and vertical deflections are observed to be consistent, repeatable, and predictable, longitudinal strains exhibit exceptional sensitivity to both strain sensor and applied load location. Large, reversing strain gradients are observed in the longitudinal direction of the bridge deck. GFRP deck system geometry, connectivity, material properties, and manufacturing imperfections coupled with the observed strains suggest that the performance of these structures should be assessed under fatigue loading conditions. Recommendations for accurately assessing longitudinal strain in GFRP bridge decks are made, and a review of existing data is suggested.

Composite Action and Adhesive Bond between Fiber-Reinforced Polymer Bridge Decks and Main Girders

This paper describes the behavior of hybrid girders consisting of fiber-reinforced polymer (FRP) bridge decks adhesively connected to steel main girders. Two large-scale girders were experimentally investigated at the serviceability and ultimate limit state as well as at failure. One of the girders was additionally fatigue loaded to 10 million cycles. Compared to the behavior of a reference steel girder, deflections of the two girders at the SLS were decreased by 30% and failure loads increased by 56% due to full composite action in the adhesive layer. A ductile failure mode occurred: Deck compression failure during yielding of the steel girder. The adhesive connections were able to prevent buckling of the yielding top steel flanges. Thus, compared to the reference steel girder, the maximum deflections at failure could be increased up to 130%. No deterioration due to fatigue loading was observed. Based on the experimental results, a conceptual design method for bonded FRP/steel girders was developed. The proposed method is based on the well-established design method for hybrid girders with concrete decks and shear stud connections. The necessary modifications are proposed.

Performance of a fibre-reinforced polymer bridge deck under dynamic wheel loading

Abstract The paper describes the research carried out by TRL Limited on behalf of the UK Highways Agency to examine the performance of fibre-reinforced polymer (FRP) bridge decks under local wheel loading. The objective of the research was to produce a draft standard giving generic design requirements for technical approval of FRP deck systems. The project included the formulation of design guidelines for fatigue. Tests were carried out on a full-scale glass FRP bridge deck under static and dynamic wheel loading. The loads were imposed using the TRL Trafficking Test Facility, which replicates the effects of the wheel of a heavy goods vehicle. The deck was subjected to over 4.6 million cycles of a 4 tonne wheel load, equivalent to 30–40 years of service traffic. A simpler approval test is proposed, applying stress cycles to small sections of deck to simulate the passage of wheels. The paper includes a description of the FRP deck, the testing and a summary of the performance of the deck.

Anchorage of Reinforced Concrete Parapets on Glass Fiber Reinforced Polymer Bridge Decks

An experimental investigation was conducted to develop an effective means of connecting glass fiber reinforced polymer (FRP) bridge decks to conventional reinforced concrete parapets. Six full-scale subassemblies were studied under quasi-static loading; two examined a prototype system installed in eastern Pennsylvania, two evaluated an improved connection detail, and two evaluated rehabilitation for the structural system after impact. Poor fabrication of the FRP on the first specimen led to brittle fracture of the deck at 20% of the expected capacity. Five properly fabricated FRP decks were subsequently tested and remained undamaged up to the ultimate capacity of the parapet. The results indicate: (1) reliance on reinforcement-to-resin anchorage transfer mechanisms result in brittle pullout failure of parapet reinforcement from the decks; (2) use of headed reinforcement anchored in the bottom deck flange enhances the ductility of the system; and (3) external steel brackets can provide adequate strength and deformation capability when rehabilitating damaged parapets.

Call for Fiber Reinforced Polymer Papers

The Journal of Bridge Engineering is pleased to announce a call for papers for an upcoming special edition focusing on fiber reinforced polymer (FRP) bridge structures and components. The objective of the special edition is to bring together a collection of papers reflecting the state of the art in the use of FRP materials for bridge structures and components. A nonexhaustive list of topics solicited in this call for papers includes • FRP bridge decks; • FRP superstructure elements (girders, stringers, diaphragms, etc.); • Hybrid and composite systems with FRP (composite FRP decks with steel or concrete girders, composite FRP/steel box girder systems, etc.); • FRP elements for long span bridges (cables, hangers, etc.); • Nonstructural FRP elements (crash barriers, lamp and sign standards, etc.); • Innovative FRP systems (e.g., use of FRP to eliminate fatiguecritical details, etc.); and • FRP for bridge erection.

Performance Evaluation of Fiber-Reinforced Polymer Composite Deck Bridges

FHWA is committed to the strategic goals of rehabilitating the nation's bridges that are structurally deficient. Fiber-reinforced polymer (FRP) composites are among the advanced materials that appear to have great potential in bridge deck repair and replacements. In West Virginia alone, more than 30 bridges have been built or rehabilitated with FRP composite materials. Katy Truss and Market Street are two such bridges constructed with FRP bridge decks, and they are being monitored. The West Virginia University Constructed Facilities Center along with the West Virginia Department of Transportation initiated field monitoring of these bridges by performing static and dynamic load tests. The response measurements from controlled truck load tests on the two bridges included (a) deck and stringer strains and (b) deflections and deck accelerations. The following static response parameters were computed from measured data: (a) degree of composite action between deck and stringer, (b) transverse load distribution ...

Performance of a fiber reinforced polymer web core skew bridge superstructure. Part I: field testing and finite element simulations

The structural behavior of a fiber reinforced polymer (FRP) web core skew bridge superstructure is studied in this two-part paper. The two-lane bridge is a simply supported superstructure with a 7.807 m span, 10.071 m wide and a 30° skew angle. The FRP bridge deck is a sandwich structure with a two-way web core matrix and faceskins, fabricated by a molding process with E-glass fibers and vinylester resins. Four field tests have been performed since then. In this first part, the bridge structural configurations and the field test results are presented. A finite element model is developed and validated by field testing to simulate the bridge structural behavior. The comparison of the field testing and numerical simulation results shows a good agreement and bridge is performing as designed.

Development of an Efficient Connector System for Fiber Reinforced Polymer Bridge Decks to Steel Girders

This paper discusses the development of an innovative and efficient connector to be used with fiber reinforced polymer (FRP) decks supported by steel girders. A summary is provided detailing various proprietary connectors currently employed by FRP deck manufacturers. The paper then describes the development and experimental testing of a clamped shear stud-type connector. Experimental testing was conducted in two phases. The first phase consisted of individual connector testing. In this phase, several variations of the connector are tested and evaluated for strength, damage development, and overall performance. Results of this phase of testing are used to select a final connection design to be used in the second phase of testing, which consisted of testing a scale model bridge that incorporates several of the proposed connectors. The bridge is subjected to static load tests and the resulting reactions and deflections from these tests are compared with comprehensive finite element models of the system.

Structural performance of a FRP bridge deck

The purpose of this paper is to present fatigue and strength experimental qualifications performed for an all-composite bridge deck. This bridge deck, made up of fiber-reinforced polymer (FRP) was installed on the campus at University of Missouri at Rolla on July 29th, 2000. The materials used for the fabrication of this 30 foot (9.144 m) long by 9 foot (2.743 m) wide deck were 3 inches (76.2 mm) pultruded square hollow glass and carbon FRP tubes of varying lengths. These tubes were bonded using an epoxy adhesive and mechanically fastened together using screws in seven different layers to form the bridge deck with tubes running both longitudinal and transverse to the traffic direction. The cross-section of the deck was in the form of four identical I-beams running along the length of the bridge. Fatigue and failure tests were conducted on a 30 foot (9.144 m) long by 2 foot (609.6 mm) wide prototype deck sample, equivalent to a quarter portion of the bridge deck. The loads for these tests were computed so as to meet American Association of State Highway and Transportation Officials (AASHTO) H-20 truckload requirements based on strength and maximum deflection. The sample was fatigued to 2 million cycles under service loading and a nominal frequency of 4 Hz. Stiffness changes were monitored by periodically interrupting the run to perform a quasi-static test to service load. Results from these tests indicated no loss in stiffness up to 2 million cycles. Following the fatigue testing, the test sample was tested to failure and no loss in strength was observed. The testing program, specimen detail, experimental setup and instrumentation, testing procedure, and the results of these tests are discussed in detail. A finite-element model of the laboratory test was also developed. The results from the model showed good correlation to deflections and longitudinal strains measured during the tests. The design of the bridge deck has been discussed in detail.

Load Testing of an FRP Bridge Deck on a Truss Bridge

New York State has constructed a fiber reinforced polymer (FRP) bridge deck as an experimental project. The goal of the project was to improve the load rating of a 50-yr old truss bridge located in Wellsburg, New York. The FRP deck weighs approximately 80-percent less than the deteriorated concrete bridge deck it replaced. Reducing the dead load increased the allowable live load capacity of the bridge without significant repair work to the existing superstructure, thus lengthening its service life. Load testing was conducted after installation of the FRP deck to study the conservativeness of the design, ascertain the assumptions made on composite action between the deck and the superstructure, and examine the effectiveness of joints in load transfer. This report describes the testing and discusses the results. The results indicate that the design was conservative. The design assumed no composite action between the deck and the superstructure, and the experimental data confirms that assumption. The study also shows that the joints are only partially-effective in load transfer between panels. Peak strains under the test loads were only a very small fraction of the ultimate strength of the FRP deck.