Evaluation of Composite Sandwich Bridge Decks with Hybrid FRP-Steel Core

A hybrid concept of composite sandwich panel with hybrid fiber-reinforced polymer (FRP)—steel core was proposed for bridge decks in order to not only improve stiffness and buckling response but also be cost efficient compared to all glass fiber-reinforced polymer (GFRP) decks. The composite sandwich bridge deck system is comprised of wrapped hybrid core of GFRP grid and multiple steel box cells with upper and lower GFRP facings. Its structural performance under static loading was evaluated and compared with the ANSYS finite element predictions. It was found that the presented composite sandwich panel with hybrid FRP-steel core was very efficient for use in bridges. The thickness of the hybrid deck may be decreased by 19% when compared with the all GFRP deck. The failure mode of the proposed hybrid deck was more favorable because of the yielding of the steel tube when compared with that of all GFRP decks.     

Designing and Testing of Concrete Bridge Decks Reinforced with Glass FRP Bars

In addition to their high strength and light weight, fiber-reinforced polymer (FRP) composite reinforcing bars offer corrosion resistance, making them a promising alternative to traditional steel reinforcing bars in concrete bridge decks. FRP reinforcement has been used in several bridge decks recently constructed in North America. The Morristown Bridge, which is located in Vermont, United States, is a single span steel girder bridge with integral abutments spanning 43.90 m. The deck is a 230 mm thick concrete continuous slab over girders spaced at 2.36 m. The entire concrete deck slab was reinforced with glass FRP (GFRP) bars in two identical layers at the top and the bottom. The bridge is well instrumented at critical locations for internal temperature and strain data collection with fiber-optic sensors. The bridge was tested for service performance using standard truck loads. The construction procedure and field test results under actual service conditions revealed that GFRP rebar provides very good and promising performance.     

Fatigue and Strength Evaluation of Two Glass Fiber-Reinforced Polymer Bridge Decks

The use of glass fiber-reinforced polymer (GFRP) bridge decks is appealing for applications where minimizing dead load is critical. This paper describes fatigue and strength testing of two types of GFRP decks being considered for use in the retrofit of an aging steel arch bridge in Snohomish County, Washington, where a roadway expansion is necessary and it is desirable to minimize the improvements to the arch superstructure. Each test used a setup designed to be as close as practicable to what will be the in situ conditions for the deck, which included a 2% cross slope for drainage. The fatigue testing consisted of a single 116 kN (26 kip) load applied for 2 million cycles, which corresponds to an AASHTO HS-25 truck with a 30% impact factor, and the strength testing consisted of multiple runs of a monotonically applied minimum load of 347 kN (78 kips). Results from the fatigue testing indicated a degradation of the stiffness of both deck types; however, the degradation was limited to less than 12% over the duration of loading. Further, the results showed both deck types accumulated permanent deck displacement during fatigue loading and one deck type used a detail with poor fatigue performance. That detail detrimentally impacted the overall deck performance and caused large permanent deck deformations. It was also found that degradation of composite behavior between the deck and girders occurs during fatigue loading and should be included in design.     

Laboratory and Field Performance of Cellular Fiber-Reinforced Polymer Composite Bridge Deck Systems

This paper addresses the laboratory and field performance of multicellular fiber-reinforced polymer (FRP) composite bridge deck systems produced from adhesively bonded pultrusions. Two methods of deck contact loading were examined: a steel patch dimensioned according to the AASHTO Bridge Design Specifications, and a simulated tire patch constructed from an actual truck tire reinforced with silicon rubber. Under these conditions, deck stiffness, strength, and failure characteristics of the cellular FRP decks were examined. The simulated tire loading was shown to develop greater global deflections given the same static load. The failure mode is localized and dominated by transverse bending failure of the composites under the simulated tire loading as opposed to punching shear for the AASHTO recommended patch load. A field testing facility was designed and constructed in which FRP decks were installed, tested, and monitored to study the decks’ in-service field performance. No significant loss of deck capacity was observed after more than one year of field service. However, it was shown that unsupported edges (or free edges) are undesirable due to transitional stiffness from approach to the unsupported deck edge.     

Evaluation of Effective Width and Distribution Factors for GFRP Bridge Decks Supported on Steel Girders

Glass fiber-reinforced polymer (GFRP) bridge deck systems offer an attractive alternative to concrete decks, particularly for bridge rehabilitation projects. Current design practice treats GFRP deck systems in a manner similar to concrete decks, but the results of this study indicate that this approach may lead to nonconservative bridge girder designs. Results from a number of in situ load tests of three steel girder bridges having the same GFRP deck system are used to determine the degree of composite action that may be developed and the transverse distribution of wheel loads that may be assumed for such structures. Results from this work indicate that appropriately conservative design values may be found by assuming no composite action between a GFRP deck and steel girder and using the lever rule to determine transverse load distribution. Additionally, when used to replace an existing concrete deck, the lighter GFRP deck will likely result in lower total stresses in the supporting girders, although, due to the decreased effective width and increased distribution factors, the live-load-induced stress range is likely to be increased. Thus, existing fatigue-prone details may become a concern and require additional attention in design.     

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.     

Effect on Superstructure Stress of Replacing a Composite RC Bridge Deck with a GFRP Deck

Glass fiber-reinforced polymer (GFRP) composite bridge decks behave differently than comparable reinforced concrete (RC) decks. GFRP decks exhibit reduced composite behavior (when designed to behave in a composite manner) and transverse distribution of forces. Both of these effects are shown to counteract the beneficial effects of a lighter deck structure and result in increased internal stresses in the supporting girders. The objective of this paper is to demonstrate through an illustrative example the implications of RC-to-GFRP deck replacement on superstructure stresses. It is also shown that, regardless of superstructure stresses, substructure forces will be uniformly reduced due to the lighter resulting superstructure.     

Performance Evaluation of FRP Composite Deck Considering for Local Deformation Effects

We examine here the replacement of a deteriorated concrete deck in the historic Hawthorne Street Bridge in Covington, Va. with a lightweight fiber-reinforced polymer (FRP) deck system (adhesively bonded pultruded tube and plate assembly) to increase the load rating of the bridge. To explore construction feasibility, serviceability, and durability of the proposed deck system, a two-bay section (9.45 by 6.7?m) of the bridge has been constructed and tested under different probable loading scenarios. Experimental results show that the response of the deck is linear elastic with no evidence of deterioration at service load level (HS-20). From global behavior of the bridge superstructure (experimental data and finite- element analysis), degree of composite action, and load distribution factors are determined. The lowest failure load (93.6?kips or 418.1?kN) is about 4.5 times the design load (21.3?kips or 94?kN), including dynamic allowance at HS-20. The failure mode is consistent in all loading conditions and observed to be localized under the loading patch at the top plate and top flange of the tube. In addition to global performance, local deformation behavior is also investigated using finite-element simulation. Local analysis suggests that local effects are significant and should be incorporated in design criteria. Based on parametric studies on geometric (thickness of deck components) and material variables (the degree of orthotropy in pultruded tube), a proposed framework for the sizing and material selection of cellular FRP decks is presented for future development of design guidelines for composite deck structures.     

Failure Study of an Aluminum Bridge Deck Panel

Aluminum bridge decks may prove to be an alternative to concrete decks for improving the performance of structural bridge systems. Combining excellent corrosion resistance with extremely low density, aluminum decks can prolong surface life, facilitate the construction process, and expand rehabilitation capabilities. Reynolds Metals Company, Richmond, Va., has invested considerable resources to develop a proprietary aluminum deck system. The Virginia Department of Transportation agreed to employ the Reynolds deck system in two projects. Using Federal Highway Administration sponsorship, the Virginia Transportation Research Council initiated a study to evaluate the aluminum deck system. The first phase of this project analyzed the static response of a 2.74 × 3.66 m (9 × 12 ft) deck panel. Both service-load tests and ultimate-load tests were performed on the panel at the Turner-Fairbank Structural Laboratory. The experimental and analytical evaluation of the ultimate load static tests is the subject of this paper. The failure load and failure mechanism were predicted with great accuracy. The model data predicted panel failure at a load of 911.89 kN (205 kips) by yielding under the load patch while failure during the laboratory test occurred at a load of 872.07 kN (196.05 kips) by gross yielding underneath the load patch.     

Behavior of Reinforced Concrete Bridge Decks on Skewed Steel Superstructure under Truck Wheel Loads

This paper focuses on the behavior of skewed concrete bridge decks on steel superstructure subjected to truck wheel loads. It was initiated to meet the need for investigating the role of truck loads in observed skewed deck cracking, which may interest bridge owners and engineers. Finite-element analysis was performed for typical skewed concrete decks, verified using in?situ deck strain measurement during load testing of a bridge skewed at 49.1°. The analysis results show that service truck loads induce low strains/stresses in the decks, unlikely to initiate concrete cracking alone. Nevertheless, repeated truck wheel load application may cause cracks to become wider, longer, and more visible. The local effect of wheel load significantly contributes to the total strain/stress response, and the global effect may be negligible or significant, depending on the location. The current design approach estimates the local effect but ignores the global effect. It therefore does not model the situation satisfactorily. In addition, total strain/stress effects due to truck load increase slightly because of skew angle.     

Thermal Compatibility and Durability of Wearing Surfaces on GFRP Bridge Decks

The paper investigates thermal compatibility between wearing surface (WS) materials and glass fiber reinforced polymer (GFRP) bridge decks, and proposes a more durable hybrid WS system for GFRP decks. Wearing surface delamination problems observed on many existing GFRP bridge decks motivated the investigation and the search for a durable WS material that could alleviate the problems. Several WS materials were bonded to GFRP panels, with and without surface preparation, and tested under various environmental conditions. In addition to the standard ASTM C884 method, the testing program included two new methods for thermal compatibility testing to reflect the in-service conditions of WSs on GFRP bridge decks. The proposed methods were developed to account for the influence of freeze–thaw–heat and submerge–freeze cycles on thermal compatibility and durability. The investigation concluded that a hybrid WS system, consisting of two-layered WS materials, has the best bond quality. Applied directly on top of a GFRP deck, the top layer of the hybrid WS system had the best tire resistance, forming a nonskid riding surface.     

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.     

Experimental Analysis of Crack Growth in GFRP Reinforced Concrete

For decades, bridge slabs have been troubled by the corrosion of steel reinforcement. The unique corrosion resistance of glass fiber-reinforced polymer (GFRP) bars makes them a promising alternative to steel bars. Experiments have been conducted to investigate the bond performance of GFRP reinforced concrete under constant amplitude cyclic fatigue loading. Each specimen was an identical length beam with a single GFRP bar at the bottom, intended to simulate a transverse strip of a typical bridge deck slab. The crack growth was monitored for specimens of different widths, simulating different transverse reinforcement spacings. Up to 2?million?cycles of cyclic loads were applied at 100% typical service load levels. No fatigue failure was encountered in the testing. The effects of moderate overloads were also investigated.     

Compound Shear-Flexural Capacity of Reinforced Concrete–Topped Precast Prestressed Bridge Decks

Modern concrete bridge decks commonly consist of stay-in-place (SIP) precast panels seated on precast concrete beams and topped with cast-in-place (CIP) reinforced concrete. Such composite bridge decks have been experimentally tested by various researchers to assess structural performance. However, a failure theory that describes the failure mechanism and accurately predicts the corresponding load has not been previously derived. When monotonically increasing patch loads are applied, delamination occurs between the CIP concrete and SIP panels, with a compound shear-flexure mechanism resulting. An additive model of flexural yield line failure in the lower SIP precast prestressed panels and punching shear in the upper CIP-reinforced concrete portion of the deck system is derived. Analyses are compared to full-scale experimental results of a tandem wheel load straddling adjacent SIP panels and a trailing wheel load on a single panel. Alone, both yield line and punching-shear theories gave poor predictions of the observed failure load; however, the proposed compound shear-flexure failure mechanism load capacities are within 2% accuracy of the experimentally observed loads. Better estimation using the proposed theory of composite SIP-CIP deck system capacities will aid in improving the design efficiency of these systems.     

Construction and Testing of an Innovative Concrete Bridge Deck Totally Reinforced with Glass FRP Bars: Val-Alain Bridge on Highway 20 East

The Val-Alain Bridge, located in the Municipality of Val-Alain on Highway 20 East, crosses over Henri River in Québec, Canada. The bridge is a slab-on-girder type with a skew angle of 20° over a single span of 49.89?m and a total width of 12.57?m. The bridge has four simply supported steel girders spaced at 3,145?mm. The deck slab is a 225-mm-thick concrete slab, with semi-integral abutments, continuous over the steel girders with an overhang of 1,570?mm on each side. The concrete deck slab and the bridge barriers were reinforced with glass fiber reinforced polymer (GFRP) reinforcing bars utilizing high-performance concrete. The Val-Alain Bridge is the Canada’s first concrete bridge deck totally reinforced with GFRP reinforcing bars. Using such nonmetallic reinforcement in combination with high-performance concrete leads to an expected service life of more than 75?years. The bridge is well instrumented with electrical resistance strain gauges and fiber-optic sensors at critical locations to record internal strain data. Also, the bridge was tested for service performance using calibrated truckloads. Design concepts, construction details, and results of the first series of live load field tests are presented.     

Strength and Serviceability of FRP Grid Reinforced Bridge Decks

The research presented in this paper evaluates the flexural performance of bridge deck panels reinforced with 2D fiber-reinforced polymer (FRP) grids. Two different FRP grids were investigated, one reinforced with a hybrid of glass and carbon fibers and a second grid reinforced with carbon fibers only. Laboratory measured load-deflection, load-strain (reinforcement and concrete), cracking, and failure behavior are presented in detail. Conclusions regarding failure mode, limit-state strength, serviceability, and deflection compatibility relative to AASHTO mandated criteria are reported. Test results indicate that bridge decks reinforced with FRP grids will be controlled by serviceability limit state and not limit-state ultimate strength. The low axial stiffness of FRP results in large service load flexural deflections and reduced shear strength. In as much as serviceability limits design, overreinforcement is recommended to control deflection violation. Consequently, limit-state flexural strength will be compression controlled for which reduced service stresses or ACI unified compression failure strength reduction factors are recommended.     

LRFD Orthotropic Plate Model for Live Load Moment in Filled Grid Decks

Due to the orthogonal elastic properties and significant two-way bending action, orthotropic plate theory may best be used to describe the behavior of concrete filled grid bridge decks. The current AASHTO LRFD specification employs an orthotropic plate model with a single patch load to predict live load moment in concrete filled grid bridge decks, which may not be conservative. This paper presents alternative equations to predict maximum moments, based on classical orthotropic plate theory, which include multiple patch loads, both the LRFD design truck and tandem load cases, and the two most common deck orientations. The predicted moments are verified through finite-element analyses.     

Nondestructive Testing of GFRP Bridge Decks Using Ground Penetrating Radar and Infrared Thermography

As glass fiber-reinforced polymer (GFRP) bridge decks are becoming a feasible alternative to the traditional concrete bridge decks, an innovative methodology to evaluate the in situ conditions are vital to GFRP bridge decks’ full implementation. Ground penetrating radar (GPR) typically performs well in detecting subsurface condition of a structural component with moisture pockets trapped within the material. On the other hand, infrared thermography (IRT) is traditionally known for its ability to detect air pockets within the material. In order to evaluate both nondestructive testing methods’ effectiveness for subsurface condition assessment of GFRP bridge deck, debonds of various sizes were embedded into a GFRP bridge deck module. A 1.5 GHz ground-coupled GPR system and a radiometric infrared camera were used to scan the deck module for condition assessment. Test results showed that both GPR and IRT retained their respective effectiveness in detecting subsurface anomalies. GPR was found to be capable of detecting water-filled defects as small as 5×5?cm2 in plan size, and as thin as 0.15 cm. Furthermore, tests on additional specimens showed that the GPR system offers some promise in detecting bottom flange defects as far down as 10 cm deep. IRT, on the other hand, showed that it is capable of finding both water-filled and air-filled defects within the top layers of the deck with solar heating as main source of heat flux. While test results showed IRT is more sensitive to air-filled defects, water-filled defects can still be detected with a large enough heating mechanism. The experiments showed that a more detailed and accurate assessment can be achieved by combining both GPR and IRT.     

Field Monitoring and Repair of a Glass Fiber-Reinforced Polymer Bridge Deck

This paper reports on the monitoring and repair of a pilot field deployment of a glass fiber-reinforced polymer (GFRP) deck on a small steel girder bridge in the Washington State. Deck deflections were monitored periodically over a 10-month period and were found to increase significantly over that time. The GFRP deck is an adhesively bonded assembly of GFRP tubes and top and bottom plates. After 9 months of service, wearing surface cracking was observed, and upon closer inspection, the top GFRP plate was found to be delaminated from the tubes over a fairly large area. Deck deflections in the area of delamination were found to be considerably larger than those observed during previous monitoring in undamaged locations. A retrofit solution was employed where the top plate was reconnected to the tubes using screws coated with a two-part epoxy that mixed when they were driven. At the time of writing the retrofit was successful in reattaching the delaminated top plate.     

Realistic Assessment for Safety and Service Life of Reinforced Concrete Decks in Girder Bridges

The lack of safety of deck slabs in bridges generally causes frequent repair and strengthening. The repair induces great loss of economy, not only due to direct cost by repair, but also due to stopping the public use of such structures during repair. The major reason for this frequent repair is mainly due to the lack of a realistic and accurate assessment system for bridge decks. The purpose of the present paper is therefore to develop a realistic assessment system which can estimate reasonably the safety, as well as the service life of concrete bridge decks, based on the deterioration models that are derived from both the traffic loads and environmental effect. A deterioration model due to chloride ingress is first established. The damage models due to repetitive traffic loads considering the dry and wet conditions of deck slabs are proposed. These models are used to calculate the remaining life of a bridge deck slab. A prediction method for service life of deck slab due to loading and environmental effects is developed based on material, as well as structural evaluation. The proposed method includes the assessment of corrosion in material level, and the analyses of flexure, shear, and fatigue in structural level. Finally, an assessment system for prediction of safety and remaining service life is developed based on the theories established in this study. The developed assessment system will allow the correct diagnosis of damage state and the realistic prediction of service life of concrete decks in girder bridges.