Structural Characterization of Hybrid Fiber-Reinforced Polymer-Glulam Panels for Bridge Decks

The structural characterization of hybrid fiber-reinforced polymer (FRP)–glued laminated (glulam) panels for bridge deck construction is examined using a combined analytical and experimental approach. The structural system is based on the concept of sandwich construction with strong and stiff FRP composite skins bonded to an inner glulam panel. The FRP composite material was made of E-glass reinforcing fabrics embedded in a vinyl ester resin matrix. The glulam panels were fabricated with bonded eastern hemlock vertical laminations. The FRP reinforcement was applied on the top and bottom faces of the glulam panel by wet layup and compacted using vacuum bagging. An experimental protocol based on a two-span continuous bending test configuration is proposed to characterize the stiffness, ductility, and strength response of FRP-glulam panels under simulated loads. Half-scale FRP-glulam panel prototypes with two different fiber orientations, unidirectional (0°) and angle-ply (±45°), were studied and the structural response correlated with control glulam panels. A simple beam linear model based on laminate analysis and first-order shear deformation theory was proposed to compute stiffness properties and to predict service load deflections. In addition, a beam nonlinear model based on layered moment-curvature numerical analysis was proposed to predict ultimate load and deflections. Correlations between experimental results and the two proposed beam models emphasize the need for complementing both analytical tools to characterize the hybrid panel structural response with a view toward bridge deck design.     

Flexural Reinforcement of Glulam Timber Beams and Joints with Carbon Fiber-Reinforced Polymer Rods

Fiber-reinforced polymer (FRP) composites have largely been used in combination with masonry and concrete structural elements in the last decade. Recent applications showed that new advantages may also be achieved in the field of timber structures, even if currently steel fasteners are used mainly in connecting systems. This study investigated the possibility of using carbon FRP (CFRP) rods as glued-in reinforcement of glulam beams and as glued-in connectors for glulam timber head joints that should transfer flexural moment between two adjacent beams. Half-scale beams were tested both with and without the presence of FRP reinforcement. Flexural behavior of CFRP-reinforced beams was compared with unreinforced beams that were used as control specimens. Two different amounts of CFRP reinforcement were used in the beam section. Experimental results showed a significant influence of the CFRP rods, because the reinforced beams demonstrated an increase in ultimate capacity and stiffness. Experimental results were also compared with numerical analysis, which showed good accordance with regard to the load and deflection values. Full-size head joints were prepared and tested. Flexural behavior of the joints was compared with the mechanical properties of monopiece beams that were used as reference specimens. Three different force transfer lengths were used for the construction of CFRP-timber joints. Experimental results showed that the use of CFRP rods in timber joints was successful, because the capacity of the CFRP-jointed beams was almost the same as that of the monolithic beams for the longest bond length that was adopted. This result is important in order to find an adequate alternative to traditional joints made with steel bolts and plates, which are unable to create rigid connections, increase dramatically the weight of timber structures, and may be subjected to corrosion in an aggressive environment. A numerical modeling based on the virtual work principle was also conducted and theoretical results were found in good accordance with the experimental results for the tested joint.     

Modified Yield Line Theory for Full-Depth Precast Concrete Bridge Deck Overhang Panels

Full-depth precast deck slab cantilevers also referred to as full-depth precast concrete bridge deck overhang panels are becoming increasingly popular in concrete bridge deck construction. To date, no simple theory is able to estimate the overhang capacity of full-depth concrete bridge deck slabs accurately. Observations suggest that interaction between flexure and shear is likely to occur as neither alone provides an accurate estimate of the load-carrying capacity. Therefore, modified yield line theory is presented in this paper, which accounts for the development length of the mild steel reinforcing to reach yield strength. Failure of the full-depth panels is influenced by the presence of the partial-depth transverse panel-to-panel seam. When applying a load on the edge of the seam, the loaded panel fails under flexure while the seam fails in shear. Through the use of the modified yield line theory coupled with a panel-to-panel shear interaction, analytical predictions are accurate within 1–6% of experimental results for critical cases.     

Experimental Performance of Full-Depth Precast, Prestressed Concrete Overhang, Bridge Deck Panels

The performance of a new full-depth precast overhang panel system for concrete bridge decks is investigated experimentally. In contrast to conventional cast-in-place deck overhangs, the proposed full-depth precast overhang system has the potential to speed up construction, reduce costs, and improve safety. Load-deformation behavior up to factored design load limits is first investigated. The panel is then loaded near its edge to examine the collapse capacity and the associated failure modes—particularly the influence of panel-to-panel connections that exist, transverse to the bridge deck axis. Comparative tests are also conducted with a conventional cast-in-place overhang system. When compared to the conventional cast-in-place overhang behavior, the experimental results show that the precast full-depth overhang introduces different behavior modes, largely due to the influence of the partial depth panel-to-panel connection, which reduces the capacity by some 13%.     

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.     

Fatigue Behavior of a Steel-Free FRP–Concrete Modular Bridge Deck System

This paper presents results of an evaluation of the fatigue performance of a novel steel-free fiber-reinforced polymer (FRP)–concrete modular bridge deck system consisting of wet layup FRP–concrete deck panels which serve as both formwork and flexural reinforcement for the steel-free concrete slab cast on top. A two-span continuous deck specimen was subjected to a total of 2.36 million cycles of load simulating an AASHTO HS20 design truck with impact at low and high magnitudes. Quasistatic load tests were conducted both before initiation of fatigue cycling and after predetermined numbers of cycles to evaluate the system response. No significant stiffness degradation was observed during the first 2 million cycles of fatigue service load. A level of degradation was observed during subsequent testing at higher magnitudes of fatigue load. A fairly elastic and stable response was obtained from the system under fatigue service load with little residual displacement. The system satisfied both strength and serviceability limit states with respect to the code requirements for crack width and deflection.     

Inspecting the Lightweight Precast Concrete Panels in the Woodrow Wilson Bridge Deck of 1982

This paper presents the results of a detailed inspection of the deck panels of the Woodrow Wilson Bridge installed in 1982. The original cast-in-place concrete deck, constructed in 1962, was replaced with full-depth lightweight precast concrete deck panels that enabled rapid construction with minimal traffic disruption. The inspection of the Woodrow Wilson deck provides valuable information about the performance of the precast concrete panels, joints, and connections after 20 years of very harsh traffic loads and environmental stressors. The deck panels performed well overall, with the only serious problems at expansion and contraction joints. All of these joints exhibited cracking and rusting. The most prevalent type of cracking appeared to be due to restrained shrinkage between the new polymer concrete, the older precast panels, and the rigid steel joints. This location is more vulnerable to cracking and leaking because there is no prestress across the joint. The multilayered corrosion protection methods used for the transverse and longitudinal post-tensioning tendons were very successful.     

Steel Hexagonal Honeycomb Core Equivalent Elastic Moduli for Bridge Deck Sandwich Panels

Glass fiber-reinforced polymer (GFRP) materials possess inherently high strength-to-weight ratios, but their effective elastic moduli are low relative to civil engineering (CE) construction materials. While elastic modulus may be comparable to that of some CE materials, the lower shear modulus adversely affects stiffness. As a result, serviceability issues are what govern GFRP deck design in the CE bridge industry. An innovative solution to increase the stiffness of a commercial GFRP reinforced-sinusoidal honeycomb sandwich panel was proposed; this solution would completely replace the GFRP honeycomb core with a hexagonal honeycomb core constructed from commercial steel roof decking. The purpose of this study was to perform small-scale tests to characterize the steel hexagonal honeycomb core equivalent elastic moduli in an effort to simplify the modeling of the core. The steel core equivalent moduli experimental results were compared with theoretical hexagonal honeycomb elastic modulus equations from the literature, demonstrating the applicability of the theoretical equations to the steel honeycomb core. Core equivalent elastic modulus equations were then proposed to model and characterize the steel hexagonal honeycomb as applicable to sandwich panel design. The equivalent honeycomb core will enable an efficient sandwich panel stiffness design technique, both for structural analysis methods (i.e., hand calculations) and finite-element analysis procedures.     

Experimental Validation of a Shear Stud Connection between Steel Girders and a Fiber-Reinforced Polymer Deck in the Transverse Direction

A fiber-reinforced polymer (FRP) deck-to-girder connection was evaluated for fatigue resistance and residual capacity in the transverse direction. The connection consisted of three shear studs cast into a trapezoidal cell of a FRP sandwich deck. Steel spirals were positioned around each shear stud to aid in grout confinement. Test fixturing consisted of multiple girders and tie downs to induce realistic loading of the connection due to wheel loads. The connection was fatigued according to AASHTO LRFD Specifications for 10.5?million?cycles (75?year design life) and tested for residual capacity. The connection survived fatigue testing without failure. The haunch exhibited minimal debonding and cracking. Connection capacity after one lifetime of fatigue cycles exceeded strength limit state requirements.     

Theoretical and Experimental Analysis of GFRP Bridge Deck under Temperature Gradient

The temperature difference between the top and bottom of a glass fiber reinforced polymer (GFRP) composite deck, ～ 65°C ( ～ 122°F), is nearly three times that of conventional concrete decks ～ 23°C ( ～ 41°F). Such a large temperature difference is attributed to the relatively lower thermal conductivity of GFRP material. In this study, laboratory tests were conducted on two GFRP bridge deck modules (10.2 and 20.3?cm deep decks) by heating and cooling the top surface of the GFRP deck, while maintaining ambient (room) temperature at the deck bottom. Deflections and strains were recorded on the deck under thermal loads. Theoretical results (using macro approach, Navier-Levy, and FEM) were compared with the laboratory test data. The test data indicated that the GFRP deck exhibited hogging under a positive temperature difference (i.e., Ttop>Tbottom, heating test; Ttop and Tbottom are temperatures at top and bottom of the deck, respectively) and sagging under a negative temperature difference (i.e., Ttop相似文献   

Relaxing the Stud Spacing Limit for Full-Depth Precast Concrete Deck Panels Supported on Steel Girders (Phase I)

The AASHTO LRFD Bridge Design Specifications state that the spacing between the shear connectors for steel girders should not exceed 610 mm (24 in.). This decision was made based on research conducted more than three decades ago. The goal of this research is to investigate the possibility of extending this limit to 1,220 mm (48 in.) for stud clusters used with full-depth precast concrete deck panels installed on steel girders. This paper presents the history of the 610 mm (24 in.) limit, various formulas developed to calculate fatigue and design capacity for stud clusters and concerns about extending the current LRFD limit. This paper also presents information on the first phase of the experimental investigation, which is conducted on push-off specimens to validate extending the limit to 1,220 mm (48 in.).     

Transverse Natural Vibration of a Beam with an Internal Joint Carrying In-Plane Flexibilities

Existing research on semirigid jointed frame includes only the rotational flexibility of the joint without consideration of the flexibility in the direction of the transverse shear force. This omission would lead to inaccuracies in the dynamic response of structures, especially in the nonlinear analysis. This paper investigates the dynamic behavior of a bolted joint which has flexibility in both the tangential and rotational directions. The joint is prestressed with axial tension in the bolt shank. It is represented as a virtual connection spring element at the intersection between the beam and the supporting member. The formulation of the hybrid beam–column element including the end springs is presented, and the dynamic behavior of a cantilever beam with this nonlinear semirigid joint is studied. The natural frequencies and mode shapes remain relatively unchanged only for a limited range of the joint stiffnesses, and the eigenpair is influenced by the instantaneous stiffness of the joint defined at a point on the hysteretic loop, particularly when the initial moment stiffness is small.     

Analysis of an Orthotropic Deck Stiffened with a Cement-Based Overlay

Over the past years, with increasing traffic volumes and higher wheel loads, fatigue damage in steel parts of typical orthotropic steel bridge decks has been experienced on heavily trafficked routes. A demand exists to find a durable system to increase the fatigue safety of orthotropic steel bridge decks. A solution might be to enhance the stiffness of the traditional orthotropic bridge deck by using a cement-based overlay. In this paper, an orthotropic steel bridge deck stiffened with a cement-based overlay is analyzed. The analysis is based on nonlinear fracture mechanics, and utilizes the finite-element method. The stiffness of the steel deck reinforced with an overlay depends highly on the composite action. The composite action is closely related to cracking of the overlay and interfacial cracking between the overlay and underlying steel plate (debonding). As an example, a real size structure, the Far? bridges located in Denmark, are analyzed. The steel box girders of the Far? bridges spans 80?m, and have a depth of 3.5?m, and a width of 19.5?m. The focus of the present study is the top part of the steel box girders, which is constructed as an orthotropic deck plate. Numerous factors can influence the cracking behavior of the cement-based overlay system. Both mechanical and environmental loading have to be considered, and effects such as shrinkage, temperature gradients, and traffic loading are taken into account. The performance of four overlay materials are investigated in terms of crack widths. Furthermore, the analysis shows that debonding is initiated for a certain crack width in the overlay. The load level where cracking and debonding is initiated depends on the stress-crack opening relationship of the material.     

Performance Evaluation of Repair Technique for Damaged Fiber-Reinforced Polymer Honeycomb Bridge Deck Panels

All-composite, fiber-reinforced polymer honeycomb (FRPH) sandwich panels are an innovative application of modern composite materials in civil engineering. These panels have become increasingly popular for use as full-depth bridge decks and have been used to span both transversely between steel or concrete girders and longitudinally between abutments. Although several bridges using FRPH panels have been installed in recent years, a method to repair the panels if they are damaged has not been thoroughly investigated. This paper presents the analysis and full-scale evaluation of a 9.75 m (32 ft) long FRPH member that was subjected to severe core-face delamination damage and subsequently repaired. As such, the work presented herein is the first of its kind to be conducted for FRPH bridge members. The damaged member when repaired was shown to have approximately 65% more capacity than a similar undamaged member. The additional capacity was achieved using a single wrapping layer over the face plates and sinusoidal core. This wrapping layer is believed to have prevented a failure (at the resin bond line) between the face plates and core by engaging a shear-friction type clamping force. The contribution of the wrap layer is considered using simple calculations, rigorous finite-element models, and experimental data. Acoustic emission monitoring was used to compare the performance of the damaged and repaired specimens under sustained load.     

Fiber Reinforced Polymer Shear Strengthening of Reinforced Concrete Beams with Transverse Steel Reinforcement

The paper aims to contribute to a better understanding and modeling of the shear behavior of reinforced-concrete (RC) beams strengthened with carbon fiber reinforced polymer (FRP) sheets. The study is based on an experimental program carried out on 11 beams with and without transverse steel reinforcement, and with different amounts of FRP shear strengthening. The test results provide some new insights into the complex failure mechanisms that characterize the ultimate shear capacity of RC members with transverse steel reinforcement and FRP sheets. After the discussion of the above topics, a new upper bound of the shear strength is introduced. It should be capable of taking into account how the cracking pattern in the web failing under shear is modified by the presence of FRP sheets, and how such a modified cracking pattern actually modifies the anchorage conditions of the sheets and their effective contribution to the ultimate shear strength of the beams.     

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.     

Transverse Cracking of Concrete Bridge Decks: Effects of Design Factors

Early transverse cracking is one of the dominant forms of bridge deck defects experienced by a large number of transportation agencies. These cracks often initiate soon after the bridge deck is constructed, and they are caused by restrained shrinkage of concrete. Transverse cracks increase the maintenance cost of a bridge structure and reduce its life span. Most of the past efforts addressing transverse bridge deck cracking have focused on changes over the years in concrete material properties and construction practices. However, recent studies have shown the importance of design factors on transverse bridge deck cracking. This paper presents results of a comprehensive finite-element (FE) study of deck and girder bridge systems to understand and evaluate crack patterns, stress histories, as well as the relative effect of different design factors such as structural stiffness on transverse deck cracking. The results of this study demonstrate the development of transverse deck cracking and emphasize the importance of these design factors. They also recommend preventive measures that can be adopted during the design stage in order to minimize the probability of transverse deck cracking.     

Testing, Analysis, and Evaluation of a GFRP Deck on Steel Girders

North Carolina has recently installed a fiber-reinforced polymer (FRP) deck on steel girders at a site in Union County. The bridge was instrumented with foil strain gauges, strain transducers, and displacement transducers. The bridge was then tested with a simulated MS-22.5 design load. Experimental data confirmed full composite interaction between the girders and the FRP deck panels. The neutral axis was measured to be 383?mm above the bottom flange of the 618-mm-deep girder. It was found that composite action could be estimated within 3% using a transformed section analysis of the deck panels. For two lanes loaded, the maximum live load distribution factor was computed to be 0.75. When looking at the overall performance of the structure, the deck deflected 5?mm, with the allowable stress at least 10 times over the maximum stress measured in the material. The girder deflection of 7?mm was well within the parameters set forth by AASHTO. Simple span deflection equations were found to conservatively model the anticipated deflection of the girders when using the transformed section properties.     

Field Investigation on the First Bridge Deck Slab Reinforced with Glass FRP Bars Constructed in Canada

Recently, there has been a rapid increase in using noncorrosive fiber-reinforced polymers (FRP) reinforcing bars as alternative reinforcement for bridge deck slabs, especially those in harsh environments. A new two-span girder type bridge, Cookshire-Eaton Bridge (located in the municipality of Cookshire, Quebec, Canada), was constructed with a total length of 52.08 m over two equal spans. The deck was a 200-mm-thick concrete slab continuous over four spans of 2.70 m between girders with an overhang of 1.40 m on each side. One full span of the bridge was totally reinforced using glass fiber-reinforced polymer (GFRP) bars, while the other span was reinforced with galvanized steel bars. The bridge deck was well instrumented at critical locations for internal temperature and strain data collection using fiber optic sensors. The bridge was tested for service performance using calibrated truckloads as specified by the Canadian Highway Bridge Design Code. The construction procedure and field test results under actual service conditions revealed that GFRP rebar provides very competitive performance in comparison to steel.     

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.