Design Optimization Procedures for Fiber Reinforced Plastic Bridges

A simplified optimization procedure is described for a novel fiber reinforced plastic bridge system. The bridge system is modeled using a transformed anisotropic plate that is discretized using the Ritz method. This provides a structural model that is incorporated into a stiffness-based optimization algorithm using the optimality criteria method. The resulting procedure provides a useful design tool that can be used to produce a minimum weight design without resorting to finite-element analysis, which is only used to check the strength of the final design. A two-lane highway bridge serves as a demonstration problem.     

Static and Fatigue Testing of Hybrid Fiber-Reinforced Polymer-Concrete Bridge Superstructure

This paper presents the experimental results from static and fatigue testing on a scale model of a hybrid fiber-reinforced polymer (FRP)–concrete bridge superstructure. The hybrid superstructure was designed as a simply-supported single span bridge with a span of 18.3 m. Three trapezoidal glass fiber-reinforced polymer (GFRP) box sections are bonded together to make up a one-lane superstructure, and a layer of concrete is placed in the compression side of those sections. This new design was proposed in order to reduce the initial costs and to increase the stiffness of GFRP composite structures. Static test results showed that the bridge model meets the stiffness requirement and has significant reserve strength. The bridge model was also subjected to two million load cycles to investigate its fatigue characteristics. The fatigue testing revealed that the structural system exhibits insignificant stiffness degradation.     

Constructability Analysis of the Bridge Superstructure Rotation Construction Method in China

Constructability analysis can provide valuable input to optimizing urban bridge construction in terms of reducing impacts on traffic, safety, and overall project budget and duration. This paper presents a constructability analysis of the superstructure rotation method for bridge construction. The method includes building the bridge parallel to the obstacle being overpassed (a river or a highway) and then rotating the superstructure into place. The method has been used successfully in over one-hundred bridges (mostly in China). The paper documents two case studies of bridges that used this method and provides an analysis of the constructability of the method. This includes identification of the factors influencing the constructability of the methods and lists of design and construction objectives/strategies that support the constructability of bridges using this method.     

1000m~3高炉料车斜桥的静力分析

通过AutoCAD作图法对某钢厂1000m3高炉料车斜桥上料过程进行了静力学分析,计算得出了斜桥及卷扬机卷筒、绳轮、钢丝绳等设备和材料在空料车、正常装焦、正常装矿、过载装矿、料车卡住等各种工况下的受力,为结构专业进行计算提供了依据。     

Fatigue Behavior of Carbon Fiber Reinforced Polymer-Strengthened Reinforced Concrete Bridge Girders

This study examines the effects of one-dimensional fiber-reinforced polymer (FRP) composite rehabilitation systems on the flexural fatigue performance of reinforced concrete bridge girders. Eight 508?mm deep and 5.6?m long reinforced concrete T-beams, with and without bonded FRP reinforcement on their tensile surfaces, were tested with a concentrated load at midspan under constant amplitude cyclic loading. The objective of this investigation is to establish the effect that these repair systems have on the fatigue behavior and remaining life of the girders. Results indicate that the fatigue behavior of such retrofit beams is controlled by the fatigue behavior of the reinforcing steel. The fatigue life of a reinforced concrete beam can be increased by the application of an FRP retrofit, which relieves some of the stress carried by the steel. The observed increase in fatigue life, however, is limited by the quality of the bond between the carbon FRP and concrete substrate. Debonding, initiating at midspan and progressing to a support, is common and is driven partially by the crack distribution and shear deformations of the beam.     

Shear Modulus of Standard Pultruded Fiber Reinforced Plastic Material

Research to determine the shear modulus of standard pultruded fiber reinforced plastic (FRP) material is reviewed and appraised. It is found that different test methods have given shear moduli data in the range from 1.3 to 5.1 GPa, with varying degrees of scatter. Pultruded material is comprised of alternate layers of two distinct glass reinforcement types. By applying micromechanical modeling, it is shown that the in-plane shear modulus of the continuous unidirectional rovings layer is similar to that of the continuous filament (or strand) mat layer, and that these layer moduli, generally, lie in the range 3.5 to 4.8 GPa (depending on fiber volume fraction). This finding indicates that the significant difference (>1.3 times) between the in-plane (3 GPa or less) and the St. Venant torsion (always >4 GPa) shear moduli is likely to be due to the experimental test procedures and the physical interpretation of shearing, rather than the layer construction of the material. For structural profiles, it is seen that the shear modulus of 3 GPa in company design manuals is often less than measured. Researchers require correlated elastic constant data if elastic deflections and instability loads for structural members can be accurately predicted using elastic theory. Further work is, therefore, recommended to establish standard test and analytical methods for the determination of shear moduli of pultruded FRP material.     

Filament-Wound Glass Fiber Reinforced Polymer Bridge Deck Modules

The demand for the development of efficient and durable bridge decks is a priority for most of the highway authorities worldwide. This paper summarizes the results of an experimental program designed to study the behavior of an innovative glass fiber reinforced polymer (GFRP) bridge deck recently patented in Canada. The deck consisted of a number of triangular filament wound tubes bonded with epoxy resin. GFRP plates were adhered to the top and bottom of the tubes to create one modular unit. The experimental program, described in this paper, discusses the evolution of two generations of the bridge deck. In the first generation, three prototype specimens were tested to failure, and their performance was analyzed. Based on the behavior observed, a second generation of bridge decks was fabricated and tested. The performance was evaluated based on load capacity, mode of failure, deflection at service load level, and strain behavior. All decks tested exceeded the requirements to support HS30 design truck loads specified by AASHTO with a margin of safety. This paper also presents an analytical model, based on Classical Laminate Theory to predict the load-deflection behavior of the FRP decks up to service load level. In all cases the model predicted the deck behavior very well.     

Fatigue Behavior of Reinforced Concrete Beams Strengthened with Carbon Fiber Reinforced Plastic Laminates

Although there has been growing interest and field applications of poststrengthening concrete structures using carbon fiber reinforced plastic (CFRP) laminates, very little information exists regarding the flexural fatigue behavior of reinforced concrete beams strengthened with CFRP. This paper presents the results of an investigation into the fatigue behavior of reinforced concrete beams poststrengthened with CFRP laminates. The results of twenty 3 m and six 5 m beams loaded monotonically and cyclically to failure are discussed. Comparisons are made between beams without and with CFRP strengthening. The effect on fatigue life of increasing the amount of CFRP used to strengthen the beams is also examined.     

Stay-in-Place Fiber Reinforced Polymer Forms for Precast Modular Bridge Pier System

This paper presents an innovative modular construction of bridge pier system with stay-in-place fiber reinforced polymer (FRP) forms filled with concrete. Two 1/6 scale precast modular frames were prepared of a prototype bridge pier system. Three different types of connections were considered: male-female, dowel reinforced with or without tube embedment, and posttensioned. The frames were load tested in negative and positive bending. Subsequently, the cap beams were cut from the frames and tested to failure in four-point bending. Posttensioned joints exhibited the most robust and ductile behavior and proved to be the preferred method of joining stay-in-place forms. Even with dowel bars, the male-female joints lacked the necessary structural integrity in the pier frames. Better surface preparation for FRP units and higher quality grouting may improve the response. Embedment of the columns into the footing provided additional stiffness for the connection. The study indicated that internal reinforcement is not necessary for the stay-in-place forms outside the connection zone. The experiments also showed the importance of maintaining appropriate tolerances and match casting for male-female and embedment connections. Overall, however, feasibility of the precast modular FRP system was demonstrated in this study.     

Performance Evaluation of Reinforced Concrete Bridge Columns Wrapped with Fiber Reinforced Polymers

This study investigates the performance of new bridge columns wrapped with fiber reinforced polymers (FRP) when exposed to aggressive environmental conditions. This has been accomplished through field monitoring and laboratory tests. As part of the field monitoring, temperature data were collected at various locations of bridge columns. In addition, visual inspection of two bridges was performed periodically for over a period of two years. No evidence of deterioration of the FRP wraps was detected during that period. Laboratory tests were performed to investigate how FRP wraps protect reinforced concrete columns from corrosion, and freeze–thaw laboratory tests were conducted to study the impact of temperature cycles on the mechanical behavior of FRP-wrapped columns. From the corrosion experimental tests, it was found that FRP provides excellent protection against aggressive agents (salty water or moisture) even when a single layer is used. Compression tests were conducted on specimens subjected to freeze–thaw cycles. It was found that minor thermal cycles have no effect on the performance of FRP-wrapped concrete specimens. However, for large thermal cycles, some degradation of ductility in the axial and the hoop directions was observed.     

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.     

Flexural and Torsional Properties of Pultruded Fiber Reinforced Plastic I-Profiles

Experimental determination of the full section flexural and torsional properties of pultruded fiber reinforced plastic I-profiles is described. Based on beam theory approximations, test configurations for determining the various section properties are established. Tests were conducted on three different I-profiles with a range of span-to-depth ratios. Major and minor axis flexural rigidities and flexural moduli, determined from three- and four-point bending tests, show close correlation. Major and minor axis transverse shear rigidities and shear moduli show significant variation, due to differing effective areas of the cross section resisting transverse shear and differing fiber content and orientation in the web and flanges. St. Venant torsional shear moduli, determined from uniform torsion tests, are consistent but significantly greater than the transverse shear moduli, which may be due to variations in fiber content, orientation, and lay up. Warping torsional rigidities, determined from nonuniform torsion tests, are consistent with values deduced from minor axis flexural rigidities, indicating that the influence of shear deformation on restrained torsional warping is insignificant.     

Modeling of Tension-Stiffening Behavior of Reinforced Concrete Ties Strengthened with Fiber Reinforced Plastic Sheets

A model to analyze the behavior of reinforced concrete tension ties strengthened with fiber reinforced plastic (FRP) laminates is developed that allows introduction of a nonlinear constitutive relationship for materials and bond-slip laws at the steel and FRP interface. Experimental results are introduced and compared with analytical results confirming the model reliability. By using the model, a numerical study is carried out to provide evidence of the influence of the amount of fibers and the tension-stiffening behavior of strengthened elements. Considering elements with the same mechanical percentage of reinforcement but composed of different amounts of steel and fibers, the stiffness is influenced only after steel yielding, even if the crack width is reduced by the external strengthening. Finally, evidence is provided for the reduction of tension stiffening in strengthened elements due to reduction of crack spacing.     

Experimental Study of a Bonded Plastic Fiber Reinforced Polymer Connector Assembly

In this paper the physical behaviors of a connection assembly comprising a molded glass reinforced plastic [plastic fiber reinforced polymer (PFRP)] connector unit currently commercially manufactured from sheet molding compound and two pultruded PFRP box section beams/columns are examined. A detailed review highlights the apparent lack of research in this area. A limited number of studies have indicated the potential benefits of this joining technology in comparison to mimicking steel-type connections in which ductility is exploited. Reflecting the internal asymmetries of the connector unit, rotationally similar tests have been undertaken in which the connection assembly has been subjected to loading and boundary conditions inducing predominantly shear and bending states, respectively. Load-displacement characteristics, strain measurements, and failure modes are reported. In the context of the basic geometric design of the connector unit and low strength parent material, the connection assembly is shown to perform well, mobilizing up to 26% of the ultimate bending strength of the pultruded box section and demonstrating the potential of the joining technology.     

Prediction of the Failure Time of Glass Fiber Reinforced Plastic Reinforced Concrete Beams under Fire Conditions

A model is proposed to predict the time to failure of reinforced concrete beams in a fire. The model is developed specifically to predict the lifetime of beams reinforced with glass fiber reinforced plastic rebar, but is applicable to beams with any form of reinforcement. The model is based on the calculations for flexural capacity and shear capacity of beams embedded within ACI design codes where time and temperature dependent values for rebar modulus and strength and concrete strength replace the static design values. The base equations are modified to remove safety factors and where necessary the temperature induced reductions in strength for concrete and steel are derived using the equations presented by EUROCODE 2. In order to validate the model it was used to predict the failure times of steel rebar reinforced beams that had been documented in the literature. There was excellent agreement between the model and the reported lifetimes for these conventional beams. The model was applied to predict the lifetimes of two beams that had been manufactured and tested for destruction in a fire by the research group. The model predicted that the failure mode of the beams would be because of rebar rupture as opposed to the design condition of concrete crushing and this was confirmed by the experimental test results. The model provided reasonable agreement with experimental results with a lifetime of 108?min predicted based on flexural failure and 94 and 128?min observed in the experiments.     

Estimates of Skew Wind Speeds for Bridge Flutter

When estimating the stability of a long-span bridge under wind, the basic study is most often made by considering the wind as it approaches the bridge at right angles to its long axis. However, maximum wind at a given site seldom approaches exactly normal to this axis, but will generally be skew instead. A common assumption is that a given skew wind velocity will be critical for flutter if its cosine component normal to the bridge deck equals the critical bridge normal-wind velocity. Although this does not provide a completely inaccurate estimate, the latter can be sharpened somewhat by considering an available physical approximation to the aeroelastic wind-structure interaction under the skew wind. This approximation is derivable from the experimental analysis of the wind-normal flutter condition and its associated key flutter derivatives, particularly the one linked to deck torsional instability.     

Influence of Shear Deformation on Buckling of Pultruded Fiber Reinforced Plastic Profiles

Theoretical studies of the influence of shear deformation on the flexural, torsional, and lateral buckling of pultruded fiber reinforced plastic (FRP)-I-profiles are presented. Theoretical developments are based on the governing energy equations and full section member properties. The solution for flexural buckling is consistent with the established solution based on the governing differential equation. The new solutions for torsional and lateral buckling incorporate a reduction factor similar to that for flexural buckling. The solution for lateral buckling also incorporates the influence of prebuckling displacements. Closed form solutions for a series of simply supported, pultruded FRP I-profiles, based on experimentally determined full section flexural and torsional properties, indicate the following conclusions. For members subjected to axial compression, shear deformation can reduce the elastic flexural and torsional buckling loads by up to approximately 15% and 10%, respectively. For members subjected to bending, prebuckling displacements can increase the buckling moments by over 20% while shear deformation decreases the buckling moments by less than 5%.     

Static Finite-Element Analysis of Bridge Fenders for Barge Impact

Fender systems between channel piers are currently required by the U.S. Coast Guard for guidance of vessels under bridges. Because their only function is to guide the vessels through navigational channels under the bridges, these fender systems are not designed to withstand any lateral impact. The objective of this paper is to analyze the possibility of transforming bridge fender systems into pier protection against barge impact. A finite-element model of the fenders currently used by the Florida Department of Transportation was created using ANSYS software and subjected to a static load equivalent to the barge impact force. Because it may be uneconomical and impractical for fenders to be designed to withstand the total barge impact forces, they were also tested for 33% of such load. The results show that the fender systems currently used by the Florida Department of Transportation are too weak to function as bridge protection systems because they are unable to resist even 33% of the impact force without total destruction of the system.     

Fiber-Reinforced Plastic Jackets for Ductility Enhancement of Reinforced Concrete Bridge Columns with Poor Lap-Splice Detailing

This paper presents an inclusive testing program conducted on scaled models of reinforced concrete (RC) bridge columns with insufficient lap-splice length. Thirteen half-scale circular and square column samples were tested in flexure under lateral cyclic loading. Three columns were tested in the as-built configuration whereas ten samples were tested after being retrofitted with different composite-jacket systems. A brittle failure was observed in the as-built samples due to bond deterioration of the lap-spliced longitudinal reinforcement. The jacketed circular columns demonstrated a significant improvement in their cyclic performance. Yet, tests conducted on square jacketed columns showed a limited improvement in clamping on the lap-splice region and for enhancing the ductility of the column.     

Development of a Specification for Bridge Seismic Retrofit with Carbon Fiber Reinforced Polymer Composites

The U.S. Interstate 80 bridge over State Street in Salt Lake City is very near the Wasatch fault, which is active and capable of producing large earthquakes. The bridge was designed and built in 1965 according to the 1961 American Association of State Highway Officials specifications, which did not consider earthquake-induced forces or displacements. The bridge consists of reinforced concrete bents supporting steel plate welded girders. The bents are supported on cast-in-place concrete piles and pile caps. A seismic retrofit design was developed using carbon fiber reinforced polymer (CFRP) composites, which was implemented in the summer of 2000 and the summer of 2001, to improve the displacement ductility of the bridge. The seismic retrofit included column jacketing, as well as wrapping of the bent cap and bent cap-column joints for confinement, flexural, and shear strength increase. This paper describes the specifications developed for the CFRP composite column jackets and composite bent wrap. The specifications included provisions for materials, constructed thickness based on strength capacity, and an environmental durability reduction factor. Surface preparation, finish coat requirements, quality assurance provisions, which included sampling and testing, and constructability issues regarding the application of fiber composite materials in the retrofit of concrete bridges are also described.