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This study evaluates the strength and long-term performance of CFRP prestressed panels in a bridge deck, compare the behavior of bridge decks designed with the empirical and conventional methods of AASHTO, and a new limit-state design, and examinne the influence of lap splices between precast panels on deck cracking.
Decks manufactured with fiber-reinforced polymer (FRP) composite materials are used in highway bridges. A performance evaluation of FRP composite decks subjected to simulated traffic loads that induce repetitive stress cycles under extremely high and low temperature is presented. Fatigue testing of three FRP composite bridge deck prototypes and one FRP-concrete hybrid bridge deck prototype under two extreme temperature conditions: -30 C ( -22 F), and 50 C (122 F) was conducted. The fatigue response of the deck prototypes was correlated with the baseline performance of a conventional reinforced concrete deck subjected to similar test conditions. Design loads were applied simultaneously at two points using servo-controlled hydraulic actuators specially designed and fabricated to perform under extreme temperatures. Quasi-static load-deflection and load-strain characteristics were determined at predetermined fatigue cycle levels. No significant distress was observed in any of the composite deck prototypes during ten million load cycles. The effects of extreme temperatures and accumulated load cycles on the load-deflection and load-strain response of FRP composite and FRP-concrete hybrid bridge decks are discussed based on the experimental results.
Corrosion of reinforced concrete structures has been a significant problem for many state and transportation agencies since the application of deicing salts was introduced. Much research has been conducted to develop corrosion protection systems that can prolong the life span of reinforced concrete structures. The Colorado Department of Transportation (CDOT) has several routine and experimental measures to prevent corrosion of the rebar including epoxy-coated rebar, calcium nitrite admixture, organic corrosion inhibitors, a thick cover of quality concrete, and a waterproofing membrane covered by an asphalt overlay. An extensive literature review was performed to collect information on various corrosion protection systems that have been used in the U.S. and around the world. Current CDOT practices in terms of corrosion protection measures were reviewed. A draft inspection plan for Colorado's bridge structures was proposed.
A literature review concerning the objectives of the project was completed. A significant number of published papers, reports, etc., were examined to determine the effectiveness of full depth precast panels for bridge deck replacement. A detailed description of the experimental methodology was developed which includes design and fabrication of the panels and assembly of the bridge. The design and construction process was carried out in cooperation with the project Technical Review Panel. The major components of the bridge deck system were investigated. This includes the transverse joints and the different materials within the joint as well as composite action. The materials investigated within the joint were polymer concrete, non-shrink grout, and set-45 for the transverse joint. The transverse joints were subjected to direct shear tests, direct tension tests, and flexure tests. These tests exhibited the excellent behavior of the system in terms of strength and failure modes. Shear key tests were also conducted. The shear connection study focused on investigating the composite behavior of the system based on varying the number of shear studs within a respective pocket as well as varying the number of pockets within a respective panel. The results indicated that this shear connection is extremely efficient in rendering the system under full composite action. Finite element analysis was conducted to determine the behavior of the shear connection prior to initiation of the actual full scale tests. In addition, finite element analysis was also performed with respect to the transverse joint tests in an effort to determine the behavior of the joints prior to actual testing. The most significant phase of the project was testing a full-scale model. The bridge was assembled in accordance with the procedures developed as part of the study on full-depth precast panels and the results obtained through this research. The system proved its effectiveness in withstanding the applied loading that exceeded eight times the truck loading in addition to the maximum negative and positive moment application. Only hairline cracking was observed in the deck at the maximum applied load. Of most significance was the fact that full composite action was achieved between the precast panels and the steel supporting system, and the exceptional performance of the transverse joint between adjacent panels.
Bridges B-0071 and B-0171 in Hamilton County, Ohio have been in service for about fifty years. They are short span bridges with prestressed concrete girders. Until late 2001, they had conventional reinforced concrete decks, which have been replaced with fiber reinforced polymer (FRP) decks. Two girders in bridge B-0171 were replaced with new prestressed girders. These bridges are significant as there are few instances of FRP decks on concrete girders. The Hamilton County Engineers Office contracted with the Civil Engineering Department at the University of Cincinnati to perform load testing on the bridges. Information gained from this research will seek to confirm the safety of the new technology, evaluate construction and design techniques with reference to the FRP deck, and determine overall performance of the bridge to provide understanding of the system. The two short span prestressed concrete bridges with fiber reinforced polymer decks were subjected to four sets of nondestructive truckload testing. Strain gauges were placed along the height of the girder cross-section, and longitudinally and transversely across the bottom of the deck. Displacement transducers were placed to measure overall girder displacement, relative deck displacement, deck panel separation, and deck-girder connection separation. A three-dimensional finite element analysis model was created to replicate the performance of each bridge. The two new prestressed girders in bridge B-0171 strengthened the bridge considerably and increased its load carrying capacity. But the old prestressed girders in bridge B-0071 and bridge B-0171 did not show any sign of deterioration. The four sets of test data collected over a two-year period show that the age effect on structural behavior is very small for both the bridges. The deck had very little influence on the distribution of loads in the structure for these bridges. Due to low deck stiffness and incomplete connectivity, the FRP deck did little to strengthen the girders. The long term monitoring of the deck result complied with the short term testing as reported by Eder8. The finite element model closely matched with the structural components of the original bridge. The new improved model is a better representation as it was calibrated with four sets of field data collected over a period of two years. The field test data from both tests shows that the girders are simply supported on the abutment. But the girders in the model are designed as fixed end beams to have a reasonable value for the modulus of concrete used in the model. In reality it can be assumed that the support condition is between fixed and simply supported. It was also demonstrated that the deck had very little influence on the distribution of loads in the structure for these bridges. The majority of the load transfer between girders was most likely due to the diaphragms. The Impact Factor based on one set of experimental results was 1.217. However, for analysis the LRFD value of 1.33 was used. The Load Rating Factor for bridge B-0071 was 1.66 and for bridge B-0171 was 2.48 with the governing truck loading being the Design load Type Tandem. These rating factors were based on girder performance only due to insufficient deck information.
The Colorado Department of Transportation (CDOT) recently completed a bridge structure at the I-225/Parker Road Interchange southeast of Denver using innovative construction materials. Part of the bridge deck was constructed of a crack resistant high-performance concrete (HPC) mix and fiber reinforced polymeric reinforcement (FRP) under the sponsorship of the Innovative Bridge Research and Construction (IBRC) program of the Federal Highway Administration (FHWA). To support and validate the design of the bridge deck using innovative materials, a series of studies were conducted at the University of Colorado at Boulder. The studies include the development of HPC mixes, evaluation of the mechanical properties of FRP reinforcing bars under static and cyclic fatigue loads with environmental preconditioning, evaluation of the load carrying capacities of full-scale precast panels prestressed with FRP tendons, and finally, evaluation of the long-term fatigue endurance of a model bridge deck, part of which had a design similar to the actual bridge deck with FRP reinforcement at I-225/Parker Road. Furthermore, the applicability of the AASHTO empirical method to the topping slab of precast panel decks was also investigated.