Note on Chloride-Induced Corrosion of Reinforced Concrete Bridge Decks

This technical note presents numerical results to predict the corrosion initiation time of reinforced concrete bridge decks using measured surface chloride accumulation. Based on actual core measurements, the surface chloride, which is mainly derived from the deicing salts used during winter maintenance operations, is assumed to increase linearly over a period of time and then remains constant afterward. The chloride ions penetrate the concrete by diffusion and corrosion is initiated when the concentration of the ions around the reinforcement steel reaches a critical value needed to break the passive film surrounding the steel. The corrosion initiation time is computed for different values of the diffusion coefficient and the concrete cover. Such results are useful for scheduling bridge deck maintenance and rehabilitation programs.     

Analysis of Life-Cycle Maintenance Strategies for Concrete Bridge Decks

This paper presents the development of a project-level decision support tool for ranking maintenance scenarios for concrete bridge decks deteriorated as a result of chloride-induced corrosion. The approach is based on a mechanistic deterioration model and a probabilistic life-cycle cost analysis. The analysis includes agency and user costs of alternative maintenance scenarios and considers uncertainties in the agency cost and the corrosion rate in the deterioration model. The tool presented in this paper can be used to find the optimal condition index of a given bridge deck that minimizes life-cycle cost. Based on the results obtained on three existing bridge decks, it is shown that the total life-cycle cost (user cost plus agency cost) is a nonlinear function of the maximum tolerable condition of the deck, Sm, and that for a practical range of Sm, the relationship between total life-cycle cost and Sm is convex.     

Corrosion Response of a Decommissioned Deteriorated Bridge Deck

This paper summarizes the results of field tests on the decommissioned Montreal Dickson Bridge, undertaken over a grid of 0.25 by 0.25?m on four randomly selected 5 by 6?m deck patches, and the associated laboratory tests as part of a detailed research program aimed at determining why the bridge deteriorated so rapidly. The basic cause of deterioration was determined to be the lack of quality control (concrete mix composition, placing, compaction, and curing) and the resulting higher permeability of the concrete cover and the associated chloride ion ingress. As a consequence, the resistivity of the concrete was low and reflected in a high steel bar mass loss due to corrosion at several locations on the bridge after a period of only 35 years.     

Fatigue and Strength Performance of Concrete-Filled Steel-Grid Bridge Deck

The present paper reports on the results from a series of full-scale experimental tests carried out on concrete-filled steel-grid bridge deck assemblies. The testing focused on assessing the fatigue performance and ultimate strength response of a full-depth-overfilled concrete-filled steel-grid deck configuration. The results from the experimental testing program described herein are compared with the predicted deck responses as per the current AASHTO provisions contained in the LRFD and 16th edition specifications.     

Connection of Concrete Railing Post and Bridge Deck with Internal FRP Reinforcement

The use of fiber-reinforced polymer (FRP) reinforcement is a practical alternative to conventional steel bars in concrete bridge decks, safety appurtenances, and connections thereof, as it eliminates corrosion of the steel reinforcement. Due to their tailorability and light weight, FRP materials also lend themselves to the development of prefabricated systems that improve constructability and speed of installation. These advantages have been demonstrated in the construction of an off-system bridge, where prefabricated cages of glass FRP bars were used for the open-post railings. This paper presents the results of full-scale static tests on two candidate post–deck connections to assess compliance with strength criteria at the component (connection) level, as mandated by the AASHTO Standard Specifications, which were used to design the bridge. Strength and stiffness until failure are shown to be accurately predictable. Structural adequacy was then studied at the system (post-and-beam) level by numerically modeling the nonlinear response of the railing under equivalent static transverse load, pursuant to well-established structural analysis principles of FRP RC, and consistent with the AASHTO LRFD Bridge Design Specifications. As moment redistribution cannot be accounted for in the analysis and design of indeterminate FRP RC structures, a methodology that imposes equilibrium and compatibility conditions was implemented in lieu of yield line analysis. Transverse strength and failure modes are determined and discussed on the basis of specification mandated requirements.     

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.     

Fatigue Life Evaluation of Concrete Bridge Deck Slabs Reinforced with Glass FRP Composite Bars

Since bridge deck slabs directly sustain repeated moving wheel loads, they are one of the most bridge elements susceptible to fatigue failure. Recently, glass fiber-reinforced polymer (FRP) composites have been widely used as internal reinforcement for concrete bridge deck slabs as they are less expensive compared to the other kinds of FRPs (carbon and aramid). However, there is still a lack of information on the performance of FRP–reinforced concrete elements subjected to cyclic fatigue loading. This research is designed to investigate the fatigue behavior and fatigue life of concrete bridge deck slabs reinforced with glass FRP bars. A total of five full-scale deck slabs were constructed and tested under concentrated cyclic loading until failure. Different reinforcement types (steel and glass FRP), ratios, and configurations were used. Different schemes of cyclic loading (accelerated variable amplitude fatigue loading) were applied. Results are presented in terms of deflections, strains in concrete and FRP bars, and crack widths at different levels of cyclic loading. The results showed the superior fatigue performance and longer fatigue life of concrete bridge deck slabs reinforced with glass FRP composite bars.     

Influence of Reinforcement on the Behavior of Concrete Bridge Deck Slabs Reinforced with FRP Bars

This paper presents the results of an experimental study to investigate the role of each layer of reinforcement on the behavior of concrete bridge deck slabs reinforced with fiber-reinforced polymer (FRP) bars. Four full-scale concrete deck slabs of 3,000?mm length by 2,500?mm width and 200?mm depth were constructed and tested in the laboratory. One deck slab was reinforced with top and bottom mats of glass FRP bars. Two deck slabs had only a bottom reinforcement mat with different reinforcement ratios in the longitudinal direction, while the remaining deck slab was constructed with plain concrete without any reinforcement. The deck slabs were supported on two steel girders spaced at 2,000?mm center to center and were tested to failure under a central concentrated load. The three reinforced concrete slabs had very similar behavior and failed in punching shear mode at relatively high load levels, whereas the unreinforced slab behaved differently and failed at a very low load level. The experimental punching capacities of the reinforced slabs were compared to the theoretical predictions provided by ACI 318-05, ACI 440.1R-06, and a model proposed by the writers. The tests on the four deck slabs showed that the bottom transverse reinforcement layer has the major influence on the behavior and capacity of the tested slabs. In addition, the ACI 318-05 design method slightly overestimated the punching shear strength of the tested slabs. The ACI 440.1R-06 design method yielded very conservative predictions whereas the proposed method provided reasonable yet conservative predictions.     

Bridge Deck Patching Material Evaluation

Deck patching is a common practice used when bridge decks have local deterioration but do not yet warrant full replacement. Rapid setting patch materials provide a quick and economical way to patch deteriorated areas without significant lane closure time. While these materials set quickly and often achieve high early strength, their long-term performance in corrosive environments and under heavy traffic loads is sometimes poor. In addition, little guidance is provided in terms of standardized testing for these materials that addresses the key properties needed for long-term service life. This paper details a testing program that evaluates a number of deck patch materials and the development of a testing protocol for material evaluation.     

Penetrating Sealants for Concrete Bridge Decks—Selection Procedure

The major parameter controlling the effectiveness of penetrating sealants as a means of protecting concrete bridge deck surface is the depth of penetration. The factors affecting the depth of sealant penetration are identified both through a fundamental approach and with reference to the literature on penetrating sealants, concrete deterioration, durability, and permeability. Penetration properties and the use of silane and siloxane as concrete surface sealers are discussed. The effects of surface cleaning methods and the drying period are discussed. Penetrating sealants are effective if proper surface cleaning and application procedures are employed. However, moisture state within the first 6-mm depth controls the depth of sealant penetration. Thus, the factors that affect the drying period before sealant application are identified. Penetrating sealants selection procedure incorporating available test methods is outlined based on the knowledge gained through the fundamental studies of flow phenomenon and literature.     

Nondestructive Assessment of Damage in Concrete Bridge Decks

Impact-echo tests were performed on a precast, reinforced concrete bridge slab that was removed from a maintenance bridge built in 1953 in South Carolina. Impact-echo tests were first performed to nondestructively assess the initial condition and the distribution of damage throughout the slab by analyzing the variation in propagation wave velocity. It was found that the velocity varied by as much as 900?m/s throughout the slab. After the in-service condition was assessed, the slab was subjected to a full-scale static load test in the laboratory and impact-echo tests were again performed, this time to evaluate the initiation and progression of damage (stiffness loss and crack development) within the slab. After structural failure of the slab, a reduction in propagation wave velocity up to 6% was observed correlating to a reduction in slab stiffness. Cracks were detected within the concrete slab that were not visible from the surface. Areas with preexisting damage experienced more crack growth when subjected to the load test than those that were initially intact. Locations exhibiting stiffness loss, crack propagation, and localized damage can be differentiated such that the method can be used to make decisions between rehabilitating and replacing concrete bridge decks depending upon the severity of damage.     

Detection of Common Defects in Concrete Bridge Decks Using Nondestructive Evaluation Techniques

The transportation infrastructure in the United States is deteriorating and will require significant improvements. Consequently, innovations in the area of transportation infrastructure maintenance and rehabilitation are keys to the health and wellness of this valuable national asset. A major component of maintenance and rehabilitation is the ability to accurately assess the condition of the transportation infrastructure. This can be accomplished in part by using nondestructive evaluation techniques. Several nondestructive techniques have been used on concrete bridge decks and have proven to be efficient and effective. This paper aims at studying the different nondestructive evaluation techniques used in the assessment of concrete bridge deck conditions. An experimental investigation to evaluate the ability of infrared thermography, impact echo, and ground penetrating radar to detect common flaws in concrete bridge decks is developed and discussed. Results from this study showed the ability of these methods to detect defects with varying precision. Capabilities of the methods were verified and comparisons among the methods were made.     

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.     

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   

Behavior of Field Splice Details in Precast Concrete-Filled Steel Grid Bridge Deck

Redecking operations executed on urban bridges that experience large traffic volumes frequently require carefully orchestrated construction sequences carried out during times of nonpeak traffic. In such a construction environment, only bridge deck options that exhibit a high degree of modularity in conjunction with ease of installation are considered as viable options for a given redecking operation. As a further requirement, the deck installation must also be expected to perform essentially trouble free, with minimal maintenance, for very long periods of time in extremely harsh environments. The present research investigates the behavior of two new deck splice details for use in bridge applications involving precast concrete-filled steel grid deck panels. The research is primarily experimental in nature and is carried out using full-scale deck panel specimens. However, in an effort to better understand the experimental results, 3D finite-element models of the deck specimens are also constructed and studied. This paper summarizes the results from this experimental and analytical program of study.     

Performance Evaluation of FRP Bridge Deck Component under Torsion

Torsional response of fiber-reinforced polymeric (FRP) composites is more complex than conventional materials. Therefore, understanding torsional response of FRP components along with shear behavior leads to development of safe and accurate design specifications. Experimental data of multicellular FRP bridge deck components have been compared with simplified theoretical model studies focused on torsional rigidity, equivalent in-plane shear modulus, in-plane shear strain, and joint efficiency. Simplified classical lamination theory (SCLT) is used to predict torsional rigidity. Results from SCLT, experimental data, and finite-element analysis validate proposed methodology to find torsional rigidity. Data on torsional rigidity and equivalent in-plane shear modulus correlated (less than 12%) with results from SCLT and finite-element analysis. In-plane shear strain based on SCLT is also concordant with test results. In an FRP deck system with 100% joint efficiency, the two-dimensional effect (plate action) on torsional rigidity results in a 20% higher rigidity when compared to a beam model. However, if a refined model has only 80% joint efficiency, then plate action results in a 6% difference from the beam model. In addition, service load design criteria for FRP decks under shear must not excess 16% of the ultimate strain by accounting for environmental and aging effects.     

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%.     

Finite-Element Modeling of Bridge Deck Connection Details

Many steel bridges built prior to 1960 have bridge deck connections that are subject to high cycle fatigue. These connections may be nearing their fatigue limit and will require increased inspection and repair over the next 10–20 years. The Winchester Bridge on Interstate 5 in Roseburg, Ore., required the extensive replacement of connection details because of fatigue crack growth. This report describes the results of a study to assess the loading conditions for the connection details on the Winchester Bridge. Finite-element modeling methods were used to characterize the structure, on both a global and local level. The global model provided the boundary conditions for the local model of the connection details. The local model included the effects of rivet preload and friction. Finite-element analysis results were validated by hand calculation. The analysis showed significant variation in connection detail stress range, depending on the detail’s longitudinal and lateral location.     

Performance of Coated Reinforcing Bars in Cracked Bridge Decks

The presence of cracks in bridge decks that are reinforced with epoxy-coated reinforcing (ECR) bars has raised some concerns among bridge and maintenance engineers in the state of Iowa. To study the effects of deck cracking on the performance of ECR bars, several concrete cores that contained reinforcing bars were collected from 80 bridges that are located in different counties throughout the state of Iowa. These samples were collected from cracked and uncracked areas of the bridge decks. Concrete powder samples were collected from these cores and were analyzed in the laboratory to determine the diffusion of the chloride in the bridge decks. This study revealed that no sign of corrosion was detected for the ECR rebars that were taken at the uncracked bridge deck locations. In addition, no delamination or spalling was observed for the bridge decks where bars in the core samples, which were taken at the cracked bridge deck locations, exhibited signs of corrosion. The collected ECR rebars samples were rated according to the degree of the corrosion that was observed on each bar. These ratings were used to develop condition/age relationships that were utilized to estimate the functional service life of bridge decks that are reinforced with ECR bars.     

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.