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.     

Artificial Neural Network Model of Bridge Deterioration

Accurate prediction of bridge condition is essential for the planning of maintenance, repair, and rehabilitation. An examination of the assumptions (for example, maintenance independency) of the existing Markovian model reveals possible limitations in its ability to adequately model the procession of deterioration for these purposes. This study uses statistical analysis to identify significant factors influencing the deterioration and develops an application model for estimating the future condition of bridges. Based on data derived from historical maintenance and inspection of concrete decks in Wisconsin, this study identifies 11 significant factors and develops an artificial neural network (ANN) model to predict associated deterioration. An analysis of the application of ANN finds that it performs well when modeling deck deterioration in terms of pattern classification. The developed model has the capacity to accurately predict the condition of bridge decks and therefore provide pertinent information for maintenance planning and decision making at both the project level and the network level.     

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.     

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.     

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.     

Life-Cycle Cost Analysis using Deterministic and Stochastic Methods: Conflicting Results

Life-cycle cost analysis is an essential approach to differentiating alternative rehabilitation strategies for steel bridge paint systems. An economic analysis (EA), which is a deterministic method, and the Markov decision process (MDP), which is a stochastic method, were used to carry out the life-cycle cost analysis. These analyses were applied to data from two state Departments of Transportation. The deterioration curves for steel bridge paint condition rating against age were constructed. Different rehabilitation scenarios were proposed for steel bridge paint. The EA and the MDP were used to analyze and differentiate among the proposed rehabilitation scenarios. The results of the EA were different from those of MDP for the two data sets. MDP favored the “do nothing” scenario until the end of paint life and then a complete repainting. EA indicated that the scenario “do spot repairs at state 3 of the paint life” and repeat that until the end of the bridge life was superior. The results were analyzed to determine the reason for the conflict.     

Small-Format Aerial Photography for Highway-Bridge Monitoring

Small-format aerial photography (SFAP) is a low-cost solution for bridge-surface imaging and is proposed as a remote bridge-inspection technique to supplement current bridge visual inspection. Providing top-down views, photos taken from airplanes flying at 305?m (1,000?ft) allow for the visualization of subinch (i.e., large) cracks and joint openings on bridge decks or highway pavements. An onboard global positioning system can help geo-reference images collected and allow automated damage detection. However, the site lighting, surrounding tree shades, and highway surface reflectivity may affect the quality of the images. Several examples of bridge evaluation using SFAP are presented to demonstrate the capability of remote sensing as an effective tool for bridge-construction monitoring and condition assessment. A deck condition rating technique for large crack detection is proposed to quantify the condition of the existing bridge decks.     

Performance Evaluation of Deteriorating Highway Bridges Located in High Seismic Areas

This paper studies the life-cycle performance and cost of reinforced concrete highway bridges subjected to earthquake ground motions while they are continuously exposed to the attack of chloride ions. The penetration of chloride ions into the concrete is simulated through a finite difference approach that takes into account all the parameters that can affect the corrosion process. From simulation results, the corrosion initiation time is predicted, and the extent of structural degradation is calculated over the entire life of the bridge. A group of detailed bridge models with various structural attributes are developed to evaluate the changes in the structural capacity and seismic response of corroded bridges. For the purpose of the probabilistic seismic risk assessment of bridges, the seismic fragility curves are generated and updated at regular time intervals. The time-dependent fragility parameters are employed to investigate the life-cycle cost of bridges by introducing a performance index that combines the effects of probable seismic events and chloride-induced corrosion. The proposed approach provides a multihazard framework that leads to more realistic performance and cost estimates.     

Identification of Environmental Categories for Markovian Deterioration Models of Bridge Decks

In general, state-of-the-art bridge management systems have adopted Markov-chain models to predict the future condition of bridge elements and networks in different environments when various maintenance actions are implemented. However, the categories used to describe the various possible environments for a bridge element are neither accurately defined nor explicitly linked to the external factors affecting the element deterioration. In this paper, a new approach is proposed to provide transportation agencies with an effective decision support tool to identify the categories that best define the environmental and operational conditions specific to their bridge structures. This approach is based on genetic algorithms to determine the combinations of deterioration parameters that best fit each environmental category. The proposed approach is applied to develop Markovian deterioration models for concrete bridge decks using actual data obtained from the Ministére des Transports du Québec. This application illustrates the ability of the proposed approach to correlate the definition of environmental categories to parameters, such as highway class, region, average daily traffic, and percentage of truck traffic, in an accurate and efficient manner.     

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.     

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.     

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.     

Influence of Deck Material on Response of Cable-Stayed Bridges to Live Loads

During the last three decades, cable-stayed bridges have proven to be first-class structures providing vital transport links. Together with the construction process, erection procedure, and site conditions, the choice of material for the deck is a principal factor in the overall cost of construction. The effects of variable long-span bridge loads on the design of steel, composite, and concrete decks are investigated. Recent American and British long-span bridge loads have been used that are based on direct observations of modern traffic conditions. The three-dimensional finite-element models prepared for the study are based on the geometric and material properties of the Quincy Bayview cable-stayed bridge. Many cable arrangements are considered for the studied concrete, composite, and steel decks. A nonlinear analysis of the cable-stayed bridge models is carried out. The results of the different deck materials are compared. It is shown that the choice of material for the deck can be greatly affected by the distribution of stays and by the intensity of the live load adopted.     

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.     

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.     

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.     

Prediction of Remaining Service Life of Bridge Decks Using Machine Learning

This paper demonstrates that it is feasible to use either the k-nearest-neighbor instance-based learning (IBL) technique or the inductive learning (IL) technique for engineering applications in classification and prediction problems such as estimating the remaining service life of bridge decks. It is shown that IBL is more efficient than IL: The best achieved percentages of correctly classified instances are 50% as generated by k-nearest-neighbor IBL and 41.8% when generated by the C4.5/IL learning algorithm. From a machine learning (ML) standpoint both these values are considered low, but this is attributed to the fact that the deterioration model used to compute the remaining service life turned out to be inadequate. It is based on a methodology developed under the Strategic Highway Research Program (SHRP) for life-cost analysis of concrete bridges relative to reinforcement corrosion. Actual bridge deck surveys were obtained from the Kansas Department of Transportation that include the type of attributes needed for the SHRP methodology. The experimentation with the ML algorithms reported here also describes the experience one may go through when faced with an imperfect model, or with incomplete data or missing attributes.     

Dynamic Response of Three Fiber Reinforced Polymer Composite Bridges

Fiber reinforced polymer (FRP) composite bridge decks are gaining the attention of bridge owners because of their light self-weight, corrosion resistance, and ease of installation. Constructed Facilities Center at West Virginia University working with the Federal Highway Administration and West Virginia Department of Transportation has developed three different FRP decking systems and installed several FRP deck bridges in West Virginia. These FRP bridge decks are lighter in weight than comparable concrete systems and therefore their dynamic performance is equally as important as their static performance. In the current study dynamic tests were performed on three FRP deck bridges, namely, Katy Truss Bridge, Market Street Bridge, and Laurel Lick Bridge, in the state of West Virginia. The dynamic response parameters evaluated for the three bridges include dynamic load allowance (DLA) factors, natural frequencies, damping ratios, and deck accelerations caused by moving test trucks. It was found that the DLA factors for Katy Truss and Market Street bridges are within the AASHTO 1998 LRFD specifications, but the deck accelerations were found to be high for both these bridges. DLA factors for Laurel Lick bridge were found to be as high as 93% against the typical design value of 33%; however absolute deck stress induced by vehicle loads is less than 10% of the deck ultimate stress.     

Life-Cycle Costs of Commercial Roof Systems

The roofing industry in the United States generates annual revenues in excess of $23 billion. This represents a significant annual investment in infrastructure maintenance cost and the opportunity cost of these resources can significantly detract from an owner’s ability to invest in other areas. In addition, a failed or failing roof system represents a heightened opportunity for failure in the building envelope and inherently increases the risk of additional costs. Present roof asset management practice typically bases replacement decisions on fixed intervals, inspection results, maintenance issues, and, occasionally, failure risk. This paper develops a model for evaluating occupant costs and considering their impact in the roof management decision process through a total life-cycle cost (LCC) model that includes user/occupant cost model and correlates minimum total cost with improved intervention points in the asset deterioration cycle. The model is estimated from and applied to the extensive roof systems at Carnegie Mellon University in Pittsburgh, Pa. For these roofs, we find that the least cost roof service lives are roughly 30 years, but there can be considerable variation around this average for individual roofs.