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Author: Nabil F. Grace Publisher: ISBN: Category : Concrete beams Languages : en Pages : 229
Book Description
This study developed a procedure to identify concrete bridge decks that are exhibiting the characteristics associated with falling concrete. Field exploratory work on reinforced concrete bridge decks was supported by analytical and laboratory investigations. The field work included visual inspection, non-destructive tests, and sampling of full-depth cores and powder samples from the bottom of the bridge deck. Chief variables assessed were the chance of corrosion by the half-cell potential, chloride content at the location of the bottom reinforcement, and the concrete pH level. The chloride diffusivity was estimated from the chloride profile. The laboratory investigation was performed on bridge deck beams. The beams were constructed from concrete containing chloride levels known to cause corrosion as well as from a control concrete. Beams were subjected to freeze-thaw or saltwater followed by repeated loading to simulate field conditions. The following characteristics were quantified: chance of corrosion, corrosion rate, chloride content, flexural response as a function of environmental exposure and repeated loads, and ultimate strength. The size of the porous zone around the reinforcement was determined using an environmental scanning electron microscope. Finally, a strategy was developed to assess if a bridge deck exhibited the characteristics associated with falling concrete. The strategy included visual inspection of cracking and spalling, assessment of chance of corrosion, chloride content, and pH levels. If any of these measures exceed critical levels a service life calculation needs to be performed. Based on existing mathematical models, the time to corrosion initiation and time to corrosion cracking can be predicted. The resulting time is then compared to the age of the bridge. From this information proper planning for future repair needs can be made.
Author: Nabil F. Grace Publisher: ISBN: Category : Concrete beams Languages : en Pages : 229
Book Description
This study developed a procedure to identify concrete bridge decks that are exhibiting the characteristics associated with falling concrete. Field exploratory work on reinforced concrete bridge decks was supported by analytical and laboratory investigations. The field work included visual inspection, non-destructive tests, and sampling of full-depth cores and powder samples from the bottom of the bridge deck. Chief variables assessed were the chance of corrosion by the half-cell potential, chloride content at the location of the bottom reinforcement, and the concrete pH level. The chloride diffusivity was estimated from the chloride profile. The laboratory investigation was performed on bridge deck beams. The beams were constructed from concrete containing chloride levels known to cause corrosion as well as from a control concrete. Beams were subjected to freeze-thaw or saltwater followed by repeated loading to simulate field conditions. The following characteristics were quantified: chance of corrosion, corrosion rate, chloride content, flexural response as a function of environmental exposure and repeated loads, and ultimate strength. The size of the porous zone around the reinforcement was determined using an environmental scanning electron microscope. Finally, a strategy was developed to assess if a bridge deck exhibited the characteristics associated with falling concrete. The strategy included visual inspection of cracking and spalling, assessment of chance of corrosion, chloride content, and pH levels. If any of these measures exceed critical levels a service life calculation needs to be performed. Based on existing mathematical models, the time to corrosion initiation and time to corrosion cracking can be predicted. The resulting time is then compared to the age of the bridge. From this information proper planning for future repair needs can be made.
Author: Charles William Protasio Publisher: ISBN: Category : Languages : en Pages : 530
Book Description
Concrete bridge deck deterioration, especially premature deterioration, is a major problem for the state transportation agencies throughout the United States. Moreover, this deck deterioration, which manifests itself in the form of cracking, scaling and spalling, accounts for a large portion of the number of the nation's structurally deficient bridges. In particular, the New England states have expressed concern over the dilemma of repair versus replacement strategies for those decks on the grey zone (deck condition code 4-6). Thus, the purpose of this thesis is to provide a preliminary investigation into the systematic approach to the repair versus replacement decision-making process for deteriorated concrete decks. For a large number of states, the existing decision-making process is characterized by a piecemeal synthesis oriented towards emphasizing the advantages of one repair or replacement alternative and underestimating its disadvantages. An actual cost-effective comparison of all possible alternatives is not routinely undertaken.
Author: Kandi Rebecca Wieberg Publisher: ISBN: Category : Concrete bridges Languages : en Pages : 292
Book Description
"This study involved the investigation of the causes of spalling observed in several partial-depth precast prestressed bridge decks in the state of Missouri. Recently it has been observed that several bridges in Missouri with this type of construction have experienced spalling of concrete at the edges of the panels revealing an extreme condition of corrosion in the prestressing tendons, some to the point of rupture. Ground penetrating radar (GPR), which has been shown to be successful in bridge deck evaluation, was used to determine the relative condition of the prestressing tendons as well as the relative condition of the concrete throughout the deck in order to identify areas of cracking and corrosion. Particular techniques were used in an attempt to identify areas of delamination at the interface between the precast panels and cast-in-place topping slab, namely the acquisition of data from both the top and bottom deck surfaces as well as specialized data interpretation techniques. Core control and visual inspection were utilized to interpret and validate the GPR data. Half-cell, resistivity and rebound hammer testing was performed on bridge deck panels to determine the corrosion levels of the prestressing strands and material properties of the panels. Findings indicate that spalling in the PPC panels is the result of the penetration of water and chlorides through the reflective cracking in the CIP topping, to the interface between the CIP topping and the PPC panels, then through the PPC panels to the prestressing tendons located near the panel joints. Increased crack control in the CIP topping delays the onset of spalling at the panel joints. Most deterioration is occurring near the area of reflective cracking in the CIP topping and not in the area of concrete over the middle of the panels. Some delamination is occurring at the CIP topping and panel interface"--Abstract, leaf iii.
Author: Yunping Xi Publisher: ISBN: Category : Bridges Languages : en Pages : 83
Book Description
Early age cracking on concrete bridge decks has been experienced by many state departments of transportation (DOTs). In Colorado the cracking problem on newly constructed bridge decks has not been completely solved. In this study, the extent and causes of the cracking problem were investigated, and necessary changes to alleviate the cracking problem were identified. To achieve these goals, current Colorado Department of Transportation (CDOT) practice was reviewed and compared with other DOTs practices for construction of bridge decks. A database analysis of field inspection results was performed.
Author: Yail J. Kim Publisher: ISBN: Category : Concrete Languages : en Pages : 73
Book Description
This report presents a case study on the evaluation of bridge decks using various non-destructive test methods. The primary interest lies in quantifying delaminated areas in deck concrete covered with asphalt overlays. Analytical and computational models are formulated to decompose the intensity of GPR scales into two categories: i) initiation and progression of corrosion and ii) delamination of deck concrete, which show good agreement with repaired areas. Parametric investigations emphasize the significance of rebar spacing and concrete cover in determining the extent of deck delamination.
Author: United States. Congress. House. Committee on Public Works and Transportation. Subcommittee on Investigations and Oversight Publisher: ISBN: Category : Transportation Languages : en Pages : 894
Book Description
Distributed to some depository libraries in microfiche.
Author: Aqeed Mohsin Chyad Publisher: ISBN: Category : Concrete bridges Languages : en Pages : 138
Book Description
Bridges are key elements in the US transportation system. There are more than six hundred thousand bridges on the highway system in the United States. Approximately one third of these bridges are in need of maintenance and will cost more than $120 billion to rehabilitate or repair. Several factors affect the performance of bridges over their life spans. Identifying these factors and accurately assessing the condition of bridges are critical in the development of an effective maintenance program. While there are several methods available for condition assessment, selecting the best technique remains a challenge. Therefore, developing an accurate and reliable model for concrete bridge deck deterioration is a key step towards improving the overall bridge condition assessment process. Consequently, the main goal of this dissertation is to develop an improved bridge deck deterioration prediction model that is based on the National Bridge Inventory (NBI) database. To achieve the goal, deterministic and stochastic approaches have been investigated to model the condition of bridge decks. While the literatures have typically proposed the Markov chain method as the best technique for the condition assessment of bridges, this dissertation reveals that some probability distribution functions, such as Lognormal and Weibull, could be better prediction models for concrete bridge decks under certain condition ratings. A new universal framework for optimizing the performance of prediction of concrete bridge deck condition was developed for this study. The framework is based on a nonlinear regression model that combines the Markov chain method with a state-specific probability distribution function. In this dissertation, it was observed that on average, bridge decks could stay much longer in their condition ratings than the typical 2-year inspection interval, suggesting that inspection schedules might be extended beyond 2 years for bridges in certain condition rating ranges. The results also showed that the best statistical model varied from one state to another and there was no universal statistical prediction model that can be developed for all states. The new framework was implemented on Michigan data and demonstrated that the prediction error in the combined model was less than each of the two models (i.e. Markov and Lognormal). The results also showed that average daily traffic, age, deck area, structure type, skew angle, and environmental factors have significant impact on the deterioration of concrete bridge decks. The contributions of the work presented in this dissertation include: 1) the identification of the significant factors that impact concrete bridge deck deterioration; 2) the development of a universal deterioration prediction framework that can be uniquely tailored for each state’s data; and 3) supporting the possibility of extending inspection schedules beyond the typical 2-year cycles. Future work may involve: 1) evaluating each of the factors that impact the deterioration rates in more depth by refining the investigation ranges; 2) investigating the possibility of revising the regular bridge deck inspection intervals beyond the 2-year cycles; and 3) developing deterioration prediction models for other bridge elements (i.e. superstructure and substructure) using the framework developed in this dissertation.
Author: Us Army Corps Of Engineers Publisher: Military Bookshop ISBN: 9781780397603 Category : Technology & Engineering Languages : en Pages : 192
Book Description
This manual provides guidance on evaluating the condition of the concrete in a structure, relating the condition of the concrete to the underlying cause or causes of that condition, selecting an appropriate repair material and method for any deficiency found, and using the selected materials and methods to repair or rehabilitate the structure. Guidance is also included on maintenance of concrete and on preparation of concrete investigation reports for repair and rehabilitation projects. Considerations for certain specialized types of rehabilitation projects are also given.
Author: John B. Vrable Publisher: Transportation Research Board National Research ISBN: Category : Technology & Engineering Languages : en Pages : 1304
Author: Nabil F. Grace
Author: Nabil F. Grace
Author: Charles William Protasio
Author: Kandi Rebecca Wieberg
Author: Robert J. Frosch
Author: Yunping Xi
Author: Yail J. Kim
Author: United States. Congress. House. Committee on Public Works and Transportation. Subcommittee on Investigations and Oversight
Author: Aqeed Mohsin Chyad
Author: Us Army Corps Of Engineers
Author: John B. Vrable