Condition assessment and safety verification of existing bridges and decisions as to whether bridge posting is required are addressed through analysis, load testing, or a combination of methods. Bridge rating through structural analysis is by far the most common procedure for rating existing bridges. The American Association of State Highway and Transportation Officials (AASHTO) Manual for Bridge Evaluation (MBE), First Edition permits bridge capacity ratings to be determined through allowable stress rating (ASR), load factor rating (LFR) or load and resistance factor rating (LRFR); the latter method is keyed to the AASHTO LRFD Bridge Design Specifications, which is reliability-based and has been required for the design of new bridges built with federal findings since October, 2007. A survey of current bridge rating practices in the United States has revealed that these three methods may lead to different ratings and posting limits for the same bridge, a situation that carries serious implications with regard to the safety of the public and the economic well-being of communities that may be affected by bridge postings or closures. To address this issue, a research program has been conducted with the overall objective of providing recommendations for improving the process by which the condition of existing bridge structures is assessed. This research required a coordinated program of load testing and finite element analysis of selected bridges in the State of Georgia to gain perspectives on the behavior of older bridges under various load conditions. Structural system reliability assessments of these bridges were conducted and bridge fragilities were developed for purposes of comparison with component reliability benchmarks for new bridges. A reliability-based bridge rating framework was developed, along with a series of recommended improvements to the current bridge rating methods, which facilitate the incorporation of various in situ conditions of existing bridges into the bridge rating process at both component and system levels. This framework permits bridge ratings to be conducted at three levels of increasing complexity to achieve the performance objectives, expressed in the terms of reliability, that are embedded in the LRFR option of the AASHTO Manual of Bridge Evaluation. This research was sponsored by the Georgia Department of Transportation, and has led to a set of Recommended Guidelines for Condition Assessment and Evaluation of Existing Bridges in Georgia.

According to Transportation Association of Canada (TAC), the rough estimate of number of bridges in Canada is 80,000 with the replacement value of $35 billion. A large number of bridges will need replacement during 2005 to 2015 which will result in 50% annual increase in replacement cost. Recent alarming incidents of the Laval De la Concorde Overpass collapse (2006), Canada and the I-35W Mississippi River bridge collapse (2007), USA show the gravity of the situation. One of the main factors responsible for this situation is the present available techniques of the bridge condition monitoring and rehabilitation are not able to cope up with the drastic deterioration and ageing of the bridges. The widely employed method for bridge inspection is visual inspection, and it lacks the reliability-based assessment of bridge and its components. The instrumentation of the bridge with Structural Health Monitoring (SHM) systems and assessment of the bridge condition and behaviour based on the information obtained from SHM systems is one of the promising solutions of the present problem. The main focus of the current research is to integrate SHM data with traditional information (e.g. visual inspection), develop a reliability based structural condition index using the updated information on a structures operational performance, and assessing the value of information for SHM in regard to the overall lifecycle cost of a structure. This study develops a methodology for a reliability based assessment of the bridge components using SHM system information, and information updating by fusing SHM data with traditional information for precise evaluation of expected life cycle cost. The methods developed herein have been demonstrated through a case study based on an existing bridge namely, the Crowchild Bridge in Calgary, Alberta. A finite element model of the bridge has been developed and validated against the field data. This validated model has been used to simulate the static load test on the bridge, deterioration in the bridge and to study the bridge response under the different loading conditions. The artificial neural network (ANN) technique has been used for the diagnosis of the SHM data, and then the reliability index of the bridge deck has been calculated using the Monte Carlo Simulation technique. A method for updating the bridge deck repair strategy is introduced based on the reliability index calculation. The maintenance and rehabilitation strategy is updated based on the hypothetical results. The results of updated strategy are compared with un-updated one using the Bayesian Theorem. The expected life cycle cost is evaluated considering the capital cost, maintenance and rehabilitation cost, user cost, and failure cost. Capital cost is treated as deterministic while maintenance and rehabilitation cost, and user cost are considered probabilistic. Each individual cost and then total cost is calculated per m 2 . The value of information is also discussed.

With the development in global economic and transportation engineering, the traffic loads on brides have been growing steadily, which become potential safety hazards for existing bridges. In particular, long-span suspension bridges support heavy traffic volumes and simultaneous truck loads on the bridge deck, and thus the safety and serviceability of the bridge deserves investigation. In this book, a multiscale reliability method is presented for the safety assessment of long-span bridges. The multiscale failure condition of stiffness girders is the first-passage criteria for the large-scale model and the fatigue damage criteria for the small-scale model. It is the objective of this book to provide a more in-depth understanding of the vehicle-bridge interaction from the random vibration perspective. This book is suitable for adoption as a text book or a reference book in an advanced structural reliability analysis course. Furthermore, this book also provides a theoretical foundation for better understanding of the safety assessment, operation management, maintenance and reinforcement for long-span bridges and motivates further research and development for more advanced reliability and serviceability assessment techniques for long-span bridges.

This book provides structural reliability and design students with fundamental knowledge in structural reliability, as well as an overview of the latest developments in the field of reliability engineering. It addresses the mathematical formulation of analytical tools for structural reliability assessment. This book offers an accessible introduction to structural reliability assessment and a solid foundation for problem-solving. It introduces the topic and background, before dealing with probability models for random variables. It then explores simulation techniques for single random variables, random vectors consisting of different variables, and stochastic processes. The book addresses analytical approaches for structural reliability assessment, including the reliability models for a single structure and those for multiple structures, as well as discussing the approaches for structural time-dependent reliability assessment in the presence of discrete and continuous load processes. This book delivers a timely and pedagogical textbook, including over 170 worked-through examples, detailed solutions, and analytical tools, making it of interest to a wide range of graduate students, researchers, and practitioners in the field of reliability engineering.

Bridge design and construction technologies have experienced remarkable developments in recent decades, and numerous long-span bridges have been built or are under construction all over the world. Cable-supported bridges, including cable-stayed bridges and suspension bridges, are the main type of these long-span bridges, and are widely used in highways crossing gorges, rivers, and gulfs, due to their superior structural mechanical properties and beautiful appearance. However, cable-supported bridges suffer from harsh environmental effects and complex loading conditions, such as heavier traffic loads, strong winds, corrosion effects, and other natural disasters. Therefore, the lifetime safety evaluation of these long-span bridges considering the rigorous service environments is an essential task. Features: Presents a comprehensive explanation of system reliability evaluation for all aspects of cable-supported bridges. Includes a comprehensive presentation of the application of system reliability theory in bridge design, safety control, and operational management. Addresses fatigue reliability, dynamic reliability and seismic reliability assessment of bridges. Presents a complete investigation and case study in each chapter, allowing readers to understand the applicability for real-world scenarios. Reliability and Safety of Cable-Supported Bridges provides a comprehensive application and guidelines for system reliability techniques in cable-supported bridges. Serving as a practical educational resource for both undergraduate and graduate level students, practicing engineers, and researchers, it also intends to provide an intuitive appreciation for probability theory, statistical methods, and reliability analysis methods.

A majority of US highway bridges were constructed in the mid-20th century. Today, bridge owners have to consider increases in traffic demands and also face concerns related to sustainability, resilience and livability which were virtually unknown in the 1950s. In this context, transportation stakeholders face increasingly complex decisions for repair, retrofit or renewal of their assets. Legislature demands data-driven decisions based on quantitative and reliable bridge condition and performance evaluation. Different technology tools that can provide objective condition evaluations have become available but given the inertia in the practice of bridge engineering and a lack of understanding the challenges to their reliable applications, their use remain limited. Consequently, management decisions are still primarily made without leveraging objective measurement data and without a mechanistic understanding of bridge behavior and performance. To explore the current state-of-the-art in performance and condition evaluation of constructed systems by leveraging technology, a 30-year old highway bridge in New Jersey, exhibiting multiple complex performance deficiencies, was transformed into a field laboratory. To identify the root causes of performance concerns, Visual Inspection, Operational Monitoring, Forced Excitation Testing, Controlled Load Testing, Non-destructive Probes, Long-term Monitoring and Finite Element Modeling and Parameter Identification were conducted within a Structural Identification framework. The results showed that root causes of some performance deficiencies of the test bridge could be identified only through the application of field measurements and analyses integrated by following a scientific approach - such as Structural Identification, especially for deficiencies related to unexpected dynamic amplifications and the long-term effects of vibrations. Controlled Load Testing was especially useful in demonstrating the location and impacts of damage although such an approach can only be considered for the most critical cases due to its high cost and disruption to operations. Operational monitoring was shown as a sufficient and cheaper alternative for structural identification permitting the development of a lesser resolution digital twin of the bridge, which was critical in identifying the root causes of its deficiencies and formulating meaningful interventions.