Review of Inspection, Evaluation and Maintenance of Suspension Bridges, and Inspection, Evaluation and Maintenance of Suspension Bridges: Case Studies edited by Sreenivas Alampalli and William J. Moreau

The book, consisting of two volumes, is an excellent resource for anyone who is interested in the technical and operational aspects of suspension bridges; it was published by CRC Press in November 2015. The first volume consists of 12 chapters. Each of these chapters is written by those responsible for the maintenance and operation of many of the world’s most well-known suspension bridges and is intended to address one major aspect of the design, inspection, evaluation, and maintenance of suspension bridges. Chapter 1 of the book provides an excellent overview of suspension bridges, including forms and components of suspension bridges, analysis methods, variations in forms of suspension bridges, and lessons learned from failures of suspension bridges. This chapter discusses pioneering achievements in suspension bridges, and critically examines how limited structural theory and material limitations affected early bridge designs and prompted experimentation, theorization, and discovery. Chapter 2 focuses on the design and construction of suspension bridges, including various structural components that make up the suspension bridge, types of suspension bridges, general design philosophy and procedures, and construction sequence. Inspection results play a major role in determining the appropriate short- and long-term cost-effective bridge management actions, including periodic and corrective maintenance actions, the rehabilitation of various bridge components, and eventually, the replacement of the major components or the entire structure. Chapter 3 provides an in-depth discussion of the visual inspection aspects of suspension bridges. Of particular significance is the author’s perspective based on experience in the inspection and maintenance of suspension bridges in the New York State region. Chapter 4 discusses the construction processes involved in forming suspension cables, the deterioration of cable strands, the methods of evaluation of cable strength and service life, and the methods of prevention of cable corrosion. This chapter provides discussion on these aspects through case histories and actual examples of suspension bridges and presents pros and cons of two evaluation tools, presented from a bridge owner’s perspective. While deterioration because of corrosion is discussed in Chapter 4, Chapter 5 focuses extensively and exclusively on the corrosion of strands in the main cable, including corrosion-mitigation strategies. Quite uniquely, the chapter provides best-practice guidance on inspecting for signs of corrosion, which primarily and frequently are because of moisture entering the cable, and mitigation strategies based on years of suspension bridge maintenance experience by bridge owners.

Chapters 6–11 focus on maintenance aspects of suspension bridges. Maintenance of suspension bridge cables and suspender ropes is critical for ensuring the safety and long life of these bridges. In Chapter 6, the authors comprehensively discuss the maintenance of these components, including fabrication considerations, routine and detailed inspections, the monitoring of suspension cables, and strategies for the preservation of these bridges. The discussion of these important issues is enriched with the experiences of the authors and numerous illustrations of maintenance issues. Main-cable preservation through dehumidification is the new direction for cable protection within the industry. Extensive research has shown that a cable dehumidification system to eliminate internal water and humidity from suspension cables by sending dry air inside is effective in preventing the corrosion of suspension cables. This system is being used in more than 13 suspension bridges around the world. Chapter 7 focuses extensively on the development, installation, and performance of cable dehumidification systems based on a number of case studies of such systems in Japan. Cable bands are another critical component in suspension bridges to transfer loads from suspenders to the main cable. Cable bands and their bolts are friction-critical connections requiring spot checking of cable-band bolt tension on a 5- to 10-year cycle and a more extensive retightening effort every 20–25 years, or after any intrusive main-cable inspection. Chapter 8 extensively discusses the inspection, maintenance, and state of the practice of cable bonds. The safety and sustainability of suspension bridges depend on the ability of structural engineers in the maintenance of cable anchorages that transfer cable loads to the bedrock. Chapter 9 discusses common problems, mitigation attempts, and their effectiveness associated with maintaining anchorage enhancements based on a survey of bridge owners. Chapter 10 presents maintenance aspects of anchorages based on the authors’ experiences and knowledge of the methods and solutions used for the George Washington Bridge, which is a major historic bridge in the United States. Suspension cables are a key component of suspension bridges and cannot be replaced easily in the case of deterioration in strength. Nevertheless, suspension cables need to be rehabilitated, replaced, or strengthened to meet the demands because of growing traffic loads and newer design/maintenance specifications. However, such actions require innovative solutions. Chapter 11 discusses the use of supplemental cables to improve the factor of safety and live load capacity during the widening of the roadway. Security risk management is an essential component of the management process of suspension bridges because of their symbolic and iconic nature, the high volumes of traffic they carry, and the tremendous life-safety and economic consequences in the event of any significant damage to suspension bridges. Generally, the risk associated with suspension cable bridges is relatively high and requires good security risk management strategies. Chapter 12 presents extensive discussion on all aspects of the security risk management process, successful strategies, and risk-based assessments, including the matrix analysis of counterterrorism enhancements, for suspension bridges.

Volume 2 of this book contains case studies on 11 suspension bridges around the world: (1) Manhattan Bridge, (2) Akashi Kaikyo Bridge, (3) Tsing Ma Bridge, (4) Storebælt East Suspension Bridge, (5) Forth Road Bridge, (6) Bronx–Whitestone Bridge, (7) George Washington Bridge, (8) Angus L. Macdonald Bridge, (9) Mid-Hudson Bridge, (10) Shantou Bay Suspension Bridge, and (11) Kingston–Port Ewen Bridge. These case studies not only provide extensive information on the design, construction, maintenance, and rehabilitation of these bridges but also show how the science and engineering of suspension bridges evolved through the years around the world.

Overall, both volumes of the book cover all aspects of suspension bridges, including history, design, inspection, maintenance, and rehabilitation, based on the unique experiences of the owners who have maintained these bridges for decades. Illustrations that convey important information to readers based on case histories of suspension bridges are plentiful, clear, and always supportive of the text. This two-volume book is truly a unique contribution and is a must-read for bridge engineers and owners involved in any aspect of suspension bridges. The authors of the individual chapters and the editors of the two volumes are congratulated for this exemplary work, which will be an invaluable asset in the training of a future generation of bridge owners and engineers.