Click for next page ( 5


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 4
4 the case of the anchorage zones, nearly impossible. Those who are tasked with the inspection and maintenance of stay cables face challenges for which proven and accepted methodologies and tools are limited and often very costly. For example, the internal deterioration and failure of an Argentine stay cable in 1996 was not detected beforehand by visual means. This synthesis report will present the latest information available on inspection and maintenance of stay cables, ex- plains various tools and methods available, and examines their track record or future potential in addressing stay cable eval- uations. To better understand the applicability and complexi- ties of various methods and approaches, a brief overview of FIGURE 2 Sitka Harbor Bridge in Alaska, the oldest cable- different stay cable designs and materials is also presented. stayed bridge in the United States (Frank and Breen 2004). OBJECTIVES AND SCOPE The objective of this synthesis is to identify and explain effec- The pace of construction of new cable-stayed bridges in tive and promising inspection and maintenance techniques the United States grew rapidly in the 1990s and early 2000s. for stay cables in cable-stayed bridges. Both short- and long- Today, cable-stayed bridges have entirely replaced truss term approaches are discussed. This synthesis is based on the bridges on new medium- to long-span crossings. For exam- following: ple, all new crossings of the Mississippi River in the last 15 to 20 years have been with cable-stayed bridges, whereas A comprehensive review of domestic and inter- these spans were exclusively truss bridges before that time. national literature to identify various techniques and The essential factor is the cost-effectiveness of the system, their track records, as well as documented problems and aided by its elegance. case studies; The total number of cable-stayed bridges in the United Formal and informal surveys of state and provincial de- States recently surpassed 35, with several other bridges in partments of transportation (DOTs) in the United States planning or under construction. These include bridges in the and Canada, cable suppliers, testing companies, bridge planning stages in New York City, St. Louis, and one spanning designers, researchers, and contractors to determine the the Mississippi River between Mississippi and Arkansas. The current state of practice and identify future trends in con- St. Louis bridge, if implemented, would have a main span of dition assessments and repair and retrofit of stay cables. 610 m (2,000 ft), and will be the longest cable-stayed span in These surveys were conducted by means of a question- the Western Hemisphere (Brown 2001b). The world record for naire and through meetings, telephone conversations, cable size will belong to the Maumee River Bridge in Toledo, and e-mail exchanges with knowledgeable individuals; Ohio, scheduled for completion in late 2006 (DSI 2004). This Examination of test reports and condition assessment bridge incorporates stays with 156 seven-wire strands 15.2 mm results from major inspections and cable-stayed bridges; (0.6 in.) in diameter and cable diameters of up to 508 mm Review of a limited number of maintenance and inspec- (20 in.) (Marsh 2003). The longest span cable-stayed bridge tion manuals for cable-stayed bridges; and in the world is the Tatara Bridge in Ehime, Japan, with a main A patent search using the U.S. Patent and Trademark span of 890 m (2,920 ft). However, the Stonecutters Bridge Office database. in Hong Kong will surpass Tatara with a span of 1018 m (3,339 ft) when it is completed in 2008 (Brown 2001a). This synthesis includes the following types of information: The Millau Bridge in France (Viaduc de Millau) is the Methods for inspections and assessments including NDT world's tallest bridge and spans France's Tarn River Valley. methods, It consists of multiple cable-stayed spans with span lengths Repair methods, of approximately 340 m and a total length of approximately Methods for control of cable vibrations including rain 2.5 km. The deck is approximately 270 m above the valley wind vibrations, and the pylons reach 343 m above the ground. Control of moisture from internal or external sources, Fatigue in stay cables, The challenges in inspection and maintenance of cable- Case studies of stay cable failures, stayed bridges are enormous. The main tension elements Repair and retrofit issues and details, (MTEs) within a cable bundle are, in most cases, hidden from Effectiveness and costs of various inspection and repair the view of inspectors. Access to cables for visual inspections methods, or nondestructive testing (NDT) is generally difficult, and in Limitations of available technologies,