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Codes, Guidelines and Standards

Recommended LRFD Guidelines for the Seismic Design of Highway Bridges

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Part I: Specifications and Part II: Commentary and Appendices (MCEER/ATC 49) are based on significant enhancements in the state of knowledge and state of practice resulting from research investigations and lessons learned from earthquakes over the last 15 years. The Recommended Guidelines consist of specifications, commentary, and appendices developed to be compatible with the existing load-and-resistance-factor design (LRFD) provisions for highway bridges published by the American Association of State Highway and Transportation Officials (AASHTO). The new, updated, provisions are nationally applicable and cover all seismic zones, as well as all bridge construction types and materials. They reflect the latest design philosophies and approaches that will result in highway bridges with a high level of seismic performance.

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Liquefaction Study Report (MCEER/ATC-49-1) presents the results of a study of the effects of liquefaction and associated hazards, lateral spreading and flow. The study investigated liquefaction hazard implications for the design of bridges from the perspective of real sites and real structures. The study scope was limited to two sites in relatively high seismic locations, one in Washington State and the other in Missouri. Actual site profile data and bridge configurations were used. The results for the 475-year and 2,475-year events were compared to assess the implications of using the larger event for design. Additionally, the conduct of the study helped synthesize an overall approach for handling liquefaction-induced movements in the recommended design provisions. The report includes a CD-ROM containing detailed information for each study site.

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The Design Examples illustrate use of the recommended LRFD guidelines. The two examples are the eighth and ninth in a series originally developed for FHWA to illustrate the use of the AASHTO Division 1-A Standard Specifications for Highway Bridges. The eighth design example was performed on a five-span continuous cast-in-place concrete box girder bridge and the ninth design example was performed on a three-span continuous steel girder bridge. Each example emphasizes different features that must be considered in the seismic analysis and design process.

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The New York City Seismic Code

The New York City Seismic Code: Local Law 17/95 was adopted on February 21, 1995, in order to help seismically moderate New York City be more resilient should an earthquake occur. Moderate earthquakes take place approximately once every hundred years in the city, and a stronger earthquake cannot be ruled out.