Codes, Guidelines and Standards
Recommended LRFD Guidelines for the Seismic Design of Highway Bridges
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.
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.
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.
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.
