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Freedman, Jeffrey L. Barnes, David F. Barber, Raymond M. Trujillo, Jeff C. Dettloff, Timothy J. Long,Thomas P. Bowers, Terry B. Hastings, Wayne J. Farris, Gregg A. Freeby U. DOT, Joseph L. Nallapaneni, Kendal R. Allen, Thomas E. Cortez, Gregg C.
Frederick, Michael E. Raczynski N. Sauser, Christopher H. Westbrook U. Structure Excavation and Backfill 2. Removal of Existing Structures 3. Temporary Works 4. Driven Foundation Piles 5. Drilled Shafts 6. Ground Anchors 7. Earth-Retaining Systems 8. Concrete Structures 9. Reinforcing Steel Prestressing Steel Structures Steel Grid Flooring Painting Stone Masonry Concrete Block and Brick Masonry Timber Structures Preservative Treatment of Wood Bearing Devices Bridge Deck Joint Seals Railings Waterproofing Slope Protection Miscellaneous Metal Pneumatically Applied Mortar Steel and Concrete Tunnel Liners Metal Culverts Concrete Culverts Wearing Surfaces Embedment Anchors Thermoplastic Culverts Aluminum Structures Shock Transmission Units With the advent of the automobile and the establishment of highway departments in all of the American states dating back to just before the turn of the century, the design, construction, and maintenance of most U.
It was natural, therefore, that these engineers, acting collectively as the AASHTO Highways Subcommittee on Bridges and Structures, would become the author and guardian of this first bridge standard. It quickly became the de facto national standard and, as such, was adopted and used by not only the state highway departments but also other bridge-owning authorities and agencies in the United States and abroad.
The title was soon revised to Standard Specifications for Highway Bridges and new editions were released about every four years. The body of knowledge related to the design of highway bridges has grown enormously since and continues to do so.
Theory and practice have evolved greatly, reflecting advances through research in understanding the properties of materials, in improved materials, in more rational and accurate analysis of structural behavior, in the advent of computers and rapidly advancing computer technology, in the study of external events representing particular hazards to bridges such as seismic events and stream scour, and in many other areas. The pace of advances in these areas has accelerated in recent years.
The work was completed in , and, as might be expected with continuing research, the Standard Specifications were found to have discernible gaps, inconsistencies, and even some conflicts. Beyond this, the specification did not reflect or incorporate the most recently developing design philosophy, load-and-resistance factor design LRFD , a philosophy which has been gaining ground in other areas of structural engineering and in other parts of the world such as Canada and Europe.
From its inception until the early s, the sole design philosophy embedded within the Standard Specifications was one known as working stress design WSD. Beginning in the early s, WSD was adjusted to reflect the variable predictability of certain load types, such as vehicular loads and wind forces, through adjusting design factors, a design philosophy referred to as load factor design LFD. A further philosophical extension considers the variability in the properties of structural elements, in similar fashion to load variabilities.
While considered to a limited extent in LFD, the design philosophy of LRFD takes variability in the behavior of structural elements into account in an explicit manner.
LRFD relies on extensive use of statistical methods, but sets forth the results in a manner readily usable by bridge designers and analysts.
Instead, changes balloted and approved by at least two-thirds of the members of the Subcommittee will be published in the next full edition of the Specifications, to be published on a three-year cycle. Each member has one vote. The U. Department of Transportation is a non-voting member. Orders for Specifications may be placed by visiting our website, bookstore. A free copy of the current publication catalog can be downloaded from our website or requested from the Publications Sales Office.
The Subcommittee would also like to thank Mr. John M. Kulicki, Ph. Inquiries as to intent or application of the specifications should be sent to the same address. Customary units only. Per a decision by the subcommittee in , SI units will no longer be included in this edition or future interims. References If a standard is available as a stand-alone publication—for example, the ACI standards—the title is italicized in the text and listed in the references.
Unit abbreviations are always set in roman type, while variables and factors are set in italic type. Temporary Works If not otherwise provided for in the contract, structure excavation shall include the furnishing of all necessary equipment and the construction and subsequent removal of all cofferdams, shoring, and water control systems which may be necessary for the execution of the work.
If not otherwise specified in the contract documents, it Subsection If the contract does not include a separate pay item or items for such work, structure excavation shall include all necessary clearing and grubbing and the removal of existing structures within the area to be excavated. Classification, if any, of excavation will be indicated in the contract documents and set forth in the proposal. The removal and disposal of buried natural or man- made objects are included in the class of excavation in which they are located, unless such removal and disposal are included in other items of work.
The working drawings for protection from caving shall be submitted sufficiently in advance of proposed use to allow for their review; revision, if needed; and approval without delay to the work.
AASHTO LRFD Bridge Construction Specifications. 4th Edition