Major changes and revisions to this edition are as follows: 1. The Interim Specifications of , , , , , and have been adopted and are included. The commentaries from through are provided and have been cross-referenced with each other, where appropriate. The Federal Highway Administration and the States have established a goal that the LRFD standards be used on all new bridge designs after ; only edits related to technical errors in the seventeenth edition will be made hereafter. These Standard Specifications are applicable to new structure designs prior to and for the maintenance and rehabilitation of existing structures.
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Compliance with standards — the basics of quality products. By Claude Goguen, P. It is a nonprofit, nonpartisan association representing highway and transportation departments in the United States and Puerto Rico.
It represents five transportation modes: air, highways, public transportation, rail and water. Its primary goal is to foster the development, operation and maintenance of an integrated national transportation system.
All state Departments of Transportation are active members, as are several substate and federal transportation agencies in the United States. Many transportation agencies in other countries belong to the association as associate non-voting members.
The association provides a forum for consideration of transportation issues and is frequently called upon by the U. Congress to conduct surveys, provide data and testify on transportation legislation though a non-government body.
AASHTO has developed a strategic plan to include the following goals: Re-establish transportation as a national priority.
Provide world-class technical services. Assist state DOTs with leadership and performance. The primary intent of this goal is to attain a world leadership role in the development of transportation standards and other technical services. This goal will focus on: increasing the number of beneficiaries; ensuring continued state DOT participation in critical technical activities; expanding training opportunities for transportation agency professionals; and developing centers of excellence in safety, operations, finance and freight transportation.
That meeting in the U. Capitol, held Dec. Under the leadership of its first president, Henry Shirley of Maryland, the participants approved a legislative proposal authorizing participation of the federal government in highway construction. That proposal, subsequently presented to the U. Congress, laid the groundwork for the historic Federal Aid Highway Act of Since then, the association has worked to strengthen and sustain the national highway and transportation system.
These efforts have included the advocacy of other landmark federal legislation from the act that launched the Interstate Highway System in to the still-pending reauthorization of the Transportation Equity Act for the 21st Century. Other AASHTO milestones include: Production of standards and specifications for highway design, construction and safety Establishment of uniform symbols for road maps Creation of nationwide route numbering of the primary U.
This happened after various federal agencies were brought together under the U. Department of Transportation, and state governments followed suit with similar reorganization. Standard specifications for highway bridges For many years, precast manufacturers of underground products used designs that complied with either AASHTO HS or Alternate Military Loading Interstate Loading , whichever standard correlated to the worst condition that could be applied to the structure.
The recommendations from this document are included in ASTM specifications written for underground precast concrete structures such as C, C, C, C and C As the Interstate Highway System evolved in the s, one of its goals was to transport military vehicles.
The Alternative Military Load also known as Interstate Load was created to cover axle loads from heavy military equipment. There was some concern during the end of the 20th century that the HS20 truck load rating did not adequately reflect actual conditions. Thus, the HS20 axle load of 32, pounds 14, kg becomes an HS25 axle load of 40, pounds 18, kg.
The increased load can, in some cases, create the need for additional reinforcing steel and a thicker top slab on underground structures installed in areas exposed to heavy truck loads. LRFD is based on new developments in bridge engineering, sound principles and a logical approach to ensure constructability, safety, serviceability, inspectability, economy and aesthetics. The LRFD philosophy is consistent with other major bridge design codes adopted or being developed in Asia, Canada, Europe and other parts of the world.
Subsequent to the development of the new LRFD specifications, FHWA announced that all state bridge projects using federal funding must use the new and superior code. Standard specifications for transportation materials and methods of sampling and testing AASHTO publishes another set of specifications that precasters may often reference in manufacturing and quality control of their products: the Standard Specifications for Transportation Materials and Methods of Sampling and Testing.
The latest version is the 30th edition and contains material specifications and test methods commonly used in the construction of highway facilities, including 10 new and 69 updated specifications and test methods.
Many of the specifications that are pertinent to precast concrete have equivalencies in ASTM. Not all of the corresponding standards specific to various precast products manholes, pipe, box culverts and others are listed here visit www.
For precasters who manufacture products that are part of transportation projects such as manholes, pipe, box culverts, stormwater structures, utility vaults, traffic barriers, and retaining and sound walls , an awareness of the background and purpose of AASHTO standards helps to emphasize the importance of manufacturing specification-compliant, quality precast concrete products.
Claude Goguen, P.
AASHTO Standard Specifications for Highway Bridges 17th_TOC