Office of Structures Local Assistance
For More Information
All structures - both state and local - that have the Type Selection meeting held on or after October 1, 2006 must be designed using the new LRFD specifications, with the exceptions noted below. Currently the primary design specification for California structures consists of the following:
The Seismic Design Criteria will continue to be the governing specification for the seismic design of structures. Other Caltrans manuals that govern structure design such as Bridge Design Aids and Bridge Memos to Designers will eventually be updated in order of importance to design production. The Bridge Design Practice manual will eventually be rewritten.
Bridge decks and soffits will be designed per new Memo to Designers 10-20.
As stated in the CA Amendments section 10.5.1 foundations for intermediate supports are to be designed using LRFD. This means that the entire bent/pier system - cap, columns/pier, footing, and foundation soil or piles, are to be designed using LRFD. Section 10.5.1 also states that there is an exception for abutments, which are to be designed using SLD and the Caltrans Bridge Design Specifications dated April 2000. Although the section refers to "foundations for end supports", the practical effect is that the entire abutment must be designed using the April 2000 specifications. Current Caltrans design practice is to design the entire abutment using SLD with the loads obtained from the new HL93 load group. This new load is heavier than the old HS20-44 (because the truck and lane loads are combined) and a more robust abutment design including a larger foundation is to be expected. The reason that abutments have been deferred is that they are essentially retaining walls and load factors for earth pressure are still under development.
The General Notes will state which elements of the structure are designed by the old specifications and which are designed by the new. The proper format of the General Notes is shown in Memo to Designers 1-47.
LRFD implementation for earth retaining systems and underground structures (box culverts, pipes, arches, etc.) has been deferred by the FHWA until no later than October 2010. New design programs and manuals are being developed for these structures and LRFD implementation could occur sooner than that date.
|More information regarding LRFD can be found at the following web sites:|
|AASHTO Bookstore (LRFD manuals and revisions for bridges and structures)|
|AASHTO Subcommittee on Bridges and Structures - LRFD|
|Federal Highway Administration - Bridge Technology - LRFD|
Following are links to documents issued by the Federal Highway Administration and the California Department of Transportation ordering the implementation of the LRFD Specifications.
|Federal Highway Administration|
|June 2000: Load and Resistance Factor Design Policy Memorandum|
|January 2007: Clarification of Load and Resistance Factor Design Policy Memorandum|
|California Department of Transportation|
|January 2009- Implementation of the 4th Edition of the AASHTO LRFD Bridge Design Specifications|
|March 2007 : Implementation of the AASHTO LRFD Bridge Design Specifications|
|April 2006: Implementation of the AASHTO LRFD Bridge Design Specifications|
|January 2006: Notice of Change in the Bridge Design Specifications|
|The Consulting Engineers and Land Surveyors of California (CELSOC) occasionally offers training.|
|The FHWA's National Highway Institute is currently offering classes for LRFD design.|
|The University of California at Berkeley is currently offering classes for LRFD design.|
|FOR MORE INFORMATION|
|For structures on the State highway system contact the Liaison Engineer assigned to your Transportation District:|
|Office of Special Funded Projects - Liaison Engineers|
|For structures on local roads and highways contact the Local Assistance Engineer assigned to your city or county:|
|Office of Structures Local Assistance Telephone 916-227-3330|