This design memorandum is to provide guidance on the design specification requirements, stamping and signing responsibilities for retaining walls, noise walls and moment slabs. This design memorandum supersedes the design memorandum issued on February 28, 2007.

The Design Manual has a flow chart for Retaining Wall Design Process (see Figures 1130-4a and 1130-4b). This flow chart applies to all wall types for determining if the Bridge and Structures Office prepares the PS&E. In situations where it will be more efficient for the Bridge and Structures Office to prepare the PS&E, such as standard retaining walls adjacent to either special design walls or bridges, a request can be submitted from the Region Design Office to the Bridge and Structures Office. All PS&E prepared by the Bridge and Structures Office shall be stamped and signed in accordance with the Memorandum dated June 4th, 2008.

Structural details designed by the HQ Geotechnical Division shall be included in the wall plan set as a self contained sheet(s). These sheets will include all information provided by the geotechnical engineer, the names of the engineers who provided this information and the name of the detailer from the Bridge & Structures Office (who prepared the sheet) in the title block, and the stamps of the geotechnical engineers or supervisors involved. These sheets will be numbered and included with the other wall plan sheets provided by the Bridge & Structures Office.

All retaining walls shall include seismic design load combinations. The design acceleration for retaining walls shall be determined in accordance with the AASHTO Guide Specifications for LRFD Seismic Bridge Design. Once the design acceleration is determined, the designer shall follow the applicable design specification requirements listed below:

Exceptions to the cases described above may occur with approval from the Bridge Design Engineer and/or

Background

While the Bridge and Structures Office has adopted the AASHTO LRFD Bridge Design Specifications – 2007 & Interims, several wall types either have not yet been brought up to that standard or those wall types are not covered by that standard. To assist designers with knowing what design specification they are responsible to meet and to track the process of moving all wall designs to the current specifications, this document is created.

Additional confusion and concern has arisen about responsibility for plan sheets. Components designed by the HQ Geotechnical Division were being included on Bridge Plan Sheets with supervisors’ stamps that did not oversee the work. To avoid these conditions, the work performed by each office will be separated onto different plan sheets with the names of the engineers involved and the stamps of the correct supervisors included for signatures.

If you have any questions regarding this issue, please contact Monique Pawelka at 705-7754, Stuart Bennion at 705-7168, or Bijan Khaleghi at 705-7181.

cc:   Mohammad Sheikhizadeh, Bridge Construction - 47354

Click here for a PDF of this design memo.