Affiliations: Bridge Engineer, Parsons Brinckerhoff, Princeton, NJ, USA | Department of Civil and Environmental Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
Note: [] Corresponding author. Husam Najm, Ph.D., P.E., Associate Professor, Department of Civil and Environmental Engineering, Rutgers, The State University of New Jersey, 623 Bowser Road, Piscataway, NJ 08854, USA. Tel.: +1 732 445 7980; Fax: +1 732 445 0577; E-mail: hnajm@rci.rutgers.edu
Abstract: In October of 2007 the AASHTO LRFD Bridge Design Specification became the mandatory design specifications for highway structures in the United States. This has introduced a number of changes in the design and analysis procedures that engineers have to follow. This paper evaluates the differences between the ASD standard specifications and the LRFD specification and how they apply to the design of earth retaining structures. Several design examples were carried out to examine the effect of the new design standards on structural proportioning and cost. For cantilever abutments and retaining walls 4.6 m and taller, the difference between the LRFD specifications and the ASD standard specifications was insignificant. However, designing shorter abutments and retaining walls using the LRFD specifications can result in an increase in footing length of about 30% and an increase in cost of approximately 10% of the cost of the retaining structures. While these cost impacts to a structure can be significant in some designs, the AASHTO LRFD specifications provides a safe and reliable method of design which is of paramount importance to engineers and the public.
