Arizona DOT Posts New Geotechnical LRFD Policy Memos
The Arizona DOT has posted three new LRFD geotechnical policy memoranda and revised three others. Use of LRFD or Load and Resistance Factor Design is now mandatory on all federally funded roadway projects and agencies and consultants have had plenty of issues with the transition. ADOT has been one of the more proactive agencies at implementing the geotechnical aspects of the AASHTO LRFD Code and providing guidance to consultants in the form of these policy memos.
The first three ADOT policy memos were released in 2008. These included two related to Drilled Shafts – One describing the procedures for analyzing axial capacity at both strength and service limit states (now referred to as DS-1), and one describing an ADOT policy related to axial capacity in gravelly soils (DS-2). The third memo described the procedure for analyzing spread footings for both bearing resistance and settlement (SF-1). The revisions to these three memos seem fairly minor, mostly corrections and changes to reflect a new naming system for all the memos.
The three new memos include a discussion of the procedures for analyzing lateral resistance of drilled shafts (DS-3), spread footing limiting eccentricity (SF-2) and spread footing sliding and bearing resistance (SF-3).
So if you are practicing outside Arizona, why should you care about these memos? First of all, my former employer, NCS Consultants, LLC was largely responsible for these memos despite the fact that they are formally issued by ADOT directly. Naresh Samtani at NCS is a recognized expert in LRFD, and the work that NCS has done for ADOT is closely looked at by other DOTs, the FHWA and even AASHTO. So at a minimum, they offer additional interpretation and guidance for implementing LRFD for geotechnical features, but you may see other DOTs issuing similar guidance, or possibly some changes in the AASHTO code itself. [Source: ]