I received my copy of the 4th edition AASHTO LRFD code, 2007. The good news is that it is not any bigger than the 3rd edition, but at 3.5 inches thick, it is still the largest binder in my library.
More good news, there does not seem to be any significant changes for the geotechs. So If you have the 3rd edition with the 2006 interims, I would say you probably don't need to get the 4th edition (at least not yet). Here is my summary of the changes.
Section 3 - Loads and Load Factors
Added definition and notation for Apparent Earth Pressure (AEP). The load factor for AEP has been added to Table 3.4.1-2. The maximum load factor is 1.35 and the minimum load factor is listed as not applicable.
Section 10 - Foundations
The list of revisions says there are changes in Sections 10.6.2.4.3 and 10.6.3.1.2a, but all I saw were some formatting changes. It doesn't look like anything has changed from the 2006 interims.
Section 11 - Abutments, Piers, and Walls
The resistance factor for the passive resistance of vertical elements has changed from 1.0 to 0.75 in Table 11.5.6-1. Also there has been some changes to the text in 11.9 regarding testing of ground anchors. The 2006 interims said that pullout tests "shall" be performed, now it is "may" be performed. The commentary has also been revised about pullout testing on sacrifical anchors and references to the AASHTO LRFD Construction Specifications have been added regarding the testing of ground anchors.
More good news, there does not seem to be any significant changes for the geotechs. So If you have the 3rd edition with the 2006 interims, I would say you probably don't need to get the 4th edition (at least not yet). Here is my summary of the changes.
Section 3 - Loads and Load Factors
Added definition and notation for Apparent Earth Pressure (AEP). The load factor for AEP has been added to Table 3.4.1-2. The maximum load factor is 1.35 and the minimum load factor is listed as not applicable.
Section 10 - Foundations
The list of revisions says there are changes in Sections 10.6.2.4.3 and 10.6.3.1.2a, but all I saw were some formatting changes. It doesn't look like anything has changed from the 2006 interims.
Section 11 - Abutments, Piers, and Walls
The resistance factor for the passive resistance of vertical elements has changed from 1.0 to 0.75 in Table 11.5.6-1. Also there has been some changes to the text in 11.9 regarding testing of ground anchors. The 2006 interims said that pullout tests "shall" be performed, now it is "may" be performed. The commentary has also been revised about pullout testing on sacrifical anchors and references to the AASHTO LRFD Construction Specifications have been added regarding the testing of ground anchors.
