Sliding resistance factors for abutments, AASHTO LRFD 9th Ed.

[Enginerdad]

I find myself disagreeing with our geotechnical engineer's report, but I'd like to get some feedback from others before I bring it up with them. In their report, they give the resistance factors for sliding of abutments as 0.8 and cite Table 10.5.5.2.2-1. They also give the resistance factor for sliding of wingwalls as 1.0, citing Table 11.5.7-1. For those unfamiliar, Section 10 is Foundations and Section 11 is Walls, Abutments, and Piers. A quick glance at the tables and their titles and I would agree with the geotech on their selection of resistance factors. However, Section 11.5.5 - Resistance Requirements indicates that the resistance factors used should be from Table 11.5.7-1. I'm links to images of the relevant sections, and if you have access to a copy of AASHTO LRFD you can also read adjoining sections for context.

I'd appreciate anybody else's interpretation.

Table 10.5.5.2.2-1
Table 11.5.7-1
Section 10.5.5

 

[HTURKAK]

I do not have 9th Ed. The followings are copy and paste from 6th ed.

10.5.5.2.2—Spread Footings

The resistance factors provided in Table 10.5.5.2.2-1 shall be used for strength limit state design of spread footings,



Table 10.5.5.2.2-1—Resistance Factors for Geotechnical Resistance of Shallow Foundations at the Strength Limit State

C10.5.5.2.2 The resistance factors in Table 10.5.5.2.2-1 were developed using both reliability theory and calibration by
fitting to Allowable Stress Design (ASD). In general, ASD safety factors for footing bearing capacity range from 2.5 to
3.0, corresponding to a resistance factor of approximately 0.55 to 0.45, respectively, and for sliding, an ASD safety
factor of 1.5, corresponding to a resistance factor of approximately 0.9. Calibration by fitting to ASD controlled
the selection of the resistance factor in cases where statistical data were limited in quality or quantity.

Table 11.5.7-1—Resistance Factors for Permanent Retaining Walls.


My interpretation is that the scope is clear and , Table 10.5.5.2.2-1 shall be used for shallow foundations ( spread ftgs ) and Table 11.5.7-1—Resistance Factors for Abutments and Retaining walls ..












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