Proposed Specifications for LRFD Soil-Nailing Design and Construction (2011) / Chapter Skim
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Pages 127-135
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From page 127... ...
Therefore, the sliding and basal heave limit states can be modeled only approximately with this program. SNAILZ can model up to seven soil layers.
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From page 128... ...
In summary, the only practical way to use SNAILZ with a LRFD format is to set all load factors equal to 1.0, which is consistent with a service limit state for overall stability as is currently adopted in the LRFD Bridge Design Specifications (AASHTO, 2007)
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From page 129... ...
for a specified set of input parameters, including soil nail length. In the Nail Service Load Design Mode, the program provides the maximum in-service tensile forces in the soil nails that are used for the design of the nail bar diameter and facing characteristics resistances.
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From page 130... ...
Because the calibrated pullout resistance factors are values that are close to 0.5 (a value that would have been derived through a calibration with safety factors) , the results between the LRFD and ASD methods are expected to be similar.
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From page 131... ...
behind the wall. The wall is to be constructed in medium-dense silty sand with clay seams with the soil nails shown in Figure D-4.
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From page 132... ...
I Load Combination and Load Resistance Factors The combination of loads for the project conditions is adopted from AASHTO (2007)
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From page 133... ...
, the overall stability of the SNW is assessed using the load combination for service limit state. The resistance factors in Table D-4 are used based on the recommendation of AASHTO (2007)
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From page 134... ...
Overall, the comparisons indicate that the required soil nail length calculated using the LRFD method and the proposed resistance factors are comparable with those obtained with the ASD method. For all cases considered, the length difference is on average approximately 4 percent larger in the LRFD method.
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From page 135... ...
The reason for these similar trends, which were already apparent in Chapter 3, stem from the fact that the calibrated resistance factors for pullout are very similar to those that could have been obtained directly from a calibration using factors of safety. The differences were small between LRFD and ASD methods using the same program (i.e., GOLDNAIL)
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