Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities
Figure E Number of DOTs referencing various head deflection (service)
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- 5.2.7 Design Procedure
- 5.2.8 Engineer Responsibilities
- 5.2.9 Resistance Factor
| Figure E Number of DOTs referencing various head deflection (service). 5.2.6 Seismic Assessing lateral resistance related to seismic events is mentioned in ten documents. Some manuals simply mention the use of liquefied p-y curves, others recommend an iterative procedure to identify loads due to lateral spreading, and others offer opinions and discuss the various methods available. 5.2.7 Design Procedure A staged design procedure is only detailed in six documents. These include Arizona, California, Louisiana, Massachusetts, Pennsylvania, and Washington. The details of each procedure will not be discussed herein, as the steps are sufficiently different except for the inclusion of a deflection analysis with computer software. 5.2.8 Engineer Responsibilities The respective responsibilities of the structural engineer and geotechnical engineer are discussed in 18 of the documents. The most common approach, in twelve of the 18 documents, is to have the geotechnical engineer supply soil parameters or p-y curves and loads associated with liquefaction (when appropriate) to the structural engineer. The structural engineer then performs the structural and lateral analysis. Some of these publications indicated that the results are to be reviewed by the geotechnical engineer for verification. Another, less common, published approach, in three of the 18 documents, has the geotechnical engineer develop the parameters or p-y curves and liquefaction loads and perform the lateral load analysis. In this case, the structural engineer performs only the structural design of the pile. In the remaining three documents, the p-y curves are stated to be provided by the geotechnical discipline, but there is no specific statement that the structural discipline is to perform the lateral analysis. 271 5.2.9 Resistance Factor The use of a resistance factor (Φ) is only mentioned in eight of the state transportation agency documents, possibly due to codification of resistance factors within current AASHTO LRFD specifications. Even though AASHTO (2014) indicates that p-y curves are not factored since they already represent the ultimate condition (Cit allows that p-y parameters should be reduced for extreme event seismic liquefaction (10.7.4). The use of resistance factors varies and includes defining specific resistance factors for specific cases, as is done by Idaho, or indicating that a resistance factor of 1.0 should be used for lateral analyses (consistent with AASHTO design specifications, or indicating that no resistance factor should be used. From an analysis standpoint, the use of a resistance factor of 1.0 is mathematically the same as not including a resistance factor because it does not change the resistance used in the analysis. The Idaho Transportation Department states two different values for the Service and Extreme Limit States and 0.90 for the Strength Limit State. The use of resistance factors is further discussed in Section 0, regarding design methodology for drilled shafts from FHWA GEC 010 (2010). Download 6.03 Mb. Share with your friends:
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