The applicability of DFSAP and LPILE programs for static and liquefied soil structural analysis cases have been studied by the Bridge and Structures Office and the Geotechnical Division. As a result, the Bridge Design Office and the Geotechnical Division have decided to put into effect the following guidelines on the use of DFSAP and LPILE programs:
The adequacy of the DFSAP program for all foundation types and all soils profiles has been recently questioned by the Bridge Office and Consultant engineers. To address these concerns, a parametric study for a range of foundations and soil profiles has been conducted using DFSAP and L-Pile to determine the best approach to characterize the soil for liquefied conditions. Based on the results of this study, it has been determined that both DFSAP and L-Pile provide reasonable and consistent solutions if the input soil parameters are properly reduced to account for the effects of liquefaction as described in the WSDOT Geotechnical Design Manual Chapter 6 Method 2. However, it was also determined that the L-Pile built in liquefaction model tends to produce non-conservative and inconsistent results except for relatively short smaller diameters piles. At this point, the Bridge Office and Geotechnical Division recommend that the built in liquefaction options in both programs not be used.
cc: Mohammad Sheikhizadeh, Bridge Construction - 47354