Abstract
Background:The analysis of piled foundations, where horizontal environmental loads play a very important role, has taken foundation design a step further in the 1970s and 80s. Nonlinear analyses considering P-y, T-z and Q-z curves became the state-of-the-art which also included group effect calculations thanks to an approximation proposed by [1] on the [2] equations. For some reason, however, foundation design continued to be refined using finite element calculations, but the corresponding developments never made their way into the main offshore platform design codes such as [3,4].Objective:Considering the enormous advantage that this brings for topics such as group effect and negative friction, it is obvious that opening the offshore market to this enhancement is totally desirable. This is exactly what this paper is trying to achieve.Method:In order to increase the accuracy of the prediction of piled foundations lateral displacements when group effect is considerable, a complete 3D model will be proposed using the finite element method and compared to the codes’ model and also experimental data.Results:The model in DIANA showed good performance in comparison to the codes’ model and experimental data for the single pile. When the pile group model, when the codes’ have known deficiencies, was tested, both efforts on each pile and mean displacement of the pile group fit the experimental data. However, the behavior of each pile of the group, if separately analyzed, didn’t fit many experimental data, which was attributed to the soil model utilized.Conclusion:This improved modeling procedure has been proven to improve the lateral displacement prediction of a piled foundation when group effect is considerable, when compared to codes [3,4] proposed models. However, the study of more accurate soil models could help on achieving more realistic results.
Highlights
The analysis of piled foundations, where horizontal environmental loads play a very important role, has taken foundation design a step further in the 1970s and 80s
While the offshore researchers made their developments based on a model considering a beam on elastic foundation and nonlinear soil resistance based on single dimensional soil curves, the power plant research was focusing on 3D nonlinear finite element soil models, into which the piles were embedded, producing a more accurate and general overall solution, whose development continued to be enhanced into the 21st century
Figs. (10-16) contain the [6] 2005 measured test results compared to those extracted from DIANA and those obtained by [7] using SPLICE
Summary
The analysis of piled foundations, where horizontal environmental loads play a very important role, has taken foundation design a step further in the 1970s and 80s. The design of piled foundations was greatly enhanced during the 70s and 80s because of the need to cope with the large horizontal forces, which the environment produces on structures such as offshore fixed platforms, bridges, nuclear power plants and tall buildings. Expect this elegant enhanced solution to find its way into the offshore market, but for some strange reason it failed to do so, wherefore it is fair to say that the present day offshore structure design codes deal with the design of piled foundations considering technology that became obsolete over the last 30 years. All other structures deal with this problem more efficiently but the power plant designers are by far the most advanced They take group effect into account automatically by modeling their piles embedded into a full 3D finite element mesh. The object of this paper is to encourage offshore platform code and software developers to make use of the resources already available in the market, in order to perform more accurate analyses of fixed offshore platform piled foundations
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