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GGU-UNDERPIN: Predeformations

When a number of excavation phases are under study, deformations from a previous phase can be implemented as lowering of supports at the new anchor points for the next phase. According to the EAB (R 11), however, such studies are not usually necessary.

In a continuous beam analysis, it is a simple matter to introduce the corresponding support displacements. In a rod framework application that does not consider anchors and struts as mere supports, the same lowering of the support must be introduced at the anchor toe as at the anchor head; otherwise a large proportion of the resultant load would be transferred to the anchor. Thus, apart from being able to define displacement boundary conditions, GGU-UNDERPIN also offers a menu item dealing with predeformations. If you wish to enter predeformations by hand, or need to, this must be done as displacements under predeformations and not as displacement boundary conditions. Of course, once this is done, GGU-UNDERPIN takes care of the rest. You also have the option of automatically adopting predeformations from a previous analysis.

Designing an underpinning body involves a multitude of different adjustments, making it all too easy to lose one's bearings. GGU-UNDERPIN is thus designed to ask numerous questions, which, apart from controlling correct entry of data, also check plausibility, special preferences, and compatibility with the EAB. When a data entry error is recognised, an warning box appears and analysis is put on hold. Responses to inconsistencies in respect to plausibility or special preferences always offer two options:

  • accept warning and begin analysis;

  • accept warning and do not begin analysis.

When GGU-UNDERPIN draws your attention to special preferences, the dialog box is always designed so that simply pressing [Return] will not terminate the analysis.

GGU-UNDERPIN is designed for a high degree of user interaction, with the aim of avoiding erroneous and unwanted preferences (see above). Batch processing for the background processing of a number of files simultaneously is incompatible with this concept. Therefore, GGU-UNDERPIN does not create a single dataset when dealing with a number of construction phases. All phases must be dealt with in separate datasets. The only disadvantage of this is the treatment of predeformations. If you want predeformations from a previous construction phase to be automatically taken into consideration, this previous phase must already have been analysed (obviously) and be available as a dataset (on your hard disk). This dataset must be given as the dataset from which the predeformations are to be determined for the new construction phase. Since there is no re-analysis of the old phase, this dataset and the results obtained with it must be saved. If you should mistakenly select a dataset that contains no results, GGU-UNDERPIN will inform you of this. Otherwise, there are no restrictions. The name of the file with the predeformations is saved with the current dataset, where it is available for future use.

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