| Two new methods have been developed for dynamic analysis of soil-pile-structure systems. One method, the full method, is exceptionally versatile and can be used to analyze foundation(s) with closely spaced piles including batter piles subjected to arbitrary seismic loads or transient loads, such as impact loads. The method employs specially designed inter-pile elements in both two- and three-dimensions. These elements model the soil and pile together within the same element and retain compatibility of displacements between the soil and pile part of the element. The other method, the simplified method, is a new substructuring method which can be applied to directly loaded foundation(s) with vertical piles. The method is very cost effective for analysis of foundation(s) with several clusters of pile groups and isolated single piles.; Both methods can handle arbitrary shape flexible foundation cap(s) embedded in a layered viscoelastic half space. The effects of pile-soil-pile and soil-cap interaction can be considered simultaneously.; Both methods are based on a recently developed substructure method the flexible volume method. This method, when compared to other substructuring methods simplifies the impedance problem and eliminates the seismic scattering problem. This is accomplished by assuming that interaction occurs at all nodes of the embedded part of the structure.; The two methods are formulated in the frequency domain, using the complex response method. Transient loadings are handled by Fast Fourier Transform techniques.; The methods have been implemented in the computer program SASSI. The effectiveness and accuracy of the methods and the computer program have been proven by comparing several solutions obtained by the program with previously published analytical solutions.; An extensive parametric study of dynamic stiffness and damping coefficients of pile groups shows the effects of different parameters on pile group response. A new dimensionless frequency ratio is introduced to simplify the interpretation of the interaction phenomenon.; A piloted offshore platform has been analyzed using both the full and the simplified method. The results of this analysis confirms the accuracy, effectiveness and applicability of the methods to practical problems. |
