O. von Estorff

Coupled BEM/FEM approach for nonlinear soil/structure interaction

Abstract A general coupled boundary element/finite element formulation is presented for the investigation of dynamic soil/structure interaction including nonlinearities. It is applied to investigate the transient inelastic response of structures coupled with a halfspace. The structure itself and the surrounding soil in the near field are modeled with finite elements. In this part of the model inhomogeneities and an elastoplastic material behavior with hardening effects can be taken into account. The remaining soil region, i.e. the elastic halfspace, is discretized with the boundary elements. Thus wave radiation to infinity is included in the model. In representative examples it is shown that the methodology is computationally powerful and can be used efficiently for the nonlinear analyses of complex soil/structure interaction problems.

Fluid-structure interaction by coupling BEM and nonlinear FEM

Abstract Various numerical procedures, which each have respective merits and drawbacks, are available for the investigation of fluid–structure interaction problems. This paper concentrates on the coupling of the finite element method, used to model the structure, and the boundary element method representing the fluid. Both methods are formulated in the time domain and a special algorithm is developed to realize the coupling. In particular, nonlinear effects, such as material nonlinearities, large displacements or unilateral boundary conditions, may be taken into account in the structural model, while an infinite expansion of the fluid region is included in the boundary element formulation. Numerical examples exhibit the applicability of the new approach. It is observed that nonlinearities may have a considerable effect on the behavior of the fluid-structure system.

Dynamic response analysis of rigid foundations and of elastic structures by Boundary Element procedures

Boundary element procedures are employed in the frequency as well as in the time domain to determine the dynamic response of rigid foundations and of flexible elastic structures when placed on or embedded in an elastic soil medium under plane strain conditions. Parametric studies examining the damping effect dependence on the soil medium and on the embedment depth are presented.

Dynamic interaction effects in underground traffic systems

Abstract Dynamic interaction effects in tunnel systems subjected to above and below ground traffic loads are studied numerically under conditions of plane strain. Linear elastic or viscoelastic material behavior for both the structure and the soil is assumed. Two numerical schemes are employed in the computations for comparison purposes. The first works in the time domain and combines the finite element method for the structure with the boundary element method for the soil, while the second works in the frequency domain and uses the boundary element method for both the structure and the soil. The dynamic behaviour of a typical tunnel system is studied in detail for a variety of dynamic and geometric parameters in order to assess their effects on the system.

Dynamic response of 2D and 3D block foundations on a halfspace with inclusions

Abstract The present study aims to demonstrate how the dynamic behaviour of structures is affected by local inhomogeneities inside the soil. Particularly, the influence of block-shaped elastic inclusions directly beneath a vertically vibrating block foundation is considered. Comparisons between a 2D and a 3D modelling of the soil—structure system are made. It can be observed that, depending on the stiffness of the inclusion and especially on the excitation frequency, the dynamic response of the foundation may either increase or decrease.

The Effect of Non-Convex Boundaries on Time Domain Boundary Element Solutions

There exist mainly two types of numerical analysis techniques: the ‘domain’ type methods (e.g. the finite difference method and the finite element method) and the ‘boundary’ type methods (e.g. the Trefftz method and the boundary element method). When treating problems in unbounded domains, the boundary element method seems to be the most appropriate technique because it correctly accounts for the radiation to infinity, and it also has the advantage that the number of space dimensions as well as the modeling effort is considerably smaller than in domain-type methods. Moreover, the dynamic behavior of a structure resting on the soil mass is influenced to an important extent by the geometry of its foundation (shallow or deep foundation) and by the type of the soil model. Using the BEM, it is a very easy matter to consider various types of geometries.

Ausbreitung transienter akustischer Wellen-Untersuchungen mit einer Zeitschritt-Randelementmethode

ÜbersichtUnter Benutzung des Reziprozitätssatzes von Graffi wird eine zeitabhängige Integro-Differen-tialgleichung und daraus eine Zeitschritt-Randelementmethode hergeleitet. Sie ist bei beliebigen kompressiblen, nicht-viskosen Flüssigkeiten (akustischen Medien) anwendbar und besonders zur Ermittlung transienter Druckwellen in unendlichen oder halb-unendlichen Gebieten geeignet. Als Anwendung wird das Staudammproblem, dabei vor allem der Einfluß der Topographie und der dynamischen Interaktion mit dem Untergrund untersucht.SummaryBy using Graffis reciprocal theorem a time-dependent integro-differential equation and therefrom a time step boundary element method is derived. It is applicable to arbitrary compressible but non-viscous fluids (acoustic media), especially suitable for determining transient pressure waves in infinite or semi-infinite domains. As an application of the method, a reservoir-dam system is analyzed, especially considering the influence of the topography and of the dynamic interaction with the soil.