TY - CONF A1 - Auersch, Lutz A1 - Markfort, Greta T1 - Static and dynamic behaviour of pile foundations in homogeneous and inhomogeneous soils N2 - Offshore wind energy towers are dynamically loaded by waves and wind. Pile foundations provide stiffness and damping and should be properly calculated. A combined finite-element boundary-element method for the dynamic interaction of flexible structures and the soil has been developed. The flexible structures such as single piles or complete wind energy towers are modeled by the finite element method whereas the homogeneous or layered soil is modeled by the boundary element method which uses the Green’s functions for interior loads in the layered half-space to establish the dynamic stiffness matrix of the soil. Soils with a stiffness that is continuously increasing with depth can be modeled as multi-layer soils with step-wise increasing stiffness. The effects of different parameters such as the stiffness of the soil, the axial and bending stiffness of the pile, and the radius of the cylindrical contact area will be analysed for the different components of excitation (vertical, horizontal, rotation and coupling). The results can be determined as specific power laws which are different for the different load cases and for the different soil models (Winkler support, homogeneous continuum, continuum with increasing stiffness). The dynamic effect of radiation damping will be analysed by the frequency-dependent compliance functions. A clear layering of the soil can cause noticeable changes in the dynamic compliances as reductions of the stiffness and the damping in certain frequency ranges (below and around layer resonance frequencies). The distribution of the displacements along the pile help to explain the observed laws. An example of an offshore wind energy tower has been modeled and calculated for wind, wave and weight loads. The resonances of the tower are usually limited by the radiation damping which is strongest for a soft soil. T2 - COMPDYN 2017 CY - Rhodes, Greece DA - 15.06.2017 KW - Pile foundation KW - Finite-element boundary-element method KW - Pile bending stiffness KW - Soil stiffness KW - Continuously inhomogeneous soils KW - Layered soils KW - Wind energy tower PY - 2017 SP - 4675 EP - 4690 PB - NTUA CY - Athens AN - OPUS4-42089 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Auersch, Lutz ED - M. Papadrakakis, ED - D.C. Charmpis, ED - N.D. Lagaros, ED - Tsompanakis, Y. T1 - Simple and advanced boundary-element method for the soil and its application to railway dynamics T2 - COMPDYN 2007 CY - Rethymno, Crete, Greece DA - 2007-06-13 KW - Finite-element boundary-element method KW - Explicit Green´s functions KW - Track vibration KW - Tunnel vibration KW - Vehicle-track-soil interaction KW - Radiation damping PY - 2007 SP - 1 EP - 12 CY - Athen AN - OPUS4-15015 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Auersch, Lutz ED - Náprstek, J. ED - Horácek, J. ED - Okrouhlík, M. ED - Marvalová, B. ED - Verhulst, F. ED - Sawicki, J.T. T1 - Reducing ground-borne micro-vibrations by plate foundations T2 - Vibration problems ICOVP 2011 - 10th international conference on vibration problems CY - Prague, Czech Republic DA - 2011-09-05 KW - Plate-soil interaction KW - Wave excitation KW - Vibration reduction KW - Finite-element boundary-element method PY - 2011 SN - 978-94-007-2068-8 SN - 0930-8989 N1 - Serientitel: Springer proceedings in physics – Series title: Springer proceedings in physics VL - 139 SP - 329 EP - 335 PB - Springer AN - OPUS4-24804 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Auersch, Lutz ED - Papadrakakis, M. ED - Papadopoulos, V. ED - Plevris, V. T1 - How to quantify the vibration reduction of railway tracks N2 - Railway tracks, which reduce the ground vibration, are necessary if the trains are passing near to building. Today the reduction effect of railway tracks is often determined by the complex (time domain) simulation of the passage of a complete train. This method of evaluating the reduction is very time consuming and the results include some arbitrary scatter. It is worth to look for simpler methods which yield clearer results in shorter time. This contribution presents the combined finite-element boundary-element method as a detailed method for the track-soil interaction and, on the other hand, some possible simplifications. One important idea for the reduction assessment is to split the reduction in a vehicle-track interaction part and a track transfer part. The track transfer is not influenced by the vehicle and by single axle loads and it can be calculated as a homogeneous problem along the track. The reduction of some tracks (for example of floating slab tracks) can be dominated by this track transfer function whereas other tracks (for example tracks with soft rail pads) are completely determined by the vehicle-track-interaction part. The different force transfer functions and the ground vibration ratios of tracks with elastic rail pads or elastic sleeper pads are shown as a result of the FEBEM model under a fixed harmonic axle load. The force transfer proves to be a useful quantity for to assess the vibration reduction of railway tracks. T2 - COMPDYN 2013 - 4th ECCOMAS Thematic conference on computational methods in structural dynamics and earthquake engineering CY - Kos Island, Greece DA - 2013-06-12 KW - Railway induced ground vibration KW - Mitigation measures KW - Railway tracks KW - Finite-element boundary-element method KW - Wavenumber integrals KW - 1-D insertion loss PY - 2013 SP - 1 EP - 19 AN - OPUS4-29313 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -