Filtern
Erscheinungsjahr
Dokumenttyp
- Beitrag zu einem Tagungsband (59)
- Vortrag (52)
- Zeitschriftenartikel (18)
- Beitrag zu einem Sammelband (9)
- Buchkapitel (5)
- Posterpräsentation (2)
Schlagworte
- Offshore (8)
- Structural Health Monitoring (7)
- Cyclic loading (6)
- Offshore pile foundation (6)
- Ballast (5)
- Beschleunigung (5)
- Eisenbahnbrücken (5)
- SHM (5)
- Schotteroberbau (5)
- Structural health monitoring (5)
Organisationseinheit der BAM
- 7 Bauwerkssicherheit (48)
- 7.2 Ingenieurbau (48)
- 7.4 Baustofftechnologie (11)
- 9 Komponentensicherheit (6)
- 9.3 Schweißtechnische Fertigungsverfahren (5)
- 3 Gefahrgutumschließungen; Energiespeicher (2)
- 3.3 Sicherheit von Transportbehältern (2)
- 7.1 Baustoffe (2)
- 8 Zerstörungsfreie Prüfung (2)
- 5 Werkstofftechnik (1)
Paper des Monats
- ja (2)
Eingeladener Vortrag
- nein (52)
The purpose of the work presented in this paper is to analyze locally (at the element level) the contact behavior of a soil-pile contact problem. Therefore, a 2D shear test is modeled using the Finite Element Method. The formulation of a 4 nodded zero-thickness interface element of Beer is chosen with a linear interpolation function. Four constitutive contact models adapted for contact problems have been implemented. The Mohr-Coulomb and Clough and Duncan models were chosen initially, due to the ease of implementation and few number of parameters needed. After, more complicated models in the framework of elasto-plasticity such as: Lashkari and Mortara were implemented for the first time into the finite element code of the shear test problem. They include other phenomena such as: relative density of soil, the stress level and sand dilatancy. From the results the relation between shear displacement and shear stress has been deduced. Finally, a discussion of the advantages and the drawbacks during computation of each model is given at the end.
This paper presents the impact of dynamic loading on the deterioration of ballasted track. Firstly it is discussed which types of loading can be observed at the track. The effects of cyclic and dynamic loading on the ballast assembly are discussed with respect to the different boundary conditions of physical model tests compared to those existing in reality. For dynamic loading, on the one hand, the displacements and rotations of single particles at the surface become more important. On the other hand, the load distribution caused by an impact like loading is different from a quasistatic loading. Finally, large scale tests are presented. When comparing the dynamic loading sequences with the solely cyclic loading, limits are found for a vibration level that is associated with an accelerated accumulation of permanent deformations.
The new crack luminescence method offers the possibility of making fatigue surface cracks in metallic materials more visible during inspections through a special coating system. This coating system consists of two layers, whereby the first layer has fluorescent properties and emits visible light as soon as it is irradiated by UV light. The top layer is black and is designed to prevent the fluorescent layer from emitting if no crack develops in the underlying material. The technique proved particularly useful in a wide variety of fatigue tests of steel components under laboratory conditions. Moreover, it has the potential to be used in various industrial applications. To enable industrial deployment and integration into maintenance strategies, a concept study is developed in this contribution, resulting in a qualification framework that can serve as a foundation for determining the reliability of the crack luminescence system in terms of a probability of detection curve. Within this study, factors causing measurement variability and uncertainty are being determined and their influences assessed. Due to the extension of the system by a moving computer vision system for automated crack detection using artificial intelligence, additional long-term effects associated with structural health monitoring systems need to be incorporated into an extended probability of detection study as part of the technical justification. Finally, important aspects and findings related to design of experiments are discussed, and a framework for reliability assessment of a new optical crack monitoring method is presented, emphasizing the influence of various uncertainty parameters, including long-term effects such as system ageing.
Support structures of wind turbines in German offshore wind farms are regularly inspected. Currently, inspection outcomes are generally not systematically recorded. This prevents their consistent handling and processing, which is a key requirement to enable an efficient structural integrity management. As part of the DiMoWind-Inspect project, a data model and reference designation system for such inspection results is developed to facilitate their identification, localization, quantification, tracing and linking throughout the lifetime of a wind farm and beyond. The inspection results together with structural health monitoring results and information on repairs form the basis for assessing and predicting the structural condition, estimating the remaining lifetime, and planning of future inspections, structural health monitoring, and repairs. As a basis for developing a digital structural integrity management, a generic framework is proposed in this paper, which describes the stakeholders, data, models, processes and workflows of the integrity management of support structures in offshore wind farms and their interrelations. The framework adopts a building information modelling approach to describe the information relevant to the structural integrity management. The central digital space of the framework is a common data environment. An implementation of the framework will enable a digital structural integrity management in which inspection, structural health monitoring, repair, assessment and planning outcomes generated throughout the life cycle of a wind farm can be consistently collected, managed, shared and processed by the relevant shareholders.
The response of many geotechnical systems, whose structural behavior depends on shearing effect, is closely related to soil structure interaction phenomenon. Experimentally it is found that the localisation of these effect happens at a narrow soil layer next to the structure. Numerically, this behavior can be modelled through inter-face elements and adequate constitutive models. In this work, a constitutive model in the framework of Gen-eralized Plasticity for sandy soils has been chosen to be adapted for the interface zone. From the direct shear experiments a sandy soil at loose and dense states under different normal pressures is considered. The adapted constitutive model is able to reproduce contraction and dilatation of the soil according to its relative density and it shows a good agreement with the experimental data.
A mechanical structure supported by nonlinear springs subjected to an external load is considered. If all mechanical parameters of the system were known, the displacement of the system subjected to this load could be easily calculated. If not all of the parameters are known, but the load and the displacement are measured at one location, an inverse problem exists. In the presented problem the nonlinear springs are unknown and have to be determined. At first glance a problem needs to be solved, which is underdetermined due to the number of unknown variables. However, evolutionary computing can be applied to solve this inverse, nonlinear and multimodal problem. Sometimes a prior knowledge exists on certain system properties, which is difficult to implement into analytical or numerical solver. This knowledge can play a decisive role in identifying the system properties and it can be easily included as boundary condition when applying evolutionary algorithm. This article examines how and under what conditions the spring resistances can be identified. The procedure is exemplified at a mechanical system of a pile foundation.
This paper presents a three dimensional numerical model which is can be used to
investigate the effects on the track and in its vicinity due to a train passage. The numerical
model for train track interaction is based on a time domain dynamic finite
element model. Due to the unbounded nature of the soil the truncated boundary of the
finite element domain is modelled with the scaled boundary finite element method,
which is a semi-analytical approach. The application for a heterogeneous track along
the track line is exemplified by a track with a bridge structure, where close attention
is paid to the wheel-rail contact force. The results indicate that the wheel-rail contact
force is not symmetrical around the bridge structure and an optimisation in terms of a
backfilling area and under-sleeper-pads can improve such a transition.
A comprehensive numerical model for the analysis of offshore foundations under a general transient loading is presented here. The theoretical basis of the model lies on the Swansea formulation of Biot's equations of dynamic poroelasticity combined with a constitutive model that reproduces key aspects of cyclic soil behaviour in the frame of the theory of generalised plasticity. On the practical side, the adoption of appropriate finite element formulations may prevent the appearance of spurious numerical instabilities of the pore pressure field. In this respect, the use of a coupled enhanced-strain element is here proposed. On the other hand, the practicality of the presented model depends ultimately on its computational efficiency. Some practical recommendations concerning the solution strategies, the matrix storage/handling procedures and the parallel multi-processor computation are here provided. Finally, the performance of the model with a benchmark study case and its practical application to analyse the soil–structure interaction of an offshore monopile under a realistic transient storm loading are discussed.