Wind-structure interaction simulations for the prediction of ovalling vibrations in silo groups

Wind-induced ovalling vibrations were observed during a storm in October 2002 on several empty silos of a closely spaced group consisting of 8 by 5 thin-walled silos in the port of Antwerp (Belgium). The purpose of the present research is to investigate if such ovalling vibrations can be predicted by means of numerical simulations. More specifically, the necessity of performing computationally demanding wind-structure interaction (WSI) simulations is assessed. For this purpose, both one-way and two-way coupled simulations are performed. Before considering the entire silo group, a single silo in crosswind is simulated. The simulation results are in reasonably good agreement with observations and WSI simulations seem to be required for a correct prediction of the observed ovalling vibrations

Pre-posterior analysis of inspections incorporating degradation of concrete structures

The framework of pre-posterior decision analysis has a large potential as a decision support tool in structural engineering. It seems ideally suited to tackle problems related to determining the value of Structural Health Monitoring and is commonly applied in inspection and maintenance planning. However, the application of this methodology for integrated life-cycle cost decision making related to monitoring of time-dependent and spatial degradation phenomena in concrete structures, needs further investigation. In this work, the timedependent and spatial degradation phenomena will be coupled to the pre-posterior decision making approach and applied on concrete beams under bending, subjected to corrosion of the reinforcement. A framework is set up to determine the value of information of inspections enabling adequate decision-making. The methodology incorporates Bayesian updating based on the uncertain inspection outcomes. The framework will be illustrated by application on a simply supported reinforced concrete beam

A first assessment of the interdependency of mesh motion and free surface models in openfoam regarding wave-structure interaction

Mesh motion is of key importance in assuring adequate CFD modelling of wave- structure interaction problems, such as wave impact on floating offshore wind turbines and seakeeping of ships. Wave forcing often leads to large displacements of floating structures. As a consequence, the fluid domain boundaries need to move in order to accommodate for these wave-induced displacements. The mesh quality needs to be preserved at all times to guarantee accurate and stable results for the rigid body displacements as well as for the fluid variables. Mesh deformation techniques, in particular algebraic mesh motion methods, have been widely used within the OpenFOAM framework during the last decade. Unfortunately, stability is easily jeopardized in case of large displacements. Large mesh deformation gives rise to computation- ally demanding and unstable results. Sliding meshes have been used to address this issue, but they are cumbersome for multi-degree of freedom motion. Therefore, overset methods have been implemented in recent versions of OpenFOAM. Especially, the newly implemented overset meth- ods in the OpenFOAM branch foam-extend, have shown to give good results for an acceptable runtime. Simultaneously, considerable progress has been made on the development of alternatives for alge- braic volume-of-fluid methods for free surface modelling, which notoriously suffer from smearing effects. Although it seems reasonable to expect that the choice in free surface model combined with a certain mesh motion technique will have an influence on the overal result, the interde- pendency between mesh motion techniques and free surface modelling has not been studied yet. This paper aims at taking the first steps towards a better understanding of this mesh motion-free surface interdependency and, as such, facilitate an informed choice

Computational fluid-structure interaction simulations for wind induced vibrations in silo groups

During a storm in October 2002, wind induced ovalling vibrations were observed on several empty silos of a closely spaced group consisting of 8 by 5 silos in the port of Antwerp (Belgium). First, a thorough understanding of the fluid flow around the group is required to clarify the underlying mechanisms for the vibration. Since the configuration and orientation of the group drastically change the pressure distribution on the silos of the group, the flow regime around and within the silo group has been simulated for 7 angles of incidence between 0 and 90, leaving other parameters unchanged (e.g. spacing ratio, Reynolds number,...). The flow regime shows similarities with the flow within tube arrays (e.g. heat exchangers) and the flow around rectangular cylinders. By a ‘one way coupling’ of static (time averaged) and dynamic (fluctuating) pressure loadings on the cylinder surfaces it is examined if the excitation of ovalling vibrations in the silo group is possible. Two probable causes of observable silo vibrations in the group are observed. The first, as a result of large static wind pressures and fluctuating drag and lift coefficients, might lead to rigid body motions of the statically deformed silos. The second, due to higher dynamic pressure oscillations, can excite ovalling oscillations in the third and fourth eigenmodes at the lee side of the group, corresponding with the lowest eigenfrequencies of the silos and the visually detected vibrations in 2002. Although it is shown by this ‘one way coupling’ that ovalling vibrations can be excited in the group, more advanced ‘two way coupled’ fluid-structure interaction simulations are required to determine the underlying mechanism inducing these aeroelastic deformations

Measurements and Numerical Prediction of High Speed Train Vibrations

This paper discusses the experimental validation of a numerical prediction model for train induced vibrations. The model fully accounts for the dynamic interaction between the train, the track and the soil. The track is modelled as a longitudinally invariant system, where two beams represent the rails, while a plate with a rigid cross section represents the subgrade. The track is located at the surface of a horizontally layered elastic halfspace. The translational invariance of the problem geometry enables a solution of the equations of motion in the frequency–wavenumber domain. The model is validated by means of vibration measurements that have been performed at the occasion of the homologation tests of the new HST track on the line L2 between Brussels and K¨oln during the passage of an IC train and a Thalys HST at variable speed

An overview of p-refined Multilevel quasi-Monte Carlo Applied to the Geotechnical Slope Stability Problem

[EN] Problems in civil engineering are often characterized by significant uncertainty in their material parameters. Sampling methods are a straightforward manner to account for this uncertainty, which is typically modeled as a random field. A popular sampling method consists of the classic Multilevel Monte Carlo method (h-MLMC). Its most distinctive feature consists of a hierarchy of h-refined meshes, where most of the samples are taken on coarse and computationally inexpensive meshes, and few are taken on finer but computationally expensive meshes. We present an improvement upon the classic Multilevel Monte Carlo, called the prefined Multilevel quasi-Monte Carlo method (p-MLQMC). Its key features consist of a mesh hierarchy constructed from a p-refinement scheme combined with a deterministic set of samples points (quasi-Monte Carlo points). In this work we show how the uncertainty needs to be accounted for and present results comparing the total computational cost of the h-ML(Q)MC and p-MLQMC method. Specifically, we present two novel approaches in order to account for the uncertainty in case of p-MLQMC. We benchmarking the different multilevel methods on a slope stability problem, and find that p-MLQMC outperforms h-MLMC up to several orders of magnitude.The authors gratefully acknowledge the support from the Research Council of KU Leuven through project C16/17/008 “Efficient methods for large-scale PDE-constrained optimization in the presence of uncertainty and complex technological constraints”. The computational resources and services used in this work were provided by the VSC (Flemish Supercomputer Center), funded by the Research Foundation - Flanders (FWO) and the Flemish Government – department EWI.Blondeel, P.; Robbe, P.; François, S.; Lombaert, G.; Vandewalle, S. (2022). An overview of p-refined Multilevel quasi-Monte Carlo Applied to the Geotechnical Slope Stability Problem. En Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference. Editorial Universitat Politècnica de València. 25-35. https://doi.org/10.4995/YIC2021.2021.12236OCS253