@article{BrehmZabelBucher, author = {Brehm, Maik and Zabel, Volkmar and Bucher, Christian}, title = {Optimal reference sensor positions for applications in model updating using output-only vibration test data based on random excitation: Part 2 - improved search strategy and experimental case study}, series = {Mechanical Systems and Signal Processing}, journal = {Mechanical Systems and Signal Processing}, abstract = {Optimal reference sensor positions for applications in model updating using output-only vibration test data based on random excitation: Part 2 - improved search strategy and experimental case study}, subject = {Angewandte Mathematik}, language = {en} } @article{BrehmZabelBucher, author = {Brehm, Maik and Zabel, Volkmar and Bucher, Christian}, title = {An automatic mode pairing strategy using an enhanced modal assurance citerion based on modal strain energies}, series = {Journal of Sound and Vibration}, journal = {Journal of Sound and Vibration}, doi = {10.1016/j.jsv.2010.07.006}, pages = {5375 -- 5392}, abstract = {In the context of finite element model updating using output-only vibration test data, natural frequencies and mode shapes are used as validation criteria. Consequently, the correct pairing of experimentally obtained and numerically derived natural frequencies and mode shapes is important. In many cases, only limited spatial information is available and noise is present in the measurements. Therefore, the automatic selection of the most likely numerical mode shape corresponding to a particular experimentally identified mode shape can be a difficult task. The most common criterion for indicating corresponding mode shapes is the modal assurance criterion. Unfortunately, this criterion fails in certain cases and is not reliable for automatic approaches. In this paper, the purely mathematical modal assurance criterion will be enhanced by additional physical information from the numerical model in terms of modal strain energies. A numerical example and a benchmark study with experimental data are presented to show the advantages of the proposed energy-based criterion in comparison to the traditional modal assurance criterion.}, subject = {Angewandte Mathematik}, language = {en} } @inproceedings{BrehmZabelBucheretal., author = {Brehm, Maik and Zabel, Volkmar and Bucher, Christian and Ribeiro, D.}, title = {AN AUTOMATIC MODE SELECTION STRATEGY FOR MODEL UPDATING USING THE MODAL ASSURANCE CRITERION AND MODAL STRAIN ENERGIES}, editor = {G{\"u}rlebeck, Klaus and K{\"o}nke, Carsten}, organization = {Bauhaus-Universit{\"a}t Weimar}, issn = {1611-4086}, doi = {10.25643/bauhaus-universitaet.2833}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20170314-28330}, pages = {18}, abstract = {In the context of finite element model updating using vibration test data, natural frequencies and mode shapes are used as validation criteria. Consequently, the order of natural frequencies and mode shapes is important. As only limited spatial information is available and noise is present in the measurements, the automatic selection of the most likely numerical mode shape corresponding to a measured mode shape is a difficult task. The most common criterion to indicate corresponding mode shapes is the modal assurance criterion. Unfortunately, this criterion fails in certain cases. In this paper, the pure mathematical modal assurance criterion will be enhanced by additional physical information of the numerical model in terms of modal strain energies. A numerical example and a benchmark study with real measured data are presented to show the advantages of the enhanced energy based criterion in comparison to the traditional modal assurance criterion.}, subject = {Angewandte Informatik}, language = {en} } @article{MostBucher, author = {Most, Thomas and Bucher, Christian}, title = {New concepts for moving least squares: An interpolating non-singular weighting function and weighted nodal least squares}, series = {Engineering Analysis with Boundary Elements}, journal = {Engineering Analysis with Boundary Elements}, pages = {461 -- 470}, abstract = {New concepts for moving least squares: An interpolating non-singular weighting function and weighted nodal least squares}, subject = {Angewandte Mathematik}, language = {en} } @article{BucherMost, author = {Bucher, Christian and Most, Thomas}, title = {A comparison of approximate response functions in structural reliability analysis}, series = {Probabilistic Engineering Mechanics}, journal = {Probabilistic Engineering Mechanics}, pages = {154 -- 163}, abstract = {A comparison of approximate response functions in structural reliability analysis}, subject = {Angewandte Mathematik}, language = {en} } @article{MostBucher, author = {Most, Thomas and Bucher, Christian}, title = {Energy-based simulation of concrete cracking using an improved mixed-mode cohesive crack model within a meshless discretization}, series = {International Journal for Numerical and Analytical Methods in Geomechanics}, journal = {International Journal for Numerical and Analytical Methods in Geomechanics}, pages = {285 -- 305}, abstract = {Energy-based simulation of concrete cracking using an improved mixed-mode cohesive crack model within a meshless discretization}, subject = {Angewandte Mathematik}, language = {en} } @article{MostBucher, author = {Most, Thomas and Bucher, Christian}, title = {Probabilistic analysis of concrete cracking using neural networks and random fields}, series = {Probabilistic Engineering Mechanics}, journal = {Probabilistic Engineering Mechanics}, pages = {219 -- 229}, abstract = {Probabilistic analysis of concrete cracking using neural networks and random fields}, subject = {Angewandte Mathematik}, language = {en} } @article{BucherFrangopol, author = {Bucher, Christian and Frangopol, D.M.}, title = {Optimization of lifetime maintenance strategies for deteriorting structures considering probabilities of violating safety, condition, and cost thresholds}, series = {Probabilistic Engineering Mechanics}, journal = {Probabilistic Engineering Mechanics}, pages = {1 -- 8}, abstract = {Optimization of lifetime maintenance strategies for deteriorting structures considering probabilities of violating safety, condition, and cost thresholds}, subject = {Angewandte Mathematik}, language = {en} } @article{MostBucher, author = {Most, Thomas and Bucher, Christian}, title = {Stochastic simulation of cracking in concrete structures using multi-parameter random fields}, series = {International Journal of Reliability and Safety}, journal = {International Journal of Reliability and Safety}, pages = {168 -- 187}, abstract = {Stochastic simulation of cracking in concrete structures using multi-parameter random fields}, subject = {Angewandte Mathematik}, language = {en} } @inproceedings{MostBucherMacke, author = {Most, Thomas and Bucher, Christian and Macke, M.}, title = {A NATURAL NEIGHBOR BASED MOVING LEAST SQUARES APPROACH WITH INTERPOLATING WEIGHTING FUNCTION}, editor = {G{\"u}rlebeck, Klaus and K{\"o}nke, Carsten}, organization = {Bauhaus-Universit{\"a}t Weimar}, doi = {10.25643/bauhaus-universitaet.2994}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20170327-29943}, pages = {17}, abstract = {The Element-free Galerkin Method has become a very popular tool for the simulation of mechanical problems with moving boundaries. The internally applied Moving Least Squares approximation uses in general Gaussian or cubic weighting functions and has compact support. Due to the approximative character of this method the obtained shape functions do not fulfill the interpolation condition, which causes additional numerical effort for the imposition of the essential boundary conditions. The application of a singular weighting function, which leads to singular coefficient matrices at the nodes, can solve this problem, but requires a very careful placement of the integration points. Special procedures for the handling of such singular matrices were proposed in literature, which require additional numerical effort. In this paper a non-singular weighting function is presented, which leads to an exact fulfillment of the interpolation condition. This weighting function leads to regular values of the weights and the coefficient matrices in the whole interpolation domain even at the nodes. Furthermore this function gives much more stable results for varying size of the influence radius and for strongly distorted nodal arrangements than classical weighting function types. Nevertheless, for practical applications the results are similar as these obtained with the regularized weighting type presented by the authors in previous publications. Finally a new concept will be presented, which enables an efficient analysis of systems with strongly varying node density. In this concept the nodal influence domains are adapted depending on the nodal configuration by interpolating the influence radius for each direction from the distances to the natural neighbor nodes. This approach requires a Voronoi diagram of the domain, which is available in this study since Delaunay triangles are used as integration background cells. In the numerical examples it will be shown, that this method leads to a more uniform and reduced number of influencing nodes for systems with varying node density than the classical circular influence domains, which means that the small additional numerical effort for interpolating the influence radius leads to remarkable reduction of the total numerical cost in a linear analysis while obtaining similar results. For nonlinear calculations this advantage would be even more significant.}, subject = {Architektur }, language = {en} }