@misc{Adler, type = {Master Thesis}, author = {Adler, Maria}, title = {Energiedissipation durch F{\"u}gestellend{\"a}mpfung in Leichtbauanwendungen}, doi = {10.25643/bauhaus-universitaet.4394}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20210316-43949}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {71}, abstract = {In vielen Leichtbauanwendungen ist der begrenzende Faktor die Schwingungsanf{\"a}lligkeit der Bauteile. Eine M{\"o}glichkeit der Begrenzung von Schwingungsamplituden ist der gezielte Einsatz von Reibungsd{\"a}mpfung in Leichtbaustrukturen. In dieser Arbeit wird der Einfluss dieser Art von Energiedissipation auf Leichtmetallstrukturen sowie topologieoptimierte Bauteil untersucht. Betrachtet werden dabei die Positionierung, Dimensionierung sowie die Reibeigenschaften dissipativer Elemente.}, subject = {Leichtbau}, language = {de} } @misc{Ansari, type = {Master Thesis}, author = {Ansari, Meisam}, title = {Simulation methods for functional and microstructured composite materials}, doi = {10.25643/bauhaus-universitaet.4278}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20201103-42783}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {110}, abstract = {In this thesis, a generic model for the post-failure behavior of concrete in tension is proposed. A mesoscale model of concrete representing the heterogeneous nature of concrete is formulated. The mesoscale model is composed of three phases: aggregate, mortar matrix, and the Interfacial Transition Zone between them. Both local and non-local formulations of the damage are implemented and the results are compared. Three homogenization schemes from the literature are employed to obtain the homogenized constitutive relationship for the macroscale model. Three groups of numerical examples are provided.}, subject = {Simulation}, language = {en} } @article{AnsariTartaglioneKoenke, author = {Ansari, Meisam and Tartaglione, Fabiola and K{\"o}nke, Carsten}, title = {Experimental Validation of Dynamic Response of Small-Scale Metaconcrete Beams at Resonance Vibration}, series = {materials}, volume = {2023}, journal = {materials}, number = {volume 16, issue 14, article 5029}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/ma16145029}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20230818-64154}, pages = {1 -- 17}, abstract = {Structures and their components experience substantially large vibration amplitudes at resonance, which can cause their failure. The scope of this study is the utilization of silicone-coated steel balls in concrete as damping aggregates to suppress the resonance vibration. The heavy steel cores oscillate with a frequency close to the resonance frequency of the structure. Due to the phase difference between the vibrations of the cores and the structure, the cores counteract the vibration of the structure. The core-coating inclusions are randomly distributed in concrete similar to standard aggregates. This mixture is referred to as metaconcrete. The main goal of this work is to validate the ability of the inclusions to suppress mechanical vibration through laboratory experiments. For this purpose, two small-scale metaconcrete beams were cast and tested. In a free vibration test, the metaconcrete beams exhibited a larger damping ratio compared to a similar beam cast from conventional concrete. The vibration amplitudes of the metaconcrete beams at resonance were measured with a frequency sweep test. In comparison with the conventional concrete beam, both metaconcrete beams demonstrated smaller vibration amplitudes. Both experiments verified an improvement in the dynamic response of the metaconcrete beams at resonance vibration.}, subject = {Beton}, language = {en} } @article{AnsariZachariasKoenke, author = {Ansari, Meisam and Zacharias, Christin and K{\"o}nke, Carsten}, title = {Metaconcrete: An Experimental Study on the Impact of the Core-Coating Inclusions on Mechanical Vibration}, series = {materials}, volume = {2023}, journal = {materials}, number = {Volume 16, Issue 5, article 1836}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/ma16051836}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20230315-49370}, pages = {1 -- 18}, abstract = {Resonance vibration of structures is an unpleasant incident that can be conventionally avoided by using a Tuned Mass Damper (TMD). The scope of this paper contains the utilization of engineered inclusions in concrete as damping aggregates to suppress resonance vibration similar to a TMD. The inclusions are composed of a stainless-steel core with a spherical shape coated with silicone. This configuration has been the subject of several studies and it is best known as Metaconcrete. This paper presents the procedure of a free vibration test conducted with two small-scaled concrete beams. The beams exhibited a higher damping ratio after the core-coating element was secured to them. Subsequently, two meso-models of small-scaled beams were created: one representing conventional concrete and the other representing concrete with the core-coating inclusions. The frequency response curves of the models were obtained. The change in the response peak verified the ability of the inclusions to suppress the resonance vibration. This study concludes that the core-coating inclusions can be utilized in concrete as damping aggregates.}, subject = {Beton}, language = {en} } @phdthesis{Bianco, author = {Bianco, Marcelo Jos{\´e}}, title = {Coupling between Shell and Generalized Beam Theory (GBT) elements}, doi = {10.25643/bauhaus-universitaet.4391}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20210315-43914}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {265}, abstract = {In the last decades, Finite Element Method has become the main method in statics and dynamics analysis in engineering practice. For current problems, this method provides a faster, more flexible solution than the analytic approach. Prognoses of complex engineer problems that used to be almost impossible to solve are now feasible. Although the finite element method is a robust tool, it leads to new questions about engineering solutions. Among these new problems, it is possible to divide into two major groups: the first group is regarding computer performance; the second one is related to understanding the digital solution. Simultaneously with the development of the finite element method for numerical solutions, a theory between beam theory and shell theory was developed: Generalized Beam Theory, GBT. This theory has not only a systematic and analytical clear presentation of complicated structural problems, but also a compact and elegant calculation approach that can improve computer performance. Regrettably, GBT was not internationally known since the most publications of this theory were written in German, especially in the first years. Only in recent years, GBT has gradually become a fertile research topic, with developments from linear to non-linear analysis. Another reason for the misuse of GBT is the isolated application of the theory. Although recently researches apply finite element method to solve the GBT's problems numerically, the coupling between finite elements of GBT and other theories (shell, solid, etc) is not the subject of previous research. Thus, the main goal of this dissertation is the coupling between GBT and shell/membrane elements. Consequently, one achieves the benefits of both sides: the versatility of shell elements with the high performance of GBT elements. Based on the assumptions of GBT, this dissertation presents how the separation of variables leads to two calculation's domains of a beam structure: a cross-section modal analysis and the longitudinal amplification axis. Therefore, there is the possibility of applying the finite element method not only in the cross-section analysis, but also the development for an exact GBT's finite element in the longitudinal direction. For the cross-section analysis, this dissertation presents the solution of the quadratic eigenvalue problem with an original separation between plate and membrane mechanism. Subsequently, one obtains a clearer representation of the deformation mode, as well as a reduced quadratic eigenvalue problem. Concerning the longitudinal direction, this dissertation develops the novel exact elements, based on hyperbolic and trigonometric shape functions. Although these functions do not have trivial expressions, they provide a recursive procedure that allows periodic derivatives to systematise the development of stiffness matrices. Also, these shape functions enable a single-element discretisation of the beam structure and ensure a smooth stress field. From these developments, this dissertation achieves the formulation of its primary objective: the connection of GBT and shell elements in a mixed model. Based on the displacement field, it is possible to define the coupling equations applied in the master-slave method. Therefore, one can model the structural connections and joints with finite shell elements and the structural beams and columns with GBT finite element. As a side effect, the coupling equations limit the displacement field of the shell elements under the assumptions of GBT, in particular in the neighbourhood of the coupling cross-section. Although these side effects are almost unnoticeable in linear analysis, they lead to cumulative errors in non-linear analysis. Therefore, this thesis finishes with the evaluation of the mixed GBT-shell models in non-linear analysis.}, subject = {Biegetheorie}, language = {en} } @misc{Bock2004, type = {Master Thesis}, author = {Bock, Sebastian}, title = {Approximation mit polynomialen L{\"o}sungen der Lam{\´e}schen Differentialgleichung}, doi = {10.25643/bauhaus-universitaet.640}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-6409}, school = {Bauhaus-Universit{\"a}t Weimar}, year = {2004}, abstract = {Grundidee der Arbeit ist es, L{\"o}sungen von Randwertaufgaben durch Linearkombinationen exakter klassischer L{\"o}sungen der Differentialgleichung zu approximieren. Die freien Koeffizienten werden dabei durch die Bestimmung der besten Approximation der Randwerte berechnet. Als Basis der Approximation werden vollst{\"a}ndige orthogonale und nahezu orthogonale Funktionensysteme verwendet. Anhand ausgew{\"a}hlter Beispiele mit Randvorgaben unterschiedlicher Glattheit wird am Beispiel der Kugel die prinzipielle Anwendbarkeit der Methode getestet und hinsichtlich der Entwicklung des Fehlers der N{\"a}herungsl{\"o}sung, der Stabilit{\"a}t des Verfahrens und des numerischen Aufwandes untersucht. Die erhaltenen Resultate geben einen begr{\"u}ndeten Anlass, die Anwendung der Methode als Bestandteil einer hybriden analytisch-numerischen Methode, insbesondere der Verkn{\"u}pfung mit der FEM, weiterzuverfolgen.}, subject = {Legendre-Funktion}, language = {de} } @phdthesis{Hatahet, author = {Hatahet, Tareq}, title = {On the Analysis of the Disproportionate Structural Collapse in RC Buildings}, doi = {10.25643/bauhaus-universitaet.3740}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20180329-37405}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {243}, abstract = {Increasing structural robustness is the goal which is of interest for structural engineering community. The partial collapse of RC buildings is subject of this dissertation. Understanding the robustness of RC buildings will guide the development of safer structures against abnormal loading scenarios such as; explosions, earthquakes, fine, and/or long-term accumulation effects leading to deterioration or fatigue. Any of these may result in local immediate structural damage, that can propagate to the rest of the structure causing what is known by the disproportionate collapse. This work handels collapse propagation through various analytical approaches which simplifies the mechanical description of damaged reinfoced concrete structures due to extreme acidental event.}, subject = {Beton}, language = {en} } @misc{Hollerbuhl2005, type = {Master Thesis}, author = {Hollerbuhl, Lutz}, title = {Simulation der Sch{\"a}digung der K{\"o}lnbreintalsperre w{\"a}hrend des Ersteinstaus 1978}, doi = {10.25643/bauhaus-universitaet.587}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-5877}, school = {Bauhaus-Universit{\"a}t Weimar}, year = {2005}, abstract = {Die Arbeit befasst sich mit der {\"o}sterreichischen Bogenstaumauer K{\"o}lnbrein, die w{\"a}hrend des Ersteinstaus gesch{\"a}digt wurde. Diese Sch{\"a}den, sowie m{\"o}gliche Ursachen sind anhand von Literaturquellen dokumentiert. Nach Erstellung eines Rechenmodells wurden, durch ein Randelementeprogramm, Rissfortschrittsberechnungen durchgef{\"u}hrt und mit dem realen Bauwerk verglichen. Zum Einsatz kamen die Anwendungen „OSM", „FRANC3D" und „BES" der Cornell-University.}, subject = {Rissausbreitung}, language = {de} } @phdthesis{Itam, author = {Itam, Zarina}, title = {Numerical Simulation of Thermo-Chemo-Hygro-Mechanical Alkali-Silica Reaction Model in Concrete at the Mesoscale and Macroscale}, doi = {10.25643/bauhaus-universitaet.2335}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20141218-23352}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {164}, abstract = {Alkali-silica reaction causes major problems in concrete structures due to the rapidity of its deformation which leads to the serviceability limit of the structure being reached well before its time. Factors that affect ASR vary greatly, including alkali and silica content, relative humidity, temperature and porosity of the cementitious matrix,all these making it a very complex phenomenon to consider explicitly. With this in mind, the finite element technique was used to build models and generate expansive pressures and damage propagation due to ASR under the influence of thermo-hygrochemoelastic loading. Since ASR initializes in the mesoscopic regions of the concrete, the accumulative effects of its expansion escalates onto the macroscale level with the development of web cracking on the concrete surface, hence solution of the damage model as well as simulation of the ASR phenomenon at both the macroscale and mesoscale levels have been performed. The macroscale model realizes the effects of ASR expansion as a whole and shows how it develops under the influence of moisture, thermal and mechanical loading. Results of the macroscale modeling are smeared throughout the structure and are sufficient to show how damage due to ASR expansion orientates. As opposed to the mesoscale model, the heterogeneity of the model shows us how difference in material properties between aggregates and the cementitious matrix facilitates ASR expansion. With both these models, the ASR phenomenon under influence of thermo-chemo-hygro-mechanical loading can be better understood.}, subject = {Strukturmechanik}, language = {en} } @misc{Kessel2005, type = {Master Thesis}, author = {Kessel, Marco}, title = {Implementierung rechteckiger Scheibenelemente mit B-Spline Ans{\"a}tzen n-ter Ordnung}, doi = {10.25643/bauhaus-universitaet.682}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-6822}, school = {Bauhaus-Universit{\"a}t Weimar}, year = {2005}, abstract = {Diese Arbeit stellt die Implementierung von Scheibenelementen mit B-Spline Ans{\"a}tzen n-ter Ordnung speziell f{\"u}r rechteckige Gebiete mit orthogonaler Vernetzung vor. Dabei kam insbesondere eine spezielle elementbasierte Formulierung auf Grundlage der einzelnen B-Spline Segmente zum Einsatz, die zur Aufbringung von Randbedingungen an den R{\"a}ndern modifizierte B-Splines benutzt. In der Folge entstehen verschiedene Elementtypen zur Diskretisierung von rechteckigen Gebieten, deren Erzeugung, Speicherung und Anwendung im Zusammenhang mit der Finiten Elemente Methode Gegenstand der Arbeit sind. Anhand von untersuchten Beispielen werden die erfolgreiche Implementierung nachgewiesen und verschiedene Eigenschaften der Methode herausgestellt.}, subject = {B-Splines}, language = {de} }