TY - JOUR A1 - Ansari, Meisam A1 - Tartaglione, Fabiola A1 - Könke, Carsten T1 - Experimental Validation of Dynamic Response of Small-Scale Metaconcrete Beams at Resonance Vibration JF - materials N2 - 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. KW - Beton KW - metaconcrete KW - Schwingungsdämpfung KW - damping aggregate KW - vibration absorber KW - free vibration test KW - frequency sweep test Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20230818-64154 UR - https://www.mdpi.com/1996-1944/16/14/5029 VL - 2023 IS - volume 16, issue 14, article 5029 SP - 1 EP - 17 PB - MDPI CY - Basel ER - TY - JOUR A1 - Ansari, Meisam A1 - Zacharias, Christin A1 - Könke, Carsten T1 - Metaconcrete: An Experimental Study on the Impact of the Core-Coating Inclusions on Mechanical Vibration JF - materials N2 - 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. KW - Beton KW - Schwingungsdämpfung KW - metaconcrete KW - damping aggregate KW - vibration absorber Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20230315-49370 UR - https://www.mdpi.com/1996-1944/16/5/1836 VL - 2023 IS - Volume 16, Issue 5, article 1836 SP - 1 EP - 18 PB - MDPI CY - Basel ER - TY - THES A1 - Ansari, Meisam T1 - Simulation methods for functional and microstructured composite materials T1 - Simulationsmethoden für funktionalisierte und mikrostrukturierte Verbundwerkstoffe N2 - 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. N2 - In dieser Arbeit wird ein generisches Modell für das nichtlineare Materialverhalten des Betons unter Spannung vorgeschlagen. Ein Mesoskalenmodell wird aufgebildet, welches die heterogene Materialstruktur des Betons darstellt. Das Mesoskalenmodell besteht aus drei Phasen: groben Zuschlägen, Mörtelmatrix und Übergangszone zwischen Zuschlag und Matrix. Es werden sowohl die lokale als auch die nichtlokale Formulierung des Schädigungsgrades implementiert und die Ergebnisse verglichen. Drei Homogenisierungsmethoden aus der Literatur werden verwendet, um die homogenisierte konstitutive Beziehung für das Makroskalenmodell zu erhalten. Drei Gruppen von numerischen Beispielen werden angeführt. KW - Simulation KW - Verbundwerkstoff KW - Beton KW - Meso-Scale KW - Composite KW - Concrete Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20201103-42783 ER - TY - THES A1 - Hatahet, Tareq T1 - On the Analysis of the Disproportionate Structural Collapse in RC Buildings N2 - 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. T3 - ISM-Bericht // Institut für Strukturmechanik, Bauhaus-Universität Weimar - 2018,2 KW - Beton KW - disproportionate collapse KW - buildings KW - reinforced concrete KW - catenary action KW - compressive arching KW - dynamic amplifification KW - structural robustness Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20180329-37405 ER - TY - THES A1 - Kurukuri, Srihari T1 - Homogenization of Damaged Concrete Mesostructures using Representative Volume Elements - Implementation and Application to SLang N2 - This master thesis explores an important and under-researched topic on the so-called bridging of length scales (from >meso< to >macro<), with the concept of homogenization in which the careful characterization of mechanical response requires that the developed material model >bridge< the representations of events that occur at two different scales. The underlying objective here is to efficiently incorporate material length scales in the classical continuum plasticity/damage theories through the concept of homogenization theory. The present thesis is devoted to computational modeling of heterogeneous materials, primarily to matrix-inclusion type of materials. Considerations are focused predominantly on the elastic and damage behavior as a response to quasistatic mechanical loading. Mainly this thesis focuses to elaborate a sound numerical homogenization model which accounts for the prediction of overall properties with the application of different types of boundary conditions namely: periodic, homogeneous and mixed type of boundary conditions over two-dimensional periodic and non-periodic RVEs and three-dimensional non-periodic RVEs. Identification of the governing mechanisms and assessing their effect on the material behavior leads one step further. Bringing together this knowledge with service requirements allows for functional oriented materials design. First, this thesis gives attention on providing the theoretical basic mechanisms involved in homogenization techniques and a survey will be made on existing analytical methods available in literature. Second, the proposed frameworks are implemented in the well known finite element software programs ANSYS and SLang. Simple and efficient algorithms in FORTRAN are developed for automated microstructure generation using RSA algorithm in order to perform a systematic numerical testing of microstructures of composites. Algorithms are developed to generate constraint equations in periodic boundary conditions and different displacements applied spatially over the boundaries of the RVE in homogeneous boundary conditions. Finally, nonlinear simulations are performed at mesolevel, by considering continuum scalar damage behavior of matrix material with the linear elastic behavior of aggregates with the assumption of rigid bond between constituents. KW - Schadensmechanik KW - Finite-Elemente-Methode KW - Beton KW - Homogenisierung KW - Repräsentative Volumen Elemente KW - Mesoskala KW - Homogenization KW - Representative Volume Elements KW - Mesoscale Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-6670 N1 - Der Volltext-Zugang wurde im Zusammenhang mit der Klärung urheberrechtlicher Fragen mit sofortiger Wirkung gesperrt. ER -