TY - JOUR A1 - Alemu, Yohannes L. A1 - Habte, Bedilu A1 - Lahmer, Tom A1 - Urgessa, Girum T1 - Topologically preoptimized ground structure (TPOGS) for the optimization of 3D RC buildings JF - Asian Journal of Civil Engineering N2 - As an optimization that starts from a randomly selected structure generally does not guarantee reasonable optimality, the use of a systemic approach, named the ground structure, is widely accepted in steel-made truss and frame structural design. However, in the case of reinforced concrete (RC) structural optimization, because of the orthogonal orientation of structural members, randomly chosen or architect-sketched framing is used. Such a one-time fixed layout trend, in addition to its lack of a systemic approach, does not necessarily guarantee optimality. In this study, an approach for generating a candidate ground structure to be used for cost or weight minimization of 3D RC building structures with included slabs is developed. A multiobjective function at the floor optimization stage and a single objective function at the frame optimization stage are considered. A particle swarm optimization (PSO) method is employed for selecting the optimal ground structure. This method enables generating a simple, yet potential, real-world representation of topologically preoptimized ground structure while both structural and main architectural requirements are considered. This is supported by a case study for different floor domain sizes. KW - Bodenmechanik KW - Strukturanalyse KW - Optimierung KW - Stahlbetonkonstruktion KW - Dreidimensionales Modell KW - ground structure KW - TPOGS KW - topology optimization KW - 3D reinforced concrete buildings Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20230517-63677 UR - https://link.springer.com/article/10.1007/s42107-023-00640-2 VL - 2023 SP - 1 EP - 11 PB - Springer International Publishing CY - Cham ER - TY - THES A1 - Büchner, Stefan T1 - Methoden zur Ermittlung von Materialkennwerten für numerische Berechnungen in der Geotechnik T1 - Methods for investigation of soil properties for numerical calculations in geotechnics N2 - Bei der Bearbeitung geotechnischer Aufgabenstellungen treten häufig Probleme bei der Vorhersage des Setzungsverhaltens von Böden auf. Numerische Methoden auf Basis finiter Elemente oder finiter Differenzen werden oftmals als Hauptinstrumente der Prognose verwendet. Dabei erzielen sie jedoch nicht selten Ergebnisse, die im Nachhinein als unbefriedigend bezeichnet werden müssen. Eine Begründung dafür liegt in der Verwendung linearer Stoffgesetze, die auf Ansätze aus der Elastizitätstheorie beruhen. Werden höherwertige Stoffgesetze eingesetzt, so fehlen oftmals gesicherte Aussagen zu den erforderlichen Bodenkennwerten. Diese müssen durch ein umfangreiches Versuchsprogramm mit einer aufwendigen Auswertung bestimmt werden. Ziel dieser Arbeit ist es daher, eine robuste Methode zu entwickeln, die in der Lage ist, aus Messwerten (Feld) und Versuchsergebnissen (Labor) geeignete Parameter für Modelle mit nichtlinearer Konsolidationstheorie zu ermitteln. Dazu werden die Möglichkeiten der Mathematik ausgenutzt, welche inverse Methoden zur Verfügung stellt, mit denen man mehrere Bodenkennwerte (hauptsächlich Steifigkeiten und Durchlässigkeiten) gleichzeitig unter Be-rücksichtung ihrer Wechselbeziehungen zueinander bestimmen kann. Als Instrumentarium dafür steht das Programm AdConsol-1D zur Verfügung, welches die inverse Parameterermittlung auf Basis mathematischer Optimierungsmethode ermöglicht. Ein Test- und Versuchsdamm, der im Finnischen Haarajoki (Haarajoki Test Embankment) errichtet wurde und über längeren Zeitraum messtechnisch überwacht wurde, dient als Validationsbeispiel. Dieser wurde auf sehr verformungsempfindlichem Boden errichtet. Durch Aufbereitung und Auswertung der Feld- und Laborversuche am Haarajoki Test Embankment wurden die Grundlagen für die inverse Parameterermittlung geschaffen. Dazu wurde eine Methode zur Konstruktion plausib-ler Porenwasserüberdrücke aus Setzungsmessungen und Laborversuchsdaten entwickelt. Mit den Werten der Optimierung wurde ein Modell im 2D FEM Programm Plaxis erstellt, welches die in Haarajoki gemessenen Setzungen und Porenwasserdrücke möglichst genau reproduzieren sollte. Es zeigte sich, dass sich Bodenparameter des eindimensionalen nichtlinearen Konsolidati-onsmodells nicht problemlos auf ein 2D FEM Modell übertragen lassen. Insbesondere fehlen gesicherte Aussagen über die Größe des horizontalen Durchlässigkeitskoeffizienten kx und des Referenzsekantenmoduls E50Ref aus dem Triaxialversuch. Die inverse Berechnung für sich betrachtet verlief dahingegen zufrieden stellend mit dem eindimensionalen Modell in AdConsol-1D. Auf dieser Grundlage ist die Erstellung einer realistischen Prognose des weiteren Konsolidationsverlaufes am Haarajoki Test Embankment möglich. N2 - In geotechnics, problems frequently appear in the prediction of settlements for soils. Numerical Methods based on Finite Elements or Finite Differences are often used as main instruments for prediction. These methods often produce unsatisfying results. One reason is the utilization of linear material laws which are based on the theory of elasticity. Introducing ad-vanced material laws secure informations lack for required soil parameters. They need to be determined in an extensive test programm with complex evaluation.The intention is, to develop a robust method, which is able to determine adequate parameters from measurements and laboratory examinations using a one dimensional nonlinear theory of consolidation. In addidtion the possibilities of mathematics are used, which provide invers methods for the simultaneous determination of several soil parameters (especially stiffness and permeability parameters) and their correlations. As instrument the programm AdConsol-1D was available, which offers the invers parameter investigation on basis of mathematical optimization meth-ods. An embankment for tests and examination, the Haarajoki Test Embankment serves as validation example. Pore pressures and cumulative settlements were observed for a long time period at the embankment, which was built on very soft soil. The conditioning and evaluation of field and laboratory tests from the Haarajoki Test Embankment accomplished a basis for the invers parameter determination. For that purpose a method for designing plausible excess pore pressures, using measurements of settlements and laboratory test datas, was developed. A model was constracted with the 2D FEM programm Plaxis using the values from the opti-mization, which ought to reproduce the measured settlements and excess pore pressures from Haarajoki Test Embankment as accurately as possible. It was shown, that the soil properties from the one-dimensional non-linear consolidation model can’t be assigned without problems onto a 2D FEM model. Especially lack firmed information about the value of horizontal permeability kx and the modulus for the secant stiffness in standard drained triaxial tests (E50Ref). Whereas the invers calculation itself produced a satisfying result with the one-dimensional model of AdConsol-1D. On that basis the construction of a realistic prediction of former consolidation process at Haarajoki Test Embankment is possible. KW - Konsolidation KW - Inverses Problem KW - Bodenmechanik KW - Parameterschätzung KW - Kennwertermittlung KW - nichtlineare Konsolidationstheorie KW - numerische Berechnungen KW - mathematische Optimierungsmethoden KW - non-linear consolidation KW - determination of soil properties KW - numerical methods Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-5524 N1 - Der Volltext-Zugang wurde im Zusammenhang mit der Klärung urheberrechtlicher Fragen mit sofortiger Wirkung gesperrt. ER - TY - JOUR A1 - Strukelj, A. T1 - Some Problems in Obtaining the Green's Function of the Layered Soil N2 - The frame of this paper is the development of methods and procedures for the description of the motion of an arbitrary shaped foundation. Since the infinite half-space cannot be properly described by a model of finite dimensions without violating the radiation condition, the basic problems are infinite dimensions of the half-space as well as its non-homogeneous nature. Consequently, an approach has been investigated to solve this problem indirectly by developing Green's function in which the non-homogeneity and the infiniteness of the half-space has been included. When the Green's function is known, the next step will be the evaluation of contact stresses acting between the foundation and the surface of the half-space through an integral equation. The equation should be solved in the area of the foundation using Green's function as the kernel. The derivation of three-dimensional Green's function for the homogeneous half-space (Kobayashi and Sasaki 1991) has been made using the potential method. Partial differential equations occurring in the problem have been made ordinary ones through the Hankel integral transform. The general idea for obtaining the three-dimensional Green's function for the layered half-space is similar. But in that case some additional phenomena may occur. One of them is the possibility of the appearance of Stonely surface waves propagating along the contact surfaces of layers. Their contribution to the final result is in most cases important enough that they should not be neglected. The main advantage of results presented in comparing to other obtained with numerical methods is their accuracy especially in the case of thin layers because all essential steps of Green's function evaluation except of the contour integration along the branch cut have been made analytically. On the other hand the disadvantage of this method is that the mathematical effort for obtaining the Green's function is increasing drastically with the increase of the number of layers. Future work will therefore be directed in simplifying of the above described process KW - Bodenmechanik KW - Geschichtetes Medium KW - Green-Funktion Y1 - 1997 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-5388 ER -