The failure of one structural element can lead to the failure of further structural elements and thus to the collapse of large sections or the entire structure. Such disproportionate collapses have been discussed and investigated for some years, but mainly for buildings. In the field of bridge engineering, this phenomenon attracts only sporadic attention. Although international guidelines for cable-stayed bridges require that the loss of one cable must not lead to the collapse of the entire structure, comprehensive analyses that include non-linear dynamic effects are rare. To simply account for dynamic effects, a quasi-static analysis with a dynamic amplification factor of 2.0 is recommended. This value is possibly too large, leading to uneconomic solutions. Therefore, this work examines the structural response of a cable-stayed bridge to the loss of one cable by means of dynamic analyses including large displacements. The effects of cable sag, transverse cable vibrations and structural damping are determined and dynamic amplification factors are computed.
Local failure of one structural element may result in the failure of another element of the same structure. Failure might thus progress throughout a major part or all of the structure. Design criteria for preventing such a progression of collapse are discussed. Investigative methods and design strategies for creating collapse-resistant structures are presented and compared. In addition to the better-known approaches providing specific local resistance or alternate load paths, an approach based on isolation of collapsing sections is described and discussed.
Resumo -Neste artigo, apresentam-se os modelos e um método para análise da convergência de um algoritmo genético para determinação das matrizes de ponderação do Regulador Linear Quadrático. O objetivo de controle é a alocação de autoestruturas em sistemas dinâmicos multivariáveis, a qual é imposta pela lei de Controle Ótimo, e o objetivo do procedimento da análise é promover a aceleração da convergência por meio de métricas que estão fundamentadas em momentos estatísticos de primeira e segunda ordem. O desempenho dos modelos é avaliado sob o ponto de vista da construção da população inicial, populações do processo de busca e população final. A análise de convergência conduz ao desenvolvimento de regras baseadas em métricas da função de fitness. Os testes de avaliação dos modelos de busca genética e da eficiência da lei de controle são realizados em um modelo dinâmico de 6 a ordem que representa uma aeronave.
Für den abschnittsweisen Ersatzneubau der Deelbögebrücke wurde in Zusammenarbeit zwischen dem Landesbetrieb Straßen, Brücken und Gewässer Hamburg (LSBG), dem Ingenieurbüro Grassl und dem Lehrstuhl für Massivbau der Ruhr-Universität Bochum ein Verfahren zur nachträglichen Zwischenverankerung von Querspanngliedern entwickelt. Dieses ermöglicht den Erhalt eines Teils der Brücke für eine ungestörte Verkehrsführung während der Bauzeit. Eine Stahlklemmkonstruktion überträgt über Reibschluss die freiwerdende Vorspannkraft und leitet sie über Druckkräfte in den verbleiben Überbau wieder ein. Der Beitrag zeigt den Entwurf für den Rückbau, die Entwicklung und experimentelle Untersuchung der Stahlklemmkonstruktion und die erfolgreiche Umsetzung der Baumaßnahme.Subsequent anchorage of transverse prestressing cables clamping devices to rebuild Deelböge Bridge a clamping device to subsequently anchor transverse prestressing bars is developed. It transfers the released prestressing forces via shear friction to clamping steel plates and then by direct compressive contact to the surrounding concrete. The device is applied to stepwise rebuild the Deelböge Bridge in Hamburg continuously ensuring an ongoing traffic on one side of the bridge during building activities. The contribution lays out the conceptual design of the bridge rebuilt, the theoretical and technical elaboration of the clamping device as well as its successful application on site.
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