Niels Jørgen Gimsing

Direct measurements of buffeting wind forces on bridge decks

Abstract Direct measurements of the forces induced by the buffeting action of wind on a motionless bridge deck have been carried out at the Danish Maritime Institute. The wind tunnel experiments aimed at defining the spatial distribution of the wind loading as a function of the deck width and the scales of the incident turbulence. This paper presents the main findings of the experiments and illustrates the impetus behind this research which was to evaluate, for closed-box girder bridge decks, the error margin of the wind load predictions based on the strip assumption.

A study on improving the design of hybrid stress-ribbon bridges and their aerodynamic stability

Abstract Preliminary designs were made for the proposals for the ‘stress-ribbon cable-stayed suspension’ and the ‘stress-ribbon suspension’ bridges with an open-grating deck plate for pedestrian use. The findings of this study revealed the followings: That the horizontal component of tensile force in the cables can be reduced up to 1/23 of the conventional concrete stress-ribbon bridges; the maximum deflection of the girder under asymmetrical live load can be well controlled by installing central clamps; the critical flutter speed is sufficiently high; and that vortex-induced oscillation does not occur. The application of the proposals for hybrid structures to vehicle bridges was also examined.

Aerodynamic stability of non-symmetrically erected suspension bridge girders

Abstract An aeroelastic model of a suspension bridge at its deck erection stages was wind tunnel tested. With a shallow streamlined box as its deck cross-section, the flutter-type instability was the main concern. An interesting observation was that the bridge was found to be more stable when the suspended deck was extended in a non-symmetric manner as opposed to the traditional symmetric erection schedule. It is possible to use non-symmetric deck configurations as a stabilizing measure during the deck erection.

Wind engineering aspects of the east bridge tender project

Abstract The present paper presents a review of simple analytical models available in the literature for assessment of structural dynamic and aerodynamic performance of suspension bridges. Analytical predictions are compared to results obtained from structural FEM-models and comprehensive wind tunnel tests carried out for a box girder suspension bridge of 1624 meter main span. Satisfactory correlation is obtained for basic natural frequencies and for flutter and buffeting predictions. A modification to the Selberg formula is suggested which accounts for the enhancement of aerodynamic stability through a windward shift of the section centre of gravity.

Debonding of FRC Composite Bridge Deck Overlay

ABSTRACT A new type of composite bridge deck is currently under research. The concept is to achieve composite action by the adhesion between a thin layer of fiber reinforced concrete cast on a steel plate. Of special concern is the strength of the bond between the concrete and steel plate in the case of vertical cracking of the overlay. Based on a nonlinear 2D finite element model a theoretical parameter study has been conducted in relation to debonding of a concrete overlay. Discrete crack theory was used to model vertical cracking of the overlay and interfacial cracking (debonding) between the steel plate and concrete. Two parameter studies were made. One concerns the fracture energy of the overlay and steel-concrete interface. These results show that the composite performance is dependent primarily on fracture energy of the concrete overlay, and less on the fracture energy of the steel-concrete interface. In the other, the mixed mode behaviour of the steel-concrete interface is studied in relation to the interfacial failure criterion.

Wind design of the Great Belt East Bridge: A historic retrospect

Abstract The evolution within the wind design of large bridges is clearly reflected in the design process for the Great Belt East Bridge that started with a large and heavy truss bridge and were concluded with a slender and light suspension bridge.