Abstract
Modern design solutions in cable-stayed bridges give a significant importance to the seismic response in the transverse direction. This work is focused on the dynamic interaction between the deck and the towers, exploring the key role of different vibration modes. An extensive parametric analysis is proposed to address the influence of the main span length, the tower geometry, the cable-system arrangement, the width and height of the deck and the soil conditions. It is demonstrated that the vibration modes that govern the seismic response of cable-stayed bridges in the transverse direction involve the interaction between the tower and the deck, but the order of these modes and the parts of the deck that are affected change with the main span length. It is also observed that the interaction between the deck and the towers during the earthquake is maximised if their isolated vibration frequencies are close to each other, leading to a significantly large seismic demand. Analytical expressions are proposed to obtain the critical frequencies of the towers for which these interactions arise, and recommendations are given to define the tower geometry in order to avoid such problematic scenarios.
Highlights
Cable-stayed bridges represent optimum solutions for an ever expanding range of spans and usually constitute the backbones of infrastructure networks
To the best of the author’s knowledge, there are no previous papers focused on the transverse seismic response of cable-stayed bridges accounting for the contribution of different vibration modes and the influence of the tower shape, among other structural features
The results show that it is possible to extend the range of spans in which the fundamental mode M1 is dominant, and to reduce in turn the domain of S1, by increasing the flexibility of the tower through the definition of its transverse geometry
Summary
Cable-stayed bridges represent optimum solutions for an ever expanding range of spans and usually constitute the backbones of infrastructure networks. To the best of the author’s knowledge, there are no previous papers focused on the transverse seismic response of cable-stayed bridges accounting for the contribution of different vibration modes and the influence of the tower shape, among other structural features. This is the scope of the present work, which presents an extensive numerical analysis in a wide range of main span lengths, tower shapes, cable-arrangements, deck widths and distances between the deck and the foundation level. This work demonstrates that the seismic response and the interaction between the deck and the tower in the transverse direction is maximised when their frequencies (calculated separately) are close to each other, proposing simple analytical expressions to predict these problematic scenarios
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