Delong Zuo

Analytical and Numerical Study of Deck-Stay Interaction in a Cable-Stayed Bridge in the Context of Field Observations

This paper addresses the mechanism of coupled deck-stay motions in cable-stayed bridges. Field observations of deck-stay interactions are summarized and an analytical model is developed to simulate such interactions. Using this model, a dynamic analysis of an example stay is conducted to illustrate the mechanism underlying the coupled motions. Three-dimensional finite-element models of a cable-stayed bridge are presented to confirm that coupling of deck-stay motions can occur in actual structures. A comparison between the results from the analytical and numerical models indicates that the proposed analytical model can reasonably explain the observed deck-stay interactions. In particular, it is shown that coupled motions are associated with the veering of natural frequency loci and mode localization and that the distributions of generalized masses between decks and cables are useful indexes for assessing the degree of coupling.

Characteristics of Tornado-Like Vortices Simulated in a Large-Scale Ward-Type Simulator

Tornado-like vortices are simulated in a large-scale Ward-type simulator to further advance the understanding of such flows, and to facilitate future studies of tornado wind loading on structures. Measurements of the velocity fields near the simulator floor and the resulting floor surface pressures are interpreted to reveal the mean and fluctuating characteristics of the flow as well as the characteristics of the static-pressure deficit. We focus on the manner in which the swirl ratio and the radial Reynolds number affect these characteristics. The transition of the tornado-like flow from a single-celled vortex to a dual-celled vortex with increasing swirl ratio and the impact of this transition on the flow field and the surface-pressure deficit are closely examined. The mean characteristics of the surface-pressure deficit caused by tornado-like vortices simulated at a number of swirl ratios compare well with the corresponding characteristics recorded during full-scale tornadoes.