Dynamic excitation of cables by deck and/or tower motion

Abstract

Large-amplitude cable vibrations have been observed on many major cable-stayed bridges. One possible source of excitation is movement of the deck and/or tower. Of particular concern is parametric excitation, whereby small deck/tower motion at one frequency can cause large cable motion at half the frequency under certain conditions. More commonly, deck/tower motion causes direct excitation of the cable at the same frequency in the same plane. Since cables have low damping, the response amplitudes can be large and geometric non-linearities can become important. Current design guidelines treat the axial and transverse components of end motion separately, but for an inclined cable subject to vertical deck motion at the lower anchorage and/or in-plane horizontal motion at the upper anchorage, both components occur simultaneously, modifying the behaviour considerably. This paper gives simplified results of non-linear mathematical modelling of inclined cable dynamics, with experimental validation, with the aim of providing more reliable guidelines for use in design. The proposed guidelines are summarised an appendix.

Editorial

“…They have provided us with N a case study on design and construction of the Fabian Way cable-stayed bridge steel superstructure in Swansea (Sanders et al, 2010) N a case study on design and construction aspects of the Busan-Geoje fixed link on Korea's south coast that incorporates concrete cable-stayed bridges (Yeoward et al, 2010) N a worldwide overview of cable-stayed variations with unconventional layouts of cables that can help to achieve maximum structural efficiency (Ruiz-Teran and Aparicio, 2010) N a feasibility study into the suspension cable replacement/ augmentation on the Forth Road Bridge in Scotland that may be required if current maintenance strategies should find difficulty in bringing erosion of the cable to a halt (Colford and Clark, 2010) N a review of the design for the new Forth replacement crossing that has been proposed to augment the capacity of the existing two Forth crossings in Scotland, especially if current capacity should have to be reduced (Carter et al, 2010) N a study into cable excitation in cable-stayed bridges caused by small movements of deck and/or tower (Macdonald et al, 2010).…”