Dynamic Properties of Stay Cables on the Bill Emerson Bridge

摘要

An experimental study was conducted to investigate dynamic response characteristics of the stay cables on the Bill Emerson Bridge in Missouri, USA. The natural frequencies and inherent damping ratios of selected stay cables are estimated based on the decaying free-vibration of the cables. Testing of selected stay cables was performed in three phases: before grouting, after grouting, and after the installation of one line of cross ties. After the installation of grout, cable frequencies decreased by 10-16%. Damping ratios for the grouted cables were found to be in the range of 0.12 to 0.45% of critical with Scruton numbers ranging generally from 2-4, below the target value of five for cables with aerodynamic surface treatments. When cross ties are added to the stay cables, the individual stays become a network of cables with both local and global modes and significantly higher frequencies. This results in cables that are more difficult to excite and a cable network with greater energy dissipation capability.