Dynamic Model Studies of Ruck-A-Chucky Bridge

The prototype bridge is a 1,300-ft (400-m) span box-girder type with a horizontal radius of 1,500 ft (458 m) and supported on 48 cables individually anchored to the canyon walls. The model scale selected was 1/200 and a distorted model was constructed to study the global behavior of the system to ground shaking applied in all three coordinates. Preliminary testing included the measurement of static live-load response, system damping, and natural frequencies and mode shapes. These are compared with the results of linear analysis. Shaking tests were conducted on a 20-ft x 20-ft (6.1-m x 6.1-m) two-component table. The principal dynamic behavior is shown in the form of time-history plots of selected quantities, and maximum response values are compared with linear analysis. It is concluded that linear analysis provides dynamic response data accurate enough for design purposes, that cable vibrations have little influence on the gross behavior of the system, and that the system damping is not appreciably affected by the cable system.