Seismic Analysis of Suspension Bridge Superstructures

Reliable seismic design is necessary for long-span suspension bridges. The dynamic characteristics of long-span suspension bridges are very different from those of short-span bridges. Long-span suspension bridges have basic periods longer than 10 sec, and more than a hundred natural periods closely distributed in the range 0.3 to 5 sec. The present bridge seismic design code in China is not suitable for long-span suspension bridges. Taking the Tsing Ma bridge, Hong Kong, and the Humen bridge as examples, the paper discusses the effects on suspension bridge responses of the response spectrum segments longer than 5 sec, methods of combining the maximum modal responses, the numbers of modes included in mode combinations, the vertical components of earthquake ground acceleration recordings (accelerograms), and the time durations of accelerograms.