Analysis Method Of Earthquake-resistant Code For Middle-or Long-span Bridge And The Parameter Selection

Bridges are usually important public facilities and so much attention has been given to evaluating their safety during earthquakes. The construction of middle- or long-span bridges is also developing rapidly with the high speed economic developments in the world. Therefore seismic analysis methods for bridges have received much attention during the past years, it is well recognized that the seismic spatial effects are important for middle- or long-span bridges. However, the response spectrum method (RSM) adopted as the most important tool by the Code is unable to deal with such problems, the time history method is not popular because of its very low efficiency. The random vibration approach is theoretically superior in dealing with such multiple excitation problems, however it has hardly been practically applied due to its computational complexity. The pseudo excitation method (PEM) has brocken its efficiency-bottleneck, and it is possible to adopt the random vibration approach in new 〈Earthquake-resistant Code for highway engineering〉In order to apply the random vibration approach to seismic designs of bridges, there are some important issues to solve, such as how to produce the equivalent ground acceleration PSD (power spectral density) curves from the ground ARS (acceleration response spectrum) curves stipulated by the code and deal with multi-component earthquake excitations. In this paper, these issues are researched. The works includes: (1) a great number of SDOF vibrators with periods within 10 s, and five bridges with different spans, basic periods and different types are investigated numerically in detail. It is shown that for bridges with the basic periods within 8 seconds, by modifying a probabilistic parameter, the precision of Kaul method will be remarkably improved; however its use is still as simple as before. (2) The combination of earthquake excitations stipulated by new 〈Earthquake-resistant Code for highway engineering〉 is a copy of European Committee for Standardization, in this paper lots of calculate works are used for validating these rules.