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AASHTO Bridge Seismic Isolation Design

AASHTO Bridge Seismic Isolation Design

AASHTO Bridge Seismic Isolation Design

Hi again guys,

I recently been tasked to identify the required stiffnesses of the bearing that will be used on our bridge project. From my previous thread, I learned worked examples on different conditions of bridges under the FHWA guidelines. Now, I am again seeking guidance on how to design our bridge using AASHTO's guidelines for seismic isolation design (2010). I was able to get the design examples done by NSCHRP (NSCHRP 20-7/Task 262(M2)), however, the conditions were different from our bridge.

Our bridge is under Type III Soil under the Japan Road Association(JRA) classification which is equivalent to Site Class E or F of AASHTO LRFD 2012. From the seismic isolation code, they mentioned 4 analysis procedures for seismically isolated bridges, namely: Simplified method, Single Mode Spectral method, Multimodal Spectral method, and Time-History method. Given our soil condition, its evident that non-linear time-history analysis is the most appropriate procedure to do, however, from our country, such records are not available. That is why I tried to study the simplified method and multimodal spectral method to make my analysis from nonlinear to linear.

Now, as I progress with these methods, I found out that for Soil Type F the simplified method is not allowed. Hence, I am reaching out to you guys for your expertise regarding this matter. Your help will be much appreciated.


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