AASHTO Seismic Design

[dmsuit]

I am a non-US citizen but using US standards for bridge design. I have few questions about AASHTO Seismic Design:

Firstly, I have noticed that AASHTO released a new performance based seismic design code: "Guides Specifications for LRFD Seismic Bridge Design". But in the Foreword it says that it can be applied to the noncritical and non-essential bridges. Is this mean that it can be applied to only "other bridges" as defined in AASHTO 17th ed.? If so do you know why?

Second question is, can I use in that case CALTRANS Seismic Criteria for the essential bridges? Which people use CALTRANS in US in which case? The reason why I would like to use a displacement based code is that the minimum spiral condition for confinement in plastic hinge zones is a constant value in AASHTO and ends up with a non-practical reinforcement areas if the columns are large.

 

[bridgebuster]

First, in the US a Guide Specification is just that, a guide. It also means that it hasn't been adopted by AASHTO members as the officail way to do things.

Regarding your first question: Essential bridges, critical bridges, etc are designated by the owner. This has to do with emergency response during and after the seismic event.

Rewgarding your second question: It's up to you to convince your client. More than a decade ago, I did the same thing - followed Caltrans procedures. In the state I was working seismic design was new to all of us. No one would deny that California was way ahead of everyone else.