Earthquake on Single-span Steel Tied-Arch Bridge , Seismic Review 1

[tatox]

Hi, I am not in US, but using AASHTO for design reference. I need friends for discussion, and your experience.
AASHTO LRFD said 3.10.9
a. Seismic analysis is not required for single-span bridges, regardless of seismic zone.
b. Connections between the bridge superstructure and the abutments shall be designed for the minimum force requirements Acceleration coefficient x tributary permanent load,
c. Minimum support length should comply specified, or it will need Locked up devices / Damper.
d. Abutment of single span not designed by acceleration-augmented soil pressure [commentary]

QUESTIONs:
1. This is for simple girder superstructures only, or it can be simple span complex structures like high skewed bridge, or more-than 100m long span truss, or steel arch bowstring tied-bridge, or network arch bridge / nielsen-lohse bridge.
2. If it is not including the special single-span bridge superstructures, then the steel superstructures need a special detail design for ductility, plastic hinge, pushover analysis?
3. How about others code? EC3 code? JRA code?
4. Then I think the single-span or simple-span maybe not needed LRB, HDRB, or seismic isolation devices? except if the lateral force to the substructure is so huge that require a lot of piles. And this a lot of pile cannot be made because project space limitation.

Regards.
tatox

 

[BridgeSmith]

Paragraph 3 under 3.10.1:

"The provisions herein shall apply to bridges of conventional construction. The Owner shall specify and/or approve appropriate provisions for nonconventional construction.

What you're describing I think would be considered nonconventional. A truss or a tied arch will have a significant amount of mass at considerable distance above or below the horizontal diaphragm (the deck). The moments due to the motion-induced inertial forces of arches or trusses and their bracing elements will have to be resisted by a moment frame integrated into the bracing for the arches or trusses. This is much easier to accomplish with the trusses or arches below the deck, or at least mostly below the deck.

Rod Smith, P.E., The artist formerly known as HotRod10