scope:

Specifications

The structural design of movable bridges shall conform to the requirements of the latest edition of the AASHTO LRFD Bridge Design Specifications including all applicable interim changes, except as modified or supplemented herein.

Bridge Types

General

Movable bridges shall be of the following types, unless otherwise specified by the Engineer:

• bascule span bridges,
• swing span bridges, or
• vertical lift bridges.

Contract Documents

The contract documents shall specify, or the Engineer shall determine the following:

• the type of movable bridge,
• for bascule span bridges, the type of bascule,
• for swing span bridges, the type of center. Swing span bridges should be the center bearing type, unless there is a compelling reason otherwise.
• for vertical lift bridges, the type of tower, location of the prime mover(s) and provisions for keeping the moving span level, and
• the system of emergency operation, if any, and the standby power system, if any.

Prohibited Structure Types

Pin-connected trusses shall not be used for movable spans.