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PREFACE:
These Guide Specifications shall be taken to apply to the design and construction of conventional bridges to resist the effects of earthquake motions.
For non-conventional bridges, the Owner shall specify appropriate provisions, approve them, or both. Critical/essential bridges are not specifically addressed in these Guide Specifications.
A bridge should be classified as critical/essential as follows: Bridges that are required to be open to all traffic once inspected after the design earthquake and usable by emergency vehicles and for security, defense, economic, or secondary life safety purposes immediately after the design earthquake.
Bridges that should, as a minimum, be open to emergency vehicles and for security, defense, or economic purposes after the design earthquake and open to all traffic within days after that event.
Bridges that are formally designated as critical for a defined local emergency plan. For other types of construction (e.g., suspension bridges, cable-stayed bridges, truss bridges, arch type bridges, and movable bridges), the Owner shall specify or approve appropriate provisions. Seismic effects for box culverts and buried structures need not be considered except where failure of the box culvert or buried structures will affect the function of the bridge.
The potential effects of unstable ground conditions (e.g., liquefaction, landslides, and fault displacements) on the function of the bridge should be considered. The provisions in these Guide Specifications should be taken as the minimum requirements.
Additional provisions may be specified by the Owner to achieve higher performance criteria for repairable or minimum damage attributed to essential or critical bridges. Where such additional requirements are specified, they shall be site or project specific and are tailored to a particular structure type.
No detailed seismic structural analysis should be required for a single-span bridge or for any bridge in SDC A. Specific detailing requirements are applied for SDC A. For single-span bridges, minimum support length requirement shall apply according to Article 4.12. C3.1 For the purpose of these provisions, conventional bridges have slab, beam, box girder, and truss superstructures; have pier-type or pile-bent substructures; and are founded on shallow- or piled-footings or shafts. Non-conventional bridges include bridges with cable-stayed or cable-suspended superstructures, bridges with truss towers or hollow piers for substructures, and arch bridges.
