DESIGN SPECIFICATIONS FOR HIGHWAY BRIDGES - IISEE

5.4 Limit States of Bridges for Seismic Performance Level 3
(1) Limit states of bridges for Seismic Performance Level 3 shall be properly
established so that only the structural member in which the generations of plastic
hinges are allowed deforms plastically within a range of the ductility limit of the
member.
(2) The structural member in which the generations of plastic hinges are allowed shall
be selected so that reliable energy absorption is ensured.
(3) These structural members shall be properly combined in accordance with the
structural character of the bridge. Then, the limit state of each member shall be
appropriately determined in consideration of the combination.
5.5 Basic Principles to Verify Seismic Performance
(1) The seismic performance shall be verified by a proper method in accordance with
factors such as design earthquake ground motions, structural type and limit states
of the bridge.
(2) For bridges without complicated seismic behavior, the above provision (1) is deemed
to have met if the seismic performances are verified in accordance with the static
methods specified in Chapter 6. On the other hand, for bridges with complicated
seismic behavior, the seismic performances shall be verified in accordance with the
dynamic methods specified in Chapter 7 in order to meet provision (1).
5.6 Unseating Prevention Measures of Bridge Superstructure
(1) Adequate measures against unseating of superstructures shall be taken when the
superstructure separates structurally from the substructure, and with large
relative displacements.
(2) Provision (1) is deemed to be satisfactory if the unseating prevention systems
specified in Chapter 16 are installed.
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