DESIGN SPECIFICATIONS FOR HIGHWAY BRIDGES - IISEE

Chapter 15 Verification of Sesmic Performance of Bearing
Support System
15.1 General
(1) Bearing support system capable of having functions required by Section 4.1 of the
PartⅠCommon Provisions shall be fundamentally designed for horizontal and
vertical forces due to Level 1 and Level 2 Earthquake Ground Motion (referred as
“Type B bearing supports” hereafter). In particular, the bearing support system of
seismically-isolated bridges and bridges with horizontal force distributed structures
shall conform to the above provision.
However, in the case superstructures which do not mainly vibrate due to the
restraints of abutments, or in the case Type B bearing supports cannot be adopted, a
bearing support system together with excessive displacement stoppers may be
designed in the following manner: Functions of the bearing support system shall be
ensured for horizontal and vertical forces due to Level 1 Earthquake Ground
Motion, and the bearing support system and the excessive displacement stoppers
specified in Section 15.5 shall jointly resist the horizontal forces due to Level 2
Earthquake Ground Motion (referred as “Type A bearing supports” hereafter).
(2) Both Type A and Type B bearing supports shall be verified with the provisions
shown in Section 15.3, and the design seismic forces specified in Section 15.2.
(3) In order to fully ensure functions of bearing support system, the bearing support
system shall be designed with consideration of the structural details of the supports
specified in Section 15.4, as well as superstructural details in Subsections 14.2.2 and
14.3.2.
15.2 Design Seismic Force for Performance Verification of Bearing Support
System
(1) Design horizontal seismic forces of Type B bearing supports for Level 2 Earthquake
Ground Motion shall be equal to the lateral strength of piers considering plastic
behavior, or equal to the horizontal forces at the maximum response displacements
of foundations considering plastic behavior.
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