PROPOSAL OF LIMIT STATE AND SEISMIC ASSESSMENT INDEX FOR HOLLOW RC PIERS FOCUSING ON NEUTRAL AXIS OF CROSS SECTION

Abstract

 Hollow-section RC piers, which can reasonably secure bending stiffness, have been widely adopted for high piers in mountainous regions. However, it has been noted that hollow-section RC piers exhibit brittle failure with abrupt axial settlement at limit states, and thus, plasticization is not permitted under current seismic design standards. Consequently, seismic retrofitting of hollow-section RC piers is being actively pursued. However, as retrofitting all existing hollow-section RC piers would require considerable time, it is necessary to appropriately assess the prioritization of the seismic retrofitting. In this paper, a new limit state for hollow-section RC piers is defined by focusing on the position of the neutral axis in the cross section, and a method for determining the priority of seismic retrofitting based on this limit state is proposed. The results show that the proposed limit state offers high reliability in evaluating the ultimate displacement of hollow-section RC piers, where the axial settlement of column occur, and it could serve as an indicator for developing rational seismic retrofitting plans for existing hollow-section RC piers.