Development of Aseismic Column with Self-Centering Capacity Only during Restoration

Abstract

Self-centering columns (SC), while attracting interest for their high recoverability, do not dissipate seismic energy as efficiently as conventional reinforced concrete or steel columns, potentially leading to a more significant seismic response. This study proposes a concept aimed at enhancing both energy dissipation during earthquakes and postearthquake restoration performance. This is achieved by exhibiting an SC capacity only during restoration. The proposed aseismic column consists of a central component, the SC core constructed from steel tubes filled with high-strength mortar, and energy-dissipation (ED) components made from steel plates. This SC core generates a moderate SC force sufficient to counteract the P-Δ effect. Given the minimal SC force from the SC core, the plasticization effect of the ED components becomes more conspicuous during large earthquakes, resulting in the emergence of a spindle-shaped lateral load capacity, leading to residual displacement in the columns. During restoration after earthquakes, the SC force emerges when the ED components are removed. The residual displacements of the columns can be gradually reduced during this process. Cyclic loading tests are conducted on the proposed column prototype followed by removal tests of the ED components with vertical axial forces acting on the column with residual displacement. In the cyclic loading tests, we confirmed the superior ED performance of the proposed column prototype, although residual displacement occurred in the column. In the ED component removal tests, a substantial reduction in the residual displacement of the column was observed when the ED components were removed. Specifically, the residual displacements were reduced by up to 96.2%, to a value of only 0.13% of the column height. In conclusion, the proposed concept can achieve superior energy absorption during earthquakes and high restoration performance afterward.