Improving Recovery of Rocking Systems

Rocking walls continue to gain interest in seismic regions due to their ability of re-centering the building system after major earthquakes. However, they have low inherent damping, thus they are often supplemented with energy dissipating elements. A rocking wall enhanced with partially debonded longitudinal bars for providing energy dissipation is named as a hybrid rocking wall (HRW). While HRWs combine re-centering with adequate energy dissipation, inspection and replacement of the energy dissipating bars may not be economically achieved after a major earthquake. This paper proposes an improvement to HRWs with the use of partially debonded longitudinal bars that are locally heat-treated to strategically concentrate hysteretic action in replaceable bar segments. The effect of the heat treatment protocol on the stress-strain properties and microstructure of reinforcing bars is investigated experimentally and a procedure for locally heat-treating standard reinforcing bars is established. Combining the experimental data of heat treatment with an analytical model for HRWs, the reversed-cyclic behavior of the proposed HRW is investigated to characterize the energy dissipation through the heat-treated bar segments, the re-centering capability of the HRW, and other key design parameters of the proposed wall system.