The damage investigation of inelastic SDOF structure under the mainshock–aftershock sequence-type ground motions

• This paper studies the effect of aftershock on the damage of inelastic SDOF structure.
• Aftershock ground motions are scaled to different relative intensity PGAas/PGAms.
• Aftershock ground motion of PGAas/PGAms≤0.5 has negligible effect on ductility demand.
• Aftershock has more obvious effects on hysteretic energy than on ductility demand.

Structures located in seismically active regions may be subjected to mainshock–aftershock sequence-type ground motions, which are characterized by the presence of strong aftershock ground motions after the mainshock and separated by short intervals of time. This manuscript investigates the damage of inelastic SDOF structure with four hysteretic models and three response demand parameters. The relative intensity of the aftershock ground motion to the mainshock ground motion is defined, denoted by PGAas/PGAms. The aftershock ground motions are scaled to have different levels of PGAas/PGAms. The results indicate that the effect of aftershock on ductility demand is slight for PGAas/PGAms≤0.5 and can be ignored in engineering practice. The aftershock ground motion has more significant influence on the normalized hysteretic energy and damage index than on ductility demand. The effect of aftershock ground motion with larger PGAas/PGAms on the response demand is generally more obvious for non-degrading system than for degrading system.