Nonlinear resonance vibration method to estimate the damage level on heat-exposed concrete

•Fire-damage induces hysteretic nonlinear behavior of concrete.•Hysteretic nonlinearity parameter increased with elevating exposure temperature.•The proposed method based on nonlinear resonance vibration is remarkably sensitive.•A relationship is developed to estimate peak temperature of exposure, as damage level on heat-exposed concrete.

After exposing concrete structures to fire, a promising in-situ evaluation method is required to evaluate the subsequent durability of the concrete. Fire-damage to concrete includes the formation of contact-type defects based on physicochemical changes, which are a dominant factor in fire-damage. The phenomenon of nonlinear resonance vibration is the shift of resonance frequency depending on input amplitude and it can sensitively reflect the occurrence of contact-type defects. This study attempts to estimate damage level to which concrete under heat-exposed, based on the proposed method to measure a hysteretic nonlinearity parameter. The experimental study was performed on 100 concrete samples with different mix proportions and fire scenarios. As a result, a relationship is proposed by which to estimate damage level on heat-exposed concrete, based on the correlation with the peak temperature and the hysteretic nonlinearity parameter.