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.