Time-lag effect of temperature-induced strain for concrete box girder bridges

Temperature load is one of the most common and vital environmental loads for bridge in-service. However, the significant variability of temperature and the time-lag effect severely affects the damage identification and structure evaluation based on temperature response. The time-lag effect refers to the phenomenon that the temperature-induced response lags behind the temperature itself. Through a large amount of measured data mining, this paper summarizes the typical characteristics and general laws of the time-lag effect. Besides, the numerical simulation of the time-lag effect is realized via the finite element method. Furthermore, the spatial and temporal mechanism of the time-lag effect is explored. The extensive numerical simulation results and measured data verification revealed that the temperature change rate is the root cause of the time-lag effect. And the time delay of temperature-induced strain is just the appearance. Finally, based on the mechanism of the time-lag effect, an elimination method is proposed, which adopts the temperature change rate and temperature amplitude as key indexes. With this method, the stable slope of temperature-induced strain can be gained. This provides a solid basis for further structural evaluation based on the temperature effect. The exploration of the time-lag effect mechanism deepens the understanding of the temperature response and provides a new perspective for the structural early warning and assessment based on temperature load.