The bridge deflection scope has changed greatly

and the traditional threshold method has became unfitted.The regression model is built to describe the partial deflection curve

then to predict the next deflection threshold interval.Simulation results verify the effectiveness of the designed method and theoretical discussions.The mean-square error（MSE）of two experiment are 0.6847and 0.4854

and the true deflection value are in prediction threshold interval when the input temperature value is 15.61

the true deflection is 288.89

the stylebook data number is 130

the prediction threshold interval is 289.0488±0.4708

and the stylebook data number is 32

the prediction threshold interval is 289.0193±0.1376.