Abstract：In view of the relatively few researches and practices on the safety monitoring of small and medium span bridges at home and abroad, the influence of the ratio of live load on the selection of bridge safety monitoring and evaluation methods was analyzed and selected accordingly, and the early warning threshold value based on the structure response characteristics of small and medium bridges was set. The formula of data validity coefficient for dynamic acquisition of small and medium bridges was derived. Taking Luojiaba Bridge as an example, its monitoring data was analyzed. The results show that the small and medium bridges should use the live load response monitoring value to evaluate the safety status during the operation period. According to the setting of the early warning threshold value based on the structure response characteristics of small and medium bridges, the influence of calibration coefficient and data validity coefficient should be considered on the basis of the finite element theoretical calculation value. The applied bridge γ=0.81, the strain index Z1=43 με, Z2=57 με, the deflection index Z1=6.32 mm, Z2=8.42 mm. According to accidental achievement of the first and second warning conditions of strain and deflection index, it is judged that the proposed bridge is in the first level (yellow) early warning state, and there is no safety problem. Therefore, it is necessary to pay attention to the overload vehicles crossing the bridge.
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2020, Vol. 39 
