The Rapid Assessment Techniques Of Bridge Capacity In The Alpine Region

Reinforced concrete structure has been applied widely in bridge engineering with its good performance and cost advantages of the economy since the 20th century. In the Tibet region, there are a large number of small and medium-span girder bridges, mostly are simple beam bridges. However, the coupling effects of some unfavorable factors,such as environmental erosion, material aging, load long-term effects, fatigue effects and mutation effects, inevitably lead to damage accumulation and resistance decay of the structural and system during the bridge in the service. Due to the different environment and the factors that affect the complexity of the bearing capacity of bridges, the existing assessment methods of carrying capacity can't make a reliable assessment of the bridges truly and systematically. Therefore, it is particularly important to do the right assessment of the carrying capacity prediction for the bridge structure, especially the old bridge structure. The purpose of this article,which is based on《Evaluation of highway bridge carrying capacity testing procedures》(requests authorization edition) of the Ministry of Transportation, is to establish a kind of carrying capacity assessment technique for the existing bridges in the Tibetan region,by the AHP and the Variable Weight Theory.The advantages and disadvantages of the common bridge bearing capacity evaluation methods are compared in the present thesis, also the research status of bridge bearing capacity assessment at home and abroad are studyed widely; based on mastering the reliability theory system and method of bearing capacity assessment, the research content and ideas of this article are proposed. According to the internal and external factors of the bridge bearing capacity decay, the attenuation of the bridge carrying capacity due to the bridge operating environment in Tibet is studied. According to the survey result of Tibet field bridge disease and combining the particular climate and environment of the alpine region in Tibet, the main factors of bridge disease aroused operating environment in Tibet is analyzed. Then, by counting the special climatic conditions in Tibet areas, analyzing mechanism of disease,and combining the main determinant of bridge disease under the influence of Tibet climate, the key indicators of the assessment of the bridge bearing capacity in Tibet are found outAt last, based on《Evaluation of highway bridge carrying capacity testing procedures》of the Ministry of Transportation, by the AHP and the variable weight theory, and according to the analysis of evaluation indicators of the capacity, reduced cross section of concrete and steel and deterioration factor are calculated with taking the scientific and reasonable result. The reduced performance of the steel strength was added in the course of the original carrying capacity assessment. Besides, in the checking coefficient, the original evaluation index was amended according to the actual work in Tibet and the weight was recalculated. Finally, a kind of carrying capacity assessment technique for the existing old bridges in the Tibetan region is established.