Reserach On Concrete-filled Steel Tube Arch Bridge Damage Evaluation

Bridges collapse brings serious consequences such as people casualties and property loss. The existing damage identify methods often base on a single labeled damage variable and conclude the damage location and degree through comparing before and after bridge damaged. The practice shows that these methods rely on the selected indicators. At the same time it requires measurement efficiency. Because of the limited recognition, it is necessary to find some more efficient and general evaluation method. Combining FAHP-BP with static load and dynamic load experiment method is one of typical representative of the methods which can balance the efficiency, economy and recognition effect.Mechanics theory of the inherent frequency, displacement mode, curvature mode and strain mode also comparing with the sensitivity of the four indicates as well as the characteristics are studied which base on discuss the domestic and foreign bridge damage identification. Firstly, bridge damage is defined and its features are analyzed. Secondly, optimization algorithm of FAHP-BP neural network damage evaluation theory is developed with three levels index system. Then Static load and dynamic load experiment are design to the18th span of one long-span arch bridge as an sample to acquire damage variables. Static damage variable are including maximum deflection of main beam, maximum drop-out of main arch ring, cables force of different loading conditions, the residual deflection and percentage surplus deflection in mid-cross which takes up in total deflection. Dynamic damage variables are including moving deflections, natural frequency of vibrations, damping ratios, coefficient of impacts which caused by different loading conditions. By comprehensive assessment with code through FAHP-BP, it is conclude that the bridge belong to THIRD SERIES type. Meanwhile smoothness and stiffness of deck, bearing capacity of steel tube arch ring and box beam fulfill design requirements. The damage assessment method in this study can be used in the same CFST arch bridges.