Old Rigid Frame Arch Bridge Structural Safety Of Fuzzy Comprehensive Evaluation

The bridge system has always been a key part of highway transportation, which is playing a vital role in the national economy. In the past decade, focus has been put on the construction of new bridges while the old ones were given less attention. Due to the aging, damage, increase of vehicle loads and lack of maintenance, the bearing capacity of old bridges are continuously deteriorating, which hampers the reconstruction of old road system. It is an urgent task to get a reliable testing and assessment method for those old bridges with the aim to provide solid basis for decision-making and guidance for the maintenance of expressway bridges.As an example, the frame-like bridge over Jining canal and 327 national highwaywas analyzed as a space model, with the damage failure mechanism of frame arch bridges being discussed in the paper. The model for the comprehensive evaluation of existing RC frame arch bridges was established with the application of opaque system based on layer analysis and the consideration of structural damage. Nine factors to affect the bridges' reliability were taken into account: solid web section, main arch, minor arch, upper chord, slightly-bent slab, lateral beam, chief joint, footing and erosion of foundation. Four features including the bearing capacity, deformation, cracks and connection detailing were introduced to evaluate each member of the bridges. The proportion coefficients of 1^st and 2^nd grade evaluation were decided by layer analysis method. The affiliation functions of the bearing capacity, deformation, cracks were also determined by distribution function of F distribution.