Analysis On Diseases Of Highway Bridge And Geological Disaters Prevention In Mountainous Areas

The design work of bridge and culvert is the important part of the highway construction, which is the key nodus of the roads network layout.With the development of transportation and increased servicing life, bridges disease problem has become increasingly prominent, such as geological disasters, extreme weather and other external factors.Which are harmful to the bridge's safety and the comfort of the driving directly or indirectly. But there is no uniform standard to calculate the bearing capacity, only bases on experience reduction, which is not so currect in designing. Therefore make the correct diagnosis in the assessment of existing bridges, and propsoses the right solutions is an important thing.Because of this, the thesis bases on the practical support projects, which carries out a census of the common diseases and disasters of thousands of bridges in 11 expressways in Hunan province, classifies systematically and summarizes the common disease of the expressway-bridges. Then focuses on the typical disease, analyzes the affect on capacity and durability of bridges, and use reliability theory to evaluate.Which is very significant in evaluating the security state of sercicing bridges. The main research work can be summarized as follows:Firstly, various bridge maintenance and disease are classified statistics on the status of more than 11 highway bridges in accordance with specifications , obtaines the proportion of bridge type in different diseases and expressways bridge grade for each variety of bridge, and analyzes the typical structure and causes of disease;Secondly, statistics show that disease almost happen in everyhollow slab bridge, which own 76.4% in the second and third grade disease bridges, its outstanding disease is the slab's horizontal, vertical cracks, horizontal cracks are mainly because of insufficient strength, hinge joint damages caused by Large transverse distribution factors, The paper establishes two models to contrast,calculate and analyze the stress of each model under live load. Employes the distortion theories to analyze the reasons of regular longitudinal crack in the thin-walled hollow slab of 20m span, obtaines the relationship between reinforcement ratio, roof and floor thickness and distortion stress.The result carris out that the distortion effect is the dominant reason causing the longitudinal cracks of the hollow slab;Thirdly, use reliability theory to calculate and evaluate, select the same bridge's construction design and optimization results under the normal use of the limit state to analyze. Take crack width as the control condition, according to adopt computer programming technology, calculates the relationship curve between the ratio of the reinforcement and reliable degree.Then proposes improvements from the design point of view, and use a economic and reasonable methord to refrofit the whole bridge;Fourthly, Take typical geological disasters as the research object, such as landslides, collapse and so on, which are serious harm to expressway bridges. Considering the successful disposal measurement of geological disasters in the bridges along the line, the thesis analysis the stability of landslide and the damage to bridge by using the finite element program and provides the general principles and characteristic of bridges in mountainous highway to deal with frequent geological disasters. At last, the thesis explores the new countermeasure of bridge construction in mountainous area in the field of bridge type-elect and structure calculation, provides a reference to the same kind bridges in the future.