| In recent years,along with the development of traffic in China,a portion of bridges have been damaged to a certain degree and the quantity of dangerous bridges is increasing year by year,the carrying capacity of many bridges is falling. In order to insure smooth transportation,it is an urgent affair to maintain or reinforce these bridges. Thus,to study strengthening method about the dangerous bridges has deep signification of theory and practice in China.It is very complex to analyze the internal forces of the existing dangerous bridges,obviously there are some shortcomings in traditional method,according to the character of the dangerous bridges,the finite element method is used to analyze the internal forces of the bridge in this paper.In this paper,using large-scale current finite element software,analysising Nanbu Jialingjiang bridge as engineering example,considering the united action of arcade and of arch with the structure on crown,the author build several 3D finite element models including original bridge,dangerous bridge,all phases of strengthening bridges and strengthened bridge.In order to decide the most unfavorable load case accurately and quickly,using static analysis method this paper draws out the influence surface of bend moment for main section;Base on built models the paper analyzes the internal forces on entirely strengthening process and knows the damaged degree of dangerous bridge and does feasibility studying on its strengthening method;finally,the paper simply analyzes the unite action of arcade and of arch with the structure on crown. The result indicates that the strengthening method is feasible.Otherwise,the paper calculates uses 3D finite element model to avoid the shortage of traditional method,the internal force analysis is an important basement to choose reliable strengthening schema. The method of strengthening connected with internal forces analysis has some reference value to other dangerous construction.
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