| Recently, the highway had unprecedented developed with the enhancement of comprehensive national power in our country.In order to provide fastly and comfortable driving condition, high qualities of the bridges were required in the highway.The high qualities were better continuous performance and less expansion joints. Because of the first simply then continuously supported small span box-girder bridge combines the advantages of the continuous beam bridges and the precast beam bridges, it had been widely applied and developed.Firstly, this thesis summarizes development situation, present research status, analysis theory and method of the first simply then continuously supported structure systerm.On the basis of the simulative research results, the method is applied to analyze some controversial problems(such as the concrete pouring sequence of continuous ends, the applying sequence of prestressing force) in this kinds of structural transformative/untranformative system. Some important conclusions are drawn: the concrete pouring sequence of continuous ends and the applying sequence of prestressing force should be in accordance with the principle of "interval end".Secondly, taking six-spans the first simply then continuously supported bridge for example, this paper analyzes in considerable details the effect of concrete creep upon the internal force of the structure during service period of the bridge, in which the parameters such as loading duration. concrete ages, the number of spans, the humidity of circumstance and later period length of prestressing tendons are considered, and also proposes the corresponding improvements to the design of such type of bridge structure in accordance with the analytical results obtained therefrom.Finally, on the basis of different national codes, effects of temperature gradient to this structure systerm are analyzed in the thesis and next direction and emphasis of research are pointed out . |
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