| Summary: | 碩士 === 逢甲大學 === 土木工程所 === 94 === Due to the demands of riverbed hydraulic conditions, the long-span bridges had became more and more popular in Taiwan in the last decade. However, serious destruction of the long-span bridges under construction had also happened twice at the same time. Through the two case studies, it can be acknowledged of reasons for causing destruction such as: (1) the balance cantilever type of construction were adopted; (2)destruction were found at the unbalance end of continuous beams with unequal spans before construction completion; (3) the conditions of foundation soils of the damaged piers that located in or near the harbour district were looser than those in othrer piers; (4) the manual for bridge design and construction does not request them manual reader to consider the effect posed by change of soil conditions of nearby two piers.
To provdide more information for updating the bridge manual and to prevent destruction of a long-span bridge with unequal spans at both sides of a pier under construction to occur in the future, the SAP2000 finite element program was utilized to perform bridge structure analysis including construction simulations under different types of soil conditions. Thorough discussions, several solutions were made. That is, the influences of the loosening conditions of foundation soils and the reducing structure stiffness for the supporting frame on the structure behavior of a large span bridge under construction were investigated. Finally, the reasons for causing destruction were obtained and some useful methods for destruction prevention were proposed.
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