| For large-span prestressed concrete bridge,prestress loss may cause that the actual stress of the bridge structure is difficult to be consistent with the design stress, that is to say, the design stress can not reflect the real stress condition of the structure, the quality of the project isseriouslyaffected. At present, there are many ways to determinethe prestress loss, but there is noone simple and effective method to accurately determine the loss of prestress.Systematic study for the effective prestressattenuation law of concrete bridges is little.This thesisrelies on Huayang super large bridge,during the cantilever casting construction phase, magnetic fluxsensors are mounted on the outside of the bellows of prestressed tendonswhich are monitored.Law of prestress loss is researched by measure the effective prestress of prestressed tendons in every stages of construction. The main research contents include the following aspects:(1)The theoretical calculation method for the loss of prestressbased on current code and theory which arerelated to prestress loss is determined.(2)The monitoring scheme of prestress loss is designed by the construction code and construction scheme.Prestressing loss at each construction stage is obtained by using magnetic fluxsensors test effective prestressof prestressed tendons.Measured data has been analyzed and law of prestress loss has been summarized,Suggestions that can reduceprestress loss are maked by summarying the problemappearring in the monitoring process.(3)According to theoretical formula,the loss of prestress is calculated. At the same time,bridgemodel is simulated by using Midas/Civil software. Prestress loss that are obtained by this two methods are compared with measured results. The result shows that the measured results and theoretical calculations and model simulation coincide quite well.Suggestions that candecrease the prestress loss during the cantilever casting construction phase are put forward. |
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