【摘要】：國內(nèi)外大跨徑預(yù)應(yīng)力混凝土連續(xù)剛構(gòu)橋在運營多年后相繼出現(xiàn)跨中下?lián)虾土后w開裂,裂縫和變形的相互耦合更加劇了橋梁的病害,嚴重影響到橋梁結(jié)構(gòu)的安全和正常使用性能。考慮預(yù)應(yīng)力筋松弛和混凝土收縮徐變相互耦合的預(yù)應(yīng)力損失計算中,分析方法的正確性和收縮徐變預(yù)測模型的準(zhǔn)確性決定了計算結(jié)果的精度性。研究表明,收縮徐變預(yù)測模型的誤差會比計算方法帶來的誤差更明顯。國內(nèi)外廣泛采用的混凝土收縮徐變預(yù)測模型,是基于大量的普通混凝土長期試驗數(shù)據(jù)經(jīng)統(tǒng)計學(xué)方法擬合的公式,與目前廣泛使用的高強度混凝土結(jié)構(gòu)不符。為研究混凝土收縮徐變預(yù)測模型對連續(xù)剛構(gòu)橋預(yù)應(yīng)力損失和預(yù)拱度的影響,選取NCHRP 496報告提供的高強度混凝土收縮徐變預(yù)測模型和現(xiàn)橋規(guī)中JTG D62-04預(yù)測模型,以薛家壩2#大橋為主要分析對象,開展了基于高強混凝土收縮徐變模式的預(yù)應(yīng)力損失與預(yù)拱度的數(shù)值計算研究:①系統(tǒng)歸納現(xiàn)廣泛使用的各種收縮徐變預(yù)測模型和基于高強度混凝土試驗的預(yù)測模型NCHRP 496。根據(jù)實際指定條件,對比分析各種模型的預(yù)測值差異和特點,主要分析構(gòu)件理論厚度和混凝土強度因素對各種預(yù)測模型的影響,重點對比JTG D62-04和NCHRP 496因混凝土強度的變化所引起的預(yù)測值之間的差異;②基于按齡期調(diào)整的有效模量法,開展考慮混凝土收縮徐變、預(yù)應(yīng)力筋松弛和普通鋼筋相互作用的截面應(yīng)力時效重分布計算方法的研究,推導(dǎo)出相應(yīng)的預(yù)應(yīng)力長期損失的計算公式;③重點依托實際工程薛家壩2#大橋,利用Midas/Civil有限元分析程序,對比分析JTG D62-04和NCHRP 496對結(jié)構(gòu)長期預(yù)應(yīng)力損失和豎向撓度的影響差異。以赫章特大橋作為輔助算例,驗證計算分析結(jié)果的正確性和適用性。研究表明,現(xiàn)行橋規(guī)JTG D62-04收縮徐變預(yù)測模型未能準(zhǔn)確考慮高強度混凝土的影響。JTG D62-04有高估高強度混凝土徐變特性和低估收縮應(yīng)變特性的趨勢,并且低估了因混凝土收縮徐變引起的長期預(yù)應(yīng)力損失值,造成施工預(yù)拱度的設(shè)置偏小,這在一定程度上解釋了橋梁跨中下?lián)线^大的普遍現(xiàn)象。因此,為了能夠準(zhǔn)確分析高強度混凝土收縮徐變效應(yīng),建議規(guī)范JTG D62-04提供的收縮徐變預(yù)測模型需針對高強度混凝土加以修正完善。
[Abstract]:Long span prestressed concrete continuous rigid frame bridges at home and abroad have appeared in succession after many years of operation of mid-span deflection and beam cracking. The coupling of cracks and deformation exacerbates the disease of bridges, which seriously affects the safety and normal performance of bridge structures. The accuracy of the calculation results is determined by the correctness of the analytical method and the accuracy of the prediction model of shrinkage and creep in the calculation of prestress losses which are coupled with the relaxation of prestressed tendons and the shrinkage and creep of concrete. The results show that the error of the model is more obvious than that of the calculation method. The widely used concrete shrinkage and creep prediction model at home and abroad is based on a large number of ordinary concrete long-term test data fitted by statistical method, which is not consistent with the widely used high strength concrete structure. In order to study the influence of concrete shrinkage and creep prediction model on the prestress loss and precamber of continuous rigid frame bridge, the high strength concrete shrinkage and creep prediction model and the JTG D62-04 prediction model provided by NCHRP 496 are selected. Taking Xuejiaba2# Bridge as the main analysis object, Numerical calculation of prestress loss and pre-arch degree based on shrinkage and creep mode of high strength concrete is carried out. 1 various kinds of shrinkage and creep prediction models used widely and NCHRP 496 model based on high strength concrete test are systematically summarized. According to the actual specified conditions, the differences and characteristics of the prediction values of various models are compared and analyzed. The influence of the theoretical thickness of components and the strength of concrete on the prediction models is mainly analyzed. The difference between the predicted values of JTG D62-04 and NCHRP 496 caused by the change of concrete strength is compared. (2) based on the age-adjusted effective modulus method, the calculation method of cross-section stress aging redistribution considering the interaction of concrete shrinkage and creep, prestressed tendons relaxation and ordinary reinforcement is studied. The formula for calculating the long-term loss of prestressing force is deduced. (3) based on the actual project of Xuejiaba2# Bridge, the difference of the influence of JTG D62-04 and NCHRP 496 on the long-term prestress loss and vertical deflection of the structure is analyzed by using Midas/Civil finite element analysis program. The accuracy and applicability of the calculation results are verified by taking the Hezhang Bridge as an auxiliary example. The results show that the current JTG D62-04 shrinkage and creep prediction model of bridge gauge can not accurately consider the influence of high strength concrete. JTG D62-04 has the tendency of overestimating the creep characteristics of high strength concrete and underestimating the shrinkage strain characteristic. The long-term prestress loss caused by shrinkage and creep of concrete is underestimated, and the setting of pre-camber is small, which to some extent explains the common phenomenon of excessive deflection in bridge span. Therefore, in order to accurately analyze the shrinkage and creep effect of high strength concrete, it is suggested that the prediction model of shrinkage and creep provided by JTG D62-04 should be modified and perfected for high strength concrete.
【學(xué)位授予單位】：重慶交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：U441;U448.23

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本文編號：2356560