【摘要】：在懸臂施工中,為保證兩懸臂端在同一水平線上,需要設置合理的預拱度,使成橋線性達到設計的預測值。施工中影響預拱度的設置因素有很多,其中,混凝土徐變的影響貫穿橋梁的施工過程以及使用過程。由于徐變產(chǎn)生的撓度難以確定,并且徐變的影響因素又有很多,所以混凝土徐變對預拱度的影響受到廣泛的關注。本文在已有的研究成果上,采用MIDAS/Civil分析軟件對老漳河大橋建立有限元模型,計算在不同的徐變模型下產(chǎn)生的預拱度,并與實測數(shù)據(jù)比較;同時,模擬分析老漳河大橋在混凝土徐變、預應力荷載、掛籃荷載作用下的施工預拱度,并研究了在各因素作用下成橋預拱度的變化規(guī)律。得出結(jié)論如下:(1)ACI徐變系數(shù)預測模型的預測值較為準確,在橋墩附近的預測值稍微偏小,整體的徐變預測值與實測值基本相符,而JTG D62-2004橋涵設計規(guī)范模型和CEB-FIP模型對結(jié)構(gòu)撓度的整體預測偏小。在對預拱度預測時,不僅可以按照JTG D62-2004橋涵設計規(guī)范預測外,還可考慮ACI預測模型,對預測值進行調(diào)整。(2)通過對模型的分析,短期來講,在施工中的最大懸臂狀態(tài)下,混凝土徐變使梁段產(chǎn)生的豎向變形最接近總變形,是設置施工預拱度時的首要考慮因素。(3)長期來講,混凝土徐變?nèi)允且鹆簶蜷L期下?lián)系闹饕?橋梁撓度會隨時間的發(fā)展而不斷的增加。其中,引起混凝土徐變的濕度、溫度也會對下?lián)嫌杏绊�。相對濕度越�?下?lián)暇驮叫?相對溫度降低,下?lián)显黾�。因�?設計時需要建立與施工環(huán)境相符的模型,并考慮影響徐變的因素,提高橋梁的長期可靠性。(4)對于其他因素,如縱向預應力損失和汽車荷載,也是影響成橋預拱度的重要因素。其中,頂板縱向預應力損失產(chǎn)生的撓度比底板預應力損失產(chǎn)生撓度變形大。所以在預拱度設置時,也需要充分考慮,使預拱度的預測更加精確。
[Abstract]:In the cantilever construction, in order to ensure that the two cantilever ends are on the same horizontal line, it is necessary to set a reasonable pre-arched degree to make the bridge linearly reach the predicted value of the design. There are many factors that affect the pre-arch degree in construction, among which, the concrete creep affects the construction process and the use process of the bridge. Because the deflection produced by creep is difficult to determine, and there are many factors affecting creep, the influence of creep on pre-camber of concrete has been paid more and more attention. In this paper, based on the existing research results, the finite element model of Laozhang River Bridge is established by using MIDAS/Civil analysis software, and the pre-arch degree produced under different creep models is calculated and compared with the measured data. The pre-arch degree of Laozhang River Bridge under concrete creep, prestressed load and hanging basket load is simulated and analyzed, and the variation law of pre-arch degree of the bridge under the action of various factors is studied. The conclusions are as follows: (1) the prediction value of ACI creep coefficient prediction model is more accurate, the prediction value near bridge pier is slightly smaller, and the overall creep prediction value is basically consistent with the measured value. JTG D62-2004 bridge and culvert design code model and CEB-FIP model for the overall prediction of structural deflection is small. In the prediction of pre-camber, not only according to JTG D62-2004 bridge and culvert design code, but also according to the ACI prediction model, the predicted value can be adjusted. (2) through the analysis of the model, in the short term, under the maximum cantilever state in construction, The vertical deformation caused by concrete creep is the most close to the total deformation, which is the primary consideration factor in setting the pre-arch degree of construction. (3) in the long run, concrete creep is still the main cause of long-term deflection of beam bridge. The deflection of the bridge will increase with the development of time. Among them, the humidity that causes concrete creep, temperature also can have an effect on downwarping. The greater the relative humidity, the smaller the deflection, and the lower the relative temperature, the higher the deflection. Therefore, it is necessary to establish a model consistent with the construction environment, and to improve the long-term reliability of the bridge by taking into account the factors affecting creep. (4) for other factors, such as longitudinal prestress loss and vehicle load, It is also an important factor affecting the pre-arch of the bridge. The deflection caused by the longitudinal prestressing loss of the roof is larger than that by the prestressing loss of the bottom slab. Therefore, in the setting of pre-arch, we also need to take full account to make the prediction of pre-arch more accurate.
【學位授予單位】：河北工程大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：U445.466

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本文編號：2180435