本文選題：高強混凝土　切入點：連續(xù)剛構(gòu)橋　出處：《重慶大學》2014年碩士論文　論文類型：學位論文

【摘要】：近年來，隨著預應力混凝土結(jié)構(gòu)，大跨度結(jié)構(gòu)的蓬勃發(fā)展，，混凝土的強度不斷提高，結(jié)構(gòu)中的徐變現(xiàn)象也越來越受到人們的關(guān)注。徐變和收縮是很多材料的固有時變特性，特別是混凝土材料，徐變從養(yǎng)護時便開始發(fā)展，一直持續(xù)到結(jié)構(gòu)服役期結(jié)束。隨著混凝土強度、結(jié)構(gòu)跨度的不斷增大，徐變所產(chǎn)生的影響也越來越大，特別是在預應力混凝土結(jié)構(gòu)以及大跨度混凝土結(jié)構(gòu)中。徐變會造成預應力損失，從而影響預應力混凝土結(jié)構(gòu)的使用性能，；大跨度結(jié)構(gòu)中，徐變會降低預拱度，是撓度增大。結(jié)構(gòu)的時間依存性變形主要由徐變、彈性變形、收縮和溫度變形構(gòu)成，而徐變變形大小可以達到瞬時彈性變形的2~4倍，因此，在結(jié)構(gòu)設計中考慮徐變對結(jié)構(gòu)使用性能的影響是十分必要的。而目前大多數(shù)收縮徐變的模型都是針對C20~C40的普通混凝土或者強度等級為LC30以下的輕骨料混凝土，但對于預應力混凝土和高強混凝土，適用性好、精度高、計算相對簡便的模型目前并不存在，并且考慮預應力混凝土結(jié)構(gòu)的大量使用這一客觀事實，提出一個適合高強混凝土的收縮徐變預測模型迫在眉睫。 在大量的資料和數(shù)據(jù)、混凝土試驗以及工程實例的基礎上，本文主要工作及成果如下： ①搜集對比國內(nèi)外影響較大的各種收縮徐變預測模型，參考幾種常見的徐變機理，對中國建科院模型(1986)，歐洲混凝土學會-國際預應力協(xié)會1978模型(CEB-FIP1978)，美國混凝土協(xié)會209委員會模型(ACI209(1982))，Bazant和Panula提出的BP系列模型(主要是RILEM B3模型)，GL2000模型以及日本土木學會推薦的日本《混凝土示方書》中的模型，共六種模型的考量因素、數(shù)學表達式形式、精度水準等進行了詳細的定性對比分析。利用B3變異系數(shù)法，對各個模型的精度進行定量的對比分析，結(jié)果反映出GL2000模型整體性能最優(yōu)，其次是B3模型和日本混凝土示方書中的模型。 ②在已知混凝土徐變模型的前提下，提出了對應力歷史進行劃分的階梯法和脈沖法，以及對計算過程做相應基本假定的逐次法。同時，進行了高強混凝土的收縮徐變試驗，通過對比，發(fā)現(xiàn)已有模型與試驗結(jié)果不能很好地吻合。于是在日本規(guī)范的基礎上，利用試驗數(shù)據(jù)進行擬合，計算相應組合系數(shù)，得到修正的徐變預測模型，并編制程序計算徐變度，和試驗值進行對比。 ③在對牛角坪大橋進行長期觀測后，對得到的應變和撓度數(shù)據(jù)進行分析。利用Python和Abaqus Scripting Interface腳本接口，進行二次開發(fā)，根據(jù)符合牛角坪大橋使用的高強混凝土的徐變規(guī)律和ACI209（1982）提出的徐變規(guī)律創(chuàng)建新的材料屬性，對徐變應變和撓度進行計算。得到了應變和撓度共同符合的變形發(fā)展規(guī)律，即在早齡期階段，徐變應變和徐變引起的撓度均發(fā)展很快，一般1~3年內(nèi)可以達到70~80%，之后隨著時間推移，盡管應變和變形仍然在發(fā)展，但增長速率逐漸放緩。
[Abstract]:In recent years, with the rapid development of prestressed concrete structures, the strength of concrete has been improved, and the creep phenomenon in the structure has been paid more and more attention. Creep and shrinkage are the inherent time-varying characteristics of many materials. In particular, the creep of concrete materials develops from the time of curing until the end of the service period. As the strength of concrete and the span of the structure increase, the influence of creep becomes more and more great. Especially in prestressed concrete structures and long-span concrete structures, creep will cause prestress losses, thus affecting the performance of prestressed concrete structures, and in long-span structures, creep will reduce the pre-arch degree. The time dependent deformation of the structure is mainly composed of creep, elastic deformation, shrinkage and temperature deformation. It is necessary to consider the influence of creep on the performance of the structure in structural design. At present, most models of shrinkage and creep are aimed at ordinary concrete with C20C40 or lightweight aggregate concrete with strength below LC30. However, for prestressed concrete and high strength concrete, the models with good applicability, high accuracy and relatively simple calculation are not present at present, and the objective fact that prestressed concrete structures are widely used is taken into account. It is urgent to put forward a model for predicting shrinkage and creep of high strength concrete. Based on a large number of data, concrete tests and engineering examples, the main work and results of this paper are as follows:. (1) collecting and comparing various kinds of shrinkage and creep prediction models with great influence at home and abroad, referring to several common creep mechanisms, The BP series models (mainly RILEM B3 model, GL2000 model and Japanese civil engineering model) proposed by the Chinese Institute of Science and Technology, the European Institute of concrete and the International Prestress Association 1978 model CEB-FIP 1978, the American concrete Association 209 Committee Model ACI 209 / 1982 Bazant and Panula have been studied. The model in Japan's concrete Square Book will be recommended, In this paper, the factors of consideration, mathematical expression form, precision level of six models are analyzed qualitatively and qualitatively, and the accuracy of each model is compared and analyzed quantitatively by using B3 variation coefficient method. The results show that the overall performance of the GL2000 model is the best, followed by the B3 model and the model in the Japanese concrete square book. 2 on the premise of known concrete creep model, the step method and pulse method are put forward to divide the stress history, and the successive method to make the corresponding basic assumptions for the calculation process is put forward. At the same time, the shrinkage and creep tests of high strength concrete are carried out. By comparison, it is found that the existing model does not agree well with the test results. Therefore, the modified creep prediction model is obtained by fitting the test data and calculating the corresponding combination coefficients on the basis of the Japanese standard. A program was compiled to calculate the creep degree, and the test value was compared. 3After the long-term observation of Niujiaoping Bridge, the strain and deflection data obtained are analyzed. The secondary development is carried out by using Python and Abaqus Scripting Interface script interface. According to the creep law of high strength concrete used in Niujiaoping Bridge and the creep law proposed by ACI 209 / 1982), the creep strain and deflection are calculated. That is, at the early age stage, the creep strain and the deflection caused by creep both develop rapidly, and generally can reach 70 ~ 80 in 1 ~ 3 years, and then, with the passage of time, although the strain and deformation are still developing, the growth rate gradually slows down.
【學位授予單位】：重慶大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：U448.23;U441

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