本文選題：形變　切入點：破壞準則　出處：《西南交通大學》2014年博士論文

【摘要】：大跨度預應力混凝土箱梁橋在運營中過量下?lián)虾推毡殚_裂一直困擾著橋梁工程師,是一個亟待研究解決的問題。過去,人們習慣從受力角度去分析和研究這一問題,雖然取得了一些成果,但沒有解決根本問題。本文緊緊抓住材料破壞的形變本質,從研究混凝土材料形變與破壞的關系出發(fā),建立混凝土的形變破壞準則,探討大跨度預應力混凝土箱梁橋開裂的形變機理。1、對國內部分大跨度預應力混凝土箱梁橋的典型裂縫進行了調查研究,分析了導致這些裂縫的荷載因素和變形因素,總結了國內外的既有研究成果,指出從受力分析不能很好地解釋部分裂縫的成因,提出從形變角度來研究大跨度預應力混凝土箱梁橋的開裂問題。2、將固體材料在應力作用下的形狀和體積變化定義為形變,在直角坐標系下以應變張量表示,推導了在八面體上和在Haigh-Westergaard坐標系下的形變量。指出混凝十的形變包括瞬時形變和徐變形變,建議使用非線彈性正交異性本構模型計算瞬時形變,按依時本構模型計算徐變形變。本文在總結混凝土在單軸、雙軸和三軸等不同應力狀態(tài)下空間徐變規(guī)律的基礎上提出了基于徐變泊松比的單徐變度依時本構模型；在分析混凝土徐變機理的基礎上,提出了球徐變度和偏徐變度的概念,建立了混凝土的雙徐變度依時本構模型。3、指出固體材料破壞的本質是形變超過自身的承受能力而發(fā)生形體失穩(wěn),在此基礎上探討了混凝土材料的形變破壞理論。研究了混凝土材料形變與破壞的關系,分別以應力空間破壞準則推導了混凝土形變破壞準則,根據以試驗數據直接建立的應變空間破壞準則建立了考慮徐變形變的混凝土形變破壞準則。4、為了驗證混凝土形變破壞準則,提出并建立了一套基于單軸加載設備實現混凝土立方體試件雙軸加載和基于普通應變計實現混凝土立方體試件空間應變測試的方法,試驗結果與計算結果隨應力發(fā)展的趨勢吻合較好,但應變值在高應力水平時存在一定偏差。根據試驗和計算得到的形變結果,分別計算形變破壞判斷指標r/r*,在應強比σ3/σ3f較小時,二者吻合較好,應強比σ3/σ3f較大時有一定偏差,這是由于試驗測試應變存在偏差造成的。整體上,形變破壞判斷指標r/r*隨應強比σ3/σ3f變化的趨勢吻合較好,在σ3/σ3f0.90～0.95時,r/r*1,可以判定混凝土未破壞,在σ3/σ30.90時,r/r*隨σ3/σ3f迅速增大,在接近極限強度點時r/r*超過臨界值,可以判定混凝土破壞,較好地驗證了本文提出的混凝土形變破壞準則。5、比較研究了幾種常用的收縮徐變模型,根據考慮因素、適用范圍及預測結果優(yōu)劣,選擇GL2000模型用于分析大跨度預應力混凝土箱梁橋的收縮徐變效應。提出了考慮箱梁截面非均勻收縮的結構收縮效應計算方法,考慮混凝土空間徐變的結構徐變效應計算方法。在研究混凝土箱梁的口照輻射溫度場和比較研究國內外幾種梯度溫度模式的基礎上,分析了大跨度預應力混凝土箱梁橋的結構溫度效應。6、以一座大跨度預應力混凝土箱梁橋為例,應用本文提出的結構效應計算方法采用實體單元有限元對結構進行了分析,根據計算結果利用形變破壞準則從形變角度很好地解釋了腹板斜裂縫的形成機理。
[Abstract]:Large span prestressed concrete box girder bridge in the operation of excessive deflection and crack generally has been plagued by bridge engineers, is an urgent need to study and solve the problem. In the past, people used to force from the point of view to analyze and study this issue, although achieved some results, but did not solve the fundamental problem. The paper grasps the essence of deformation the failure of materials, from the perspective of the relationship between deformation and damage of concrete materials, the deformation failure criterion of concrete is established, the.1 deformation mechanism of cracking of large span prestressed concrete box girder bridge, the typical crack of large span prestressed concrete box girder bridges are part of the domestic research, analyzes the causes of the cracks and deformation of the load factor factors, summarizes the existing research results, points out that well explain the cause of part of the crack from stress analysis cannot be put forward from the angle of deformation. .2 cracking problems of long span prestressed concrete box girder bridge, the solid material under stress shape and volume change is defined as the deformation, with the strain tensor in the Cartesian coordinate system, is derived in eight sides and in the Haigh-Westergaard coordinates of the shape variables. It is pointed out that the mixed coagulation including instantaneous deformation ten deformation and Xu recommends using non deformation, elastic orthotropic constitutive model to calculate the instantaneous deformation, according to constitutive model calculation. This paper summarizes Xu deformation of concrete under uniaxial stress state under different foundation, Xu Biangui space law and three axis of biaxial creep Poisson's ratio of the single degree of creep according to the constitutive model based on; based on the analysis of concrete creep mechanism, put forward the concept of ball creep rate and creep deflection, creep of concrete is established according to constitutive model of.3, pointed out that the destruction of solid materials Quality is the deformation exceed the capacity of its own body and the occurrence of instability, on the basis of the deformation of the concrete material damage theory. To study the relationship between the material deformation and fracture of concrete, respectively in the stress space failure criterion is deduced according to the deformation of concrete failure criterion, strain test data space to directly establish the failure criterion of concrete is established creep deformation deformation failure criterion of.4, in order to verify the deformation of concrete failure criterion, and proposes a method based on the concrete specimens under biaxial loading and based on the common strain gauge implementation of concrete specimens under uniaxial loading space strain test equipment, test results and calculation results with the stress development trend are in good agreement but there is a certain deviation, the strain value at high stress level. According to the test results and the calculated deformation, calculated form The destructive evaluation index of r/r*, should be stronger than 3/ in sigma sigma 3F is small, two good agreement, should be stronger than the 3/ sigma sigma 3F is larger when there are some errors, this is because the test strain deviation caused. On the whole, the deformation failure judgment index r/r* with 3/ is stronger than the trend of sigma sigma 3F anastomosis well, the sigma 3/ Sigma 3f0.90 ~ 0.95, r/r*1 can determine the concrete is not destroyed in the sigma 3/ Sigma 30.90, sigma Sigma r/r* increases quickly with 3/ 3F, r/r* exceeds the critical value close to the ultimate strength point, can determine the failure of concrete, verified the variable shape concrete failure criterion.5 a comparative study of shrinkage and creep, several common models, according to the consideration, the applicable scope and the performance of the prediction results, select the GL2000 model for the analysis of shrinkage and creep effect of long-span prestressed concrete box girder bridge. Considering the box girder non uniform shrinkage of the folding structure The calculation method of effect, structure calculation method considering the creep effect of concrete creep space. In the research of concrete box girder in radiation temperature field and study several temperature gradient model, analyzed the.6 structure of the temperature effect of long span prestressed concrete box girder bridge, a long-span prestressed concrete box girder bridge for example, the structure effect is presented in this paper by using the calculation method of solid finite element of structure was analyzed according to the calculation results using the deformation failure criterion from deformation angle can better explain the formation mechanism of Web diagonal cracks.

【學位授予單位】：西南交通大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：U448.213

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