鋼纖維混凝土靜力損傷及疲勞損傷研究
發(fā)布時間：2018-07-26 14:55
【摘要】：鋼纖維混凝土(SteelFiberReinforcedConcrete,簡寫為SFRC)是在普通混凝土中摻入亂向分布的短鋼纖維所形成的一種新型復合材料。它不僅具有普通混凝土的優(yōu)良特性，同時由于鋼纖維的存在限制了裂縫的開展，從而使原來本質(zhì)上是脆性的混凝土材料呈現(xiàn)出很高的抗裂性能并能推遲裂縫的出現(xiàn)、使混凝土具有較大的延性和韌性以及優(yōu)良的抗拉、抗折、抗沖擊、耐磨損、抗疲勞等特性。近年來，鋼纖維混凝土得到廣泛的應用和深入的研究。根據(jù)國內(nèi)外已有的研究成果，本文對鋼纖維混凝土靜力損傷和疲勞損傷進行了研究，主要研究內(nèi)容及結(jié)論如下： 1、給出了將試驗得到的4點彎曲梁的荷載－撓度曲線轉(zhuǎn)化為相應的應力－應變曲線的方法；根據(jù)能量等效原理和weibull統(tǒng)計分布理論推導了鋼纖維混凝土在單向荷載作用下的本構(gòu)模型及其損傷模型，只要能準確的測定出試件的彈性模量、峰值應力以及相應的峰值應變，就能得到其單向荷載作用下的本構(gòu)方程和損傷演變方程。 2、靜載破壞可看成是特殊的疲勞破壞，即極限強度加載下，承受一個循環(huán)的疲勞破壞。在此過程中，損傷也是一個逐步累積的過程。借鑒疲勞損傷的分析方法，基于損傷力學推導了單軸加載作用下描述損傷變量與應變關系的損傷演變方程。根據(jù)應變等效原理，得到對應的本構(gòu)方程。 3、對鋼纖維再生混凝土和鋼纖維卵石混凝土彎曲疲勞性能進行了試驗研究，得到不同應力水平（S=0.7,0.75,0.8,0.85）下的疲勞壽命。分析結(jié)果表明：應力水平S與對數(shù)疲勞壽命lgN成直線關系，相關系數(shù)在0.99以上，因鋼纖維和粗骨料之間的界面連接強度不同，在任何應力水平下鋼纖維再生混凝土的疲勞壽命都比鋼纖維卵石混凝土大。綜合已有文獻回歸得到的彎曲疲勞載荷作用下的疲勞壽命方程，可作為彎曲疲勞荷載作用下疲勞壽命的估算。鋼纖維再生混凝土和鋼纖維卵石混凝土彎曲疲勞應變演化曲線呈現(xiàn)三階段發(fā)展規(guī)律，隨著循環(huán)比的增加，鋼纖維再生混凝土的疲勞應變比鋼纖維卵石混凝土的疲勞應變發(fā)展慢。由此可見，利用再生骨料作為粗骨料的鋼纖維再生混凝土不僅能“變廢為寶”，減少環(huán)境污染，實現(xiàn)資源的重復利用，而且其疲勞壽命和疲勞應變發(fā)展都優(yōu)于鋼纖維卵石混凝土。 4、利用威布爾分布和對數(shù)正態(tài)分布對鋼纖維再生混凝土和鋼纖維卵石混凝土的疲勞壽命試驗結(jié)果進行檢驗，結(jié)果表明本次試驗的彎曲疲勞壽命較好地服從對數(shù)正態(tài)分布和兩參數(shù)威布爾分布。不同存活率P和應力水平S下，單對數(shù)疲勞方程和雙對數(shù)疲勞方程的線性關系是成立的，其相關系數(shù)R均在0.99以上；存活率P對鋼纖維卵石混凝土的回歸系數(shù)B和b影響很小，可取其平均值作為通用結(jié)果，而存活率P對鋼纖維卵石混凝土各回歸系數(shù)影響很小，可取其平均值作為通用結(jié)果。 5.通過對二級配鋼纖維混凝土疲勞試驗數(shù)據(jù)進行回歸，提出了二級配鋼纖維混凝土彎曲疲勞方程，，其回歸系數(shù)可以達到0.971以上，比采用其他擬合公式更接近試驗結(jié)果。 6.提出了描述鋼纖維混凝土的疲勞應變演化曲線的疲勞應變方程，結(jié)果顯示，擬合曲線與試驗曲線能很好吻合。根據(jù)疲勞模量與疲勞應變幅值成反比的關系，由疲勞應變演化方程得到疲勞模量演化方程。利用疲勞模量演化方程對已有疲勞模量試驗結(jié)果進行擬合，結(jié)果顯示，該式表達的疲勞模量演化曲線與相應的試驗曲線吻合很好，其相關系數(shù)均在0.99以上，說明該式適合描述鋼纖維混凝土的疲勞模量演化曲線。 7、分別用疲勞應變和疲勞模量定義鋼纖維混凝土疲勞損傷，得到的典型的損傷變量演化曲線顯示，由最大疲勞應變和疲勞殘余應變定義的損傷變量演化曲線基本一致，且相差很��；而由疲勞模量定義的損傷變量演化曲線明顯大于由疲勞應變定義的損傷變量演化曲線，當循環(huán)比為0.9時，由疲勞應變定義的損傷變量約0.35左右，而疲勞模量定義的損傷變量約為0.77，當初始循環(huán)時，疲勞模量定義的損傷變量就達到0.34左右，而疲勞應變定義的損傷變量接近0。也就是說，由疲勞模量定義的損傷變量自始至終都比疲勞應變定義的損傷變量大。 8、基于損傷力學推導了鋼纖維卵石混凝土和鋼纖維再生混凝土彎曲疲勞損傷方程，結(jié)果顯示，由疲勞損傷方程得到的回歸曲線與疲勞損傷演化曲線吻合很好。 9、根據(jù)材料的宏觀量的變化與疲勞損傷演變有本質(zhì)聯(lián)系，故由損傷變量推導得到鋼纖維混凝土剩余疲勞壽命和剩余彎曲強度的表達式。通過該式，可求得給定疲勞應力水平、不同損傷狀態(tài)下的剩余疲勞壽命和剩余彎曲強度，為有損結(jié)構(gòu)的安全評估及決策提供參考。由剩余疲勞壽命隨損傷變量以及循環(huán)比的變化曲線可知，隨著損傷變量的增大，剩余疲勞壽命曲線下降，損傷變量為0.3以內(nèi)時，剩余疲勞壽命降幅較大，且應力水平越低，降幅越明顯，應力水平為0.7時，曲線急劇下降；隨著循環(huán)比的增加，剩余疲勞壽命近似直線下降，且應力水平越低，降幅越明顯。由剩余彎曲強度隨循環(huán)比以及損傷變量的變化曲線可以看出，隨循環(huán)比的不斷增加，剩余彎曲強度逐漸降低，近似呈直線變化，當接近破壞時，剩余彎曲強度急劇下降，另外，循環(huán)比相同時，應力水平的變化對剩余彎曲強度的影響較小；而剩余彎曲疲勞強度隨損傷變量近似呈直線變化，損傷變量相同時，應力水平越高，剩余彎曲強度越大。
[Abstract]:Steel fiber reinforced concrete (SteelFiberReinforcedConcrete, SFRC) is a new type of composite made of short steel fiber mixed with random distribution in ordinary concrete. It not only has excellent properties of ordinary concrete, but also restricts the development of cracks because of the existence of steel fiber, so that it is essentially a brittle coagulation. Soil materials have high cracking resistance and can postpone the appearance of cracks, make concrete have great ductility and toughness, excellent tensile, fracture resistance, impact resistance, wear resistance, fatigue resistance and so on. In recent years, steel fiber reinforced concrete has been widely used and studied in depth. The static damage and fatigue damage of concrete are studied. The main contents and conclusions are as follows:
1, the method of converting the load deflection curve of the 4 point bending beam to the corresponding stress strain curve is given, and the constitutive model and the damage model of the steel fiber reinforced concrete under unidirectional load are derived according to the energy equivalence principle and the Weibull statistical distribution theory, so long as the elastic modulus of the specimen can be accurately measured. The constitutive equation and damage evolution equation under uniaxial loading can be obtained by volume, peak stress and corresponding peak strain.
2, the static load failure can be regarded as a special fatigue failure, that is, under the ultimate strength loading, it bears a cyclic fatigue failure. In this process, the damage is also a cumulative process. Based on the fatigue damage analysis method, the damage evolution equation describing the relationship between the damage variable and the strain is derived based on the damage mechanics. According to the strain equivalence principle, the corresponding constitutive equation is obtained.
3, the flexural fatigue behavior of steel fiber recycled concrete and steel fiber cobble concrete was tested and the fatigue life under different stress levels (S=0.7,0.75,0.8,0.85) was obtained. The results showed that the stress level S was linear with logarithmic fatigue life lgN, the number of related lines was above 0.99, and the interface between steel fiber and coarse aggregate The fatigue life of steel fiber recycled concrete at any stress level is larger than that of steel fiber reinforced concrete. The fatigue life equation under the bending fatigue load obtained by the existing literature can be used as an estimate of fatigue life under the action of bending fatigue load. Steel fiber recycled concrete and steel fiber pebble. The bending fatigue strain evolution curve of concrete presents three stages of development. With the increase of cycle ratio, the fatigue strain of steel fiber recycled concrete is slower than that of steel fiber pebble concrete. Therefore, the steel fiber recycled concrete using recycled aggregate as coarse aggregate can not only "change waste into treasure", reduce environmental pollution. To achieve the reuse of resources, the development of fatigue life and fatigue strain is better than steel fiber pebble concrete.
4, using Weibull distribution and logarithmic normal distribution to test the fatigue life test results of steel fiber recycled concrete and steel fiber gravel concrete. The results show that the bending fatigue life of this test is well obeying log normal distribution and two parameter Weibull distribution. Under different survival rates P and stress level S, single logarithmic fatigue square The linear relationship between the path and the double logarithmic fatigue equation is established. The correlation coefficient R is above 0.99, and the survival rate P has little effect on the regression coefficient B and B of the steel fiber gravel concrete. The average value should be used as the general result, while the survival rate P has little influence on the number of the regression lines of steel fiber gravel concrete, and the average value should be used as a general junction. Fruit.
5. through the regression analysis of the fatigue test data of two graded steel fiber reinforced concrete, the bending fatigue equation of two graded steel fiber reinforced concrete is proposed. The regression coefficient can reach more than 0.971, which is closer to the test results than the other fitting formulas.
6. the fatigue strain equation describing the fatigue strain evolution curve of steel fiber reinforced concrete is presented. The results show that the fitting curve is in good agreement with the test curve. According to the inverse ratio of fatigue modulus to fatigue strain amplitude, the fatigue modulus evolution equation is obtained from the evolution equation of fatigue strain. The results of the model test are fitted. The results show that the fatigue modulus evolution curve of the formula is in good agreement with the corresponding test curve, and the correlation coefficient is above 0.99. It shows that the formula is suitable for describing the fatigue modulus evolution curve of steel fiber concrete.
7, the fatigue damage of steel fiber reinforced concrete is defined by fatigue strain and fatigue modulus. The typical damage variable evolution curve shows that the damage variable evolution curve defined by the maximum fatigue strain and the fatigue residual strain is basically consistent, and the difference is very small, and the damage variable evolution curve defined by the fatigue modulus is obviously larger than that by the fatigue. The damage variable evolution curve defined by strain strain, when the cycle ratio is 0.9, the damage variable defined by the fatigue strain is about 0.35, and the damage variable defined by the fatigue modulus is about 0.77. When the initial cycle, the damage variable defined by the fatigue modulus is about 0.34, and the damage variable defined by the fatigue strain is close to 0., that is to say, fatigue. The damage variable defined by the model is always greater than the damage variable defined by fatigue strain.
8, based on the damage mechanics, the bending fatigue damage equations of steel fiber gravel concrete and steel fiber recycled concrete are derived. The results show that the regression curve obtained by the fatigue damage equation is in good agreement with the fatigue damage evolution curve.
9, the expression of residual fatigue life and residual bending strength of steel fiber concrete is derived from the damage variable according to the change of macroscopic quantity of the material and the evolution of fatigue damage. By this formula, the given fatigue stress level, residual fatigue life and residual bending strength under different damage states are obtained, which are damaged structures. The residual fatigue life with the damage variable and the change curve of cycle ratio shows that the residual fatigue life curve decreases with the increase of the damage variable and the damage variable is less than 0.3, and the lower the stress level, the more obvious, the stress level is 0.7, the curve is urgent. With the increase of the cycle ratio, the residual fatigue life decreases approximately linearly, and the lower the stress level, the more obvious. The residual bending strength decreases with the cycle ratio and the damage variable curve, and the residual bending strength decreases gradually with the continuous increase of the annular ratio. At the same time, the change of the stress level has little effect on the residual bending strength, while the residual bending fatigue strength approximated to the damage variable, and the higher the stress level, the greater the residual bending strength.
【學位授予單位】：華南理工大學
【學位級別】：博士
【學位授予年份】：2013
【分類號】：TU528.572
本文編號：2146376
[Abstract]:Steel fiber reinforced concrete (SteelFiberReinforcedConcrete, SFRC) is a new type of composite made of short steel fiber mixed with random distribution in ordinary concrete. It not only has excellent properties of ordinary concrete, but also restricts the development of cracks because of the existence of steel fiber, so that it is essentially a brittle coagulation. Soil materials have high cracking resistance and can postpone the appearance of cracks, make concrete have great ductility and toughness, excellent tensile, fracture resistance, impact resistance, wear resistance, fatigue resistance and so on. In recent years, steel fiber reinforced concrete has been widely used and studied in depth. The static damage and fatigue damage of concrete are studied. The main contents and conclusions are as follows:
1, the method of converting the load deflection curve of the 4 point bending beam to the corresponding stress strain curve is given, and the constitutive model and the damage model of the steel fiber reinforced concrete under unidirectional load are derived according to the energy equivalence principle and the Weibull statistical distribution theory, so long as the elastic modulus of the specimen can be accurately measured. The constitutive equation and damage evolution equation under uniaxial loading can be obtained by volume, peak stress and corresponding peak strain.
2, the static load failure can be regarded as a special fatigue failure, that is, under the ultimate strength loading, it bears a cyclic fatigue failure. In this process, the damage is also a cumulative process. Based on the fatigue damage analysis method, the damage evolution equation describing the relationship between the damage variable and the strain is derived based on the damage mechanics. According to the strain equivalence principle, the corresponding constitutive equation is obtained.
3, the flexural fatigue behavior of steel fiber recycled concrete and steel fiber cobble concrete was tested and the fatigue life under different stress levels (S=0.7,0.75,0.8,0.85) was obtained. The results showed that the stress level S was linear with logarithmic fatigue life lgN, the number of related lines was above 0.99, and the interface between steel fiber and coarse aggregate The fatigue life of steel fiber recycled concrete at any stress level is larger than that of steel fiber reinforced concrete. The fatigue life equation under the bending fatigue load obtained by the existing literature can be used as an estimate of fatigue life under the action of bending fatigue load. Steel fiber recycled concrete and steel fiber pebble. The bending fatigue strain evolution curve of concrete presents three stages of development. With the increase of cycle ratio, the fatigue strain of steel fiber recycled concrete is slower than that of steel fiber pebble concrete. Therefore, the steel fiber recycled concrete using recycled aggregate as coarse aggregate can not only "change waste into treasure", reduce environmental pollution. To achieve the reuse of resources, the development of fatigue life and fatigue strain is better than steel fiber pebble concrete.
4, using Weibull distribution and logarithmic normal distribution to test the fatigue life test results of steel fiber recycled concrete and steel fiber gravel concrete. The results show that the bending fatigue life of this test is well obeying log normal distribution and two parameter Weibull distribution. Under different survival rates P and stress level S, single logarithmic fatigue square The linear relationship between the path and the double logarithmic fatigue equation is established. The correlation coefficient R is above 0.99, and the survival rate P has little effect on the regression coefficient B and B of the steel fiber gravel concrete. The average value should be used as the general result, while the survival rate P has little influence on the number of the regression lines of steel fiber gravel concrete, and the average value should be used as a general junction. Fruit.
5. through the regression analysis of the fatigue test data of two graded steel fiber reinforced concrete, the bending fatigue equation of two graded steel fiber reinforced concrete is proposed. The regression coefficient can reach more than 0.971, which is closer to the test results than the other fitting formulas.
6. the fatigue strain equation describing the fatigue strain evolution curve of steel fiber reinforced concrete is presented. The results show that the fitting curve is in good agreement with the test curve. According to the inverse ratio of fatigue modulus to fatigue strain amplitude, the fatigue modulus evolution equation is obtained from the evolution equation of fatigue strain. The results of the model test are fitted. The results show that the fatigue modulus evolution curve of the formula is in good agreement with the corresponding test curve, and the correlation coefficient is above 0.99. It shows that the formula is suitable for describing the fatigue modulus evolution curve of steel fiber concrete.
7, the fatigue damage of steel fiber reinforced concrete is defined by fatigue strain and fatigue modulus. The typical damage variable evolution curve shows that the damage variable evolution curve defined by the maximum fatigue strain and the fatigue residual strain is basically consistent, and the difference is very small, and the damage variable evolution curve defined by the fatigue modulus is obviously larger than that by the fatigue. The damage variable evolution curve defined by strain strain, when the cycle ratio is 0.9, the damage variable defined by the fatigue strain is about 0.35, and the damage variable defined by the fatigue modulus is about 0.77. When the initial cycle, the damage variable defined by the fatigue modulus is about 0.34, and the damage variable defined by the fatigue strain is close to 0., that is to say, fatigue. The damage variable defined by the model is always greater than the damage variable defined by fatigue strain.
8, based on the damage mechanics, the bending fatigue damage equations of steel fiber gravel concrete and steel fiber recycled concrete are derived. The results show that the regression curve obtained by the fatigue damage equation is in good agreement with the fatigue damage evolution curve.
9, the expression of residual fatigue life and residual bending strength of steel fiber concrete is derived from the damage variable according to the change of macroscopic quantity of the material and the evolution of fatigue damage. By this formula, the given fatigue stress level, residual fatigue life and residual bending strength under different damage states are obtained, which are damaged structures. The residual fatigue life with the damage variable and the change curve of cycle ratio shows that the residual fatigue life curve decreases with the increase of the damage variable and the damage variable is less than 0.3, and the lower the stress level, the more obvious, the stress level is 0.7, the curve is urgent. With the increase of the cycle ratio, the residual fatigue life decreases approximately linearly, and the lower the stress level, the more obvious. The residual bending strength decreases with the cycle ratio and the damage variable curve, and the residual bending strength decreases gradually with the continuous increase of the annular ratio. At the same time, the change of the stress level has little effect on the residual bending strength, while the residual bending fatigue strength approximated to the damage variable, and the higher the stress level, the greater the residual bending strength.
【學位授予單位】：華南理工大學
【學位級別】：博士
【學位授予年份】：2013
【分類號】：TU528.572
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本文編號：2146376
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