Macro And Meso-mechanical Analysis On Cracking Behavior Of Concrete Cable Tower

Cable-stayed bridge got rapidly developed in designing and constructing duringthese decades. Concrete cable-stayed bridge occupy larger proportion. Tall cable towers'cracking behavior has aroused more and more attention from the researchers. Under theouter load, temperature load, concrete shrinkage and creep effect, tower of concretecable-stayed bridge suffers huge pressure transmitted by cables. According toincomplete statistics, tower fracture occurs in80%of the Chinese cable bridges, itseriously affects the cable-stayed bridge's safety and even people's life. This articleintroduced the fractal damage and the fractal fracture mechanics into safety assessmentof cable-stayed bridge's cable tower. Then, tall tower' safety state evaluation model isput forward based on fracture distribution in this paper Beginning and expansion offractures and the structure failure process are analyzed from the macroscopic andmesoscopic point of view through theoretical analysis. This paper set up a new methodsupported by the theory of fractal damage for evaluation of cable tower safety state aftercracking occurs. The relationship between the load level and fractal dimension offracture distribution after the cable tower cracking occurs is researched and it providestheoretical and experimental basis to further application to real bridge. The followingmainly innovative work has been done in this paper.?Tall tower's crack intelligent mobile video scanning device monitoringtechnology is put forward Median filtering method is put forward according to range ofall kinds of filter algorithm applicable and the crack image characteristics. Crackimage's binarization and extraction method are used to crack image segmentation.Crack monitoring information processing is realized by image mosaicing, crack vectorquantization and cracks image's simulation technology.?The solution of the three-dimension crack is equivalent to solutions of twotwo-dimension crack. One is equivalent to solution of center crack of infinite-sized plateunder the uni-axial tensile force from infinity distance, the other is equivalent tosolution of unilateral crack of infinite-sized plate under the tensile load. Relationshipbetween crack height and depth is calculated with double cantilever beam theory, itprovides a brand new method to research three-dimension crack problems. Stressintensity factor expression of tall cable tower's concrete crack is established based on crack fractal model. The relationship between stress intensity factors under linear crackassumption and irregular crack extension assumption is deduced combined with fracturemechanics theory.?Process of the initiationand propagation of cable tower's cracks is simulatedbased on the submodel technique and FRANC3D software combined with thecharacteristics of the cable-stayed bridge's tall tower. The relationships between stressintensity factor of the cable tower structure and the fractal dimension, fractal dimensionand the bearing capacity is calculated out. The relationship between weibull randomprobability distribution and the material cracks' distribution is established. The severityof the cable tower of concrete surface cracking is evaluated combined with fracturedamage mechanics and fractal theory.?In this paper, the micro particle flow numerical model based on discrete elementis established and the mesoscopic damage process of concrete is simulated with Fishsoftware. Concrete cracking performance is researched with selecting three kinds ofconcrete particle flow with different radius and number of clusters. As a result, thematerial properties improves significantly while the number of clusters increases Thelarger clusters radius is, the greater the stability of the structure system and the betternature of the enhancement effect would be. Mechanism of clusters material's damagecould be concluded as following. With the increasing of radius of clusters, proportion ofmatrix would decreases, and the matrix of micro cracks occurs more, at the same time,structure surface damages more easily.?Based on the theory of multi-scale homogenization. The finite element method isadopted to establish the concrete mesoscopic-macro equivalent mechanical propertiesof multi-scale model. At the same time, as an example, a finite element model of thesurface of the cable tower is established for macro and micro effect analysis to concrete.?Cable tower segment model test was done to verify the reliability of thetheoretical system. The relationship between the load level and fractal dimension offracture distribution after the cable tower cracking occurs is researched and it providestheoretical and experimental basis to further application to real bridge.