Papers by Author: Wei Xuan Zhu

Abstract: According to the mode II fracture test results of the concrete of the double-edge notched specimens with four-point shear loading and half symmetrical loading, the relationship of the mode II fracture toughness of two type of concrete specimens are analyzed. Based on the numerical simulation, the stress field near the crack tip is analyzed by use of the finite element method, and the mode II fracture toughness of the two types of concrete specimens are calculated with the displacement extrapolation method, and the difference with the experimental results are studied. Because of the uniform stress of the specimen with half symmetric loading, and the shear stress in the fracture process zone is much larger than the first principal stress during the entire test process, while the phenomenon of opening and torsion of the surface of cracks may appeared at the four point shear loading conditions, which leads to the fracture process of the specimen is not always the mode II fracture of pure shear.

Abstract: The bearing capacity decreases continuously along with the deterioration of material property under the action of external effects. It is important to evaluate the damage of concrete, and the damage parameter plays an important role in this process. An experimentation method has been designed, which can simulate the initial damage by mixed initiator into concrete. Using the elastic modulus of axial compression experimentation, the initial damage D0 and damage threshold value Df have been gained. The Size effect of concrete compress damage parameters is verified.

Abstract: Many damage models of concrete have been put forward till now, of which some models are applied in engineering practices. The damage parameters play an important role in the calculations of damage with these models, which is determined during experiments. However, the tests of damage on concrete are rarely made, especially about the measuring method of initial damage. The initial damage is an essential parameter to study on the damage of concrete. Being based on the theory of damage, this paper analyze of the damaged and undamaged elastic modulus of concrete. The new method of determining undamaged elastic modulus from test results has been put forward, and then the initial damage has been quantified.

Abstract: Damage parameter of concrete is widely used in design and construction of concrete structures. An experimentation method has been designed, which can simulate the initial damage by mixed initiator into concrete. Damage parameter can be obtained in laboratory with standard specimens. But practical structure is very large. It is not rational to use this parameter in practical structures. So size effect on damage parameter is studied. It is concluded that initial damage and summit damage grow with the increase of structure size, but the growth rate becomes gentle with size increasing. When the size is larger than 500 mm×500 mm, the growth rate is less than 15‰, so the results obtained from specimen in 500 mm×500 mm can be used for mass concrete structures.