Papers by Author: Jian Hou

Abstract: The elastic stress and strain fields in an elasto-plastic circular cross-section bar with semicircular groove subjected to uniaxial tension are systematically investigated using the finite element method. It is found that the stress and strain concentrations are different, especially after the partial region near the groove root yielding. The coupled influences of the loading levels and Poisson’s ratios on the stress and strain concentrations are examined. The maximum of strain concentration factor is always at the groove root, but the maximum of stress concentration factor is at the groove root only while the loading levels are lower.

Abstract: The paper deals with experimental activity on 4 scale-models of elevated pile cap foundation belonging to a real bridge. The foundation was composed of 9 piles, pile cap and pier and the special soil box was built to consider soil-pile-superstructure interaction. Two specimens were strengthened by steel protective pipe at each pile top. The tests consist of cyclically imposed displacement to 4 specimens, performed in the state key laboratory for disaster reduction in civil engineering of Tongji University. According to the test result, the peak strength of strengthening specimens is about 1.77 times of the others and the ultimate displacement is 1.66 times of the original models. Additionally, the dissipated hysteric energy capability of strengthening specimens is more than 2.15 times of the others as the equivalent viscous damping ratio is reduced by 50%. Other relevant phenomena are the pinching effect of original specimens is more obvious and the hysteretic loops of reinforced specimens are more plumpness. Moreover, the failure and collapse mechanisms of the elevated pile cap foundation were summarized. Finally, the measures to enhance the aseismic capability for elevated pile cap foundation were proposed.

Abstract: The elastic stress and strain fields of a finite-thickness plate containing two interacting holes are systematically investigated using the finite element method. The maximum stress and strain concentrations occur on the mid plane only in the thin plates. They do not occur on the mid plane and their locations are different in the same plate for the thick plates. The values of the maximum stress and the strain concentration factor and their locations depend on the distance between the two holes and the plate thickness. The stress and the strain concentration factor are different, even if in an elastic state. The stress concentration factor and the strain concentration factor on the plate surface decrease rapidly with increasing thickness and becomes lower than the values corresponding to the plane stress state and the values of the mid plane. They are too low to reflect the overall stress concentrations as the plate thickness increases. The differences between the maximum value and the surface value of the stress concentration factor, the strain concentration factor increase rapidly and tend to their respective constant values with increasing plate thickness. These constant values depend on the distance between the two holes and the difference of the stress concentration factor is larger than that of the strain concentration factor in the same plate.

Abstract: The elastic stress and strain fields in a circular cross-section bar with semielliptic groove subjected to uniaxial tension are systematically investigated using the finite element method. It is found that the stress and strain concentrations are different even if the material is in the elastic state. The relation between the stress and the strain concentration factors depends on Poisson’s ratio and the groove’s geometric configuration. The coupled influences of the shape factor of the semielliptic groove and the relative depth of the groove on the stress and strain concentrations are examined. The equations that describe the stress and strain concentration factors for different groove’s geometric configurations and Poisson’s ratios are obtained based on finite element results.

Abstract: In this paper, the elastic stress and strain fields in curved beams of finite thickness with end moments are systematically investigated using 3D finite element analysis. For a curved beam of finite thickness, the through-thickness distributions of the stress and strain concentration factors are not uniform and their distributions are different. The radius of curvature and the thickness of the beam have significant effect on the stress and stain concentrations. The relations of the maximum value and the value at the corner root of surface of the stress and strain concentration factors with different thickness for various radius of curvature are respectively obtained.