As a kind of novel material of high strength and light weight, carbon fiber materials have been widely used in construction industry to repair the damaged bridges improving its mechanical performance. In this work, the reinforced plates made of carbon fiber materials (for short CFRP) are externally bonded to the bottom of concrete beams to enhance load capacity of beams. The strain energy release rates are calculated at the interest crack in concrete beams based on virtual crack closure technology using FEM and are chosen as the criterion to determine whether the mechanical properties of beams are strengthened by being externally bonded with CFRP. The effects of main crack propagation on plain concrete beam, on concrete beam strengthened with CFRP, and on inclined crack are also discussed. The comparison between the beams with and without CFRP shows that the CFRP significantly increases the loading capacity and crack resistance. It also shows that the main crack propagation can reduce loading capacity and crack resistance regardless of strengthening. The experiment observation also supports this. It proves the validity of the method, and it is concluded that in order to increase the loading capacity and crack resistance effectively, controlling over the crack propagation is necessary.

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Focusing on the 3D topographic characteristics of rolling contact fatigue, a reconstruction method of the fatigue surface of roller based on point cloud data was proposed in this research. A 3D laser scanner was used to capture the data of point cloud on the surface of the fatigue roller. The gradient segmentation method was used to achieve segmentation of the fatigue contact surface, and the Kd-Tree algorithm in Statistical Outlier Removal filter was adopted to remove different types of noise. The greedy triangulation and hole repair and reconstruction of the curled point cloud were conducted. The experimental results showed that the segmentation accuracy of the fatigue contact surface was above 97.7%, the curling error rate of point cloud was 0.09%, and the maximum deviation of the reconstructed fatigue roller surface was 0.0199 mm. These methods can be applied to analyze the working conditions of roller specimen and contact fatigue.