Cracks and other diseases may occur in the long-term operation of highway tunnels and reduce the structural load-carrying capacity. Strengthening using carbon fiber reinforced polymer (CFRP) sheets and other materials could extend the service time of the tunnels. However, the process of strengthening tunnels is remarkably different from the process of strengthening aboveground structures because of the secondary load. In order to understand the development of stress and deformation of strengthened tunnels under secondary load, a 1 : 10 scaled model was tested to simulate the tunnel strengthened with CFRP under different damage states. The test results show that CFRP strengthening improved the stiffness of the structure and inhibited the propagation of the existing cracks. The peeling of the CFRP sheets made the strengthened structure quickly lose its load-carrying capacity, causing the instability of the structure. The failure loads of the structures strengthened at different damage states were essentially the same, with an average value of 184% of the original failure load. Nevertheless, the early strengthening helped control the structural deformation. The test results also demonstrate that the bonding strength between the CFRP and the lining is essential for strengthening effectiveness. This study provides a theoretical basis for similar engineering reinforcement designs.
As for the defects of the plate whose length and width are more than 8 times larger than the thickness direction, the finite difference numerical calculations are carried out by using the software of MATLAB. The surface temperature of defects in different positions, different thickness defects, different heating heat flow and heating time, and defects under defects are analyzed correspondingly by the program. According to the temperature difference results of the flawless surface and the flawed surface, the feasibility of infrared thermal imaging to detect the defects of the sandwich plate is analyzed to ensure the processing quality of the sandwich plate.
Steel-concrete composite structure is widely used in the present skyscraper industrial plant. This type of structure has a lot of advantages, such as high structural strength, efficient construction etc. However, the stiffness of this composite structure is lower than that of steel structures or reinforced-concrete structure, especially in the skyscraper industrial plant. The skyscraper industrial plant has a large span and high floor height, which means that the vibration comfort issues must be considered. This paper takes the actual skyscraper industrial plant under construction as the background, adopts the two methods of field measurement and finite element simulation, to obtain the first order vertical self-vibration frequency value of the steel-concrete composite slabs. The results show that the value is within the allowable range of error.
The steel tube concrete columns with steel reinforcement cages, steel plates and steel tubes has been used in super high-rise buildings, which are called concrete-filled steel tubular (CFST) columns with internal stiffeners. Based on the theory of limit equilibrium, the unified equation for the axial bearing capacity of the CFST columns with internal stiffeners is obtained. The derived equation in this study can provide reference for the future engineering applications.
Based on the fabric tensor theory and the principle of least square method, the method of block processing in the same model to explore the variation of the passive earth pressure of the transversely isotropic soil was used in the study. At the same time, primary displacement application and multiple displacement application were applied to change the angle between the large principal stress direction of the filling and the normal direction of the deposition surface to obtain the new strength parameters ci and φi of each block after the model was divided and additionally analyzing the variation of the anisotropic passive earth pressure. The study shows: 1.Considering the transverse isotropy of the soil and reaching the limit equilibrium, the passive earth pressure of the soil after multiple displacement application is not only smaller than that after primary displacement application but also closed to the theoretical solution of Coulomb’s earth pressure; 2.When the soil is inclined, the anisotropy is significant when compared with the horizontal direction.
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