• LI JUN

      Articles written in Sadhana

    • An exact dynamic stiffness matrix for axially loaded double-beam systems

      Li Xiaobin Xu Shuangxi Wu Weiguo Li Jun

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      An exact dynamic stiffness method is presented in this paper to determine the natural frequencies and mode shapes of the axially loaded double-beam systems,which consist of two homogeneous and prismatic beams with a distributed spring in parallel between them.The effects of the axial force, shear deformation and rotary inertia are considered, as shown in the theoretical formulation. The dynamic stiffness influence coefficients are formulated from the governing differential equations of the axially loaded double-beam system in free vibration by using the Laplace transform method. An example is given to demonstrate the effectiveness of this method, in which ten boundary conditions are investigated and the effect of the axial force on the natural frequencies and mode shapes of the double-beam system are further discussed.

    • Corrosion behavior of reinforcing bar in magnesium phosphate cement based on polarization curve

      LI JUN JI YONGSHENG XU ZHISHAN

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      Apart from focusing on the analysis of the characteristics of reinforcing bars during corrosion, such as open circuit potential and polarization, the study also engages in the investigation of their corrosion in magnesium phosphate cement (MPC). For a more comprehensive understanding of the rusting performances, a comparison was made by an electrochemical workstation between the reinforcing bars in the MPC system and in the ordinary cement. Meanwhile, under an optical microscope, an observation was conducted on the corrosion morphology in MPC at different ages of concrete while during MPC hydration, an exploration based on pHchanges and polarization curve theory was carried out to learn about the mechanism of the resistance of the reinforcing bars in MPC to corrosion. Despite their extremely slow rate, corrosion behaviors were practically found in the reinforcing bars in MPC. Both the changes in pH and the formation of ammonium phosphate metal complex in the weak base were considered in the study to be the control factors for the resistance of reinforcing bars in MPC to corrosion.

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