Summary
Damage of bridge cables is mainly manifested as the decrease in cable forces. These forces are affected by the boundary conditions, cable length, cable stiffness, and cable appendages, making it hard to identify the cable forces. Based on the substructure isolation method, this study proposes an approach for cable force identification to judge cable damage by adding virtual supports to each cable so that the cables share the same length and boundary conditions. The cable forces can then be identified according to the relationship between the natural frequency and cable forces. The basic concept is that the boundary sensors are transformed into virtual supports by a linear combination of the convolution of measured responses to achieve the zero boundary response. A finite element model of a suspension bridge was used to validate the proposed method in a simulation. When the virtual supports were added to the cables, the relationship between the cable forces and the natural frequency was almost linear, and the cable damage could be successfully identified with 5% noise. Finally, the effectiveness of the proposed method was verified experimentally, and the natural frequency of the isolated cable substructure was confirmed to be a highly sensitive damage indicator.
General line rogue waves in the Mel’nikov equation are derived via the Hirota bilinear method, which are given in terms of determinants whose matrix elements have plain algebraic expressions. It is shown that fundamental rogue waves are line rogue waves, which arise from the constant background with a line profile and then disappear into the constant background again. By means of the regulation of free parameters, two subclass of nonfundamental rogue waves are generated, which are called as multirogue waves and higher-order rogue waves. The multirogue waves consist of several fundamental line rogue waves, which arise from the constant background and then decay back to the constant background. The higher-order rogue waves start from a localised lump and retreat back to it. The dynamical behaviours of these line rogue waves are demonstrated by the density and the three-dimensional figures.
Displacement and pressure sensors were used to measure the displacement and pressure variations of the hydraulic cylinders in an excavator under impact loads. Taking the measured cylinder displacement as a driven boundary condition, the kinematics simulation is completed in the LMS Virtual Lab. Taking the measured cylinder thrust and the simulation results of the kinematics as driven boundary conditions, the dynamic simulation of the excavator is carried out. The CAE dynamic stress analysis of the boom and arm of the excavator is performed using ABAQUS inertial release approach under the loads on the sub-structure obtained from the above multi-body dynamic simulation and the measured data, it provides a reference for the material selection of each part of excavator boom. The good agreement between the analytical and testing results demonstrates that the present method is accurate, efficient, cost effective, and able to monitor the stress status and access the health of an excavator instead of using field testing techniques.
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