A new model for the free transverse vibration of axially functionally graded (FG) tapered Euler-Bernoulli beams is developed through the spline finite point method (SFPM) by investigating the effects of the variation of cross-sectional and material properties along the longitudinal directions. In the proposed method, the beam is discretized with a set of uniformly scattered spline nodes along the beam axis instead of meshes, and the displacement field is approximated by the particularly constructed cubic B-spline interpolation functions with good adaptability for various boundary conditions. Unlike traditional discretization and modeling methods, the global structural stiffness and mass matrices for beams of the proposed model are directly generated after spline discretization without needing element meshes, generation, and assembling. The proposed method shows the distinguished features of high modeling efficiency, low computational cost, and convenience for boundary condition treatment. The performance of the proposed method is verified through numerical examples available in the published literature. All results demonstrate that the proposed method can analyze the free vibration of axially FG tapered Euler-Bernoulli beams with various boundary conditions. Moreover, high accuracy and efficiency can be achieved.
Inerter dampers (IDs) and other inerter‐based vibration absorbers have elicited growing interest for vibration mitigation of stay cables. This study systematically investigates the vibration mitigation mechanism of tuned IDs (TIDs) for stay cables based on a continuous cable model. A TID consists of an ID connected with a spring stiffness in series (TID‐S) or parallel (TID‐P). On the basis of systematical parametric analyses, the impact of stiffness in series or parallel connections is evaluated, and the interrelations among ID, TID‐S, and TID‐P are elaborated. Subsequently, a detailed tuning procedure is summarized. Two optimal tuning formulas are also obtained to facilitate the rapid design of TID‐S and TID‐P. According to the optimized results, the damping ratios contributed by ID, TID‐S, or TID‐P to a stay cable are essentially determined by the inertance value. When the inertance deviates from the optimal value, the performance of ID drops significantly, but this adverse effect can be mitigated by tuning the stiffness in TID‐S or TID‐P.
In this study, a shear thickening fluid (STF) damper was experimented upon under different loading frequencies and amplitudes to investigate its nonlinear hysteretic behavior and energy dissipation capacity. An STF sample with 20% mass fraction and dispersion medium were prepared by nanoparticle silica (SiO2) and polyethylene glycol (PEG200). By using a parallel‐plate rheometer, steady‐state experiments were carried out to characterize the rheological properties of the sample. The results indicate that the STF sample shows an abrupt increase in viscosity/stress beyond a critical shear rate/strain. The results also show that the STF sample has good reversibility, thixotropy, and stability and can be used as a smart damping material in damper devices. Also, a prototype damper was developed and manufactured. Its nonlinear hysteretic behavior and energy dissipation capacity were experimentally investigated through the responses of damping force–displacement and damping force–velocity. The results show that the STF damper has excellent damping force as the loading condition increases and the controllability can be increased up to 3.21 times. The results also show that the energy dissipation capacity formed by damping force–displacement becomes fuller as the loading condition increases. Moreover, the results show that the graphical shapes of hysteretic loops of damping force–velocity can exhibit various styles as the STF's mechanism changes but the shapes are not stable when the velocity exceeds a certain value.
The behavior of dry stack masonry (DSM) is influenced by the interaction of the infill with the frame (especially the joints between bricks), which requires further research. This study investigates the compression and shear behaviors of DSM. First, a series of compression tests were carried out on both masonry prism with mortar (MP_m) and DSM prism (MP_ds). The failure mode of each prism was determined. Different from the MP_m, the stress-strain relationship of the MP_ds was characterized by an upward concavity at the initial stage. The compression strength of the MP_ds was slightly reduced by 15%, while the elastic modulus was reduced by over 62%. In addition, 36 shear-compression tests were carried out under cyclic loads to emphasize the influence of various loads on the shear-compression behavior of DSM. The results showed that the Mohr-Coulomb friction law adequately represents the failure of dry joints at moderate stress levels, and the varying friction coefficients under different load amplitudes cannot be neglected. The experimental setup and results are valuable for further research.
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