The seismic behavior of a single-story ten-bay confined masonry structure was investigated using substructure pseudo-dynamic tests. Only one bay of the prototype was regarded as the test model and the remainder was regarded as numerical model. The test results show that the test model withstood, with slight damage, strong earthquakes with peak ground acceleration of 1600 gal. It is found that prototypes of the tested type exhibited satisfactory seismic performance. Hence, the confinement can be reduced if the budget of the building is limited.
Due to the large ratio of surface-to-volume, surface effects can become significant in the physical properties of piezoelectric nano-sized structures. In this work, we incorporate surface effects into wave propagation analysis of a nano-sized transversely isotropic piezoelectric cylinder. To this purpose, a novel approach based on state-space formalism is used to derive the approximate governing equations. The wave propagation in a transversely isotropic piezoelectric cylinder with surface effects is then studied and exact solution is presented. Numerical results are finally given to show that surface effects will play a very pronounced role in wave propagation of piezoelectric nano-cylinders.
Dielectric elastomers have attracted considerable attention both from academia and industry alike over the last two decades due to their superior mechanical properties. In parallel, research on the mechanical properties of dielectrics has been steadily advancing, including the theoretical, experimental, and numerical aspects. It has been recognized that the electromechanical coupling property of dielectric materials can be utilized to drive deformations in functional devices in a more controllable and intelligent manner. This paper reviews recent advances in the theory of dielectrics, with specific attention focused on the theory proposed by Dorfmann and Ogden. Additionally, we provide examples illustrating the application of this theory to analyze the electromechanical deformations and the associated bifurcations in soft dielectrics. We compared the bifurcations in elastic and dielectric materials and found that only compressive bifurcation modes exist in elastic structures, whereas both compressive and tensile modes coexist in dielectric structures. We summarize two proposed ways to suppress and prevent the tensile bifurcations in dielectric materials. We hope that this literature survey will foster further advancements in the field of the electroelastic theory of soft dielectrics.
The plasma current ramp-up is an important process for tokamak discharge, which directly affects the quality of the plasma and the system resources such as volt-second consumption and plasma current profile. The China Fusion Engineering Test Reactor (CFETR) ramp-up discharge is predicted with the tokamak simulation code (TSC). The main plasma parameters, the plasma configuration evolution and coil current evolution are given out. At the same time, the volt-second consumption during CFETR ramp-up is analyzed for different plasma shaping times and different plasma current ramp rates d I P /d t with/without assisted heating. The results show that the earlier shaping time and the faster plasma current ramp rate with auxiliary heating will enable the volt-second to save 5%–10%. At the same time, the system ability to provide the volt-second is probably 470 V · s. These simulations will give some reference to engineering design for CFETR to some degree.
The equivalent force control(EFC) method is a closed-loop displacement control system using the force feedback.This paper applied the method to the full-scale three-storey frame-supported reinforced concrete short-leg masonry shear wall model and three-storey pre-cast reinforced concrete shear wall substructure test model,and completed the substructure pseudo-dynamic test on the complex model which includes the multi-degree of freedom physical substructure and the elastic non-linear numerical substructure.The test results show that the equivalent force control method for the full-scale model is feasible and can obtain the descent stage test data.
Coupled magneto-mechanical wrinkling has appeared in many scenarios of engineering and biology. Hence, soft magneto-active (SMA) plates buckle when subject to critical uniform magnetic field normal to their wide surface. Here, we provide a systematic analysis of the wrinkling of SMA plates subject to an in-plane mechanical load and a transverse magnetic field?. We consider two loading modes: plane-strain loading and uni-axial loading, and two models of magneto-sensitive plates: the neo-Hookean ideal magneto-elastic model and the neo-Hookean magnetization saturation Langevin model. Our analysis relies on the theory of nonlinear magneto-elasticity and the associated linearized theory for superimposed perturbations. We derive the Stroh formulation of the governing equations of wrinkling, and combine it with the surface impedance method to obtain explicitly the bifurcation equations identifying the onset of symmetric and antisymmetric wrinkles. We also obtain analytical expressions of instability in the thin- and thick-plate limits. For thin plates, we make the link with classical Euler buckling solutions. We also perform an exhaustive numerical analysis to elucidate the effects of loading mode, load amplitude, and saturation magnetization on the nonlinear static response and bifurcation diagrams. We find that antisymmetric wrinkling modes always occur before symmetric modes. Increasing the pre-compression or heightening the magnetic field has a destabilizing effect for SMA plates, while the saturation magnetization enhances their stability. We show that the Euler buckling solutions are a good approximation to the exact bifurcation curves for thin plates.
Membrane-type metamaterials have shown a fantastic capacity for manipulating acoustic waves in the low frequency range. They have the advantages of simple geometry, light weight, and active tunability. In general, these membrane-type metamaterials contain a rigid frame support, leading to a fixed configuration. However, in some instances, flexible and reconfigurable devices may be desirable. A soft membrane-type acoustic metamaterial that is highly flexible and controllable is designed here. Different from the previously designed membrane-type metamaterials, the stiff supporting frame is removed and the stiff mass at the center of each unit cell is replaced by the soft mass, realized by bonding fine metallic particles in the central region. In contrast to the previous studies, the propagation of elastic transverse waves in such a soft metamaterial is investigated by employing the plane wave expansion method. Both the Bragg scattering bandgaps and locally resonant bandgaps are found to coexist in the soft metamaterial. The influences of structural parameters and finite biaxial pre-stretch on the dynamic behavior of this soft metamaterial are carefully examined. It is shown that whether or not the wave propagation characteristics are sensitive to the finite deformation does not depend on the property and pre-stretch of the membrane. In addition, a broadband complete bandgap and a pseudo-gap formed by the combination of two extremely adjacent directional bandgaps are observed in the low-frequency range, and both can be controlled by the finite pre-stretch.
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