Changjiang Liu

DYNAMIC ANALYSIS FOR NONLINEAR VIBRATION OF PRESTRESSED ORTHOTROPIC MEMBRANES WITH VISCOUS DAMPING

This paper is concerned with the nonlinear damped vibration of prestressed orthotropic membrane structures. The Krylov–Bogolubov–Mitropolsky (KBM) perturbation method is employed for solving the governing equations of large amplitude nonlinear vibration of rectangular orthotropic membranes with viscous damping. Presented herein are asymptotic analytical solutions for the frequency and displacement function of large amplitude nonlinear damped vibration of rectangular orthotropic membranes with four edges simply supported or fixed. Through the computational example, we compared and analyzed the frequency results. Meanwhile, the vibration mode of the membrane and the displacement and time curve of each feature point on the membrane surface were analyzed. The results obtained herein provide a simple and convenient approach to calculate the frequency and lateral displacement of large amplitude nonlinear vibration of rectangular orthotropic membranes with low viscous damping. In addition, the results provide some computational basis for the vibration control and dynamic design of membrane structures.

Analytical and numerical studies on the nonlinear dynamic response of orthotropic membranes under impact load

Orthotropic membrane components and structures are widely used in building structures, instruments and meters, electronic engineering, space and aeronautics, etc., because of their light weights. However, the same lightweight combined with low stiffness make membranes prone to vibration under dynamic loads, and in some cases the vibration may lead to structural failure. Herein, the undamped nonlinear vibration response of pretension rectangular orthotropic membrane structures subjected to impact loading is studied by analytical and numerical methods. The analytical solution is obtained by solving the governing equations by the Bubnov-Galerkin method and the Lindstedt-Poincaré perturbation method. Numerical analysis has also been carried out based on the same theoretical model. The analytical and numerical results have been compared and analyzed, and the influence of various model parameters on membrane vibration discussed. The results obtained herein provide some theoretical basis for the vibration control and dynamic design of orthotropic membrane components and structures.

Nonlinear Instability of Dished Shallow Shells under Uniformly Distributed Load

In this paper, the nonlinear instability of dished shallow shells under a uniformly distributed load is investigated. The dimensionless governing differential equations for the problem are derived and the equations solved by using the Free-Parameter Perturbation Method with the Spline Function Method. By analyzing the instability modes of dished shallow shells, we obtain the variation rules of the maximum deflection area of initial instability of the uniformly loaded dished shallow shell, and discuss the relationship between the initial instability area and the maximum deflection area of initial instability. These results provide some theoretical basis for engineering design and instability prediction and control of shallow shell structures.

A nondestructive method for the pretension detection in membrane structures based on nonlinear vibration response to impact

The pretension of building membrane structures may relax over its service lifetime, which may cause engineering failure under external loads. Therefore, the pretension of building membrane structures should be monitored or estimated regularly to compare the actual pretension to its design pretension and then to adopt some strengthening measures to mitigate future problems. Based on the geometrically nonlinear vibration of a rectangular orthotropic membrane structure, a nondestructive detection method for monitoring its pretension is developed in this article. This method is achieved by impacting a low-velocity pellet onto the membrane surface to generate vibration and detecting its response amplitude. Then the detected amplitude is converted into a pretension estimate via a derived formula. In addition, experiments for three kinds of conventional membrane material (Heytex H5573, Xing Yi Da, and ZZF 3010) were carried out according to the theoretical idea. The experimental results proved this method is feasible and verified the theoretical derivation is reasonable.

Identifying the influences of geological factors on reservoir bank collapse by a model test

Reservoir bank collapse, which strongly influences the relocation area when water is impounded, is currently an important topic in reservoir engineering. In this work, a series of orthogonal experiments was carried out to analyze, from among the many factors that can affect bank collapse width (BCW), the effects on BCW of slope angle, material grain-size diameter, degree of density of material, wave height of reservoir water, and water level fluctuation. A detailed analysis of each parameter is presented, and the analysis of range (ANORA) calculated. The results of the study show that the most sensitive factor affecting BCW is slope angle, followed by density degree, clay proportion, wave height, and water level. Finally, a prediction formula was established based on the physical simulation experiments, and its scope of applicability is discussed. These research results provide a reliable basis for future bank collapse studies.

Farmers’ Satisfaction of Rural Facilities and Its Influencing Indicators: A Case Study of Sichuan, China

The disparity between construction targets and the real needs of farmers in the construction of rural facilities is a problem that has led to a failure in meeting farmers’ demands. This paper investigates farmers’ satisfaction and the influencing factors of rural facilities through factor analysis and logit regression model. This research led to three key findings: ( ) overall satisfaction of farmers of rural facilities is below average level; ( ) farmers’ satisfaction is affected mainly by the horizontal comparison, road facilities, electricity and signal facilities, reconstruction of public toilets, irrigation facilities, cultural and recreational facilities, renovation of fuel and kitchen, healthy facilities, village planning and renovation, and income factor; ( ) farmers’ needs are shifting from production to life type. This paper is the foundation of further analysis of the effects of significant factors on farmers’ satisfaction, providing a theoretical basis for the construction of “bottom-up” and “top-down” decision-making mechanism.