This paper presents some recent advances on the numerical solution of the classical Germain-Lagrange equation for plate bending of thin elastic plates. A meshless strategy using the Generalized Finite Difference Method (GFDM) is proposed upon substitution of the original fourth-order differential equation by a system composed of two second-order partial differential equations. Mixed boundary conditions, variable nodal density and curved contours are some of the explored aspects. Simulations using very dense clouds and parallel processing scheme for efficient neighbor selection are also presented. Numerical experiments are performed for arbitrary plates and compared with analytical and Finite Element Method solutions. Finally, an overview of the procedure is presented, including a discussion of some future development.
In this paper soil-structure interaction (SSI) effects are investigated while an array of Pressurized Tuned Liquid Column Dampers (PTLCD) is employed for seismic vibration control of buildings. This device represents the most general case of a passive damper, with different reduction options to other control devices obtained by simplifying the involved parameters. Soil conditions considerably affect the control device functioning, because dynamic parameters such as natural frequency, damping factor, and natural modes depend on the soil properties. A simplified mathematical model is developed for the building with multiple degrees of freedom connected to a flexible base. For the time-domain analysis, a computational routine is developed for the linearization of the equilibrium equations of the PTLCD, as well as details for the reduction to the other types of passive dampers. Several numerical examples are selected for the analysis of the damper efficiency in reducing seismic vibration considering SSI. These simulations include Kobe earthquake data, which is applied to the model to evaluate the device performance under different scenarios. It is verified the influence of SSI in the natural frequency and structural response, which is related to the earthquake frequency components. Results confirm that the array of PTLCD's can reduce the vibration amplitudes, being more effective for soils with higher stiffness values.
This work presents the dynamic response of a lock subjected to the horizontal S0E component of the El Centro earthquake for empty and completely filled water chamber cases, by coupled fluid-structure analysis. Initially, the lock was studied by approximation, considering it similar to the case of a double piston coupled to a two-dimensional acoustic cavity (tank), representing a simplified analytical model of the fluid-structure problem. This analytical formulation can be compared with numerical results, in order to qualify the responses of the ultimate problem to be investigated. In all the analyses performed, modeling and numerical simulations were done using the finite element method (FEM), supported by the commercial software ANSYS.
This paper presents a review of current techniques employed for dynamic analysis of concrete gravity dams under seismic action. Traditional procedures applied in design bureaus, such as the Pseudo-Static method, often neglect structural dynamic properties, as well as ground amplification effects. A practical alternative arises with the Pseudo-Dynamic method, which considers a simplified spectrum response in the fundamental mode. The authors propose a self-contained development and detailed examples of this latter method, including a comparison with finite element models using transient response of fluid-structure systems. It is verified that application of the traditional procedure should be done carefully and limited to extremely rigid dams. On the other hand, the proposed development is straightforward and in agreement with finite element results for general cases where dam flexibility plays an important role. The last few years in Brazil have indicated a growing interest in national engineering for earthquake-resistant design. The first design code dedicated exclusively to this type of analysis was approved in 2006 (NBR15421, 2006. However, computation of earthquake effects in design of special structures, such as concrete dams, aqueducts and nuclear power plants, has being done for decades, although in a simplified form. Noteworthy is the Pseudo-Static Method (or Seismic Coefficient Method), where the structural mass is treated as an accelerated rigid body. In this case, the seismic coefficient matches exactly the structural acceleration, which is usually taken as a fraction of gravitational acceleration. Due to its simplistic nature, the Pseudo-Static procedure is still widely used in the seismic analysis of structures, although condemned by international codes (FERC, 2002). This type of analysis is usually defined as traditional procedure for seismic design. In general, the Pseudo-Static Method will produce the same results for any given structure with equal mass. That is, both structures will be subjected to the same seismic loading and no consideration will be made in relation to the dynamic properties of both (such as vibration period, for example). As a consequence, dynamic amplification effects are neglected and the response is valid only for infinitely rigid structures.The traditional procedure is increasingly destined to oblivion. The main reason is the absence of dynamic properties of the structure. In the specific case of concrete dams two major hypotheses govern the problem: (i) fluid is treated as incompressible and (ii) the dam moves with uniform acceleration along its height. The method basis comes from the classic work of Westergaard (1933), published almost 80 years ago. The last decades were marked by new calculation procedures and additional contributions to the legacy of Westergaard. These new procedures, such as the PseudoDynamic Method, require additional complexity in computation of earthquake forces. On the other hand, provide a more coherent representation of dynamic effects...
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