Structural Dynamic Systems Computational Techniques And Optimization

There are various techniques to optimize either structural parameters, or structural controllers, but there are not many techniques that can simultaneously optimize the structural parameters and controller. The advantage of integrating the structural and controller optimization problems is that structure and controller interaction is taken into account in the design process and a more efficient overall design (lower control force/lighter weight) can be achieved, and also multidisciplinary design optimization can be performed. The down side is that the combined optimization problem is more difficult to formulate and solve, and computations are increased. This volume is a comprehensive treatment of dynamic analysis and control techniques in structural dynamic systems and the wide variety of issues and techniques that fall within this broad area, including the interactions between structural control systems and structural system parameters.

Computational techniques for the analysis and design of structural dynamic systems using numerical methods have been the focus of an enormous amount of research for several decades. In general, the numerical methods utilized to solve these problems include two phases: (a) spatial discretization by either the finite element method (FEM) or the finite difference method (FDM), and (b) solution of systems of time dependent second-order ordinary differential equations. In addition, the significantly powerful advances in computer systems capabilities have put on the desks of structural systems designers enormous computing power either by means of increasingly effective computer workstations or else through PCs (personal computers), whose increasing power has succeeded in marginalizing the computational power differences between PCs and workstations in many cases. This volume is a comprehensive treatment of the issues involved in computational techniques in structural dynamic systems.

Conventional seismic design has been based on structural strength in the initial design of structures, resulting in lateral force resisting systems with sufficient strength to be able to absorb and dissipate the seismic. For important structures such as urban high speed road systems, high rise buildings, hospitals, airports and other essential structures which must be quite functional after an earthquake, modern seismic structural design techniques have been developed with a view toward eliminating or significantly reducing seismic damage to such structures. This volume is a comprehensive treatment of the issues involved in modern seismic design techniques for structure with a view to significantly enhancing their capability of surviving earthquakes to an adequate degree, i.e., enhancing the ability of structural systems to withstand high level earthquakes.

Among the principal causes of failure in structural dynamic systems are exceedance of maximum structural systems design limit and structural fatigue failure. These processes are analyzed in this volume, and require sophisticated methods such as stochastic processes and their interactions with a structure as applied forces with stochastic description, finite element techniques, and other processes. Once these aspects are understood and applied, approaches to enhancing the reliability and damage tolerance of structural systems can be examined and applied to specific structural dynamic systems. This volume offers a comprehensive treatment of the issues and the sophisticated techniques involved and includes numerous illustrative examples.

Formulation of an optimal dynamic structural system design problem requires identification of design variables that describe the structural system, a cost function that needs to be minimized, and performance and safety constraints for the system. The formulation of the problem depends upon the type of application and objectives to be achieved, i.e., the shape, the sizing, or topology design problem. Specific design variable definition, cost of function and constraints are dictated by the application. This volume is a comprehensive treatment of the general methods involved in this broadly fundamental problem and provides essential techniques in specific but pervasive structural dynamic systems elements and their optimization.

Many high-rise buildings have been constructed in recent decades, particularly in Western Pacific Rim countries. Some to be completed soon and in future include: (1) Grand Gateway at XI Hul, Shanghai; (2) Tomorrow Square, Shanghai; (3) Xiamen Post and Telecommunications Buildings, Xiamen, China; (4) Petronas Twin Towers, Kaula Lumpur, Malaysia; and (5) Shanghai World Financial Center, Petronas Twin Towers and the Shanghai World Financial Center are 1,483 ft. and 1,509 ft. in height, respectively. While these represent the ultimate challenges in structural aspects of buildings, there are challenges for structural aspects of buildings of various heights. This book is a comprehensive treatment of the issues and advanced techniques involved in building and bridge structures. Numerous illustrative examples are included.

Nonlinear structural dynamic systems which are multi-degree of freedom systems involve, for instance, matrix dynamic equilibrium equations, which can be of various order up to very high order. In these equations, the nonlinear quantities can be dependent on time and other terms, such as scalar variables, which are dependent on time. Frequency response and response time derivatives would also, of course, be involved. Nonlinear terms can account for dissipative phenomena and can be due to other physical phenomena. In fact, many engineering structures involve time-dependent properties such as, stiffness elements of specific structural components which can change according to the stress level. Other examples of dynamic elements of nonlinear structural systems can include system mass and damping distribution elements which evolve with time, such as railway or highway bridges and other structures, which interact with external agencies generating the system motion (for example, trains, a queue of vehicles, or other external agencies.) This volume is a rather comprehensive treatment of many of the techniques and methods which are utilized for the analysis of nonlinear structural dynamic systems.

The finite element, an approximation method for solving differential equations of mathematical physics, is a highly effective technique in the analysis and design, or synthesis, of structural dynamic systems. Starting from the system differential equations and its boundary conditions, what is referred to as a weak form of the problem (elaborated in the text) is developed in a variational sense. This variational statement is used to define elemental properties that may be written as matrices and vectors as well as to identify primary and secondary boundaries and all possible boundary conditions. Specific equilibrium problems are also solved. This book clearly reveals the effectiveness and great significance of the finite element method available and the essential role it will play in the future as further development occurs.