Harmonic response of large engineering structures with nonlinear modifications

Download
2011
Kalaycıoğlu, Taner
During the design and development stages of mechanical structures, after each modification made in order to satisfy design criteria, dynamic characteristics of the structure change and should be determined through reanalyzing the structure dynamically. Due to the significance of computational time and cost in design processes, it is inevitable for structural modification methods, especially for large systems, to become involved in predicting the dynamic behavior of modified structures from those of the original and modifying structures. Since most engineering structures are inherently nonlinear, linear approach may not be valid no more. Therefore, conventional structural modification methods can not be directly used, instead a nonlinear structural modification method needs to be employed. In this thesis, it is aimed to adapt an effective linear structural modification method to structures with nonlinear modification or coupling. The amplitude dependencies of nonlinearities are modeled by using describing function method. Mathematical formulations are embedded in a computer program developed in MATLAB® with a graphical user interface. The software uses modal analysis results of ANSYS® for the original structure and dynamic stiffness matrix and nonlinearity information that belong to the modifying structure in order to calculate dynamic response of the modified structure. The approach is verified by applying it to both discrete and real test structures previously studied in literature and generated discrete structures, then comparing the results with prior ones and ones obtained via time domain integration, respectively. Several other case studies are also included in order to demonstrate the applicability and to investigate the performance of the method. It is concluded in this study that the structural modification method proposed can be successfully and efficiently used for structures with nonlinear modification or coupling.

Suggestions

Structural coupling of two nonlinear structures
Tepe, Çağrı; Ciğeroğlu, Ender; Department of Mechanical Engineering (2018)
In mechanical design, modelling and analysis of a complex structure can be simplified with dividing the structure into substructures; therefore, any change in the structure can be addressed easily which is referred as “structural coupling”. Utilization of proper coupling techniques, it is possible to understand the behavior of the whole structure by considering the behavior of its substructures. For linear structures, coupling is a common technique; however, in most of the engineering structures, nonlineari...
Harmonic Response of Large Engineering Structures with Nonlinear Modifications
Kalaycioglu, Taner; Özgüven, Hasan Nevzat (2011-07-06)
In a structural design, the structure may need to be modified and for each modification its dynamic characteristics may need to be determined by reanalyzing the structure dynamically. Since computational time and cost are very critical in design processes, structural modification methods become decisive, particularly for large systems, in predicting the dynamic behavior of modified structures from those of the original and modifying structures. Due to nonlinearity in most engineering structures, linearity a...
Structural Coupling of Two Nonlinear Structures
Tepe, Çağrı; Ciğeroğlu, Ender (null; 2015-02-02)
In mechanical design, modeling and analysis of a complex structure can be simplified with dividing the structure into substructures; therefore, any change in the structure can be addressed easily which is referred as “structural coupling”. Utilization of proper coupling techniques, it is possible to understand the behavior of the whole structure by considering the behavior of its substructures. For linear structures, coupling is a common technique; however, in most of the engineering structures, nonlinearit...
Structural modification with additional degrees of freedom in large systems
Canbaloğlu, Güvenç; Özgüven, Hasan Nevzat; Department of Mechanical Engineering (2009)
In the design and development stages of mechanical structures, it is important to predict the dynamic characteristics of modified structures. Since time and cost are critical in design and development stage, structural modification methods predicting the dynamic responses of modified structures from those of the original structure and modification properties are very important, especially for large systems. In this thesis structural modification methods are investigated and an effective structural modificat...
On efficient use of simulated annealing in complex structural optimization problems
Hasançebi, Oğuzhan (Springer Science and Business Media LLC, 2002-01-01)
The paper is concerned with the efficient use of simulated annealing (SA) in structural optimization problems of high complexity. A reformulation of the working mechanism of the Boltzmann parameter is introduced to accelerate and enhance the general productivity of SA in terms of convergence reliability. Two general and complementary parameters, referred as "weighted Boltzmann parameter" and "critical Boltzmann parameter," are proposed, Several alternative methodologies are suggested for these two parameter...
Citation Formats
T. Kalaycıoğlu, “Harmonic response of large engineering structures with nonlinear modifications,” M.S. - Master of Science, Middle East Technical University, 2011.