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CONTENTS
Volume 31, Number 3, February 20 2009
 

Abstract
In this paper, the dynamic behavior for a group of transmission towers linked together through electrical wires and subjected to a strong ground motion will be investigated in detail. In performing the seismic analysis, the wires and the towers concerned are modeled, respectively, by using the efficient cable elements and the 3-D beam elements both considering geometric nonlinearities. In addition, to enhance the reliability and applicability of analytical outcome, a sophisticated soil-structure interaction model will be utilized in analyses. The strength capacities and the fracture occurrences for the main members of the tower are examined with the employment of the appropriate strength interaction equations. It is expected that by aid of this investigation, those who are engaged in code constitution or in practical designing of transmission towers may gain a better insight into the roles played by the interaction force between towers and wires and by the configurations of transmission lines under strong earthquake.

Key Words
Chi-Chi earthquake; geometric nonlinearity; soil-structure interaction.

Address
Y. H. Lei; Tamkang University, Department of Software Engineering, Lanyang campus, I-lan County, 26247, Taiwan-ROC
Y. L. Chien; Tamkang University, Civil Engineering Department, Taipei, Taiwan (ROC)

Abstract
Various Pushover analysis methodologies have evolved as an easy as well as designersfriendly alternative of nonlinear dynamic analysis for estimation of the inelastic demands of structures under seismic loading for performance based design. In fact, the established nonlinear dynamic analysis to assess the same, demands considerable analytical and computational background and rigor as well as intuitive insight into inelastic behavior for judging suitability of the results and its interpretation and hence may not be used in design office for frequent practice. In this context, the simple and viable alternative of Pushover analysis methodologies can be accepted if its efficacy is thoroughly judged over all possible varieties of the problems. Though this burning issue has invited some research efforts in this direction, still a complete picture evolving very clear guidelines for use of these alternate methodologies require much more detailed studies, providing idea about how the accuracy is influenced due to various combinations of basic parameters regulating inelastic dynamic response of the structures. The limited study presented in the paper aims to achieve this end to the extent possible. The study intends to identify the range of applicability of the technique and compares the efficacy of various alternative Pushover analysis schemes to general class of problems. Thus, the paper may prove useful in judicial use of Pushover analysis methodologies for performance based design with reasonable accuracy and relative ease.

Key Words
capacity curve; demand curve; nonlinear static procedure; performance based design; performance point; Pushover analysis.

Address
Sekhar Chandra Dutta; Department of Civil Engineering, Bengal Engineering and Science University, Shibpur, Howrah 711 103, West Bengal, India
Suvonkar Chakroborty; SMS DEMAG Private Limited, West Bengal, India
Anusrita Raychaudhuri; Structural Engineering, Department of Civil Engineering, Bengal Engineering and Science University, Shibpur, Howrah 711 103, West Bengal, India

Abstract
The paper investigates the dynamic behaviour of stiffened panels. The coupled differential equations for eccentric stiffening configuration are first derived. Then a semi-analytical procedure for dynamic analysis of stiffened panels is presented. Unlike finite element or finite strip methods, where the plate is discretized into a set of elements or strips, the plate in this procedure is treated as a single element. The potential energy of the structure is first expressed in terms generalized functions that describe the longitudinal and transverse displacement profiles. The resulting non-linear strain energy functions are then transformed into unconstrained optimization problem in which mathematical programming techniques are employed to determine the magnitude of the lowest natural frequency and the associated mode shape for pre-selected plate/stiffener geometric parameters. The described procedure is verified with other numerical methods for several stiffened panels. Results are then presented showing the variation of the natural frequency with plate/stiffener geometric parameters for various stiffening configurations.

Key Words
dynamic analysis; plates; free vibration.

Address
Osama Bedair; Jacobs Canada Inc., 116 Mount Aberdeen Manor SE, Calgary, Alberta, T2Z 3N8, Canada

Abstract
When the temperature of a structure varies, there is a tendency to produce changes in the shape of the structure. The resulting actions may be of considerable importance in the analysis of the structures having non-prismatic members. Therefore, this study aimed to investigate the modeling, analysis and behavior of the non-prismatic members subjected to temperature changes with the aid of finite element modeling. The fixed-end moments and fixed-end forces of such members due to temperature changes were computed through a comprehensive parametric study. It was demonstrated that the conventional methods using frame elements can lead to significant errors, and the deviations can reach to unacceptable levels for these types of structures. The design formulas and the dimensionless design coefficients were proposed based on a comprehensive parametric study using two-dimensional plane-stress finite element models. The fixed-end actions of the non-prismatic members having parabolic and straight haunches due to temperature changes can be determined using the proposed approach without necessitating a detailed finite element model solution. Additionally, the robust results of the finite element analyses allowed examining the sources and magnitudes of the errors in the conventional analysis.

Key Words
non-prismatic member; finite element analysis; fixed-end force; temperature effects.

Address
S. Bahadir Yuksel; Department of Civil Engineering, Selcuk University, Konya, Turkey

Abstract
Mechanical connections are recognized as extremely important elements in the aspect of strength and structural safety. However, classical structural model does not consider the connection stiffness properties, and are based on models with pinned or rigid joints only. In fact, mechanical connections are deformable and behave not linearly, affecting the whole structure and inducing nonlinear behavior as well. The quantification of this effect, however, depends on the description of the working of the connectors and the wood response under embedment. The theoretical modeling of wood structures with semi-rigid connections involves not only the structural analysis, but also the modeling of both single and grouped moment resisting connectors and the study of the wood properties under embedment. The proposal of this paper is to approach these aspects, and to quantitatively study the influence of the moment resistant connection in wooden framed structures. Comparisons between rigid and semi-rigid connections and between linear and nonlinear analysis lead to quantitative results.

Key Words
wood structures; framed structures; matrix methods; structural models; semi-rigid connections.

Address
C. L. O. Santana

Abstract
Due to structural complicacy, structural health monitoring for civil engineering needs more accurate and effectual methods of damage identification. This study aims to import multi-source information fusion (MSIF) into structural damage diagnosis to improve the validity of damage detection. Firstly, the essential theory and applied mathematic methods of MSIF are introduced. And then, the structural damage identification method based on multi-mode information fusion is put forward. Later, on the basis of a numerical simulation of a concrete continuous box beam bridge, it is obviously indicated that the improved modal strain energy method based on multi-mode information fusion has nicer sensitivity to structural initial damage and favorable robusticity to noise. Compared with the classical modal strain energy method, this damage identification method needs much less modal information to detect structural initial damage. When the noise intensity is less than or equal to 10%, this method can identify structural initial damage well and truly. In a word, this structural damage identification method based on multi-mode information fusion has better effects of structural damage identification and good practicability to actual structures.

Key Words
multi-mode information fusion; structural damage identification; D-S evidence theory; sensitivity to damage; robusticity to noise.

Address
Tao Liu

Abstract
Membrane structures are quite sensitive to wind and therefore the fluid-solid interaction can not be neglected in dynamic analysis. A boundary element method (BEM) for 3D simulation of windstructure interaction in tensile membrane structures is presented in this paper. The flow is treated as incompressible and potential. The flow field is solved with boundary element method codes and structural simulation is performed by finite element method software ANSYS. The nonlinear equations system is solved iteratively, with segregated treatment of the fluid and structure equations. Furthermore this method has been demonstrated to be effective by typical examples. Besides, the influence of several parameters on the wind-structure interaction, such as rise-span ratio, prestress and the wind velocity are investigated according to this method. The results provide experience in wind resistant researches and engineering.

Key Words
membrane structures; fluid-structure interaction; boundary element method.

Address
Xu Wen

Abstract
The aim of this discussion is to expose incorrect formulations and terms in the aforementioned paper.

Key Words
multi-bay coupled shear walls; lateral forces.

Address



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