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CONTENTS
Volume 43, Number 1, July10 2012
 

Abstract
A fast precise integration method (FPIM) is proposed for solving structural dynamics problems. It is based on the original precise integration method (PIM) that utilizes the sparse nature of the system matrices and especially the physical features found in structural dynamics problems. A physical interpretation of the matrix exponential is given, which leads to an efficient algorithm for both its evaluation and subsequently the solution of large-scale structural dynamics problems. The proposed algorithm is accurate, efficient and requires less computer storage than previous techniques.

Key Words
structural dynamics system; sparse matrix; precise integration method; matrix exponential; fast algorithm

Address
Q. Gao, F. Wu, H.W. Zhang, W.X. Zhong: State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116023, P.R. China
Howson and F.W. Williams: Cardiff School of Engineering, Cardiff University, Cardiff CF24 3AA, UK

Abstract
A damped Timoshenko beam element is introduced for the DOF-efficient forced vibration analysis of beam-like structures coated with viscoelastic damping layers. The rotary inertia as well as the shear deformation is considered, and the damping effect of viscoelastic layers is modeled as an imaginary loss factor in the complex shear modulus. A complex composite cross-section of structures is replaced with a homogeneous one by means of the transformed section approach in order to construct an equivalent single-layer finite element model capable of employing the standard C0-continuity basis functions. The numerical reliability and the DOF-efficiency are explored through the comparative numerical experiments.

Key Words
multi-layered damped beam structure; damped Timoshenko beam element; forced vibration analysis; complex shear modulus; transformed section method

Address
S.G. Won, S.H. Bae, W.B. Jeong, J.R. Cho: School of Mechanical Engineering, Pusan National University, Busan 609-735, Korea
S.R. Bae: Agency for Defense Development, Jinhae 645-016, Korea

Abstract
This paper presents a computational study that explores the design of rigid steel frames by considering construction related costs. More specifically, two different aspects are investigated in this study focusing on the effects of (a) reducing the number of labor intensive rigid connections within a frame of given geometric layout, and (b) reducing the number of different member section types used in the frame. A genetic algorithm based optimization framework searches design space for these objectives. Unlike some studies that express connection cost as a factor of the entire frame weight, here connections and their associated cost factors are explicitly represented at the member level to evaluate the cost of connections associated with each beam. In addition, because variety in member section types can drive up construction related costs, its effects are evaluated implicitly by generating curves that show the trade off between cost and different numbers of section types used within the frame. Our results show that designs in which all connections are considered to be rigid can be excessively conservative: rigid connections can often be eliminated without any appreciable increase in frame weight, resulting in a reduction in overall cost. Eliminating additional rigid connections leads to further reductions in cost, even as frame weight increases, up to a certain point. These complex relationships between overall cost, rigid connections, and member section types are presented for a representative five-story steel frame.

Key Words
construction related costs; optimization of moment resisting steel frames; connection cost; member section types

Address
Byoung-Han Choi: Korea Rural Research Institute, Ansan 426-908, Korea
Abhinav Gupta and John W. Baugh Jr.: Civil Engineering, North Carolina State Univ. Raleigh, NC 27695-7908, USA

Abstract
Sliding cable joints have been developed for the cable dome structures and the suspen-dome structures to reduce the cable pre-stressing loss and obtain a uniform inner force in each hoop cable. However, the relevant investigation is less addressed on the structural behavior of the cable dome structures and the suspen-dome structures with sliding cable joints due to the lack of analysis techniques. In this paper, a closed sliding polygonal cable element was established to analyze the structural behavior of the cable dome structures and the suspen-dome structures with sliding cable joints. The structural behaviors with sliding cable joints were obtained.

Key Words
cable dome structures; suspen-dome structures; sliding cable joint; closed sliding polygonal cable element; structural behavior

Address
Hongbo Liu: Department of Civil Engineering, Tianjin University, Tianjin 300072, China
Zhihua Chen: Department of Civil Engineering, Tianjin University, Tianjin 300072, China; Tianjin Key Laboratory of Civil Engineering Structures and New Materials, Tianjin 300072, China

Abstract
This paper extends a single equation, semi-analytical approach for three-span bridges to multi-span ones for the rapid and precise determination of natural frequencies and natural mode shapes of an orthotropic, multi-span plate. This method can be used to study the dynamic interaction between bridges and vehicles. It is based on the modal superposition method taking into account intermodal coupling to determine natural frequencies and mode shapes of a bridge deck. In this paper, a four- and a five-span orthotropic roadway bridge deck are compared in the first 10 modes with a finite element method analysis using ANSYS software. This simplified implementation matches numerical modeling within 2% in all cases. This paper verifies that applicability of a single formula approach as a simpler alternative to finite element modeling.

Key Words
natural frequencies; natural mode shapes; multi-span orthotropic bridge deck; dynamic loading; traffic

Address
A. Rezaiguia, Y. Fisli, S. Ellagoune, D.F. and N. Ouelaa: Mechanics & Structures Laboratory, Guelma University, P.O.B 401, Guelma 24000, Algeria
D.F. Laefer: Urban Modeling Group, School of Architecture, Landscape, and Civil Engineering, University College, Belfield, Dublin 4, Ireland

Abstract
In this study, the stability of laminated homogeneous and non-homogeneous orthotropic truncated conical shells with freely supported edges under a uniform hydrostatic pressure is investigated. It is assumed that the composite material is orthotropic and the material properties depend only on the thickness coordinate. The basic relations, the modified Donnell type stability and compatibility equations have been obtained for laminated non-homogeneous orthotropic truncated conical shells. Applying Galerkin method to the foregoing equations, the expression for the critical hydrostatic pressure is obtained. The appropriate formulas for the single-layer and laminated, cylindrical and complete conical shells made of homogeneous and non-homogeneous, orthotropic and isotropic materials are found as a special case. Finally, effects of non-homogeneity, number and ordering of layers and variations of shell characteristics on the critical hydrostatic pressure are investigated.

Key Words
laminated conical shells; non-homogeneous orthotropic materials; freely supported edges; stability; critical hydrostatic pressure

Address
Zihni Zerin: Department of Civil Engineering, Ondokuz Mayis University, Samsun, Turkey

Abstract
Based on the first-order shear deformation theory (FSDT), and the virtual work principle, an elastic analysis for axisymmetric clamped-clamped Pressurized thick truncated conical shells made of functionally graded materials have been performed. The governing equations are a system of nonhomogeneous ordinary differential equations with variable coefficients. Using the matched asymptotic method (MAM) of the perturbation theory, these equations could be converted into a system of algebraic equations with variable coefficients and two systems of differential equations with constant coefficients. For different FGM conical angles, displacements and stresses along the radius and length have been calculated and plotted.

Key Words
truncated conical shells; thick-walled; functionally graded material (FGM); analytical solution; perturbation technique

Address
M. Ghannad: Mechanical Engineering Faculty, Shahrood University of Technology, Shahrood, Iran
M. Zamani Nejad: Mechanical Engineering Department, Yasouj University, Yasouj P.O. Box: 75918-74831, IranMechanical Engineering Department, Tarbiat Modares University, Tehran, Iran
G.H. Rahimi and H. Sabouri:

Abstract
One of the most important and challenging steps in seismic vulnerability and performance assessment of highway bridges is the determination of the bridge component damage parameters and their corresponding limit states. These parameters are very essential for defining bridge damage state as well as determining the performance of highway bridges under a seismic event. Therefore, realistic damage limit states are required in the development of reliable fragility curves, which are employed in the seismic risk assessment packages for mitigation purposes. In this article, qualitative damage assessment criteria for ordinary highway bridges are taken into account considering the critical bridge components in terms of proper engineering demand parameters (EDPs). Seismic damage of bridges is strongly related to the deformation of bridge components as well as member internal forces imposed due to seismic actions. A simple approach is proposed for determining the acceptance criteria and damage limit states for use in seismic performance and vulnerability assessment of ordinary highway bridges in Turkey constructed after the 1990s. Physical damage of bridge components is represented by three damage limit states: serviceability, damage control, and collapse prevention. Inelastic deformation and shear force demand of the bent components (column and cap beam), and superstructure displacement are the most common causes for the seismic damage of the highway bridges. Each damage limit state is quantified with respect to the EDPs: i.e. curvature and shear force demand of RC bent components and superstructure relative displacement.

Key Words
vulnerability; seismic damage; bridges; limit states; demand parameters

Address
O. Avsar: Department of Civil Engineering, Anadolu University, 26555, Eski ehir, Turkey
A. Yakut: Department of Civil Engineering, Middle East Technical University, 06531, Ankara, Turkey


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