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CONTENTS
Volume 32, Number 5, July30 2009
 

Abstract
Modern earthquake-resistant design aims to isolate architectural precast concrete panels from the structural system so as to reduce the interaction with the supporting structure and hence minimize damage. The present study seeks to maximize the cladding-structure interaction by developing an energydissipating cladding system (EDCS) that is capable of functioning both as a structural brace, as well as a source of energy dissipation. The EDCS is designed to provide added stiffness and damping to buildings with steel moment resisting frames with the goal of favorably modifying the building response to earthquake-induced forces without demanding any inelastic action and ductility from the basic lateral force resisting system. Because many modern building facades typically have continuous and large openings on top of the precast cladding panels at each floor level for window system, the present study focuses on spandrel type precast concrete cladding panel. The preliminary design of the EDCS was based on existing guidelines and research data on architectural precast concrete cladding and supplemental energy dissipation devices. For the component-level study, the preliminary design was validated and further refined based on the results of nonlinear finite element analyses. The stiffness and strength characteristics of the EDCS were established from a series of nonlinear finite element analyses and are discussed in detail in this paper.

Key Words
precast concrete; spandrel cladding panels; earthquake energy dissipation; finite element analysis; analytical modeling.

Address
H. Maneetes and A. M. Memari: Dept. of Architectural Engineering, The Pennsylvania State University, 104 Engineering Unit A, University Park, PA, 16802, U.S.A.

Abstract
In this paper the results of a series of experimental tests upon three-point bending specimens made of polystyrene and containing re-entrant corners are firstly described. Tests involved different notch angles, different notch depths and finally different sizes of the samples. All the specimens broke at the defect, as expected because of the material brittleness and, hence, the generalized stress intensity factor was expected to be the governing failure parameter. Recorded failure loads are then compared with the predictions provided by a fracture criterion recently introduced in the framework of Finite Fracture Mechanics: fracture is assumed to propagate by finite steps, whose length is determined by the contemporaneous fulfilment of energy balance and stress requirements. This fracture criterion allows us to achieve the expression of the generalized fracture toughness as a function of the tensile strength, the fracture toughness and the notch opening angle. Comparison between theoretical predictions and experimental data turns out to be more than satisfactory.

Key Words
three-point bending test; V-notch; fracture toughness; tensile strength; Finite Fracture Mechanics.

Address
Alberto Carpinteri, Pietro Cornetti, Nicola Pugno and Alberto Sapora: Dept. of Structural Engineering and Geotechnics, Politecnico di Torino, Turin, Italy
David Taylor: Dept. of Mechanical and Manufacturing Engineering, Trinity College, Dublin 2, Ireland

Abstract
A numerical method is developed to investigate the effects of some geometric parameters and density variation on frequency characteristics of the circular and annular membranes with varying density. The discrete singular convolution method based on regularized Shannon\'s delta kernel is applied to obtain the frequency parameter. The obtained results have been compared with the analytical and numerical results of other researchers, which showed well agreement.

Key Words
discrete singular convolution; circular membrane; annular membrane; non-homogeneous density.

Address
Hakan Ersoy: Akdeniz University, Faculty of Engineering, Mechanical Engineering Department, Division of Mechanics, Antalya, Turkey
Lutfiye Ozpolat and Omer Civalek: Akdeniz University, Faculty of Engineering, Civil Engineering Department, Division of Mechanics, Antalya, Turkey

Abstract
This paper describes fire performance of eight axially restrained reinforced concrete (RC) columns under a combination of two different load ratios and two different axial restraint ratios. The eight RC columns were all concentrically loaded and subjected to ISO834 standard fire on all sides. Axial restraints were imposed at the top of the columns to simulate the restraining effect of the rest of the whole frame. The axial restraint was effective when the column was expanding as well as contracting. As the results of the experiments have shown, the stiffness of the axial restraint and load level play an important role in the fire behaviors of both HSC and NSC columns. It is found that (a) the maximum deformations during expanding phase were influenced mostly by load ratio and hardly by axial restraint ratio, (b) For a given load ratio, axial restraint ratio had a great impact on the development of axial deformation during contraction phase beyond the initial equilibrium state, (c) increasing the axial restraint increased the value of restraint force generated in both the NSC and HSC columns, and (d) the development of column axial force during the contracting and cooling phase followed nearly parallel trend for columns under the same load ratio.

Key Words
high-strength concrete; column; fire performance; axial restraint; cooling phase.

Address
Bo Wu and Yi-Hai Li: State Key Laboratory of Subtropical Building Science, South China University of Technology, Guangzhou, 510640, China

Abstract
This paper reports part of a comprehensive research study conducted at the University of Queensland on the ability of CFRP web-bonded systems in strengthening an exterior beam-column joint subjected to monotonic loads. One 1/2.2 scaled plain and four CFRP repaired/retrofitted joints subjected to monotonic loads were analysed using the nonlinear finite-element program ANSYS and the results were calibrated against experiments. The ANSYS model was employed in order to account for tension stiffening in concrete after cracking and a modified version of the Hognestad

Key Words
reinforced concrete; joints; strengthening; fibre reinforced plastics; finite element method; nonlinear analysis.

Address
Seyed S. Mahini: Dept. of Civil Engineering, Yazd University, Yazd, Iran
Hamid R. Ronagh: Division of Civil Engineering, School of Engineering, The University of Queensland, Brisbane, QLD 4072, Australia

Abstract
FE model-based dynamic analysis has been widely used to predict the dynamic characteristics of civil structures. In a physical point of view, an FE model is unavoidably different from the actual structure as being formulated based on extremely idealized engineering drawings and design data. The conventional model updating methods such as direct method and sensitivity-based parameter estimation are not flexible for model updating of complex and large structures. Thus, it is needed to develop a model updating method applicable to complex structures without restriction. The main objective of this paper is to present the model updating method based on the hybrid genetic algorithm (HGA) by combining the genetic algorithm as global optimization method and modified Nelder-Mead

Key Words
hybrid genetic algorithm; finite element model updating; genetic algorithm; simplex method; modal properties.

Address
Dae-Sung Jung and Chul-Young Kim: Department of Civil and Environmental Engineering, Myongji University, San 38-2, Nam-dong, Yongin-si, Gyeonggi-do 449-728, Korea

Abstract
Current research and development of high performance concrete, together with study of phenomena that are pertinent to impact resistance, have lead to a new generation of barriers with improved properties to resist impact loads. The paper reviews major properties and mechanisms that affect impact resistance of concrete barriers as per criteria that characterize the resistance. These criteria are the perforation limit, penetration depth and the amount of front and rear face damage. From the long-known, single strength parameter that used to represent the barriers

Key Words
impact; high performance concrete; penetration; fibers; aggregates.

Address
A. N. Dancygier: Faculty of Civil and Environmental Engineering, National Building Research Institute, Technion - Israel Institute of Technology, Haifa 32000, Israel

Abstract
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Key Words
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Address
Tan Yong-Gang, Gong Feng and Zhang Zhe: School of Civil & Hydraulic Engineering, Dalian University of Technology, Dalian, China


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