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CONTENTS
Volume 29, Number 2, May30 2008
 

Abstract
A new adaptive dual reciprocity boundary element method for dynamic analysis of 3-D structures is presented in this paper .It is based on finding the best approximation function of a radial basis function (RBF) group which minimize the error of displacement field expansion. Also, the effects of some parameters such as the existence of internal points, number of RBF functions and position of collocation nodes in discontinuous elements are investigated in this adaptive procedure. Three numerical examples show improvement in dynamic response of structures with adaptive RBF in dual
reciprocity with respect to ordinary BEM.

Key Words
Adaptive Dual Reciprocity; Boundary Element; Radial Basis Functions (RBF); natural frequencies; collocation node.

Address
S.H. Razaee and A. Noorzad: Dept. of Civil Engineering, Engineering Faculty, Tehran University, Tehran, Iran

Abstract
The moving vehicle loads on a bridge deck is one of the most important live loads of bridges. They should be understood, monitored and controlled before the bridge design as well as when the bridge is open for traffic. A MOM-based algorithm (MOMA) is proposed for identifying the timevarying moving vehicle loads from the responses of bridge deck in this paper. It aims at an acceptable solution to the ill-conditioning problem that often exists in the inverse problem of moving force identification. The moving vehicle loads are described as a combination of whole basis functions, such as orthogonal Legendre polynomials or Fourier series, and further estimated by solving the new system equations developed with the basis functions. A number of responses have been combined, some numerical simulations on single axle, two axle and multiple-axle loads, being either constant or timevarying, have been carried out and compared with the existing time domain method (TDM) in this paper.
The illustrated results show that the MOMA has higher identification accuracy and robust noise immunity as well as producing an acceptable solution to ill-conditioning cases to some extent when it is used to
identify the moving force from bridge responses.

Key Words
moving force identification; method of moments (MOM); bridge-vehicle interaction; time domain method; legendre polynomials; fourier series.

Address
Ling Yu: Key Lab of Disaster Forecast and Control in Engineering, Ministry of Education of the People?s
Republic of China (Jinan University), Guangzhou 510632, P. R. China
Department of Civil and Structural Engineering, The Hong Kong Polytechnic University,
Hong Kong, P. R. China
Tommy H.T. Chan: School of Urban Development, Faculty of Built Environment & Engineering, Queensland University of Technology, GPO Box 2434, Queensland 4001, Australia
Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hong Kong, P. R. China
Jun-hua Zhu: Key Lab of Disaster Forecast and Control in Engineering, Ministry of Education of the People?s
Republic of China (Jinan University), Guangzhou 510632, P. R. China
Changjiang River Scientific Research Institute, Wuhan 430010, P. R. China

Abstract
A MOM-based algorithm (MOMA) has been developed for moving force identification from dynamic responses of bridge in the companion paper. This paper further evaluates and investigates the properties of the developed MOMA by experiment in laboratory. A simply supported bridge model and a few vehicle models were designed and constructed in laboratory. A series of experiments have then been conducted for moving force identification. The bending moment and acceleration responses at several measurement stations of the bridge model are simultaneously measured when the model vehicle moves across the bridge deck at different speeds. In order to compare with the existing time domain method (TDM), the best method for moving force identification to date, a carefully comparative study scheme was planned and conducted, which includes considering the effect of a few main parameters, such as basis function terms, mode number involved in the identification calculation, measurement stations, executive CPU time, Nyquist fraction of digital filter, and two different solutions to the ill-posed system equation of moving force identification. It was observed that the MOMA has many good properties same as the TDM, but its CPU execution time is just less than one tenth of the TDM, which indicates an achievement in which the MOMA can be used directly for real-time analysis of moving force identification in field.

Key Words
moving force identification; method of moments (MOM); bridge loads; time domain method (TDM); dynamic responses.

Address
Ling Yu: Key Lab of Disaster Forecast and Control in Engineering, Ministry of Education of the People?s
Republic of China (Jinan University), Guangzhou 510632, P. R. China
Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hong Kong, P. R. China
Tommy H.T. Chan: School of Urban Development, Faculty of Built Environment & Engineering, Queensland University of Technology, GPO Box 2434, Queensland 4001, Australia
Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hong Kong, P. R. China
Jun-hua Zhu: Key Lab of Disaster Forecast and Control in Engineering, Ministry of Education of the People?s
Republic of China (Jinan University), Guangzhou 510632, P. R. China
Changjiang River Scientific Research Institute, Wuhan 430010, P. R. China

Abstract
The seismic response analysis of an existing bridge needs a mathematical model that can be calibrated with measured dynamic characteristics. These characteristics are the periods and the associated
mode shapes of vibration and the modal damping coefficients. This paper deals with the measurements and the interpretation of the results of ambient vibration tests done on a newly erected cable stayed bridge across the Oued Dib River at Mila city in Algeria. The signal analysis of ambient vibration records will permit to determine the dynamic characteristics of the bridge. On the other hand, a 3-D model of the bridge is developed in order to assess the frequencies and the associated modes of vibration. This information will be necessary in the planning of the test on the site (locations of the sensors, frequencies to be measured and the associated mode shapes of vibration). The frequencies predicted by the finite element model are compared with those measured during full-scale ambient vibration measurements of the bridge. In the same way, the modal damping coefficients obtained by the random decrement method are compared to those of similar bridges.

Key Words
ambient vibration; cable stayed bridge; dynamic characteristics; numerical model; random decrement method.

Address
Abderrahmane Kibboua and Mohamed Naboussi Farsi:
National Earthquake Engineering Centre, C.G.S
01, Rue Kaddour RAHIM, BP 252, Hussein Dey, Alger, Algeria
Jean-Luc Chatelain and Bertrand Guillier:
Institut pour le Developpement et la Recherche, IRD
LGIT, 1381, rue de la piscine, Saint Martin d\'Heres, Grenoble, France
Hakim Bechtoula and Youcef Mehani: National Earthquake Engineering Centre, C.G.S 01, Rue Kaddour RAHIM, BP 252, Hussein Dey, Alger, Algeria

Abstract
Earthquake induced hysteretic energy demand for a structure can be used as a limiting value of a certain performance level in seismic design of structures. In cases where it is larger than the
hysteretic energy dissipation capacity of the structure, failure will occur. To be able to select the limiting value of hysteretic energy for a particular earthquake hazard level, it is required to define the variation of hysteretic energy in terms of probabilistic terms. This study focuses on the probabilistic evaluation of earthquake induced worst failure probability and approximate confidence intervals for inelastic singledegree-of-freedom (SDOF) systems with a typical steel moment connection based on hysteretic energy. For this purpose, hysteretic energy demand is predicted for a set of SDOF systems subject to an ensemble of moderate and severe EQGMs, while the hysteretic energy dissipation capacity is evaluated through the previously published cyclic test data on full-scale steel beam-to-column connections. The failure probability corresponding to the worst possible case is determined based on the hysteretic energy demand and dissipation capacity. The results show that as the capacity to demand ratio increases, the failure
probability decreases dramatically. If this ratio is too small, then the failure is inevitable.

Key Words
failure probability; hysteretic energy demand; hysteretic energy capacity; confidence interval; non-linear analysis.

Address
Bulent Akbas: Department of Earthquake and Structural Science, Gebze Institute of Technology, 41400 Gebze-Kocaeli, Turkey
Mustafa Nadar: Department of Mathematics, Gebze Institute of Technology, 41400 Gebze-Kocaeli, Turkey
Jay Shen: Department of Civil and Architectural Engineering, Illinois Institute of Technology,
60616-3793 Chicago, IL, USA

Abstract
In this paper, we present an idea of the geometry-dependent MITC method. The simple concept is exemplified to improve a 2-node iso-beam (isoparametric beam) finite element of varying
section. We first study the behavior of a standard 2-node iso-beam finite element of prismatic section, which has been widely used with reduced integration (or the equivalent MITC method) in order to avoid
shear locking. Based on analytical studies on cantilever beams of varying section, we propose the axial strain correction (ASC) scheme and the geometry-dependent tying (GDT) scheme for the 2-node iso-beam
element. We numerically analyze varying section beam problems and present the improved performance by using both ASC and GDT schemes.

Key Words
finite elements; iso-beam; MITC method; tying point.

Address
Phill-Seung Lee: Samsung Heavy Industries, Seocho, Seoul 137-857, Korea
Hyuk-Chun Noh: Civil and Environmental Engineering, Sejong University, Gwangjin, Seoul 143-747, Korea
Chang-Koon Choi: Civil and Environmental Engineering, Korea Advanced Institute of Science & Technology,Yuseong, Daejeon 305-701, Korea

Abstract
This paper focuses on the application of artificial neural networks (ANN) for optimal design of tensegrity grid as light-weight roof structures. A tensegrity grid, 2 m ? 2 m in size, is fabricated by
integrating four single tensegrity modules based on half-cuboctahedron configuration, using galvanised iron (GI) pipes as struts and high tensile stranded cables as tensile elements. The structure is subjected to destructive load test during which continuous monitoring of the prestress levels, key deflections and strains in the struts and the cables is carried out. The monitored structure is analyzed using finite element method (FEM) and the numerical model verified and updated with the experimental observations. The paper then explores the possibility of applying ANN based on multilayered feed forward back propagation algorithm for designing the tensegrity grid structure. The network is trained using the data generated from a finite element model of the structure validated through the physical test. After training, the network output is compared with the target and reasonable agreement is found between the two. The results demonstrate the feasibility of applying the ANNs for design of the tensegrity structures.

Key Words
tensegrity; finite element method (FEM); strain; artificial neural network (ANN); roof.

Address
Ramakanta Panigrahi, Ashok Gupta and Suresh Bhalla:
Department of Civil Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110 016, India

Abstract
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Key Words
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Address
Omer Civalek: Division of Mechanics, Civil Engineering Department, Faculty of Engineering, Akdeniz University, Antalya, Turkiye


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