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CONTENTS
Volume 47, Number 3, August10 2013
 

Abstract
The bending problem of Euler-Bernoulli discontinuous beams is dealt with, in which the discontinuities are due to the loads and eventually to essential constrains applied along the beam axis. In particular, the loads are modelled as random delta-correlated processes acting along the beam axis, while the ulterior eventual discontinuities are produced by the presence of external rollers applied along the beam axis. This kind of structural model can be considered in the static study of bridge beams. In the present work the exact expression of the response quantities are given in terms of means and variances, thanks to the use of the stochastic analysis rules and to the use of the generalized functions. The knowledge of the means and the variances of the internal forces implies the possibility of applying the reliability B-method for verifying the beam.

Key Words
Euler-Bernoulli beam; delta-correlated concentrated loads; generalized functions; reliability B-method

Address
G. Falsone and D. Settineri : Dipartimento di Ingegneria Civile, Universita di Messina, C.da Di Dio, 98166 Messina, Italy

Abstract
The natural sloshing frequencies of annular cylindrical TLD are parametrically investigated by experiment, aiming at the exploration of its successful use for suppressing the structural vibration of spar-type floating wind turbine subject to multidirectional wind, wave and current excitations. Five prototypes of annular cylindrical TLD are defined according to the inner and outer radii of acryl container, and eight different liquid fill heights are experimented for each TLD prototype. The apparent masses near the first and second natural sloshing frequencies are parametrically investigated by measuring the apparent mass of interior liquid sloshing to the acceleration excitation. It is observed from the parametric experiments that the first natural sloshing frequency shows the remarkable change with respect to the liquid fill height for each TLD model with different container dimensions. On the other hand, the second natural sloshing frequency is not sensitive to the liquid fill height but to the gap size, for all the TLD models, convincing that the annular cylindrical sloshing damper can effectively suppress the wave- and wind-induced tilting motion of the spar-type floating wind turbine.

Key Words
annular cylindrical sloshing damper; spar-type floating offshore wind turbine; multi-directional and varying-frequency; tilting motion; natural sloshing frequency; apparent mass

Address
S.H. Jeon, M.W. Seo, Y.U. Cho, W.G. Park and W.B. Jeong : School of Mechanical Engineering, Pusan National University, Busan 609-735, Korea

Abstract
For the purpose of investigating the free vibration response of the spatial curved beams, the governing equations are derived in matrix formats, considering the variable curvature and torsion. The theory includes all the effects of rotary inertia, shear and axial deformations. Frobenius scheme and the dynamic stiffness method are then applied to solve these equations. A computer program is coded in Mathematica according to the proposed method. As a special case, the dynamic stiffness and further the natural frequencies of a cylindrical helical spring under fixed-fixed boundary condition are carried out. Comparison of the present results with the FEM results using body elements in I-DEAS shows good accuracy in computation and validity of the model. Further, the present model is used for reciprocal spiral rods with different boundary conditions, and the comparison with FEM results shows that only a limited number of terms in the resultant provide a relatively accurate solution.

Key Words
curved beam; free vibration; variable curvature and torsion; dynamic stiffness; exact solution

Address
Li-li Zhu and Guang-xin Wang : School of Mechanical Engineering, Dalian Jiaotong University, Dalian 116028, P.R. China
Ying-hua Zhao : Institute of Road and Bridge Engineering, Dalian Maritime University, Dalian 116026, P.R. China

Abstract
A Bayesian probabilistic method is proposed for online estimation of the process noise and measurement noise parameters for Kalman filter. Kalman filter is a well-known recursive algorithm for state estimation of dynamical systems. In this algorithm, it is required to prescribe the covariance matrices of the process noise and measurement noise. However, inappropriate choice of these covariance matrices substantially deteriorates the performance of the Kalman filter. In this paper, a probabilistic method is proposed for online estimation of the noise parameters which govern the noise covariance matrices. The proposed Bayesian method not only estimates the optimal noise parameters but also quantifies the associated estimation uncertainty in an online manner. By utilizing the estimated noise parameters, reliable state estimation can be accomplished. Moreover, the proposed method does not assume any stationarity condition of the process noise and/or measurement noise. By removing the stationarity constraint, the proposed method enhances the applicability of the state estimation algorithm for nonstationary circumstances generally encountered in practice. To illustrate the efficacy and efficiency of the proposed method, examples using a fifty-story building with different stationarity scenarios of the process noise and measurement noise are presented.

Key Words
Bayesian probabilistic approach; Kalman filter; online algorithm; process noise; measurement noise; structural health monitoring

Address
Ka-Veng Yuen, Peng-Fei Liang and Sin-Chi Kuok : Department of Civil and Environmental Engineering, Faculty of Science and Technology, University of Macau, Macao, China

Abstract
High-strength strands are widely used as a key structural element in cable-stayed bridges and prestressed concrete structures. Conventional strands for stay cable and tendons in prestressed concrete structures are ϕ15.7mm coated seven-wire strands and ϕ15.2mm uncoated seven-wire strands, respectively, but the ultimate strengths of both strands are 1860MPa. The objective of this paper is to investigate the tensile behavior of a newly developed ϕ15.7mm 2,200 MPa coated strand and a ϕ15.2mm 2,400 MPa uncoated strand according to various types of mono anchorages and to propose appropriate anchorages for both strands. Finite element analyses were initially performed to find how the geometry of the anchor head affects the interaction among the anchor head, the wedge and the strand and to find how it affects the stress distributions in both parts. Tensile tests for the new strands were carried out with seven different types of mono anchorages. The test results were compared to each other and to the results obtained from the tensile tests with a grip condition. From the analysis and the test results, desirable mono anchorages for the new strands are suggested.

Key Words
high-strength strand; 2,200 MPa; 2,400 MPa; tensile test; mono anchorage; pre-stressed concrete; cable-stayed bridge

Address
Jin Kook Kim, Taek Ryong Seong : Energy Infrastructure Research Department, Steel Structure Research Division, Research Institute of Industrial Science and Technology, POSCO Global R&D Center, Incheon, Republic of Korea
Kyung Pil Jang and Seung Hee Kwon : Department of Civil and Environmental Engineering, Myongji University, Yongin, Republic of Korea

Abstract
In this study, the efficiency of adaptive neuro-fuzzy inference system (ANFIS) and genetic expression programming (GEP) in predicting the effects of infill walls on base reactions and roof drift of reinforced concrete frames were investigated. Current standards generally consider weight and fundamental period of structures in predicting base reactions and roof drift of structures by neglecting numbers of floors, bays, shear walls and infilled bays. Number of stories, number of bays in x and y directions, ratio of shear wall areas to the floor area, ratio of bays with infilled walls to total number bays and existence of open story were selected as parameters in GEP and ANFIS modeling. GEP and ANFIS have been widely used as alternative approaches to model complex systems. The effects of these parameters on base reactions and roof drift of RC frames were studied using 3D finite element method on 216 building models. Results obtained from 3D FEM models were used to in training and testing ANFIS and GEP models. In ANFIS and GEP models, number of floors, number of bays, ratio of shear walls and ratio of infilled bays were selected as input parameters, and base reactions and roof drifts were selected as output parameters. Results showed that the ANFIS and GEP models are capable of accurately predicting the base reactions and roof drifts of RC frames used in the training and testing phase of the study. The GEP model results better prediction compared to ANFIS model.

Key Words
infill wall; base reactions; roof drift; time history analysis; ANFIS; GEP

Address
M. Metin Kose and Cafer Kayadelen : Department of Civil Engineering, Faculty of Engineering & Architecture, K. Sutcu Imam University, 46050 K. Maras, Turkey

Abstract
This paper is concerned with the theoretical treatment of transient thermoelastic problems involving a functionally graded hollow cylinder with piecewise power law due to asymmetrical heating from its surfaces. The thermal and thermoelastic constants of each layer are expressed as power functions of the radial coordinate, and their values continue on the interfaces. The exact solution for the two-dimensional temperature change in a transient state, and thermoelastic response of a hollow cylinder under the state of plane strain is obtained herein. Some numerical results for the temperature change and the stress distributions are shown in figures. Furthermore, the influence of the functional grading on the thermal stresses is investigated.

Key Words
thermal stress problem; functionally graded material; hollow cylinder; piecewise power law; transient state; asymmetrical heating; plane strain problem

Address
Yoshihiro Ootao and Masayuki Ishihara : Department of Mechanical Engineering, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Nakaku, Sakai, 599-8531 Japan

Abstract
A leaf spring, especially the longitudinal type is liable and persistent element in automotive suspension system. In the present scenario the composite materials are widely used in the automobile industries has shown a great interest in the replacement of steel spring due to high strength by weight ratio. Previous investigations focused on stresses and displacement analysis of single leaf spring for different materials. The present work aims to design and analysis of leaf spring for two different cases by considering the Young\'s modulus to yield strength ratio. In the first case the analysis deals with the design and analysis of a single cantilever solid triangle beam which is an equivalent beam of a spring with three leaves having uniform strength. In the second case a 3- beams of rectangular cross section has been considered which is equivalent to a spring with three leaves. The analysis was carried out based on contact mechanics approach. The results were compared, that the fiberglass composite leaf spring is suitable for high loading capacity, reliability and efficiency.

Key Words
contact analysis; composite material; leaf spring; Young\'s modulus; yield strength

Address
R. Kumaravelan : Department of Mechanical Engineering, Velalar College of Engineering and Technology, Erode - 638012, Tamilnadu, India
S. Ramesh : Department of Mechanical Engineering, Annai Mathammal Sheela Engineering College, Namakkal - 637013, Tamilnadu, India
V.C. Sathish Gandhi : Department of Mechanical Engineering, University College of Engineering Nagercoil, Anna University, Tirunelveli Region, Konam, Nagercoil - 629004, Tamilnadu, India
M. Joemax Agu : Department of Mechanical Engineering, CSI Institute of Technology, Thovali, Nagercoil - 629302,
Tamilnadu, India
M. Thanmanaselvi : Department of Civil Engineering, University College of Engineering Nagercoil, Anna University, Tirunelveli Region, Konam, Nagercoil - 629004, Tamilnadu, India



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