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CONTENTS
Volume 34, Number 1, January10 2010
 

Abstract
The innovative intelligent fuzzy weighted input estimation method which efficiently and robustly estimates the unknown time-varying input force in on-line is presented in this paper. The algorithm includes the Kalman Filter (KF) and the recursive least square estimator (RLSE), which is weighted by the fuzzy weighting factor proposed based on the fuzzy logic inference system. To directly synthesize the Kalman filter with the estimator, this work presents an efficient robust forgetting zone, which is capable of providing a reasonable compromise between the tracking capability and the flexibility against noises. The capability of this inverse method are demonstrated in the input force estimation cases of the plate structure system. The proposed algorithm is further compared by alternating bwtween the constant and adaptive weighting factors. The results show that this method has the properties of faster convergence in the initial response, better target tracking capability, and more effective noise and measurement bias reduction.

Key Words
Kalman Filter; recursive least square estimator; fuzzy logic; input force.

Address
Ming-Hui Lee: Department of Civil Engineering, Republic of China Military Academy, Fengshan, Kaohsiung, Taiwan, R.O.C.
Tsung-Chien Chen: Department of Power Vehicle and Systems Engineering, Chung Cheng Institute of Technology, National Defense University, Dasi, Tao-Yuan, Taiwan, R.O.C.

Abstract
In order to predict the shear strengths of reinforced concrete beams, many deterministic models have been developed based on rules of mechanics and on experimental test results. While the constant and variable angle truss models are known to provide reliable bases and to give reasonable predictions for the shear strengths of members with shear reinforcement, in the case of members without shear reinforcement, even advanced models with complicated procedures may show lack of accuracy or lead to fairly different predictions from other similar models. For this reason, many research efforts have been made for more accurate predictions, which resulted in important recent publications. This paper develops probabilistic shear strength models for reinforced concrete beams without shear reinforcement based on deterministic shear strength models, understanding of shear transfer mechanisms and influential parameters, and experimental test results reported in the literature. Using a Bayesian parameter estimation method, the biases of base deterministic models are identified as algebraic functions of input parameters and the errors of the developed models remaining after the bias-correction are quantified in a stochastic manner. The proposed probabilistic models predict the shear strengths with improved accuracy and help incorporate the model uncertainties into vulnerability estimations and risk-quantified designs.

Key Words
Bayesian parameter estimation; epistemic uncertainty; model errors; error analysis; probabilistic models; reinforced concrete beams; shear strength.

Address
Junho Song and Won-Hee Kang: Dept. of Civil and Environmental Engineering, University of Illinois, Urbana-Champaign, IL 61801, USA
Kang Su Kim: School of Architecture and Architectural Engineering, University of Seoul, Korea
Sungmoon Jung: Dept. of Civil and Environmental Engineering, FAMU-FSU College of Engineering, Tallahassee, FL 32310, USA

Abstract
In Turkey, majority of industrial facilities are composed of precast buildings. However, precast buildings have suffered extensive damage during Kocaeli and Duzce (1999) and Adana-Ceyhan (1998) earthquakes. Therefore, in this study, fragilities of existing building stock and damage probabilities of precast buildings were studied. For this purpose, building inventories were prepared and variation of structural parameters was determined by investigating the design project of 65 precast buildings constructed in Denizli, Turkey. Twelve analysis models which reflect the stiffness, strength and ductility properties of building inventory were constructed. After the definition of strain based displacement limits and corresponding damage states for buildings, displacement demands were calculated by using non linear time history analysis. During the analyses 360 strong ground motion records were used. Exceedence ratios of concerned damage limits was calculated by checking the displacement demands and then PGV based fragility curves were constructed. Efficiency of strength, stiffness and ductility properties of existing precast buildings were investigated by comparing the fragility curves. The results have shown that the most effective parameters that govern the damage probabilities of precast buildings are stiffness and ductility. It was also stated that the results of fragility analysis and damage and failure observations performed after Kocaeli and Duzce Earthquakes are compatible.

Key Words
precast industrial buildings; fragility curves; strain based damage; damage states; damage estimation; nonlinear analysis.

Address
Sevket Murat Senel and Ali Haydar Kayhan: Dept. of Civil Engineering, Pamukkale University, Kinikli Kampusu, Denizli, Turkey

Abstract
Presented in this paper is the behaviour of asymmetric building isolated by the double variable frequency pendulum isolator (DVFPI). The DVFPI is an adoption of single variable frequency pendulum isolator (VFPI). The geometry and coefficient of friction of top and bottom sliding surfaces can be unequal. The governing equations of motion of the building-isolation system are derived and solved in incremental form. The analysis duly considers the interaction of frictional forces in the two principal directions developed at each sliding surface of the DVFPI. In order to investigate the behaviour of the base isolation using the DVFPI, the coupled lateral-torsional response is obtained under different parametric variations for a set of six far-fault earthquake ground motions and criterion to optimize its performance is proposed. Further, influences of the initial time period, coefficient of friction and frequency variation factors at the two sliding surfaces are investigated. The numerical results of the extensive parametric study help in understanding the torsional behaviour of the structure isolated with the double sliding surfaces as in the DVFPI. It is found that the performance of the DVFPI can be optimized by designing the top sliding surface initially softer and smoother relative to the bottom one.

Key Words
double variable frequency pendulum isolator; seismic isolation; asymmetric building; eccentricity; torsional coupling.

Address
D.P. Soni: Civil Engineering Department, Sardar Vallabhbhai Patel Institute of Technology, Vasad . 388 306, India
B.B. Mistry: Engineering College, Tuwa - 389 001, India
V.R. Panchal: Civil Engineering Department, Sardar Vallabhbhai Patel Institute of Technology, Vasad . 388 306, India

Abstract
In this paper, numerical solution of the singular integral equation for the multiple curved branch-cracks is investigated. If some quadrature rule is used, one difficult point in the problem is to balance the number of unknowns and equations in the solution. This difficult point was overcome by taking the following steps: (a) to place a point dislocation at the intersecting point of branches, (b) to use the curve length method to covert the integral on the curve to an integral on the real axis, (c) to use the semi-open quadrature rule in the integration. After taking these steps, the number of the unknowns is equal to the number of the resulting algebraic equations. This is a particular advantage of the suggested method. In addition, accurate results for the stress intensity factors (SIFs) at crack tips have been found in a numerical example. Finally, several numerical examples are given to illustrate the efficiency of the method presented.

Key Words
curved branch-cracks; stress intensity factor; singular integral equation; numerical solution.

Address
Y.Z. Chen and X.Y. Lin: Division of Engineering Mechanics, Jiangsu University, Zhenjiang, Jiangsu, 212013 P. R. China

Abstract
Nonlinear thermoelastic static response characteristics of laminated composite conical panels are studied employing finite element approach based on first-order shear deformation theory and field consistency principle. The nonlinear governing equations, considering moderately large deformation, are solved using Newton-Raphson iterative technique coupled with the adaptive displacement control method to efficiently trace the equilibrium path. The validation of the formulation for mechanical and thermal loading cases is carried out. The present results are found to be in good agreement with those available in the literature. The adaptive displacement control method is found to be capable of handling problems with multiple snapping responses. Detailed parametric study is carried out to highlight the influence of semicone angle, boundary conditions, radius-to-thickness ratio and lamination scheme on the nonlinear thremoelastic response of laminated cylindrical and conical panels.

Key Words
laminated; conical panel; thermoelastic; postbuckling; field consistency.

Address
R.M. Joshi: Dept. of Mechanical Engineering, Faculty of Technology, D. D. University, College Road, Nadiad . 387 001, India
B.P. Patel: Dept. of Applied Mechanics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi - 110 016, India

Abstract
This paper addresses the modified Dynamic Relaxation algorithm, called mdDR by minimizing displacement error between two successive iterations. In the mdDR method, new relationships for fictitious mass and damping are presented. The results obtained from linear and nonlinear structural analysis, either by finite element or finite difference techniques; demonstrate the potential ability of the proposed scheme compared to the conventional DR algorithm. It is shown that the mdDR improves the convergence rate of Dynamic Relaxation method without any additional calculations, so that, the cost and computational time are decreased. Simplicity, high efficiency and automatic operations are the main merits of the proposed technique.

Key Words
dynamic relaxation; error minimizing; fictitious mass and damping; nonlinear analysis.

Address
M. Rezaiee-pajand and J. Alamatian: Dept. of Civil Engineering, Ferdowsi University of Mashhad, Mashhad, P.O. Box. 91775-1111, Iran

Abstract
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Key Words
buckling; plate; elastic foundation.

Address
L.H. Yu: Dept. of Mathematics, National Chung Cheng University, Min-Hsiung, Chia-Yi 621, Taiwan, ROC
C.Y. Wang: Dept. of Mathematics and Mechanical Engineering, Michigan State University, East Lansing, MI 48824, USA

Abstract
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Key Words
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Address
Lili Zhu: School of Mechanical Engineering, Dalian Jiaotong University, Dalian 116028, P.R. China
Yinghua Zhao: Institute of Road and Bridge Engineering, Dalian Maritime University, Dalian 116026, P.R. China
Guangxin Wang: School of Mechanical Engineering, Dalian Jiaotong University, Dalian 116028, P.R. China


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