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CONTENTS
Volume 17, Number 5, May 2004
 

Abstract
On the basis of a structural analysis of radial gate (i.e. Tainter gate), the current paper focuses on weight minimization according to the location of the arms on a radial gate. In spite of its economical significance, there are hardly any previous studies on the optimum design of radial gate. Accordingly, the present study identifies the optimum position of the support point for a radial gate that guarantees the minimum weight satisfying the strength constraint conditions. This study also identifies the optimum position for 2 or 3 radial arms with a convex cylindrical skin plate relative to a given radius of the skin plate curvature, pivot point, water depth, ice pressure, etc. These optimum designs are then compared with previously constructed radial gates. Local genetic and hybrid-type genetic algorithms are used as the optimum tools to reduce the computing time and enhance the accuracy. The results indicate that the weights of the optimized radial gates are appreciably lower than those of previously constructed gates.

Key Words
DFP method (Davidon-Fletcher-Powell Method); genetic algorithm hybrid method; LZGA (Local Zooming Genetic Algorithm); radial gate (Tainter gate); 2-arm type; 3-arm type.

Address
Young-Doo Kwon; School of Mechanical Engineering, Kyungpook National University, Daegu 702-701, Korea
Seung-Bo Jin;System Design & Integration Department, KSLV Systems Division,
Korea Aerospace Research Institute, Korea
Jae-Yong Kim; Korea Atomic Energy Research Institute, Korea
Il-Hee Lee; Voith Turbo, Co., Korea

Abstract
The objective of this research was to evaluate the performance of metal-plate-connected truss joints subjected to cyclic loading conditions that simulated seismic events in the lives of the joints. We also investigated the duration of load factor for these joints. We tested tension splice joints and heel joints from a standard 9.2-m Fink truss constructed from 38- ?89-mm Douglas-fir lumber: 10 tension splice joints for static condition and for each of 6 cyclic loading conditions (70 joints total) and 10 heel joints for static condition and for each of 3 cyclic loading conditions (40 joints total). We evaluated results by comparing the strengths of the control group (static) with those of the cyclic loading groups. None of the cyclic loading conditions showed any strength degradation; however, there was significant stiffness degradation for both types of joint. The results of this research show that the current duration of load factor of 1.6 for earthquake loading is adequate for these joints.

Key Words
wood engineering; wood connections; duration of load; seismic loads; tension splice joint; heel joint; fink truss.

Address
Rakesh Gupta; Department of Wood Science and Engineering, 114 Richardson Hall, Oregon State University, Corvallis, OR 97331, USA
Thomas H. Miller; Department of Civil, Construction, and Environmental Egineering, Oregon State University, Corvallis, OR 97331, USA
Shawn M. Wicks Freilinger; Oregon Department of Transportation, Salem, OR 97301, USA

Abstract
This paper presents a theoretic model of a smart structure, a transversely isotropic piezoelectric thick square plate constructed with three laminas, piezoelectric-elastic-piezoelectric layer, by adopting the first order shear deformation plate theory and piezoelectric theory. This model assumes that the transverse displacements through thickness are linear, and the in-plane displacements in the mid-plane of the plate are not taken to be account. By using Fourier

Key Words
sandwich plate; piezoelectric plate; piezoelectric material; first order shear deformation theory; analytical solution; bending.

Address
Lanhe Wu, Zhiqing Jiang and Wenjie Feng; Department of Mechanics and Engineering Science, Shijiazhuang Railway Institute, Shijiazhuang 050043, P.R. China

Abstract
This paper aims to evaluate the effect of typhoons on fatigue damage accumulation in steel decks of long-span suspension bridges. The strain-time histories at critical locations of deck sections of long-span bridges during different typhoons passing the bridge area are investigated by using on-line strain data acquired from the structural health monitoring system installed on the bridge. The fatigue damage models based on Miner

Key Words
typhoon; long-span bridge; fatigue damage; stress spectrum; health monitoring.

Address
Tommy H. T. Chan; Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
Z. X. Li; College of Civil Engineering, Southeast University, Nanjing, 210096, China
J. M. Ko; Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong

Abstract
A meshless method with novel variation of point collocation by finite mixture approximation is developed in this paper, termed the meshless finite mixture (MFM) method. It is based on the finite mixture theorem and consists of two or more existing meshless techniques for exploitation of their respective merits for the numerical solution of partial differential boundary value (PDBV) problems. In this representation, the classical reproducing kernel particle and differential quadrature techniques are mixed in a point collocation framework. The least-square method is used to optimize the value of the weight coefficient to construct the final finite mixture approximation with higher accuracy and numerical stability. In order to validate the developed MFM method, several one- and two-dimensional PDBV problems are studied with different mixed boundary conditions. From the numerical results, it is observed that the optimized MFM weight coefficient can improve significantly the numerical stability and accuracy of the newly developed MFM method for the various PDBV problems.

Key Words
meshless method; finite mixture; point collocation; reproducing kernel particle; differential quadrature; least-square.

Address
J. Q. Cheng, H. P. Lee and Hua Li; Institute of High Performance Computing, 1 Science Park Road, #01-01 The Capricorn, Singapore Science Park II, Singapore 117528

Abstract
The paper presents shear lag parameters for beam-to-column connections in steel box piers. Previous researches have analyzed beam-to-column connections in steel piers using a shear lag parameter ho obtained from a simple beam model, which is not based on a reasonable design assumption. Instead, the current paper proposes a cantilever beam model and has proved the effectiveness through theoretical and experimental studies. The paper examines the inaccuracy of the previous researches by estimating the effective width, the width-span length ratio L/b, and the sectional area ratio S of a cantilever beam. Two different shear lag parameters are defined using the cantilever model and the results are compared each other. The first type of shear lag parameter hc of a cantilever beam is derived using additional moments from various stress distribution functions while the other shear lag parameter heff of a cantilever beam is defined based on the concept of the effective width. An evaluation method for shear lag stresses has been investigated by comparing analytical stresses with test results. Through the study, it could be observed that the shear lag parameter heff agrees with hc obtained from the 2nd order stress distribution function. Also, it could be observed that the shear lag parameter hc using the 4th order stress distribution function almost converges to the upper bound of test results.

Key Words
beam-to-column connection; shear lag parameter; additional moment; stress distribution function; effective width.

Address
Won-Sup Hwang and Young-Pil Kim; Department of Civil Engineering, Inha University, 253 Younghyun-Dong, Nam-Gu, Incheon 402-751, Korea
Yong-Myung Park; Department of Civil Engineering, Pusan National University, 30 Jangjeon-Dong, Geumjeong-Gu, Pusan 609-735, Korea

Abstract
An optimal design method with nonlinear elastic analysis is presented. The proposed nonlinear elastic method overcomes the drawback of the conventional LRFD method that accounts for nonlinear effect by using the moment amplification factors of B1 and B2. The genetic algorithm used is a procedure based on Darwinian notions of survival of the fittest, where selection, crossover, and mutation operators are employed to look for high performance ones among sections in the database. They are satisfied with the constraint functions and give the lightest weight to the structure. The objective function taken is the total weight of the steel structure and the constraint functions are strength, serviceability, and ductility requirement. Case studies of a planar portal frame, a space two-story frame, and a three-dimensional steel arch bridge are presented.

Key Words
nonlinear elastic analysis; optimal design; genetic algorithm.

Address
Seung-Eock Kim; Civil & Environmental Engineering, Construction Tech. Research Institute, Sejong University, Seoul, Korea
Weon-Keun Song and Sang-Soo Ma; Korea Infrastructure Safety and Technology Corporation, Korea

Abstract
An uncoupled computational model for analyzing the hygrothermal dynamic response of composite laminates has been developed. The constitutive equations, expressed in an integral form, and involving relaxation moduli are adopted, to describe the non-aging hygrothermorheologically simple materials. A Prony series represents the relaxation moduli is exploited in order to derive a recursive relationship, and thereby eliminate the storage problem that arises when dealing with material possessing memory. The problem is formulated in a descritized variational form. Mindlin and higher order finite elements are employed for spatial descretization, while the Newmark average acceleration scheme is exploited for temporal descritization. The adopted recursive formula uses only the details of the previous event to compute the details of the current one. Numerical results of the displacement fields of both thin and thick viscoelastic laminates problems are discussed to show up the effectiveness of Mindlin and higher-order shear theories.

Key Words
composite laminates; viscoelastic; finite element; hygrothermal.

Address
Amr E. Assie and Fatin F. Mahmoud; Department of Mechanical Design and Production, Faculty of Engineering, Zagazig University, Zagazig 44519, Egypt


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