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CONTENTS
Volume 32, Number 4, July10 2009
 

Abstract
A slip critical joint has various values to adopt the proper slip coefficient in various conditions of faying surfaces in the following codes: AISC, AIJ and Eurocode 3. However, the Korean Building Code still regulates the unique slip coefficient, 0.45, regardless of the diverse faying conditions. In this study, the slip resistance test, including five kinds of surface treatments were conducted to obtain the proper slip coefficients available to steel plate KS SM490A. The faying surfaces were comprised of a clean mill, rust, red lead paint, zinc primer, and shot blast treatment. The candidates for high strength bolts were torque-shear bolts, torque-shear bolts with zinc coating, and ASTM A490 bolts. Based on the test results, the specimens with a shot blasted surface and rusted surface exhibited ks, 0.61, and 0.5, respectively. It is recommended that the specimens with zinc primer exhibit ks

Key Words
slip coefficient; slip critical joint; tension; high-strength bolts; relaxation.

Address
Hwan-Seon Nah, Hyeon-Ju Lee and Kang-Seok Kim: Environmental & Structural Lab., Korea Electric Power Research Institute 65 Munji-Ro, Yusung-Gu, Daejon 305-380, Korea
Woo-Bum Kim: Architectural Engineering Department, Kongju National University, 182 Shinkwan-Dong Kongju, Chungnam, Korea

Abstract
The aim of this paper is to compare wavelet, kurtosis and pseudofractal based techniques for structural health monitoring in the presence of measurement noise. A detailed comparison and assessment of these techniques have been carried out in this paper through numerical experiments for the calibration of damage extent of a simply supported beam with an open crack serving as an illustrative example. The numerical experiments are deemed critical due to limited amount of experimental data available in the field of singularity based detection of damage. A continuous detectibility map has been proposed for comparing various techniques qualitatively. Efficiency surfaces have been constructed for wavelet, kurtosis and pseudofractal based calibration of damage extent as a function of damage location and measurement noise level. Levels of noise have been identified for each technique where a sudden drop of calibration efficiency is observed marking the onset of damage masking regime by measurement noise.

Key Words
wavelet; kurtosis; fractal; structural damage detection; signal to noise ratio.

Address
Vikram Pakrashi: Roughan & O

Abstract
This paper aims to study the large deflections of variable-arc-length elastica subjected to the terminal forces (e.g., axial force and torque). Based on Kirchhoff\'s rod theory and with help of Euler parameters, the set of nonlinear governing differential equations which free from the effect of singularity are established together with boundary conditions. The system of nonlinear differential equations is solved by using the shooting method with high accuracy integrator, seventh-eighth order Runge-Kutta with adaptive step-size scheme. The error norm of end conditions is minimized within the prescribed tolerance (10−5). The behavior of VAL elastica is studied by two processes. One is obtained by applying slackening first. After that keeping the slackening as a constant and then the twist angle is varied in subsequent order. The other process is performed by reversing the sequence of loading in the first process. The results are interpreted by observing the load-deflection diagram and the stability properties are predicted via fold rule. From the results, there are many interesting aspects such as snap-through phenomenon, secondary bifurcation point, loop formation, equilibrium configurations and effect of variable-arc-length to behavior of elastica.

Key Words
Kirchhoff

Address
Boonchai Phungpaingam, Chainarong Athisakul and Somchai Chucheepsakul: Dept. of Civil Engineering, Faculty of Engineering, King Mongkut

Abstract
A passive vibration mitigation architecture is proposed to damp transverse vibrations of guyed masts. The scheme is based on a number of pendula attached to the mast and tuned to the vibration modes to be controlled. This scheme differs from the well-known autoparametric pendulum absorber system. The equations of motion of the guyed mast with an arbitrary number of pendula are obtained. The leading bending behaviour of a typical truss mast is described by an equivalent beam model whereas the guys are conveniently modeled as equivalent transverse springs whose stiffness comprises the elastic and geometric stiffness. By assuming a mast with an inertially and elastically isotropic crosssection, a planar model of the guyed mast is investigated. The linearization of the equations of motion of the mast subject to a harmonic distributed force leads to the transfer functions of the structure without the dampers and with the dampers. The transfer functions allow to investigate the mitigation effects of the pendula. By employing one pendulum only, tuned to the frequency of the lowest mode, the effectiveness of the passive vibration potential in reducing the motion and acceleration of the top section of the mast is demonstrated.

Key Words
guyed mast; tuned pendulum dampers; vibration absorbers; vibration mitigation; truss structure.

Address
Walter Lacarbonara and Stefano Ballerini: Dipartimento di Ingegneria Strutturale e Geotecnica,Sapienza University of Rome, via Eudossiana 18, Rome 00184, Italy

Abstract
This paper presents the experimental results on the strength behavior and failure modes of box beam-to-circular column connections in steel piers. Previous research introduced parameters such as joint central angles, extension of horizontal stiffeners, and use of equivalent web depth, which ignored strength behavior and failure modes of box beam-to-circular column connections. The use of equivalent web depth d2 is not reasonable when central angle

Key Words
box beam-to-circular column connection; central angle; equivalent web depth; failure modes; concrete-filled; yield strength.

Address
Won-Sup Hwang: Dept. of Civil Engineering, Inha University, 253 Yonghyun-Dong Nam-Gu, Incheon 402-751, Korea
Young-Pil Kim: Structural Department, Yooshin Engineering Corporation, 832-40 Yoksam-Dong, Gangnam-Gu, Seoul 135-936, Korea
Tae-Yang Yoon: Steel Structure Research Lab., RIST, 79-5 Youngcheon, Dongtan, Hwasung, Kyunggido 445-813, Korea

Abstract
As it is known, laminated composite materials are increasingly used in many technological applications, and in some instance, cutouts must be made into laminated panels for practical reasons, changing the stress distribution. The present study deals with the determination of the stress concentration factor that holes of square shape cause in an orthotropic plate subjected to distributed in . plane loading. Square holes of rounded corners in a rectangular plate are considered, and the effect of different combinations of axial and tangential forces applied to its middle plane at the external edges, is studied. The mutually perpendicular axes, which define the principal axes of orthotropy, are assumed in many different directions referred to the sides of the plate. Numerical experiments by means of a finite element code is performed, evaluating the influence of the fiber orientation with respect to the edges of the plate and the characteristics of the orthotropic materials since such structures do not exhibit easily predictable behavior.

Key Words
stress concentration; S.C.F.; orthotropic plates; plane stress; finite element method.

Address
D.V. Bambill, C.A. Rossit and A. Susca: Dpto. de Ingenieria-Instituto de Mecanica Aplicada-Universidad Nacional del Sur.(8000), Bahia Blanca, Argentina
Consejo Nacional de Investigaciones Cientificas y Tecnicas-CONICET, Argentina

Abstract
In this paper, the peak horizontal ground acceleration over the bedrock (PGA) is calculated by a probabilistic seismic hazard assessment (PSHA). For this reason, at first, all the occurred earthquakes in a radius of 200 km of Sanandaj city have been gathered. After elimination of the aftershocks and foreshocks, the main earthquakes were taken into consideration to calculate the seismic parameters (SP) by Kijko (2000) method. The seismotectonic model of the considered region and the seismic sources of the region have been modeled. In this research, Sanandaj and its vicinity has been meshed as an 8 (vertical lines) * 10 (horizontal lines) and the PGA is calculated for each point of the mesh using the logic tree method and the five attenuation relationships (AR) with different weighted coefficient. These calculations have been performed by the Poisson distribution of four hazard levels. Then by using it, four regional maps of the seismic hazard regions have been provided for Sanandaj and its vicinity. The results show that the maximum and minimum value of PGA for the return periods of 75, 225, 475, 2475 years are (0.114, 0.074) (0.157, 0.101), (0.189, 0.121) and (0.266, 0.170), respectively.

Key Words
probabilistic seismic hazard assessment; seismicity parameters; peak ground acceleration; Sanandaj, Iran.

Address
Gholamreza Ghodrati Amiri: Center of Excellence for Fundamental Studies in Structural Engineering, School of Civil Engineering, Iran University of Science & Technolog, Tehran, Iran
Kaveh Andisheh: Dept. of Civil Engineering, Faculty of Engineering, University of Kurdistan, Sanandaj, Iran
Seyed Ali Razavian Amrei: School of Civil Engineering, Iran University of Science & Technology, Tehran, Iran

Abstract
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Key Words
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Address
Upendra K. Mallela and Akhil Upadhyay: Dept. of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee 247667, India


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