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CONTENTS
Volume 21, Number 1, September10 2005
 

Abstract
Foschi? connector model is used as a basic component in the development of nonlinear analysis programs for timber structures. This paper presents the extension of the model to include the effect of shaft frictional forces. The wood medium is modeled using the Foschi embedment model, while shaft friction is modeled using an elastic Coulomb-type friction model. The initial confining pressure for the case of driven fasteners is accounted for by a lateral shift of the load-embedment curve. The model is used to compute the cyclic response of both driven and inserted fasteners. The results obtained from the cases studied indicate that initial confining pressure and friction do not have a significant effect on the computed hysteretic response, however, they significantly affect the computed amount of fastener withdrawal. This model is particularly well-suited for modeling the hysteretic response of shear walls with moderate fastener withdrawal under lateral cyclic or earthquake loading.

Key Words
mechanics-based model; timber fastener; cyclic; load-embedment curve; finite element; withdrawal; friction; initial confining pressure; earthquake.

Address
Nii Allotey; Department of Civil and Environmental Engineering, The University of Western Ontario, Canada
Ricardo Foschi; Department of Civil Engineering, The University of British Columbia, Canada

Abstract
An improved shear deformable thin-walled curved beam theory to overcome the drawback of currently available beam theories is newly proposed for the spatially coupled free vibration and elastic analysis. For this, the displacement field considering the shear deformation effects is presented by introducing displacement parameters defined at the centroid and shear center axes. Next the elastic strain and kinetic energies considering the shear effects due to the shear forces and the restrained warping torsion are rigorously derived. Then the equilibrium equations are consistently derived for curved beams with non-symmetric thin-walled sections. It should be noticed that this formulation can be easily reduced to the warping-free beam theory by simply putting the sectional properties associated with warping to zero for curved beams with L- or T-shaped sections. Finally in order to illustrate the validity and the accuracy of this study, finite element solutions using the isoparametric curved beam elements are presented and compared with those in available references and ABAQUS? shell elements.

Key Words
free vibration; elastic analysis; curved beam; thin-walled; shear deformation; warping.

Address
Nam-Il Kim; Department of Civil and Environmental Engineering, University of Maryland, College Park, MD 20742, USA
Moon-Young Kim; Department of Civil and Environmental Engineering, Sungkyunkwan University,Cheoncheon-Dong, Jangan-Ku, Suwon 440-746, Korea

Abstract
This paper proposes a realistic approach to pushover analyses of reinforced concrete (RC) structures with single column type and frame type. The characteristic of plastic hinge of a single RC column subjected to fixed axial load was determined first according to column? three distinct failure modes which were often observed in the experiments or earthquakes. By using the determined characteristic of plastic hinge, the pushover analyses of single RC columns were performed and the analytical results were investigated to be significantly consistent with those of cyclic loading tests. Furthermore, a simplified methodology considering the effect of the variation of axial force for each RC column of the frame structure during pushover process is proposed for the first time. It would be helpful in performing pushover analysis for the structures examined in this study with efficiency as well as accuracy.

Key Words
performance-based design; pushover analysis; reinforced concrete column; plastic hinge.

Address
Yu-Chi Sung; Department of Civil Engineering, National Taipei University of Technology, No.1, Sec. 3,
Chung-Hsiao E. Rd., Taipei, 10608, Taiwan, R.O.C.
Kuang-Yen Liu; Department of Civil Engineering, National Taiwan University, No.1, Sec. 4, Roosevelt Road, Taipei, Taiwan, 106, Taiwan, R.O.C.
Chin-Kuo Su; Department of Civil Engineering, National Taipei University of Technology, No.1, Sec. 3,
Chung-Hsiao E. Rd., Taipei, 10608, Taiwan, R.O.C.
I-Chau Tsai and Kuo-Chun Chang; Department of Civil Engineering, National Taiwan University, No.1, Sec. 4, Roosevelt Road, Taipei, Taiwan, 106, Taiwan, R.O.C.

Abstract
When a large number of identical cylinders are placed in an array with equal separation distance, near-resonant phenomena may occur between cylinders at critical frequencies, and cause large wave forces on each element of the array. In this paper, 64 truncated circular cylinders arranged in 4 rows and 16 columns are considered to check occurrence of near-resonant phenomena and performance of theoretical predictions based on the potential flow. Experiments are conducted in head waves to measure the wave elevation along the longitudinal centerline of the model, and measured results are compared with numerical ones. Attention is focused on the spatial variation of the wave amplitude around the first near-trapped-mode frequency.

Key Words
hydrodynamic interaction; trapped mode; wave transmission; spatial distribution; truncated circular cylinders.

Address
Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-koen, Kasuga-city, Fukuoka 816-8580, Japan

Abstract
This study analyzes stress intensity factors for a number of periodic edge cracks in a semi-infinite medium subjected to a far field uniform applied load along with a distribution of eigenstrain. The eigenstrain is considered to be distributed arbitrarily over a region of finite depth extending from the free surface. The cracks are represented by a continuous distribution of edge dislocations. Using the complex potential functions of the edge dislocations, a simple as well as effective method is developed to calculate the stress intensity factor for the edge cracks. The method is employed to obtain the numerical results of the stress intensity factor for different distributions of eigenstrain. Moreover, the effect of crack spacing and the intensity of the normalized eigenstress on the stress intensity factor are investigated in details. The results of the present study reveal that the stress intensity factor of the periodic edge cracks is significantly influenced by the magnitude as well as distribution of the eigenstrain within the finite depth. The eigenstrains that induce compressive stresses at and near the free surface of the semi-infinite medium reduce the stress intensity factor that, in turn, contributes to the toughening of the material.

Key Words
stress intensity factor; eigenstrain; edge dislocation; periodic edge cracks; semi-infinite medium.

Address
Mechanical Engineering Department, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh

Abstract
This paper presents results from a study to extend a performance-based shearwall selection procedure to take into account the contributions of nonstructural finish materials (such as stucco and gypsum wallboard), construction quality issues, and their effects on the displacement performance of engineered wood shearwalls subject to seismic loading. Shearwall performance is evaluated in terms of peak displacements under seismic loading (characterized by a suite of ordinary ground motion records) considering different combinations of performance levels (drift limits) and seismic hazard. Shearwalls are analyzed using nonlinear dynamic time-history analysis with global assembly hysteretic parameters determined by fitting to actual shearwall test data. Peak displacement distributions, determined from sets of analyses using each of the ground motion records taken to characterize the seismic hazard, are post-processed into performance curves, design charts, and fragility curves which can be used for risk-based design and assessment applications.

Key Words
design; earthquake engineering; probability; seismic design; shearwall; wood structures.

Address
Jun Hee Kim; Lochsa Engineering, Inc., Las Vegas, NV, USA
David V. Rosowsky; Department of Civil Engineering, TAMU 3136, Texas A&M University, College Station,
TX 77843-3136, USA

Abstract
An efficient methodology is presented to evaluate the seismic behavior of a Fluid-Elevated Tank-Foundation/Soil system taking the embedment effects into accounts. The frequency-dependent cone model is used for considering the elevated tank-foundation/soil interaction and the equivalent spring-mass model given in the Eurocode-8 is used for fluid-elevated tank interaction. Both models are combined to obtain the seismic response of the systems considering the sloshing effects of the fluid and frequency-dependent properties of soil. The analysis is carried out in the frequency domain with a modal analysis procedure. The presented methodology with less computational efforts takes account of; the soil and fluid interactions, the material and radiation damping effects of the elastic half-space, and the embedment effects. Some conclusions may be summarized as follows; the sloshing response is not practically affected by the change of properties in stiff soil such as S1 and S2 and embedment but affected in soft soil. On the other hand, these responses are not affected by embedment in stiff soils but affected in soft soils.

Key Words
fluid-structure-foundation/soil interaction; elevated tanks; freqency domain analaysis.

Address
Karadeniz Technical University, Department of Civil Engineering, 61080, Trabzon, Turkey


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