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CONTENTS
Volume 37, Number 3, February10 2011
 

Abstract
Plant-specific analyses of 5 types of domestic reactors in Korea are performed to assure the structural integrity of the reactor pressure vessel (RPV) during transients which are expected to initiate pressurized thermal shock (PTS) events. The failure probability of the RPV due to PTS is obtained by performing probabilistic fracture mechanics analysis. The through-wall cracking frequency is calculated and compared to the acceptance criterion. Considering the fluence at the end of life expected by surveillance test, the sufficient safety margin is expected for the structural integrity of all reactor pressure vessels except for the oldest one during the pressurized thermal shock events. If the flaw with aspect ratio of 1/12 is considered to eliminate the conservatism, the acceptance criteria is not exceeded for all plants until the fluence level of 8 x 1019 n/cm2, generating sufficient margin beyond the design life.

Key Words
pressurized thermal shock; reactor pressure vessel; structural integrity; stress intensity factor; failure probability; through-wall cracking.

Address
M.J. Jhung: Korea Institute of Nuclear Safety, 19 Guseong-dong, Yuseong-gu, Daejeon 305-338, Korea
Y.H. Choi: Korea Institute of Nuclear Safety, 19 Guseong-dong, Yuseong-gu, Daejeon 305-338, Korea
Y.S. Chang: Kyung Hee University, Seocheon-dong, Giheung-gu, Yongin 446-701, Korea

Abstract
Although earthquakes generate random cyclic lateral loading on structures, a quasi-static cyclic loading pattern with gradually increasing amplitude has been commonly used in the laboratory tests because of its relatively low cost and simplicity compared with pseudo-dynamic and shake table tests. The number, amplitudes and sequence of cycles must be chosen appropriately as important parameters of a quasi-static cyclic loading pattern in order to account for cumulative damage matter. This paper aims to reach a new cyclic displacement pattern to be used in quasi-static tests of well-confined, flexure-dominated reinforced concrete (RC) columns. The main parameters of the study are sectional dimensions, percentage of longitudinal reinforcement, axial force intensity and earthquake types, namely, far-fault and near-fault.

Key Words
reinforced concrete column; seismic evaluation; loading pattern; displacement pattern; quasi-static loading.

Address
E. Yuksel: Faculty of Civil Engineering, Istanbul Technical University, Maslak-Istanbul, Turkey
M. Surmel: Graduate School of Istanbul Technical University, Maslak-Istanbul, Turkey

Abstract
The plane crack-contact problem for an infinite elastic layer with two symmetric rectangular rigid stamps on its upper and lower surfaces is considered. The elastic layer having an internal crack parallel to its surfaces is subjected to two concentrated loads P on its upper and lower surfaces trough the rigid rectangular stamps and a pair of uniform compressive stress p0 along the crack surface. It is assumed that the contact between the elastic layer and the rigid stamps is frictionless and the effect of the gravity force is neglected. The problem is reduced to a system of singular integral equations in which the derivative of the crack surface displacement and the contact pressures are unknown functions. The system of singular integral equations is solved numerically by making use of an appropriate Gauss-Chebyshev integration formula. Numerical results for stress-intensity factor, critical load factor, Qc, causing initial closure of the crack tip, the crack surface displacements and the contact stress distribution are presented and shown graphically for various dimensionless quantities.

Key Words
crack; contact; stress-intensity factor; elastic layer.

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

Abstract
Meck Plot is an adapted version of the well-known Southwell method to the case of lateraltorsional buckling, which indeed reflects the physical inter-dependence of lateral flexure (lateral displacement) and torsion (rotation) in the structure. In the recent reported studies, it has been shown experimentally and theoretically that lateral displacement of an I-beam undergoing elastic lateraldistortional mode of buckling is interestingly directly coupled with other various deformation characteristics such as web transverse strain, web longitudinal strain, vertical deflection, and angles of twist of top and bottom flanges, and consequently good results have been obtained as a result of application of the Meck\'s method on lateral displacement together with each of the aforementioned deformation variables. In this paper, it is demonstrated that even web transverse and longitudinal strains, vertical deflection, and angles of twist of top and bottom flanges of an I-beam undergoing elastic lateraldistortional buckling are two-by-two directly coupled and the application of the Meck Plot on each pair of these deformation variables may still yield reliable predictions for the critical buckling load.

Key Words
lateral-distortional buckling; elasticity; I-beams; deformation, characteristics; Meck Plot.

Address
Tadeh Zirakian :Department of Civil and Environmental Engineering, University of California, Los Angeles, Los Angeles, CA 90095-1593, USA
Seyed Ali Nojoumi: Department of Civil and Environmental Engineering, University of California, Los Angeles, Los Angeles, CA 90095-1593, USA

Abstract
As a new type of large-span space structure, suspendome is composited of the upper singlelayer reticulated shell and the lower cable-strut system. It has better mechanical properties compared to single-layer reticulated shell, and the overall stiffness of suspendome structure increases greatly due to the prestress of cable. Consequently, it can cross a larger span reasonably, economically and grandly with high rigidity, good stability and simple construction. For a better assessment of the advantages of mechanical characteristic of suspendome quantitatively, the static behavior of Kiewitt6 suspendome was studied by using finite element method, and ADINA was the software application to implement the analysis. By studying a certain suspendome, the internal forces, deformation and support constrained forces of the structure were obtained in this paper. Furthermore, the influences of parameters including prestress, stay bar length, cross-sectional area and rise to-span ratio were also discussed. The results show that the increase of prestress and vertical stay bar length can improve the stiffness of suspendome; Crosssectional area has nearly no impact on the static behavior, and the rise-to-span ratio is the most sensitive parameter.

Key Words
K6 suspendome; static behavior; influence; prestress; stay bar length; cross-sectional area; rise-to-span ratio.

Address
Kena Li: Department of Civil Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100191, China
Dahai Huang: Department of Civil Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100191, China


Abstract
Long-term properties of concrete affect structures in many respects, not excepting dynamic behaviors. This paper investigates the influence of concrete creep on the dynamic behaviors of concrete filled steel tube (CFT) arch bridges, by means of combining the analytical method for the creep of axially compressed CFT members, which is based on Model B3 for concrete creep, with the finite element model of CFT arch bridges. By this approach, the changes of the stress and strain of each element in the bridge with time can be obtained and then transformed into damping and stiffness matrices in the dynamic equation involved in the finite element model at different times. A numerical example of a long-span halfthrough CFT arch bridge shows that creep influences the natural vibration characteristics and seismic responses of the bridge considerably, especially in the early age. In addition, parameter analysis demonstrates that concrete composition, compressive strength and steel ratio have an obvious effect on the seismic response of the CFT arch bridge.

Key Words
creep; dynamic analysis; concrete filled steel tube; arch bridge; finite element model

Address
Y.S. Ma: School of Civil Engineering, Beijing Jiaotong University, Beijing, PR China
Y.F. Wang: School of Civil Engineering, Beijing Jiaotong University, Beijing, PR China
Z.K. Mao: School of Civil Engineering, Beijing Jiaotong University, Beijing, PR China


Abstract
This study investigates the use of a vibration correlation technique (VCT) to identify the buckling load of a rectangular thin plate. It is proposed that the buckling load can be determined experimentally using the natural frequencies of plates under tensile loading. A set of rectangular plates was tested for natural frequencies using an impact test method. Aluminum and stainless steel specimens with CCCC, CCCF and CFCF boundary conditions were included in the experiment. The measured buckling load was determined from the plot of the square of a measured natural frequency versus an inplane load. The buckling loads from the measured vibration data match the numerical solutions very well. For specimens with well-defined boundary conditions, the average percentage difference between buckling loads from VCT and numerical solutions is −0.18% with a standard deviation of 5.05%. The proposed technique using vibration data in the tensile loading region has proven to be an accurate and reliable method which might be used to identify the buckling load of plates. Unlike other static methods, this correlation approach does not require drawing lines in the pre-buckling and post-buckling regions; thus, bias in data interpretation is avoided.

Key Words
buckling load; vibration; natural frequency; thin plate; experiment.

Address
Pairod Singhatanadgid: Department of Mechanical Engineering, Faculty of Engineering, Chulalongkorn University,Bangkok, 10330, Thailand
Padol Sukajit: Department of Mechanical Engineering, Faculty of Engineering, Chulalongkorn University,Bangkok, 10330, Thailand



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