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CONTENTS
Volume 40, Number 4, November25 2011
 

Abstract
A one-story, wooden-frame, intermediate-bay model with Dou-Gon designed according to the Building Standards of the Song Dynasty (A.D.960-1279), was tested on a unidirectional shaking table. The main objectives of this experimental study were to investigate the seismic performance of Chinese historic wooden structure under various base input intensities. El Centro wave (N-S), Taft wave and Lanzhou wave were selected as input excitations. 27 seismic geophones were instrumented to measure the real-time displacement, velocity and acceleration respectively. Dynamic characteristics, failure mode and hysteretic energy dissipation performance of the model are analyzed. Test results indicate that the nature period and damping ratio of the model increase with the increasing magnitude of earthquake excitation. The nature period of the model is within 0.5~0.6 s, the damping ratio is 3~4%. The maximum acceleration dynamic magnification factor is less than 1 and decreases as the input seismic power increases. The frictional slippage of Dou-Gon layers (corbel brackets) between beams and plates dissipates a certain amount of seismic energy, and so does the slippage between posts and plinths. The mortise-tenon joint of the timber frame dissipates most of the seismic energy. Therefore, it plays a significant part in shock absorption and isolation.

Key Words
Chinese palace buildings; timber structure; seismic performance; shaking table test

Address
Xi-cheng Zhang, Jian-yang Xue, Hong-tie Zhao and Yan Sui: School of Civil Engineering, Xi\'an University of Architecture and Technology, Xi\'an, Shaanxi, China;
State Key Laboratory of Architecture Science and Technology in West China, Xi\'an, Shaanxi, China

Abstract
The Ting Kau Bridge in Hong Kong is a cable-stayed bridge comprising two main spans and two side spans. The bridge deck is supported by three towers, an end pier and an abutment. Each of the three towers consists of a single reinforced concrete mast strengthened by transverse cables and struts. The bridge deck is supported by four inclined planes of cables emanating from anchorages at the tower tops. In view of the heavy traffic on the bridge, and threats from typhoons and earthquakes originated in areas nearby, the dynamic behaviour of long-span cable-supported bridges in the region is always an important consideration in their design. Baseline finite element models of various levels of sophistication have been built not only to match the bridge geometry and cable forces specified on the as-constructed drawings but also to be calibrated using the vibration measurement data captured by the Wind and Structural Health Monitoring System. This paper further describes the analysis of axle loading data, as well as the generation of random axle loads and simulation of vibrations of the bridge using the finite element models. Various factors affecting the vehicular loading on the bridge will also be examined.

Key Words
cable-stayed bridge; dynamic response; finite element; numerical simulation; random vibration; vehicular axle load

Address
F.T.K. Au: Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China
P. Lou: Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China; School of Civil Engineering, Central South University, 22 Shao-shan-nan Road, Changsha, Hunan, China
J. Li: Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China; School of Civil Engineering, Shandong University, Jinan, Shandong, China
R.J. Jiang: Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China
J. Zhang: Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China
C.C.Y. Leung: Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China
P.K.K. Lee: Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China
J.H. Lee: Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China; Department of Infrastructure Civil Engineering, Chonbuk National University, Korea
K.Y. Wong and H.Y. Chan: Bridges and Structures Division, Highways Department, The Government of the Hong Kong Special
Administrative Region, China

Abstract
The elastic seismic response of plan-asymmetric multi storey steel-frame buildings is investigated under earthquake loading with particular emphasis on forward-rupture directivity and fling records. Three asymmetric building systems are generated with different torsional stiffness and varying static eccentricity. The structural characteristic of these systems are designed according to UBC 97 code and their seismic responses subjected to a set of earthquake records are obtained from the response history analysis (RHA) as well as the linear static analysis (LSA). It is shown that, the elastic torsional response is influenced by the intensity of near-fault ground motions with different energy contents. In the extreme case of very strong earthquakes, the behaviour of torsionally stiff buildings and torsionally flexible buildings may differ substantially due to the fact that the displacement envelope of the deck depends on ground motion characteristics.

Key Words
near-fault; seismic response; torsionally stiff; torsionally flexible

Address
R. Tabatabaei: Civil Engineering Department, Islamic Azad University, Kerman Branch, PO Box 76175-6114, Kerman, Iran
H. Saffari: Civil Engineering Department, Shahid Bahonar University, Iran

Abstract
Sandwich elements have high flexural rigidity and high strength per density. They also have excellent anti-vibration and anti-noise characteristics. Therefore, they are used for structures of airplanes and high speed ships that must be light, as well as strong. In this paper, the Reissner-Mindlin\'s plate theory is studied from a Hamilton\'s principle point of view. This theory is modified to include the influence of shear deformation and rotary inertia, and the equation of motion is derived using energy relationships. The theory is applied to a rectangular sandwich model which has isotropic, asymmetrical faces and an isotropic core. Investigations are conducted for five different plate thicknesses. These plates are identical to the sandwich plates currently used in various structural elements of surface effect ships (SES). The boundary conditions are set to simple supports and fixed supports. The elastic and shear moduli are obtained from the four-point bending tests on the sandwich beams.

Key Words
sandwich; plate; transverse; vibration; asymmetric faces; FRP

Address
Namshik Ahn: Department of Architectural Engineering, Free Form Architecture Institute, Sejong University, Seoul 143-747, Korea
Kangsu Lee: Korean Register of Shipping, Green and Industrial Technology Center, Daejeon 305-343, Korea

Abstract
This paper presents the seismic responses of a 1:5-scale five-story reinforced concrete building model, which represents a residential apartment building that has a high irregularity of weak story, soft story, and torsion simultaneously at the ground story. The model was subjected to a series of uni- and bi-directional earthquake simulation tests. Analysis of the test results leads to the following conclusions: (1) The model survived the table excitations simulating the design earthquake with the PGA of 0.187 g without any significant damages, though it was not designed against earthquakes; (2) The fundamental mode was the torsion mode. The second and third orthogonal translational modes acted independently while the torsion mode showed a strong correlation with the predominant translational mode; (3) After a significant excursion into inelastic behavior, this correlation disappeared and the maximum torsion and torsion deformation remained almost constant regardless of the intensity of the two orthogonal excitations; And, (4) the lateral resistance and stiffness of the critical columns and wall increased or decreased significantly with the large variation of acting axial forces caused by the high bidirectional overturning moments and rocking phenomena under the bi-directional excitations.

Key Words
earthquake simulation test; irregularity; reinforced concrete; torsion; bi-directional excitation

Address
Han Seon Lee: School of Civil, Environmental, and Architectural Engineering, Korea University, Seoul 136-713, Korea
Dong Wook Jung: Structural Engineer, OPUS PEARL Co., Seoul 135-811, Korea
Kyung Bo Lee: School of Civil, Environmental, and Architectural Engineering, Korea University, Seoul 136-713, Korea
Hee Cheul Kim: Department of Architectural Engineering, Kyunghee University, Kyunggido 447-701, Korea
Kihak Lee: Department of Architectural Engineering, Sejong University, Seoul 143-747, Korea

Abstract
In the design of earthquake resistant reinforced concrete (RC) structures, both flexural strength and deformability need to be considered. However, in almost all existing RC design codes, the design of flexural strength and deformability of RC beams are separated and independent on each other. Therefore, the pros and cons of using high-performance materials on the flexural performance of RC beams are not revealed. From the theoretical results obtained in a previous study on flexural deformability of RC beams, it is seen that the critical design factors such as degree of reinforcement, concrete/steel yield strength and confining pressure would simultaneously affect the flexural strength and deformability. To study the effects of these factors, the previous theoretical results are presented in various charts plotting flexural strength against deformability. Using these charts, a \"concurrent flexural strength and deformability design\" that would allow structural engineers to consider simultaneously both strength and deformability requirements is developed. For application in real construction practice where concrete strength is usually prescribed, a simpler method of determining the maximum and minimum limits of degree of reinforcement for a particular pair of strength and deformability demand is proposed. Numerical examples are presented to illustrate the application of both design methods.

Key Words
beams; curvature; deformability; high-strength concrete; reinforced concrete; rotation capacity

Address
J.C.M. Ho and K.J.H. Zhou: Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong

Abstract
Many novel materials, developed in recent years, have obvious properties with different modulus of elasticity in tension and compression. The ratio of their tensile modulus to compressive modulus is as high as five times. Nowadays, it has become a new trend to study the mechanical properties of these bimodular materials. At the present stage, there are extensive studies related to the strength analysis of bimodular structures, but the investigation of the buckling stability problem of bimodular rods seems to cover new ground. In this article, a semi-analytical method is proposed to acquire the buckling critical load of bimodular slender rod. By introducing non-dimensional parameters, the position of neutral axis of the bimodular rod in the critical state can be determined. Then by combining the phased integration method, the deflection differential equation of bimodular pin-ended slender rod is deduced. In addition, the buckling critical load is obtained by solving this equation. An example, which is conducted by comparing the calculation results between the three of the methods including the laboratory tests, numerical simulation method and the method we developed here, shows that the method proposed in the present work is reliable to use. Furthermore, the influence of bimodular characteristics on the stability is discussed and analyzed.

Key Words
bimodular; slender rod; buckling critical load; semi-anlytical method; nondimensional parameters

Address
Wenjuan Yao, Jianwei Ma and Baolin Hu: Department of Civil Engineering, Shanghai University, Shanghai 200072, China

Abstract
In the present study, free vibration of an axially functionally graded (AFG) pile embedded in Winkler-Pasternak elastic foundation is analyzed within the framework of the Euler-Bernoulli beam theory. The material properties of the pile vary continuously in the axial direction according to the power-law form. The frequency equation is obtained by using Lagrange\'s equations. The unknown functions denoting the transverse deflections of the AFG pile is expressed in modal form. In this study, the effects of material variations, the parameters of the elastic foundation on the fundamental frequencies are examined. It is believed that the tabulated results will be a reference with which other researchers can compare their results.

Key Words
vibration; pile; functionally graded material; Winkler-Pasternak foundation

Address
Dogan Cetin: Vocational School, Technical Programs, Yildiz Technical University, Maslak, Istanbul, Turkey
Mesut Simsek: Department of Civil Engineering, Yildiz Technical University, 34210 Davutpa a, Istanbul, Turkey


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