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CONTENTS
Volume 10, Number 6, December 2000
 

Abstract
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Key Words
active control, soil-structure interaction, state feedback gain, output feedback gain, soil parameter uncertainty, seismic effectiveness, robustness and sensitivity

Address
Chen GD, Univ Missouri, Dept Civil Engn, 111 Butler Carlton Hall, Rolla, MO 65409 USA
Univ Missouri, Dept Civil Engn, Rolla, MO 65409 USA

Abstract
To prevent major cracking and failure during earthquakes, it is important to design reinforced concrete liquid storage structures, such as water and fuel storage tanks, properly for the hydrodynamic pressure loads caused by seismic excitations. There is a discussion in recent Codes that most of the base shear, applied to liquid containment structures is resisted by inplane membrane shear rather than by transverse flexural shear. The purpose of this paper is to underline the importance of the membrane force system in carrying the base shear produced by hydrodynamic pressures in both rectangular and cylindrical tank structures. Only rigid tanks constrained at the base are considered. Analysis is performed for both tall and broad tanks to compare their behavior under seismic excitation. Efforts are made to quantify the percentage of base shear carried by membrane action and the consequent procedures that must be followed for safe design of liquid containing storage structures.

Key Words
membrane forces, reinforced concrete tanks, seismic loading, specifications

Address
Schnobrich WC, Univ Illinois, Dept Civil Engn, Urbana, IL 61801 USA
Univ Illinois, Dept Civil Engn, Urbana, IL 61801 USA

Abstract
A Wind and Structural Health Monitoring System (WASHMS) has been installed in the Tsing Ma suspension Bridge in Hong Kong with one of the objectives being the verification of analytical processes used in wind-resistant design. On 2 August 1997, Typhoon Victor just crossed over the Bridge and the WASHMS timely recorded both wind and structural response. The measurement data are analysed in this paper to obtain the mean wind speed, mean wind direction, mean wind inclination, turbulence intensity, integral scale, gust factor, wind spectrum, and the acceleration response and natural frequency of the Bridge. It is found that some features of wind structure and bridge response are difficult to be considered in the currently used analytical process for predicting buffeting response of long suspension bridges, for the Bridge is surrounded by a complex topography and the wind direction of Typhoon Victor changes during its crossing. It seems to be necessary to improve the prediction model so that a reasonable comparison can be performed between the measurement and prediction for long suspension bridges in typhoon prone regions.

Key Words
field measurement, Typhoon Victor, suspension bridge, wind characteristics, acceleration response, implication to buffeting analysis

Address
Xu YL, Hong Kong Polytech Univ, Dept Civil & Struct Engn, Kowloon, Hong Kong, Peoples R China
Hong Kong Polytech Univ, Dept Civil & Struct Engn, Kowloon, Hong Kong, Peoples R China
Tsing Ma Control Area Div, Highways Dept, Hong Kong, Hong Kong, Peoples R China

Abstract
Microvibration of high technology facilities, such as semiconductor plants and facilities with high precision equipments, due to nearby road and rail traffic has attracted considerable attention recently. In this paper, a preliminary study is conducted for the possible use of various protective systems and their performance for the reduction of microvibration. Simulation results indicate that passive base isolation systems, hybrid base isolation systems, passive floor isolation systems, and hybrid floor isolation systems are quite effective and practical. In particular, the performances of hybrid floor isolation systems are remarkable. Further, passive energy dissipation systems are not effective for the reduction of microvibration. Finally, the protections against both microvibration and earthquake are also investigated and presented.

Key Words
microvibration, protective systems, high technology facilities, vibration control, seismic response control

Address
Yang JN, Univ Calif Irvine, Dept Civil & Environm Engn, Irvine, CA 92697 USA
Univ Calif Irvine, Dept Civil & Environm Engn, Irvine, CA 92697 USA
CUNY City Coll, Dept Civil Engn, New York, NY 10031 USA

Abstract
A 3D nonlinear finite element computation model is presented in order to analyze the concrete filled rectangular tubular (CFRT) composite structures. The concrete material model is based on a hypo-elastic orthotropic approach while the elasto-plastic hardening model is employed for steel element. The comparisons between experimental and analytical results show that the proposed model is a relatively simple and effective one. The analytical results show that the capacity of inner concrete of CFRT column mainly depends on the two diagonal zones, and the confining effect of CFRT section is mainly concentrated on the corner zones. At the ultimate state, the side concrete along the section cracks seriously, and the corner concrete softens with the increase of compressive strains until failure.

Key Words
concrete filled rectangular tubular structure, nonlinear analysis, finite element method

Address
Lu XL, Tongji Univ, Res Inst Engn Struct, Shanghai 200092, Peoples R China
Tongji Univ, Res Inst Engn Struct, Shanghai 200092, Peoples R China
Fujita Corp, Tech Res Inst, Yokohama, Kanagawa, Japan

Abstract
A simplified analysis procedure utilizing the strut-tie modeling technique is developed to take a close look into the post-elastic deformation capacity of beam-column connections in ductile reinforced concrete frame structures. Particular emphasis is given to the effect of concrete strength decay and quantity and arrangement of joint shear steel. For this a fan-shaped crack pattern is postulated through the joints. A series of hypothetical rigid nodes are assumed through which struts, ties and boundaries are connected to each other. The equilibrium consideration enables all forces in struts, ties and boundaries to be related through the nodes. The boundary condition surrounding the joints is obtained by the mechanism analysis of the frame structures. In order to avoid a complexity from the indeterminacy of the truss model, it is assumed that all shear steel yielded. It is noted from the previous research that the capacity of struts is limited by the principal tensile strain of the joint panel for which the strain of the transverse diagonal is taken. The post-yield deformation of joint steel is taken to be the only source of the joint shear deformation beyond the elastic range. Both deformations are related by the energy consideration. The analysis is then performed by iteration for a given shear strain. The analysis results indicate that concentrating most of the joint steel near the center of the joint along with higher strength concrete may enhance the post-elastic joint performance.

Key Words
beam-column connections, concrete strength, cracks, joint shear steel, post-elastic deformation, strut-tie model

Address
Kim JH, Ajou Univ, Dept Architecture, Suwon 442749, South Korea
Ajou Univ, Dept Architecture, Suwon 442749, South Korea
Univ Canterbury, Dept Civil Engn, Christchurch 1, New Zealand

Abstract
Analysis of a framed structure for vertical vibration requires a lot of computational efforts because large number of degrees of freedom are generally involved in the dynamic responses. This paper presents an efficient modeling technique for vertical vibration utilizing substructuring technique and super elements. To simplify the modeling procedure each floor in a structure is modeled as a substructure. Only the vertical translational degrees of freedom are selected as master degrees of freedom in the inside of each substructure. At the substructure-column interface, horizontal and rotational degrees of freedom are also included considering the compatibility condition of slabs and columns. For further simplification, the repeated parts in a substructure are modeled as super elements, which reduces computation time required for the construction of system matrices in a substructure. Finally, the Guyan reduction technique is applied to enhance the efficiency of dynamic analysis. In numerical examples, the efficiency and accuracy of the proposed method are demonstrated by comparing the response time histories and the analysis time.

Key Words
vertical vibration, Guyan reduction, master DOF, substructuring technique, super elements

Address
Lee DG, Sung Kyun Kwan Univ, Dept Architecture, Suwon 440746, South Korea
Sung Kyun Kwan Univ, Dept Architecture, Suwon 440746, South Korea

Abstract
Dynamic responses of a bridge system with several simple spans under longitudinal seismic excitations are examined. The bridge system is modeled as the multiple oscillators and each oscillator consists of four degrees-of-freedom system to implement the poundings between the adjacent oscillators and the friction at movable supports. Pounding effects are considered by introducing the impact elements and a bi-linear model is adopted for the friction force. From the parametric studies, the pounding is found to induce complicated seismic responses and to restrain significantly the relative displacements between the adjacent units. The smaller gap size also restricts more strictly the relative displacement. It is found that the relative displacements between the abutment and adjacent pier unit became much larger than the responses between the inner pier units. Consequently, the unseating failure could take a place between the abutment and nearby pier units. It is also found that the relative displacements of an abutment unit to the adjacent pier unit are governed by the pounding at the opposite side abutment.

Key Words
bridge system, seismic excitation, pounding, friction, impact element, abutment, unseating failure

Address
Kim SH, Yonsei Univ, Dept Civil Engn, Seoul 120749, South Korea
Yonsei Univ, Dept Civil Engn, Seoul 120749, South Korea
Hoseo Univ, Dept Civil Engn, Asan 336795, South Korea

Abstract
In this paper, the adaptive nodal generation procedure based on the estimated local and global error in the element-free Galerkin (EFG) method is proposed. To investigate the possibility of h-type adaptivity of EFG method, a simple nodal refinement scheme is used. By adding new node along the background cell that is used in numerical integration, both of the local and global errors can be controlled adaptively. These errors are estimated by calculating the difference between the values of the projected stresses and original EFG stresses. The ultimate goal of this study is to develop the reliable nodal generator based on the local and global errors that is estimated posteriori. To evaluate the performance of proposed adaptive procedure, the convergence behavior is investigated for several examples.

Key Words
element-free Galerkin method, projection method, error estimation, adaptive analysis, intigration cell, nodal generation, refinement

Address
Chung HJ, Jeonju Univ, Dept Civil & Environm Engn, Chonju 560759, South Korea
Jeonju Univ, Dept Civil & Environm Engn, Chonju 560759, South Korea
Korea Adv Inst Sci & Technol, Dept Civil Engn, Taejon 305600, South Korea


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