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CONTENTS
Volume 8, Number 4, August 2008
 

Abstract
An investigation on the combined effect of foundation type, foundation flexibility, axial load and PR (semi-rigid) connections on the natural frequencies of steel frames is presented. These effects were investigated using a suitable modified FE program for cases where the foundation flexibility, foundation connectivity, and semi-rigid connections could be treated as equivalent linear springs. The effect of axial load on the natural frequency of a structure was found to be significant for slender structures subjected to high axial loads. In general, if columns of medium slenderness are designed without consideration of axial load effects, the frequency of the structure will be overestimated. Studies on the 3-story Los Angeles PR SAC frame indicate that the assumption of rigid connections at beam-column and column-base interfaces, as well as the assumption of a rigid foundation, can lead to significant errors if simplified design procedures are used. These errors in an equivalent static analysis are expected to lead to even more serious problems when considering the effect of higher modes under a non-linear dynamic analysis.

Key Words


Address
Anh Q. Vu and Roberto T. Leon : School of Civil & Environmental Engineering Georgia Institute of Technology Atlanta, GA 30332-0355 (USA)

Abstract
Visco-elastic material and thin metals were adhered to plate structures, forming the composite components that are similar to the sandwich plates, called constrained layered damped (CLD) plates. Constrained layer damping has been utilized for years to reduce vibration, and advances in computation and finite element analysis software have enabled various problems to be solved by computer. However, some problems consume much calculation time. The vibration equation for a constrained layered damped plate with simple supports and an impact force is obtained theoretically herein. Then, the results of the vibration equation are compared with those obtained using the finite element method (FEM) software, ABAQUS, to verify the accuracy of the theory. Finally, the 3M constrained layer damper SJ-2052 was attached to plates to form constrained layered damped plates, and the vibration equation was used to elucidate the damping effects and vibration characteristics.

Key Words
visco-elastic; constrained layered damped (CLD); finite element method (FEM).

Address
G.M. Luo, Y.J. Lee and C.H. Huang : Department of Engineering Science and Ocean Engineering, National Taiwan University

Abstract
A concrete filled double skin tubular (called CFDST in abbreviation) member consists of two concentric circular steel tubes and filled concrete between them. Purpose of this study is to investigate their bending characteristics experimentally. The two test parameters of the tubes considered were an inner-to-outer diameter ratio and a thickness-diameter ratio. As a result, their observed failure modes were controlled by tensile cracking or local buckling of the outer tube. Discussion is focused on the confinement effect on the filled concrete due to the both tubes and also the influence of the inner-to-outer diameter ratios on their deformability and load carrying capacity.

Key Words
composite columns; concrete filled double tubular steel member; bending moment capacity; confined effect.

Address
Kojiro Uenaka : Dept. of Civil Engineering, Kobe City College of Technology Gakuenhigashimachi 8-3,
Nishi, Kobe, 651-2194, Japan
Hiroaki Kitoh : Dept. of Urban Engineering, Osaka City University, Japan
Keiichiro Sonoda : Professor, Emeritus Osaka City University, Japan

Abstract
This study attempts to suggest bending reinforcement method by applying bending reinforcement to composite profile beam in which the concept of prefabrication is introduced. Profile use can be in place of framework and is effective in improvement of shear and bending strength and advantageous in long-term deflection. As a result of experiment, MPB-CB2 with improved module had higher strength and ductility than the previously published MPB-CB and MPB-LB. In case of bending reinforcement with deformed bar and built-up T-shape section based on MPB-CB2, the MPB-RB series reinforced with deformed bar were found to have higher initial stiffness, bending strength and ductility than the MPB-RT series. The less reinforcement effect of the MPB-RT series might be caused by poor concrete filling at the bottom of the built-up T-shape. In comparison between theoretical values and experimental values using minimum yield strength, the ratio between experimental value and theoretical value was shown to be 0.9 or higher except for MPB-RB16 and MPB-RT16 that have more reinforcement compared to the section, thus it is deemed that the reinforced modular composite profiled beam is highly applicable on the basis of minimum yield strength.

Key Words
modular; composite profiled; flexural strength; bending reinforcement; prefabrication.

Address
Hyung-Joon Ahn : Department of Architectural Engineering, Kon-Kuk University, Seoul, Korea
Soo-Hyun Ryu : Department of Architectural Design, Sahm-Yook University, Seoul, Korea

Abstract
The strengthening of reinforced concrete (RC) columns by steel angles and strips (steel cage) is one of various techniques available to increase ultimate column load. Different authors have shown the influence of the beam-column joint on the behaviour of columns strengthened by steel cages. This paper presents an experimental study carried out at the Universidad Politecnica de Valencia with the aim of analysing two different techniques to solve the strengthening close to the joint and the influence on the behaviour of RC columns strengthened steel cages. The ultimate loads obtained in the laboratory tests for these two techniques are compared to that specified by Eurocode 4.

Key Words
RC columns; strengthening; retrofitting; steel cage; beam-column joint; experimental study.

Address
Jose M. Adam?, Ester Gimenez and Pedro A. Calderon : ICITECH, Departamento de Ingenieria de la Construccion y Proyectos de Ingenieria Civil,
Universidad Politecnica de Valencia. Camino de Vera s/n, 46071 Valencia, Spain
Francisco J. Pallares : Departamento de Fisica Aplicada, Universidad Politecnica de Valencia, Camino de Vera s/n, 46071 Valencia, Spain
Salvador Ivorra : Departamento de Ingenieria de la Construccion, Obras Publicas e Infraestructura Urbana,
Universidad de Alicante. Apartado de Correos 99, 03080 Alicante, Spain


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