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CONTENTS
Volume 11, Number 4, August 2011
 

Abstract
In current ductility-based earthquake-resistant design, the estimation of design forces continues to be carried out with the application of response modification factors on elastic design spectra. It is well-known that the response modification factor (R) takes into account the force reduction, strength, redundancy, and damping of structural systems. The key components of the response modification factor (R) are force reduction (R

Key Words
design parameter; special steel moment resisting frames; response modification factor;force reduction factor; strength factor

Address
Department of Architectural Engineering, Kyonggi University, san 94-6, Iui-dong, Yeongtong-gu,Suwon-si, Gyeonggi-do, 443-760, Korea

Abstract
The new structure consisting of continuous compound spiral hoop reinforced concrete (CCSHRC)column and steel concrete composite (SCC) beam has both the advantages of steel structures and concrete structures. Two types of beam-to-column connections applied in this structural system are presented in this paper. The connection details are as follows: the main bars in beam concrete pass through the core zone for both types of connections. For connecting bar connection, the steel I-beam webs are connected by bolts to a steel plate passing through the joint while the top and bottom flanges of the beams are connected by four straight and two X-shaped bars. For bolted end-plate connection, the steel I-beam webs are connected by stiffenedextended end-plates and eight long shank bolts passing through the core zone. In order to study the seismic behaviour and failure mechanisms of the connections, quasi-static tests were conducted on both types of full-scale connection subassemblies and core zone specimens. The load-drift hysteresis loops show a plateau for the connecting bar connection while they are excellent plump for bolted end-plate connection. The shear capacity formulas of both types of connections are presented and the values calculated by the formula agree well with the test results.

Key Words
beam-to-column connection; X-shaped bar; seismic behaviour; quasi-static test; shear capacity; ductility

Address
Hongwei Ma : State Key Laboratory of Subtropical Architecture Science, South China University of Technology, Guangzhou, PR China
Weishan Jiang : School of Civil Engineering, Xi

Abstract
With the increasing use of concrete-filled steel tubes (CFST) as structural members, there is a growing need to provide suitable measures for possible strengthening or repair of these kinds of structural elements. Fibre reinforced polymer (FRP) jacketing is a recent method and is particularly attractive in which it does not significantly increase the section size, and is relatively easy to install. Thus, it can be used to enhance strength and/or ductility of CFST members. Very little information is available on the performance of FRP-strengthened CFST members under fire conditions. This paper is an attempt to study the fire performance of CFST columns strengthened by FRP. The results of fire endurance tests on FRP-strengthened circular CFST columns are presented. Failure modes of the specimens after exposure to fire, temperatures in the cross section, axial deformation and fire resistance of the composite columns are analysed. It is demonstrated that the required fire endurance can be achieved if the strengthened composite columns are appropriately designed.

Key Words
concrete-filled steel tubes (CFST); fibre reinforced polymer (FRP); strengthening; columns;insulation; confinement; fire endurance

Address
Zhong Tao, Zhi-Bin Wang and Brian Uy : Civionics Research Centre, University of Western Sydney, Penrith, NSW 2751, Australia
Lin-Hai : Department of Civil Engineering, Tsinghua University, Beijing, 100084, China

Abstract
Based on the experimental data presented in part I of these companion papers, a semi-empirical model is proposed for axial stress-strain curves of reinforced high-strength concrete square columns confined by aramid fiber reinforced polymer (FRP) jackets. Additionally, a three-dimensional finite element model is developed to simulate the mechanical behaviors of the columns. In the finite element model, both material nonlinear and contact nonlinear are taken into account. Moreover, the influence of contact nonlinear (i.e., the end friction on the contact surface between test machines and specimens) is investigated deeply. Predictions from both the semi-empirical model and the finite element model agree with the experimental results, and it is also demonstrated that the friction coefficient of end friction notably affect the properties of columns when it ranges from 0.00 to 0.25.

Key Words
reinforcement; high-strength concrete (HSC); confined columns; fiber reinforced polymers (FRP);finite element analysis; end friction.

Address
School of Civil Engineering, Beijing Jiaotong University, Beijing, 100044, PR China

Abstract
This paper presents the effects of thermal environment and temperature-dependence of the material properties on axisymmetric bending of functionally graded (FG) circular and annular plates. The material properties are assumed to be temperature-dependent and graded in the thickness direction. In order to accurately evaluate the effect of thermal environment, the initial thermal stresses are obtained by solving the thermoelastic equilibrium equations. Governing equations and the related boundary conditions, which include the effects of initial thermal stresses, are derived using the virtual work principle based on the elasticity theory. The differential quadrature method (DQM) as an efficient and robust numerical tool is used to obtain the initial thermal stresses and response of the plate. Comparison studies with some available results for FG plates are performed. The influences of temperature rise, temperature-dependence of material properties, material graded index and different geometrical parameters are carried out.

Key Words
bending analysis; functionally graded; annular plates; elasticity theory; thermal environment.

Address
N. Safaeian Hamzehkolaei and J. Vaseghi : Department of Civil Engineering, Babol University of Technology, P.O. Box 484, Babol, Iran
P. Malekzadeh : Department of Mechanical Engineering, Persian Gulf University, Bushehr 75168 , Iran


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