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Numerical analysis of ultimate strength of concrete

Numerical analysis of ultimate strength of concrete

Xie et al. / J Zhejiang Univ SCI 2005 6A(8):859-868 859

Journal of Zhejiang University SCIENCE ISSN 1009-3095

http://devegacer.com/jzus E-mail: jzus@http://devegacer.com

Numerical analysis of ultimate strength of concrete

Numerical analysis of ultimate strength of concrete

filled steel tubular arch bridges

XIE Xu (谢 旭) 1, CHEN Heng-zhi (陈衡治) 1, LI Hui (李 辉)2, SONG Shi-rui (宋世锐)3

(1Department of Civil Engineering, Zhejiang University, Hangzhou 310027, China) (2Department of Civil Engineering, Ningbo University, Ningbo 315211, China)

(3Centre for Civil & Construction Engineering, University of Manchester, Manchester, M601QD, United Kingdom)

E-mail: xiexu@http://devegacer.com; chenhengzhi78@http://devegacer.com Received July 30, 2004; revision accepted Dec. 1, 2004

Abstract: The calculation of ultimate bearing capacity is a significant issue in the design of Concrete Filled Steel Tubular (CFST) arch bridges. Based on the space beam theory, this paper provides a calculation method for determining the ultimate strength of CFST structures. The accuracy of this method and the applicability of the stress-strain relationships were validated by comparing different existing confined concrete uniaxial constitutive relationships and experimental results. Comparison of these results indicated that this method using the confined concrete uniaxial stress-strain relationships can be used to calculate the ultimate strength and CFST behavior with satisfactory accuracy. The calculation results are stable and seldom affected by concrete con-stitutive relationships. The method is therefore valuable in the practice of engineering design. Finally, the ultimate strength of an arch bridge with span of 330 m was investigated by the proposed method and the nonlinear behavior was discussed.

Key words: Concrete Filled Steel Tubular (CFST), Confined concrete, Stress-strain relationship, Ultimate strength doi:10.1631/jzus.2005.A0859 Document code: A CLC number: TU31

INTRODUCTION

As a result of the combined effects of the rolled steel tube and the core concrete, Concrete Filled Steel Tubular (CFST) structures can effectively take ad-vantage of these two materials to improve the com-pressive strength and the ductility of the structures. This kind of structure is developing quickly in China and widely used in high-rise structures and bridges. Recently, due to the development of construction projects, numerous studies on CFST structures have been implemented by both experimental investiga-tions and theoretical analyses (Cai, 2003; Han, 2000, Zhong, 1999). Although the behavior of CFST structures has been extensively examined, the con-crete core confinement is not yet well understood.

Experimental applications of CFST arch bridges began in China in the 1990s. Based on the large numbers of CFST arch bridges built in recent decades, much valuable experience has been gained in struc-tural design and building practice. However, owing to the late start of the engineering practice, research on the resistance to overturning and failure mechanism of the CFST structures is lacking. The current design methods take little account of the confinement effect of the steel tube ring on the concrete core, and only evaluate the structural stability by the elastic eigen-value. The design theories of CFST arch bridges have fallen behind the corresponding fundamental research, and the up-to-date research findings still have not been applied to engineering design.

It is well known that the arch ribs are basically compression structures. The calculation of secondary stress due to the deformation of arch axis, the analysis of the geometrical nonlinear effect and the estimation of ultimate bearing capacity are all important issues of structural design. CFST arch bridges where the cross-sectional dimensions are determined by the inner forces do not always satisfy the stabilization of the CFST arch bridges. An appropriate design method

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