Compressive stiffness and strength of concrete filled double skin (CHS inner & CHS outer) tubes
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Compressive stiffness and strength of concrete filled double skin (CHS inner & CHS outer) tubes Kang Hai Tan • Yu Fen Zhang
Received: 21 April 2010 / Accepted: 3 September 2010 / Published online: 23 September 2010 Ó Springer Science+Business Media, B.V. 2010
Abstract This paper investigated the stiffness and capacity of concrete filled double skin tubes (CFDST) column under axial compression. The column has circular hollow section (CHS) as both outer skin and inner skin. Stiffness of CFDST columns under small displacement was analyzed by the energy method. The modified elastic modulus of the between concrete and steel tubes were deduced respectively to calculate the composite stiffness of the CFDST stub column. According to the unified theory of concrete filled steel tube (CFST), the bearing capacity of the stub column was predicted by presenting the equivalent confinement coefficient of CFDST. The composite modulus and ultimate strength of the stub columns were calculated in comparison with corresponding test value, and it was found that there was good agreement between theoretical and experimental results.
K. H. Tan School of Civil and Environmental Engineering, Nanyang Technological University, BLK N1, #1A-37, Nanyang Avenue, 639798 Singapore, Singapore Y. F. Zhang (&) School of Civil Engineering, Chang’an University, Xi’an 710061, People’s Republic of China e-mail: [email protected]
Keywords Concrete-filled Double skin tubes Stiffness Strength Theorem of stationary value of potential energy Unified theory of CFST List of symbols A Overall section area of stub column Ac Section area of concrete Aso Section area of outer steel tube Asi Section area of inner steel tube Do Diameter of outer steel tube Di Diameter of inner steel tube Es Elastic modulus of steel tube Ec Elastic modulus of concrete Modified Elastic modulus of outer steel tube Eso Modified Elastic modulus of inner steel tube Eso Modified Elastic modulus of concrete Ec E0 Composite Elastic modulus calculated by superposition method Essc Composite Elastic modulus considering the confining factor fssc Compressive strength of CFDST column fso Yield strength of outer steel tube fsi Yield strength of inner steel tube fck Standard strength of concrete k Confinement coefficient to the sandwiched concrete ms Poisson’s Ratio of steel tube mc Horizontal deformation coefficient of concrete Ny Axial bearing capacity by theoretical calculation Ntest Axial bearing capacity of experimental results
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1 Introduction Concrete filled steel tube (CFST) structures have been provided a reasonable and convenient alternative in practical engineers. So in recent years Concrete filled double skin tubes (CFDST) column was developed and studied on the base of CFST. The concept of ‘‘double skin’’ composite construction was originally devised for use in submerged tube tunnels (Han et al. 2004). So far, it is believed that this structure also has a potential in nuclear containment, liquid and gas retaining structures and blast resistant shelters (Zhao and
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