Vol. 11, No. 2, pp. 127-149 (2015)
FLEXURAL PERFORMANCE OF CIRCULAR CONCRETE FILLED CFRP-STEEL TUBES
Q. L. Wang 1, * and Y. B. Shao 2
1 Professor, School of Civil Engineering, Shenyang Jianzhu University, Shenyang, P. R. China
2 Professor, School of Civil Engineering, Yantai University, Yantai, P. R. China
Received: 26 September 2012; Revised: 15 January 2014; Accepted: 26 February 2014
Sixteen circular concrete filled CFRP-steel tubular (C-CF-CFRP-ST) flexural members were tested. The test results indicate that the moment versus curvature curve at mid-span of C-CF-CFRP-ST members without longitudinal CFRP reinforcement is similar to such relationship of corresponding un-reinforced circular concrete filled steel tubular (C-CFST) flexural members. The moment versus curvature curve at mid-span for members with longitudinal CFRP reinforcement can be divided into following stages: elastic stage, elasto-plastic stage and softening stage. The longitudinal CFRP can enhance the stiffness of the specimens significantly. The steel tube and the CFRP tube could cooperate both in the transverse and in the longitudinal directions. The steel tube in the region under longitudinal tension has no confinement effect on the core concrete in the same tensile region because the concrete is in a state of contraction in transverse direction. The longitudinal strain distribution over depth of the specimens’ cross-section satisfies the plane section assumption approximately. Finite element model is built and ABAQUS is used to analyze both the moment versus curvature curves at mid-span and the deformation of the C-CF-CFRP-ST flexural members. The finite element results are found to agree well with experimental results. Interaction forces exist both in the tensile region and in the compressive region between the outer tube and the concrete. However, there is essential difference between the interaction forces in the tensile region and in the compressive region respectively. Finally, flexural load carrying capacity of the C-CF-CFRP-ST is defined, and parametric equations for calculating it are presented. The accuracy and the reliability of the proposed equations are verified.
Keywords: Circular CFRP-steel tube, In-filled concrete, Beams, Flexural performances, Interaction force, Flexural load carrying capacity