Flexural Performance of Circular Concrete Filled CFRP-Steel Tubes

Abstract

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.

Static Behavior of Axially Compressed Circular Concrete Filled CFRP-Steel Tubular (C-Cf-CFRP-St) Columns With Moderate Slenderness Ratio

“…As shown in Figure 11, the distribution of sl  is basically satisfied with the plane section assumption. Studies on CF-CFRP-ST flexural member (Wang and Shao [28]; Wang et al [36]) provided same conclusions. …”

“…Recent study shows that CF-CFRP-ST has satisfactory fire endurance time when adequate fire resistant measures have been taken (Tao et al [21]). There are many research studies about CF-CFRP-ST structures in the literature, and these studies mostly focus on Circular CF-CFRP-ST (C-CF-CFRP-ST) stub columns (Xiao et al [22]; Choi and Xiao [23]; Park et al [24]; Hu et al [25]; Li et al [26]; Teng et al [27]), C-CF-CFRP-ST flexural members (Wang and Shao [28]), Square CF-CFRP-ST (S-CF-CFRP-ST) stub columns (Tao et al [29]; Park et al [30]; Sundarraja and Ganesh [31]; Sundarraja and Ganesh [32]; Sundarraja and Ganesh [33]; Wang and Shao [34]) and S-CF-CFRP-ST flexural members (Sundarraja and Ganesh [35]; Wang et al [36]). More applications in practical engineering are columns with large slenderness ratio (as shown in Figure 2) although corresponding research is quite scarce.…”

Flexural Behavior of Double-Skin Steel Tube Beams Filled with Fiber-Reinforced Cementitious Composite and Strengthened with CFRP Sheets

“…The moment–curvature curve is applicable in the determination of the serviceability-level section flexural stiffness (K se ) and the early section flexural stiffness (K ie ) for every specimen. The K se and K ie are the secant stiffness; that are corresponding to the serviceability-level moment of 0.6 M ue and equivalent to the moment of 0.2 M ue , respectively [ 30 , 35 ]. The two specimens initially exhibited elastic behavior before been pulled down gradually to an inelastic condition where eventual moment capacity (M ue ) was attained.…”

“…In that case, the integration of the benefits of the three essential materials can be harnessed to display good structural performance. Several laboratory investigations have been considered on the composite components [ 1 , 18 , 27 , 28 , 29 , 30 ]. However, there are some gaps in the existing studies, which include the compatibility of infilled concrete with the skin section materials.…”

Volume 12 Number 3

“…A research project aiming to develop a new damage-free structural system in intensity 7 earthquake (largest intensity in Japan) using super high strength steel has been carried out from the year of 2004 to 2008, e.g., [24][25][26]. To date, a number of super high strength steel grades, e.g., H-SA700 and BT-HT880, e.g., [27][28][29], have been proposed and recognized by the Japanese government. The mechanical and chemical properties of the high strength steels are listed in Table 2.…”