Behavior of steel fiber reinforced concrete-filled steel tube columns under axial compression

Lu, Yiyan; Li, Na; Li, Shan; Liang, Hongjun

doi:10.1016/j.conbuildmat.2015.07.114

Cited by 113 publications

(26 citation statements)

References 41 publications

(52 reference statements)

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“…To qualify the ductility of a column, ductility index (DI) is often adopted by many researchers [8,38]. Similarly, for CFST jacketed columns, DI is de ned as…”

Section: Ductilitymentioning

confidence: 99%

Axial Behaviour of Slender RC Circular Columns Strengthened with Circular CFST Jackets

Zhu

et al. 2018

Advances in Civil Engineering

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is paper investigates the axial behavior of slender reinforced concrete (RC) columns strengthened with concrete filled steel tube (CFST) jacketing technique. It is realized by pouring self-compacting concrete (SCC) into the gap between inner original slender RC columns and outer steel tubes. Nine specimens were prepared and tested to failure under axial compression: a control specimen without strengthening and eight specimens with heights ranging between 1240 and 2140 mm strengthened with CFST jacketing. Experimental variables included four different length-to-diameter (L/D) ratios, three different diameter-to-thickness (D/t) ratios, and three different SCC strengths. e experimental results showed that the outer steel tube provided confinement to the SCC and original slender RC columns and thus effectively improved the behavior of slender RC columns. e failure mode of slender RC columns was changed from brittle failure (concrete peel-off) into ductile failure (global bending) after strengthening. And, the load-bearing capacity, material utilization, and ductility of slender RC columns were significantly enhanced. e strengthening effect of CFST jacketing decreased with the increase of L/D ratio and D/t ratio but showed little variation with higher SCC strength. An existing expression of load-bearing capacity for traditional CFST columns was extended to propose a formula for the load-bearing capacity of CFST jacketed columns, and the predictions showed good agreement with the experimental results. Recently, a novel technique, CFST jacketing, has become an option to strengthen concrete columns because of the superior performance of CFST columns (e.g., high loadbearing capacity and good ductility). It has been successfully applied in the strengthening of RC bridge piers [20,21]. CFST jacketing is realized by the installation of in-field welded steel tube around the original RC column and

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“…To qualify the ductility of a column, ductility index (DI) is often adopted by many researchers [8,38]. Similarly, for CFST jacketed columns, DI is de ned as…”

Section: Ductilitymentioning

confidence: 99%

Axial Behaviour of Slender RC Circular Columns Strengthened with Circular CFST Jackets

Zhu

et al. 2018

Advances in Civil Engineering

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“…Specifically, the temperature of HESM-CBCF was the highest at 80°C, whereas that of other mortars was under 75°C. Carbon black can help to improve heat-transfer properties, and carbon fibers can act as bridges across carbon black particles [16,18]. Thus, the bridge-connecting effects of carbon fiber and carbon black has the effect of improving the heat-transfer properties of the mortars (HESM-CBCF).…”

Section: Conflict Of Interestmentioning

confidence: 99%

“…2 shows the compressive strength and flexural strength of the prepared mortars at the age of 1, 7 and 28 d. A minor increase in compressive and flexural strength of the prepared mortars was observed on day 1, and it increased in the order of HESM-P, HESM-CB, HESM-CF and HESM-CBCF. These results can be interpreted to mean that the carbon additives improved the mechanical properties of the mortars [16]. At the age of 28 d, the compressive and flexural strength of the HESM-CF, tars with both added carbon black and carbon fiber (1:1 weight ratio) were denoted as HESM-CBCF.…”

mentioning

confidence: 93%

Effects of carbon additives on heat-transfer and mechanical properties of high early strength cement mortar

Lee¹,

Kim²,

Kim³

et al. 2016

Carbon letters

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The repair of mortar-based structures is critically important because mortar-based structures such as buildings, bridges, tunnels, highway and roads are inevitably degraded by deterioration or damage. To save expense during construction and to avoid traffic congestion during repair work, it is very important to reduce construction time as much as possible. In order to reduce construction time, therefore, the setting time of mortars has to be shortened. The mortars which have short setting times are called high early strength cement mortars. These high early strength cement mortars usually have a short working time of under 40 min and a compressive strength of over 24 MPa [1].During the winter, mortar-based structures such as tunnels, bridges and roads typically use geothermal heat or internal heaters to protect them from freezing [2]. To use a heat source efficiently, the heat-transfer properties of the mortars are important. However, mortars have low heat-transfer properties because mortars are generally nonconductors. Therefore, it is necessary to improve the heat-transfer properties of mortars [3][4][5][6][7].Carbon materials such as carbon fibers, carbon blacks, carbon nanotubes and graphites usually have high thermal conductivity [8][9][10]. Consequently, there have been a wide number of studies that have explored carbon material reinforced composites, or reinforced concretes, to improve their thermal conductivity and mechanical properties. In particular, carbon blacks and carbon fibers are usually used as an additive to improve thermal properties as well as strength properties [11][12][13][14].To prevent mortar-based structures from freezing in the winter, mortars have to transfer heat efficiently from the heat source, such as geothermal heat or internal heater. In this study, to improve the heat-transfer properties of mortars for repair work, the effect of carbon black and carbon fibers on the heat-transfer properties of high early strength cement mortars was investigated.High early strength cement (Jeong Woo Materials Co., Seoul, Korea) was used as a binder for the mortar. Sand was also used for the mortar, and its density and fineness modulus were 2.65 g/cm 3 and 2.70, respectively. Carbon black (Chezacarb AC-60; Unipetrol RPA, Litvinov, Czech Republic) and carbon fiber (T700SC; Toray Co., Tokyo, Japan) were used as an additive; the bulk density and specific surface area of the carbon black was 0.12 g/cm 3 and 800 m 2 /g, and the bulk density and tensile strength of the carbon fiber was 1.8 g/cm 3 and 3.70 GPa, respectively. Table 1 shows the composition (wt%) of the materials added to the mortar. The weight ratio of binder and sand was 1:3 and that of binder and water was 1:1. The additives were 2 wt% of the binder [15]. The mixing method for the mortar was conducted by the ISO 679 method. A mixture of cement and additive in water was mixed for 30 s at 140 ± 5 rpm, and followed by mixing with the added sand mixture under the same conditions. Then, the mixture, which included cement, additive, water and...

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“…Compared with normal concrete, the structural application of rubberized concrete is limited due to the decreased compressive strength. Meanwhile, with the development of high-flowing and self-compacting steel fiber reinforced concrete (SFRC) [32,33], perfect distribution pattern of steel fiber in high-strength concrete comes into reality [34,35,36,37,38], and high interfacial bond performance between the steel tube and the in-filled SFRC can be obtained [39,40,41]. This provides a new way to enhance the ductility of CFST columns.…”

Section: Introductionmentioning

confidence: 99%

Behavior of Rectangular-Sectional Steel Tubular Columns Filled with High-Strength Steel Fiber Reinforced Concrete Under Axial Compression

Liu

Ding

et al. 2019

Materials

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This paper studies the effect of high-strength steel fiber reinforced concrete (SFRC) on the axial compression behavior of rectangular-sectional SFRC-filled steel tube columns. The purpose is to improve the integrated bearing capacity of these composite columns. Nine rectangular-sectional SFRC-filled steel tube columns and one normal concrete-filled steel tube column were designed and tested under axial loading to failure. The compressive strength of concrete, the volume fraction of steel fiber, the type of internal longitudinal stiffener and the spacing of circular holes in perfobond rib were considered as the main parameters. The failure modes, axial load-deformation curves, energy dissipation capacity, axial bearing capacity, and ductility index are presented. The results identified that steel fiber delayed the local buckling of steel tube and increased the ductility and energy dissipation capacity of the columns when the volume fraction of steel fiber was not less than 0.8%. The longitudinal internal stiffening ribs and their type changed the failure modes of the local buckling of steel tube, and perfobond ribs increased the ductility and energy dissipation capacity to some degree. The compressive strength of SFRC failed to change the failure modes, but had a significant impact on the energy dissipation capacity, bearing capacity, and ductility. The predictive formulas for the bearing capacity and ductility index of rectangular-sectional SFRC-filled steel tube columns are proposed to be used in engineering practice.

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Behavior of steel fiber reinforced concrete-filled steel tube columns under axial compression

Cited by 113 publications

References 41 publications

Axial Behaviour of Slender RC Circular Columns Strengthened with Circular CFST Jackets

Axial Behaviour of Slender RC Circular Columns Strengthened with Circular CFST Jackets

Effects of carbon additives on heat-transfer and mechanical properties of high early strength cement mortar

Behavior of Rectangular-Sectional Steel Tubular Columns Filled with High-Strength Steel Fiber Reinforced Concrete Under Axial Compression

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