Effect of active and passive concrete confinement on the bond stress-slip response of steel bars in tension

To evaluate the bond behavior between the reinforcing bar and surrounding concrete, a total of six-group pullout specimens with plain steel bars and two-group specimens with deformed steel bars, serving as a reference, are experimentally investigated and presented in this study. The main test parameters of this investigation include embedment length, surface type of reinforcing bars, and bar diameter. In particular, the bond mechanism of plain steel reinforcing bars against the surrounding concrete was analyzed by comparing with six-group pullout specimens with aluminium alloy bars. The results indicated that the bond stress experienced by plain bars is quite lower than that of the deformed bars given equal structural characteristics and details. Averagely, plain bars appeared to develop only 18.3% of the bond stress of deformed bars. Differing from the bond strength of plain steel bars, which is based primarily on chemical adhesion and friction force, the bond stress of aluminium alloy bars is mainly experienced by chemical adhesion and about 0.21~0.56 MPa, which is just one-tenth of that of plain steel bars. Based on the test results, a bond-slip model at the interface between concrete and plain bars is put forward.

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Experimental Study on Measuring the Steel Stress via FBG Sensors

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.548-549.663 ◽

2014 ◽

Vol 548-549 ◽

pp. 663-667 ◽

Cited By ~ 1

Author(s):

Hong Wei Lin ◽

Yu Xi Zhao

Keyword(s):

Experimental Study ◽

Bond Stress ◽

Strain Gauges ◽

Bond Behavior ◽

Fbg Sensor ◽

Pullout Tests ◽

Steel Bar ◽

Steel Bars ◽

Fbg Sensors

Studying the bond stress-slip relationship between concrete and corroded steel bar by cutting the steel bars into two separate parts and attaching electric strain gauges in the slots is no longer suitable. To overcome the disadvantages of electric strain gauges in the measuring the stress of corroded steel bars, this paper introduced a new kind of FBG sensor measuring steel stress. By calibration tests, the proportion coefficient between variation of wavelength and steel strain was confirmed as 0.0012. The bond behavior between concrete and steel bar was also investigated by performing pullout tests on beam end specimens.

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Bond Stress–Slip Model for Steel Bars in Unconfined or Steel, FRC, or FRP Confined Concrete under Cyclic Loading

Journal of Structural Engineering ◽

10.1061/(asce)0733-9445(2009)135:5(509) ◽

2009 ◽

Vol 135 (5) ◽

pp. 509-518 ◽

Cited By ~ 60

Author(s):

M. H. Harajli

Keyword(s):

Cyclic Loading ◽

Bond Stress ◽

Confined Concrete ◽

Slip Model ◽

Steel Bars

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Basic Mechanical Properties of Duplex Stainless Steel Bars and Experimental Study of Bonding between Duplex Stainless Steel Bars and Concrete

Materials ◽

10.3390/ma14112995 ◽

2021 ◽

Vol 14 (11) ◽

pp. 2995

Author(s):

Qingfu Li ◽

Yunqi Cui ◽

Jinwei Wang

Keyword(s):

Mechanical Properties ◽

Stainless Steel ◽

Duplex Stainless Steel ◽

Concrete Strength ◽

Concrete Cover ◽

Bond Stress ◽

Reinforcing Steel ◽

Anchorage Length ◽

Steel Bar ◽

Steel Bars

In recent years, as a result of the large-scale use of stainless steel bars in production and life, people’s demand for stainless steel bars has increased. However, existing research information on stainless steel bars is scant, especially the lack of research on the mechanical properties of duplex stainless steel bars and the bonding properties of duplex stainless steel bars to concrete. Therefore, this paper selects 177 duplex stainless steel bars with different diameters for room temperature tensile test, and then uses mathematical methods to provide suggestions for the values of their mechanical properties. The test results show that the duplex stainless steel bar has a relatively high tensile strength of 739 MPa, no significant yield phase, and a relatively low modulus of elasticity of 1.43 × 105 MPa. In addition, 33 specimens were designed to study the bonding properties of duplex stainless steel bars to concrete. In this paper, the effects of concrete strength, duplex stainless steel reinforcement diameter, the ratio of concrete cover to reinforcing steel diameter, and relative anchorage length on the bond stress were investigated, and a regression model was established based on the experimental results. The results show that, with the concrete strength concrete strength from C25 to C40, the compressive strength of concrete increased by 56.1%, the bond stress increased by 27%; the relative anchorage length has been increased from 3 to 6, the relative anchorage length has doubled, and the bond stress has increased by 13%; and, the ratio of concrete cover to reinforcing steel diameter increased to a certain range on the bond stress has no significant effect and duplex stainless steel reinforcement diameter has little effect on the bond stress. The ratio of concrete cover to reinforcing steel diameter from 3.3 to 4.5 and the bond stress increased by 24.7%. A ratio of concrete cover to reinforcing steel diameter greater than 4.5 has no significant effect on the bond stress, with the average bond stress value of 20.1 MPa. The duplex stainless steel bar diameter has little effect on the bond stress for the diameters of 12 mm, 16 mm, 25 mm duplex stainless steel bar, and their average bond stress is 19.9 MPa.

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Bond position function between deformed steel bars and early-age cementitious grout

Advances in Structural Engineering ◽

10.1177/13694332211015743 ◽

2021 ◽

pp. 136943322110157

Author(s):

Gang Peng ◽

Ditao Niu ◽

Xiaopeng Hu ◽

Xiao Wu ◽

Yong Zhang

Keyword(s):

Ultimate Load ◽

Tensile Load ◽

Stress Transfer ◽

Bond Stress ◽

Load Testing ◽

Anchorage Length ◽

Steel Bar ◽

Steel Bars ◽

Two Parameters ◽

Cover Thickness

Pullout tests for the deformed steel bars in early-aged cementitious grout by considering the variables of testing ages, cover thicknesses, and diameters of steel bar were conducted, and the local bond stress–slip relationship at different positions of the anchorage length of steel bar was studied. Results indicated that, with the increase of testing age, the load-slip curves exhibited a higher ultimate load and had steeper ascending and descending branches; however, the slippage at the ultimate load exhibited a decreasing trend. Moreover, with the increase of cover thickness and diameter of steel bar, the ultimate load of pullout specimens increased obviously, while the corresponding slips generally had no obvious correlations. According to an analysis of the measured rebar strain, the distributions of the steel stress and bond stress as well as the relative slip along the embedded length were obtained under different external loads. Steel stress transfer and bond stress distribution parameters were introduced to characterize the nonuniformity of the distributions of the steel stress and bond stress along the steel bar, and the effects of the testing age, cover thickness, and diameter of steel bar on these two parameters were analyzed. Results showed that the both of these two parameters increased with the increasing tensile load, testing age, and cover thickness and with the decreasing diameter of steel bar. Thereafter, the local bond stress-slip relationships along the anchorage length and position functions reflecting the variations of these relationships were proposed.

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Bond Stress between Steel-Reinforced Bars and Fly Ash-Based Geopolymer Concrete

Advances in Materials Science and Engineering ◽

10.1155/2020/9812526 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Yifei Cui ◽

Peng Zhang ◽

Jiuwen Bao

Keyword(s):

Construction Materials ◽

Bond Stress ◽

Geopolymer Concrete ◽

Portland Cement Concrete ◽

Reinforcing Bars ◽

Bond Behaviour ◽

Relative Slip ◽

Pull Out ◽

Steel Bars ◽

Commercial Steel

Geopolymer concrete has been regarded as one of the most important green construction materials, which has been restrained in engineering applications partially due to a lack of bond studies. The structural performance of the reinforced concrete components primarily relies on the sufficient bond between the concrete and the reinforcing bars. Before being utilized in any concrete structure, GPC must demonstrate that it possesses understandable bond behaviour with commercial steel reinforcements. This work presents an experimental investigation on the bond stress of steel bars in reinforced geopolymer concrete (GPC) structures. Standard beam-end pull-out tests were conducted on GPC specimens reinforced with 16 mm plain and ribbed bars that were equipped with electrical resistance strain gauges. The longitudinal variation in the bond stress in the GPC beams during the pull-out tests was calculated and plotted, as well as the stress in steel bars. The cracks on the bond area of the GPC were compared with those of the corresponding ordinary Portland cement concrete (OPC), as well as the steel stress and bond stress. The results showed that the relative slip between plain bar and geopolymer concrete varies from 30–450 microns from the loaded end to the free end when the bond stress decreased by 83%. The relative slip between ribbed bar and geopolymer concrete varies from 280–3,000 microns from the loaded end to the free end when the bond stress decreased by 57%. Generally, GPC is different from OPC in terms of bond stress distribution.

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