• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.65-68
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• 2005

An analytical procedure to analyze reinforced concrete (RC) frame subject to cyclic as well as monotonic loadings is proposed on the basis of the layered section method. In contrast to the classical nonlinear approaches adopting the perfect bond assumption, the bond-slip effect along the reinforcing bar is quantified with the force equilibrium and compatibility condition at the post-cracking stage and its contribution is implemented into the reinforcing. The advantage of the proposed analytical procedure, therefore, will be on the consideration of the bond-slip effect while using the classical layered section method without additional consideration such as taking the double nodes. Through correlation studies between experimental data and analytical results, it is verified that the proposed analytical procedure can effectively simulate the cracking behavior of RC beams, columns and Frame accompanying the stiffness degradation caused by the bond-slip.

• Computers and Concrete
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• v.19 no.6
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• pp.625-630
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• 2017

In this paper, 54 pull-out specimens and 36 cubic specimens with different replacement ratios of fly ash in the concrete (i.e., 0%, 20%, 30%, 40%, 50%, 60%) were fabricated to evaluate the bond at the interface between fly ash concrete and steel rebar. The results showed that the general shape of the bond-slip curve between fly ash concrete and steel rebar was similar to that for the normal concrete and steel rebar. The bond strength between fly ash concrete and the steel rebar was closer to each other at the same rebar diameter, irrespective of the fly ash replacement percentage. On the basis of a regression analysis of the experimental data, a revised bond strength mode and bond-slip relationship model were proposed to predict the bond-slip behaviour of high volume fly ash concrete and steel rebar.

• Computers and Concrete
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• v.16 no.3
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• pp.449-466
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• 2015

This paper aims to study the local bond stress-slip behavior of reinforcing bars embedded in lightweight aggregate concrete (LWAC). The experimental variables of the local bond stress-slip tests include concrete strength (20, 40 and 60 MPa), deformed steel bar size (#4, #6 and #8) and coarse aggregate (normal weight aggregate, reservoir sludge lightweight aggregate and waterworks sludge lightweight aggregate). The test results show that the ultimate bond strength increased with the increase of concrete compressive strength. Moreover, the larger the rib height to the diameter ratio ($h/d_b$) of the deformed steel bars is, the greater the ultimate bond stress is. In addition, the suggestion value of the CEB-FIP Model Code to the LWAC specimen's ultimate bond stress is more conservative than that of the normal weight concrete.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.517-528
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• 2008

This paper presents a hysteretic damage model for reinforced concrete (RC) joints that explicitly accounts for the bond-slip between the reinforcing bars and the surrounding concrete. A frame element whose displacement fields for the concrete and the reinforcing bars are different to permit slip is developed. From the fiber section concept, compatibility equations for concrete, rebar, and bond are defined. Modification of the hysteretic stress-strain curve of steel is conducted for partial unloading and reloading conditions. Local bond stress-slip relations for monotonic loads are updated at each slip reversal according to the damage factor. The numerical applications of the reinforcing bar embedded in the confined concrete block, the RC column anchored in the foundation, and the RC beam-column subassemblage validate the model accuracy and show how including the effects of bond-slip leads to a good assessment of the amount of energy dissipation during loading histories.

• Computers and Concrete
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• v.7 no.5
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• pp.403-419
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• 2010

The bond mechanism for reinforcing bars in concrete is equivalent to the normal contact and friction between the inclined ribs and the surrounding concrete. Based on the contact density model for the computation of shear transfer across cracks, an open-slip coupled model was developed for simulating three-dimensional bond behavior for reinforcing bars in concrete. A parameter study was performed and verified by simulating pull-out experiments of extremely different boundary conditions: short bar embedment with a huge concrete cover, extremely long bar embedment with a huge concrete cover, embedded aluminum bar and short bar embedded length with an insufficient concrete cover. The bar strain effect and splitting of the concrete cover on a local bond can be explained by finite element (FE) analysis. The analysis shows that the strain effect results from a large local slip and the splitting effect of a large opening of the interface. Finally, the sensitivity of rebar geometry was also checked by FE analysis and implies that the open-slip coupled model can be extended to the case of plain bar.

• Steel and Composite Structures
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• v.26 no.3
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• pp.347-360
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• 2018

The aim of this paper is to evaluate the accuracy and reliability of the available bond-slip laws which are being used for the numerical modeling of Fiber Reinforced Polymer (FRP)/concrete interfaces. For this purpose, a set of Reinforced Concrete (RC) beams retrofitted with external FRP were modeled using the 3D nonlinear Finite Element (FE) approach. All considered RC beams have been previously tested and the corresponding experimental data are available in the literature. The failure modes of these beams are concrete crushing, steel yielding and FRP debonding. Through comparison of the numerical and experimental results, the effectiveness of each FRP/concrete bond-slip model for the prediction of the structural behavior of externally retrofitted RC beams is assessed. The sensitivity of the numerical results against different modeling considerations of the concrete constitutive behavior and bond-slip laws has also been evaluated. The results show that the maximum allowable stress of FRP/concrete interface has an important role in the accurate prediction of the FRP debonding failure.

• Computers and Concrete
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• v.16 no.2
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• pp.311-327
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• 2015

Employing discrete elements for considering bond-slip effects in reinforced concrete structures is very time consuming. In this study, a new modified embedded element method is used to consider the bond-slip phenomenon in structural behavior of reinforced concrete structures. A comprehensive parametric study of RC slabs is performed to determine influence of different variables on structural behavior. The parametric study includes a set of simple models accompanied with complex models such as multi-storey buildings. The procedure includes the decrease in the effective stiffness of steel bar in the layered model. Validation of the proposed model with existing experimental results demonstrates that the model is capable of considering the bond-slip effects in embedded elements. Results demonstrate the significant effect of bond-slip on total behavior of structural members. Concrete characteristic strengths, steel yield stress, bar diameter, concrete coverage and reinforcement ratios are the parameters considered in the parametric study. Results revealed that the overall behavior of slab is significantly affected by bar diameter compared with other parameters. Variation of steel yield stress has insignificant impact in static response of RC slabs; however, its effect in cyclic behavior is important.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.449-454
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• 2001

The algorithm and program which implement the bond-slip behavior of pre-tensioned concrete beams to the nonlinear strut-tie model approach, are developed in this study. The validity of the algorithm and program is verified through the strut-tie model evaluation of the strength and behavior of two pre-tensioned concrete deep beams which were failed by bond-slip.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.17-18
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• 2009

This research defined slip function using cracking behavior, bond characteristics and numerical analysis of cracking stabilized reinforced concrete member, and proposed a bond stres-slip model.

• Structural Engineering and Mechanics
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• v.66 no.4
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• pp.477-485
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• 2018

This study aims to investigate the influence of individual and hybrid fiber on the local bond-slip behavior of medium and high strength concrete after exposure to different high temperatures. Tests were conducted on local pullout specimens (150 mm cubes) with a reinforcing bar embedded in the center section. The embedment lengths in the pullout specimens were three times the bar diameter. The parameters investigated include concrete type (control group: ordinary concrete; experimental group: fiber concrete), concrete strength, fiber type and targeted temperature. The test results showed that the ultimate bond stress in the local bond stress versus slip curve of the high strength fiber reinforced concrete was higher than that of the medium strength fiber reinforced concrete. In addition, the use of hybrid combinations of steel fiber and polypropylene fiber can enhance the residual bond strength ratio of high strength concrete.