• Earthquakes and Structures
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• v.5 no.5
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• pp.527-552
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• 2013

Development of flexural yielding and large rotation ductilities in the plastic hinge zones of frame members is synonymous with the spread of bar reinforcement yielding into the supporting anchorage. Yield penetration where it occurs, destroys interfacial bond between bar and concrete and reduces the strain development capacity of the reinforcement. This affects the plastic rotation capacity of the member by increasing the contribution of bar pullout. A side effect is increased strains in the compression zone within the plastic hinge region, which may be critical in displacement-based detailing procedures that are linked to concrete strains (e.g. in structural walls). To quantify the effects of yield penetration from first principles, closed form solutions of the field equations of bond over the anchorage are derived, considering bond plastification, cover debonding after bar yielding and spread of inelasticity in the anchorage. Strain development capacity is shown to be a totally different entity from stress development capacity and, in the framework of performance based design, bar slip and the length of debonding are calculated as functions of the bar strain at the loaded-end, to be used in calculations of pullout rotation at monolithic member connections. Analytical results are explored parametrically to lead to design charts for practical use of the paper's findings but also to identify the implications of the phenomena studied on the detailing requirements in the plastic hinge regions of flexural members including post-earthquake retrofits.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.3 s.55
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• pp.197-208
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• 2009

The purpose of this research is the evaluation of the estimation equation of "CEP-FIP Model Code 1990(1991)", recently included in the domestic "Concrete Structure Design Code(2007)" in consideration of the concrete strength. As evaluation tools, crack element model applied a detailed bond-slip model as well as crack width obtained from experimental results by earlier researches. The crack element model is verified through the comparison with experimental results. The important variables in the estimation equation for the crack width in CEP-FIP Model Code 1990 are the tension stiffening effect and mean bond stress proposed in the paper to be improved in consideration of the concrete strength.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.91-100
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• 2006

This paper presents an analytical model for evaluation of crack widths in structural concrete members. The model is mathematically derived from the actual bond stress-slip relationships between the reinforcement and the surrounding concrete, and the relationships summarized in CEB-FIP Model Code 1990 are employed in this study together with the assumption of a linear slip distribution along the interface at the stabilized cracking stage. With these, the actual strains of the steel and the concrete are integrated respectively along the embedment length between the adjacent cracks so as to obtain the difference in the axial elongation. The model is applied to the test specimens available in literatures, and the predicted values are shown to be in good agreement with the experimentally measured data.

• Journal of the Korean Society for Railway
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• v.12 no.6
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• pp.944-952
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• 2009

This paper presents an analytical model for calculation of crack widths in reinforced concrete structures. The model is mathematically derived from the actual bond stress-slip relationships between the reinforcement and the surrounding concrete, and the relationships summarized in CEB-FIP Model Code 1990 and Eurocode 2 are employed in this study together with the numerical analysis result of a linear slip distribution along the interface at the stabilized cracking stage. With these, the actual strains of the steel and the concrete are integrated respectively along the embedment length between the adjacent cracks so as to obtain the difference in the axial elongation. The model is applied to the test results available in literatures, and the predicted values are shown to be in good agreement with the experimentally measured data.

• 한국도로학회:학술대회논문집
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• 2004.02a
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• pp.69-74
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• 2004

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.617-620
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• 1999

The purpose of this study is to find the influence of interface and confinement on bond between reinforcing steel and concrete subjected to monotonic and cyclic loading. The key variables for the experimental program include rib height, rib spacing for reinforcing bars and confinement. From the results obtained in this study, the following main observations can be made for the bond properties. Bond strength increases when confinement increases under monotonic and cyclic loading. Bond stiffness and strength drop remarkably after the maximum bond strength. Both bond stiffness and strength also drop at a constant slip when the number of cyclic loading increase. The bond resistance subjected to cyclic loading decreases significantly for reinforcing bars with low rib height.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.5
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• pp.51-60
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• 2008

This study is to relate the bond characteristics of CFRP rebar in high strength concrete incorporated with silica fume(SF) and metakaolin(MK). An direct bond test were performed to evaluate the effect of SF and MK on bond properties of high-strength concrete and CFRP rebar. The high strength concrete mix included four SF and MK mixes with 0%, 5%, 10% and 15%. Results of bond performance experiment in relation to pullout vs slip behavior of FRP rebar and high strength showed better performance of SF than MK. Also, the results showed the improved bond strength as replacement ratio of SF and MK increased. The relative bond strength in which $1.3{\sim}3.2$ of estimated values were obtained.

• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.745-754
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• 2007

This paper presents a unified modeling technique for tension stiffening effect in structural concrete members. The model is mathematically derived from the bond stress-slip relationships which account for splitting crack. The relationships in CEB-FIP Model Code 1990 and Eurocode 2 are employed together with the assumptions of a linear slip distribution along the interface and the uniform condition of concrete tensile contribution for the mid section of cracked member at the stabilized cracking stage. With these assumptions, a model of tension stiffening effect is proposed by accounting for the force equilibrium and strain compatibility condition associated to the steel strain and concrete contribution by bond stress. The model is applied to the test results available in literatures, and the predicted values are shown to be in good agreement with the experimentally measured behavior.

• Proceedings of the Korea Concrete Institute Conference
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• 1991.04a
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• pp.81-85
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• 1991

The object of this study is to propose the bending moment-curvature relationships based on the bond properties between concrete and steel for noncraking zone, and evaluate the flexural displacement of reinforced concrete members. The bond-slip relationship and the strain hardening effect of steel were taken into account in order to evaluate the spacing of the cracks and the curvature distribution. Calculated curvature distribution along the longitudinal axis was transformed into equivalent curvature distribution. The flexural displacement was calculated by means of double intergral of the equivalent curvature. Calculated values are in good agreement with the experimental data.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.233-241
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• 2005

The paper is presented experimental study results on bond stress between profiled steel and concrete in Profiled SPC(Profiled Steel Plate Concrete) rectangular steel tubes through an experimental program in which 13 pull-out specimens were tested. Advantages and class of composite members and current problems of construction work are noted, past research of PSSC is described. An experimental study is described and evaluated. The bond capacity is interrelated with slip at the steel concrete interface. The factors influencing the mechanism of bond stress transfer were the cross section shape, length/diameter, diameter/thickness and environmental parameters (temperature, moisture). The results of experimental program indicated that the force transfer could be characterized into two regions The first region was governed by bond with no relative slip between the profiled steel and concrete. The second region occurs after the chemical debonding. Bond stress transfer in this region was governed by frictional resistance between profiled steel and concrete and cross section shapes. The important factors influencing the magnitude of frictional resistance are the profiled steel shapes, length/diameter and environmental parameters. (temperature, moisture)