• Advances in concrete construction
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• v.1 no.1
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• pp.103-119
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• 2013

The applicability of limit analysis methods in design and assessment of concrete structures generally requires a certain plastic deformation capacity. The latter is primarily provided by the ductility of the reinforcement, being additionally affected by the bond properties between reinforcing steel and concrete since they provoke strain localization in the reinforcement at cracks. The bond strength of reinforcing bars is not only governed by concrete quality, but also by construction details such as bar ribbing, bar spacing or concrete cover thickness. For new concrete structures, a potentially unfavorable impact on bond strength can easily be anticipated through appropriate code rules on construction details. In existing structures, these requirements may not be necessarily satisfied, consequently requiring additional considerations. This two-part paper investigates in a theoretical study the impacts of the most frequently encountered construction details which may not satisfy design code requirements on bond strength, steel strain localization and plastic deformation capacity of cracked structural concrete. The first part introduces basic considerations on bond, strain localization and plastic deformation capacity as well as the fundamentals of the Tension Chord Model underlying the further investigations. It also analyzes the impacts of the hardening behavior of reinforcing steel and concrete quality. The second part discusses the impacts of construction details (bar ribbing, bar spacing, and concrete cover thickness) and of additional structure-specific features such as bar diameter and crack spacing.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.897-902
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• 2001

Recently, structure performance is maximized by using high strength concrete. In design of structure, concrete need combination with reinforcement, but use of common strength reinforcement make member complex bar placement, so high strength concrete members require increased strength reinforcement. If common strength reinforcement replaced by equal tension area of high strength reinforcement, reinforcement ratio increase and brittle failure of member may occur by material change. So, adequate upper limit of strength ratio is required to affirm ductile behavior in application of high strength reinforcement. In this study, ductility behavior was analysed by factor of reinforcement ratio, strength of concrete and reinforcement. The result indicate that ductile failure is shown under 0.35 $\rho_{b}$ in any reinforcement strength of same section and high strength concrete of 800kg/$cm^{2}$ used commonly is compatible with reinforcement of 5500kg/$cm^{2}$.

• International Journal of Concrete Structures and Materials
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• v.18 no.3E
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• pp.151-159
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• 2006

A total of 32 pullout tests were performed for the multiple headed bars relatively deeply embedded in reinforced concrete column-like members. The objective was to determine the minimum embedment depth that was necessary to safely design exterior beam-column joints using headed bars. The variables for the experiment were embedment depth of headed bar, center-to-center distance between adjacent heads, and amount of supplementary reinforcement. Regular strength concrete and grade SD420 reinforcing steel were used. The results of the test the indicated that a headed bar embedment depth of $10d_b$ was not sufficient to have relatively closely installed headed bars develop the pullout strength corresponding to the yield strength. All the experimental variables, influenced the pullout strength. The pullout strength increased with increasing embedment depth and head-to-head distance. It also increased with increasing amount of supplementary reinforcement. For a group of closely-spaced headed bars installed in a beam-column joint, it is recommended to use column ties at least 0.6% by volume, 1% or greater amount of column main bars, and an embedment depth of $13d_b$ or greater simultaneously, to guarantee the pullout strength of individual headed bars over 125% of $f_y$ and ductile load-displacement behavior.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.1
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• pp.85-93
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• 2013

In order to make a more reasonable evaluation on the stiffness of the high-strength mortar-filled sleeve bar splices under cyclic loading, we investigated and analyzed the existing experiment data of 106 full-sized reinforcing bar splices with test variables such as compressive strength of mortar, development length of reinforcement and sleeve type, etc. The following were found: 1) If mortar and the reinforcement development length with $f_{g^*}$(L/d) of more than 340 is used, the cast iron sleeve bar splices for SD350 and SD400 will have the stiffness of higher than A class of the AIJ code. 2) If mortar and the reinforcement development length with $f_{g^*}$(L/d) of more than 400 is used, the cast iron sleeve splices and pipe sleeve splices for SD500 will have the stiffness of higher than A class of the AIJ code.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.105-108
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• 2008

Although the research of high strength materials is in process briskly in the inside and outside of the country, in south korea, the research of high strength materials is insufficiency. Generally shear resistance of RC beam is influenced dominantly by amount of shear-reinforcing bars($p_w$) and yied strength($f_{wy}$). Therefore, I come to the conclusion that if use shear reinforced bar with shear reinforced bar, it leads to decrease of the quantity of shear reinforced bar and effects on the security of shear-restraint force of member. This study experimented with not only the mixture of high strength-reinforced bar and U-shaped reinforcement normal strength -reinforced bar devises efficient improvement, but also it incites improvement of bond capacity and carries out an experimental study for improvement of member resisting force, finally it evaluates bond capacity quantitatively on the lines of main reinforcement the restraint method.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.233-238
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• 2002

This study presents failure mechanisms for the pull-out strength of headed reinforcement for upper bound solution based on the limit theorem. The failure mechanisms to be presented follow the failure surface pattern of punching shear failure found in the joints of slab with a column. Several failure surfaces of the mechanisms have different characteristics for dissipation works and these mechanisms are able to interpret the role of bar details surrounding headed reinforcement.

• Journal of Applied Reliability
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• v.9 no.2
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• pp.71-80
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• 2009

This paper discusses the service life prediction methods for CFRP bar for concrete reinforcement using accelerated degradation tests. The relationship between performance degradation and the rate of a failure-causing chemical reaction is assumed for the temperature accelerated degradation tests. Methods of obtaining acceleration factors and predicting service life of the CFRP bar using the degradation model are presented.

• Computational Structural Engineering
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• v.8 no.2
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• pp.73-84
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• 1995

The study summarized in this paper is concerned with the buckling of longitudinal bars in reinforced concrete columns with numerical analysis method. The objectives of this study are (1) to investigate the stress transfer mechanism between concrete and reinforcement and (2) to propose a modeling equation. The results give an acceptable agreement between the proposed modeling equation and published computer packages as follows; (1) the proposed equation is a possible of strain softening of concrete and buckling of reinforcement. (2) the buckling of longitudinal bar is mainly influenced by spacing of hoop and location of the bar

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.110-111
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• 2019

In ACI 318-19 published recently, the conditions and development length equation to use the headed deformed bars were changed considerably. Although the use of the larger-diameter(No.14 and 18) headed deformed bars isn't yet permitted, the use of the high strength(80,000psi) headed deformed bars is permitted and the effect of bar-diameter($d_b$) on the development length is increased considerably. Therefore, structures using larger-diameter headed deformed bars will be expected to be affected by this code change. We will study the effect of the code change on the development design and find out the design optimization method to minimize the effect of the changed conditions and development length equation.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.11-12
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• 2012

This study investigates the temperature rise of reinforcement bars located in the middle of the form (for reinforcement concrete) during hot weather condition. The temperature was measured for three consecutive days before placing concrete. Test results showed that the temperature started to increase at 7:00 AM before sun rised, and peaked at around 2:00 PM. It was found that the thinner the diameter of a reinforcement bar, the higher is the speed of temperature rise and drop of the bar. The peak level of temperature for D13, D19, D25 and D32 was 54.4℃, 55.2℃, 56.4℃ and 60.2℃, respectively.