• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.571-572
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• 2009

Current design codes regarding compression lap splice dose not utilize merits of the improved strength of ultra-high strength concrete. Especially, a compression lap splice can be calculated longer than a tension lap splice according to the codes because they do not consider effects of strength of concrete and transverse reinforcement. Design equation is proposed for compression lap splice in 40 to 70 MPa of compressive strength of concrete. The proposed equation is based on 51 specimens. Through two-variable non-linear regression analysis of measured splice strengths, a splice strength equation is derived, which is converted into a splice length equation.

• Structural Engineering and Mechanics
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• v.37 no.1
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• pp.95-110
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• 2011

This paper presents a tri-uniform bond stress model for predicting the lap splice strength of reinforcing bar at the critical bond splitting failure. The proposed bond distribution model consists of three zones, namely, splitting zone, post-splitting zone and yielding zone. In each zone, the bond stress is assumed to be constant. The models for bond strength in each zone are adopted from previous studies. Combining the equilibrium, strain-slip relation and the bond strength model in each zone, the steel stress-slip model can be derived, which can be used in the nonlinear frame analysis of the column. The proposed model is applied to derive explicit equations for predicting the strength of the lap splice strengthened by fiber reinforced polymer (FRP) in both elastic and post-yield ranges. For design purpose, a procedure to calculate the required FRP thickness and the number of FRP sheets is also presented. A parametric investigation was conducted to study the relation between lap splice strength and lap splice length, number and thickness of FRP sheets and the ratio of concrete cover to bar diameter. The study shows that the lap splice strength can be enhanced by increasing one of these parameters: lap splice length, number or thickness of FRP sheets and concrete cover to bar diameter ratio. Verification of the model has been conducted using experimental data available in literature.

• Journal of the Korea Concrete Institute
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• v.23 no.2
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• pp.211-217
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• 2011

Although a compression splice length does not need to be longer than a tension splice length due to end bearing effect, current design codes impose a longer compression lap splice than a tension lap splice in high strength concrete. Hence, new criteria for the compression lap splice including concrete strength effect need to be found for economical design of ultra-high strength concrete. An experimental study has been conducted using column specimens with concrete strength of 80 and 100 MPa with transverse reinforcement. The test results showed that splice strengths improved when the amount of transverse reinforcement increased. However, end bearing strength did not increase when larger amount of transverse reinforcement is provided within the spliced zone. Therefore, the splice strength enhancement was attributed to the improvement of bond. From regression analysis of 94 test results including specimens made with concrete strength of 40 and 60 MPa, a new design equation is proposed for compression lap splice in the concrete compressive strength ranging from 40 to 100 MPa with transverse reinforcement. By using the proposed equation, the incorrect design equations for lap splice lengths in tension and compression can be corrected. In addition, the equation has a reliability equivalent to those of the specified strengths of materials.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.615-622
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• 2003

The purpose of this study is to propose the more reasonable equation of bond strength of grout-filled splice sleeve. To accomplish this objective, total 60 full-sized specimens were tested under monotonic loading. The experimental variables are compressive strength of mortar, embedment length and size of reinforcing bars. Following conclusions are obtained; 1) If the adequacy of existing equations which estimate the bond strength of grout-filled splice sleeve are investigated, they underestimate the bond strength of grout-filled splice sleeve by 8-18%. Also the existing equations have a tendency to underestimate with decrease in the embedment length of reinforcing bars. 2) From the test result of bond failure, the equation which estimates the confining pressure of grout-filled splice sleeve was proposed by making multiple regression analyses of which independent variables are embedment length of reinforcing bars and compressive strength of mortar. This equation predicted the measured bond capacity of this test more accurately than existing equations and eliminated the deviation according to the embedment length of reinforcing bars.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.6
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• pp.122-130
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• 1997

An experimental study was conducted to evaluate the bond performance of reinforcing bars embedded in high-strength concrete. Four bond specimens and ten beam splice specimens using concrete with compressive strength of 246kgf/$cm^2$ and 64lkgf/$cm^2$ were tested. The effect of several variables on basic development length and compressive strength of concrete is discussed in splice specimens. The test results showed that the current trend in concrete specification of making the splice length longer to compensate for having smaller cover and spacing may not be an effective approach.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1081-1084
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• 2008

Column specimens were constructed with main parameters significantly affecting the strength of the compression lap splice, such as lap length, spacing of lapped bars, amount and location of transverse reinforcements, and concrete strength. An experimental study has been conducted with column specimens in concrete strength of 40 to 60 MPa. Diameters of lapped reinforcing bars are 22 mm. An axial load was monotonically applied to the column specimens. All specimens failed in a brittle sudden manner and cover concrete was blasted out at maximum load. Compression lap splice strengths of specimens were evaluated from strains measured at the beginning of the lap length. Effects of the main parameters on the strengths of compression lap splice are assessed. Similarly to strengths of tension lap slice, the compression splice strength is found to be affected by lap length, spacing of lapped bars, transverse reinforcements.

• Land and Housing Review
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• v.8 no.4
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• pp.257-266
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• 2017

LH has been using ultra high strength reinforcing bars (SD500 and SD600), since 2011. Such a change requires an adjustment of the old extra rates of bar splice to reflect use of ultra high strength reinforcing bars, as these rates had been set based on SD400 bars. It is particularly difficult to calculate precisely rebar lap-splice locations for large areas, such as those in apartment buildings. This research aims to adjust the extra rates of bar splice to reflect a reasonable rate; the rebar lap-splice length is not an exact estimation, but instead, an extra rates of bar splice is set and the rebar lap-splice length is increased by 2% (D 10) - 7% (025) depending on the bar size. The subjects of this study are LH apartments undergoing frame construction. We studied the quantity estimations from the design drawings, and analyzed the settlement quantities of construction field. The results of the study revealed that, when each of the quantities are analyzed, consider adjusting the extra rates of bar splice of some rebar to 1% - 3.5%. This was caused by an overuse of reinforcing bars in onsite construction and the use of supporting bars that have not been reflected in the documents, among other reasons. Based on the results of our study, an improvement plan for the current extra rates of bar splice seems to be necessary, cutting or raising the rate depending on the analysis of the data. Through this study, we expect to contribute to the calculation of reasonable construction costs, improvements in the quality of rebar work, and improvements in the capacity of design techniques for apartment buildings.

• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.291-302
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• 2009

A compression lap splice can be calculated longer than a tension lap splice in high strength concrete according to current design codes. New criteria for the compression lap splice including the effects of concrete strength are required for practical purpose of ultra-high strength concrete. Characteristics of compression lap splice have been extensively investigated and main parameters are derived. In addition, an experimental study has been conducted with column specimens in concrete strength of 40 and 60 MPa. The strength of the compression lap splice consists of bond and end bearing and two contributors are combined. Therefore, combined action of bond and end bearing should be assessed. Compared with tension splices, concrete strength significantly affects the strength of compression splices due to short splice length and existence of end bearing. Test results show that the splice strength can be evaluated to be proportional to square root of compressive strength of concrete. The stress states of concrete surrounding spliced bars govern the strengths of bond and end bearing. Because the axial stress of the concrete is relatively high, the splice strength is not dependent on clear spacing. End bearing strength is not affected by splice length and clear spacing and is expressed with a function of the square root of concrete strength. The failure mode of specimens is similar to side-face blowout of pullout test of anchors and the strength of end bearing can be evaluated using the equation of side-face blowout strength. Because the stresses developed by bond in compression splices are nearly identical to those in tension splices, strength increment of compression splices is attributed to end bearing only.

• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.129-136
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• 2012

Compression splices are required for all compression members in almost all of the floors in high-rise buildings. Therefore, a clear understanding of the behavior of compression splices can provide a rational design of compression splices. Tests of compression splices with bearing only and bond only cases were conducted to investigate the component resistance characteristics of compression splices. Test results showed that the circumferential tensile stresses induced by bearing and bond overlapped at the end of the splice length deterred bond and bearing splices from developing target splicing strength when both normal bond and bearing splices were used. In particular, the bearing strength was more significantly reduced than the bond strength since the bearing relied on the limited area near the end of the splice length. However, the strength of the normal splice was always higher than the strength of the bond only or the bearing only case. Consequently, the study results showed that splice strength in compression cannot be improved by means of removing bond or bearing. In addition, the bond strength in bond only splices was nearly same as the bond strength in tension splices and the strength increase of compression splice is attributed to end bearing only characteristic.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.6
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• pp.47-56
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• 2012

It is known that seismic performance of existing bridges having insufficient lateral confinements and lap-splices of longitudinal reinforcements at the base of column decreases dramatically. In this study, small-scaled model tests have been performed to confirm the seismic behaviors of RC bridge piers with various lap-splice lengths. The 8 test models have circular section with diameters of 0.65 m, 0.8 m, 1.0 m, and lap-splice lengths of B-class or C-class. The test results show that the failure modes of models are not depending on the lap-splice length itself but depend on the ratio of lap-splice length to diameter, and that the displacement ductility is also affected by this ratio.