• Journal of the Korea Concrete Institute
• /
• v.19 no.2
• /
• pp.153-161
• /
• 2007

This paper investigates the lap splice performance of structural steel bars embedded in high performance fiber reinforced cementitious composite(HPFRCC) with various matrix ductilities. Matrix ductility is governed fiber type and fiber volume fraction. Fiber types were polypropylene(PP), polyethylene(PE) and hybrid fiber[polyethylene fiber+steel cord(PE+SC)]. The lap splice length$(l_d)$ was calculated according to the relevant ACI code requirements for reinforcing bars in normal concrete. As the result of tests, lap splice strength of HPFRCC using PE1.5 and hybrid fiber increased by up to $82{\sim}91$ percent more than that of concrete. Splice strength and energy absorption capacity of PE0.75+SC0.75 or PE1.5(fiber volume fraction 1.5%) specimen increased more than that of PP2.0(fiber volume fraction 2.0%) specimen. Therefore lap splice performance depends on fiber tensile strength and Young's modulus more than fiber volume fraction. Also, HPFRCC appear multiple crack and ductile postpeak behavior due to bridging of fiber in cementitious composite.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.25 no.6
• /
• pp.262-269
• /
• 2021

This paper conducts an evaluation of the structural performance of the lap splice detail of SD700 headed bar experiment for developing an RC beam with different depths joint details. The experiment variable is lap splice length, yield strength, and end anchorage of main reinforcements. For all specimens, a headed bar was applied to the main reinforcement of the beam with low depth (B2), and the beam with high depth (B1) was applied to the main reinforcement with two splice methods: straight headed bar and 90° hooked-headed bar. The experimental results were that specimens of applying SD500 and SD600 had the results of flexural fracture at the lap splice location, which maximum load was similar. For specimens of appling SD500, the 90° hooked-headed bar of B1, suppressed horizontal cracks in the lap splice section compared to the straight headed bar. Specimens of applying an SD 700 headed bar had the results of brittle anchorage failure. In addition, maximum load was increased with the lap splice length increasing. For specimens of applying SD700 headed bar, test for test maximum load/theoretical load for test development length/design development length were estimated to be 1.30~1.48 for the ACI 318-19 equation, and 1.14~1.30 for the KDS-2021 equation. Thus, ACI 318-19 equation had conservatively greater safety factors as estimated development lengththened.

• The Journal of the Convergence on Culture Technology
• /
• v.6 no.4
• /
• pp.685-692
• /
• 2020

In this study, the experimental and analytical study were performed on the location of longitudinal cracks in the middle of underground box structures. The location where the longitudinal cracking occurred was investigated that the overlapping joint of the rebar and the section of maximum tensile stress generated. Using the finite element analysis, the strength reduction ratio of the rebar was estimated by lack of overlap joint length. As the result of adequacy investigation for the length of the overlap joint presented in the design criteria, it was analytically proved that the lack of the overlap joint length could be cause the decreasing cross-sectional force and concrete cracking. As the result of this study, the adequacy of the overlapping criterion in the current design criteria was confirmed based on the finite element analysis and actual field case. In the case of overlapping joints installed in inappropriate position, it was considered that a long term crack control would be need to ensure the sufficient safety factor for the designed cross-sectional force.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.20 no.4
• /
• pp.144-152
• /
• 2016

This paper focuses on the experimental study for investigating the performance for lap splice of hooked or headed reinforcement in beam with different depths. In the experiment, seven specimens, with its variables as the lap length of headed or hooked bar, the existence of stirrups, etc., was manufactured. Bending test was conducted. Lap strengths by test were compared with the theoretical model based on KCI2012. The result showed that the cracks at failure mode occurred along the axial direction to a headed bar. The initial stiffness and the stiffness after initial crack were similar for all specimens. For HS series specimens without stirrups, a 25% increase in lap length was increased 11.8~18.1% maximum strengths. For HH series specimens without stirrups, a increase in lap length did not affect the maximum strengths because of the pryout failure of headed bar. For HS series specimens, the theoretical lap strengths based on KCI2012 considering the B grade lap and the reduction factor for stirrup were evaluated. They are smaller than the test strengths and can ensure the safety in terms of strength capacity. For HH series specimens, the stirrups in the lap zone are needed to prevent the pryout behaviour of headed bar.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.1085-1088
• /
• 2008

Splice of reinforcement is inevitable in reinforced concrete structures and, generally, lap splices are used. Lap length for tension splice is determined from development length in tension. The development length is calculated from an experimental model which was based on data of tests on anchorage and splice. Longitudinal reinforcements in flexural members are deformed and, therefore, prying action happens in spliced reinforcements unlike anchored reinforcements. The prying action induces tensile stress in cover concrete and this tensile stress plays the same role to a circumferential tensile stress caused by bond. Because splitting failure is assumed to occur when the summation of tensile stresses caused by the prying action and the bond is equal to the tensile strength of the concrete, the prying action reduces the bond strength of spliced reinforcements. A theoretical model for the prying action is developed and effects of the prying action on the bond strength are assessed. The tensile stress by the prying action is proportional to tensile strength and modulus of elasticity of reinforcements. In addition, the tensile stress is inversely proportional to spacing of reinforcements. Consequently, longer splice length is required for spliced reinforcements with small spacing in flexible members.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.12 no.6
• /
• pp.119-128
• /
• 2008

In this study, new moment-resisting precast concrete beam-column joint is proposed for moderate seismic regions. It has the connection reinforcing bars, penetrated the joint and lap-spliced with the bottom bars of precast U-shaped PC beam. To evaluate the performance for noncontact lapped splice, experimental and analytical works were conducted. Major variables for tests are the length of lap, the diameter of connection reinforcing bars, and the distance between lapped bars. Analytic research was performed nonlinear finite element method. Analytic research focused on crack pattern, load-deflection curve, comparison of internal force, evaluation of ductility strains of reinforcement bar. Results of experimental and analytical works show that the these variables has much influence on flexural strength and ductility, and joint behavior.

• Journal of the Korea Concrete Institute
• /
• v.24 no.2
• /
• pp.111-120
• /
• 2012

This paper is a report about lap splice performance of rebar embedded in the strain-hardening cement-based composites (SHCCs) under monotonic and repeated tension loading. Ten mix proportions of cement-based composites such as SHCCs and normal concrete were investigated. The study parameters are comprised of (1) types of reinforcing fibers (polyethylene and steel fiber), (2) replacement levels of expansive admixture (EXA, 0% and 10%), and (3) compressive strength (30 and 100 MPa) of cement-based composites. Lap splice lengths (ld) of rebars in SHCC materials and normal concrete were 60% and 100% of splice length calculated by code requirements for structural concrete, respectively. Test results indicated that SHCCs materials can lead to enhancements in the lap splice performance of embedded rebar. All of the fiber reinforcement conditions (PE-SHCC and PESF-SHCC) considered in this study produced considerable improvements in the tensile strength, cracking behavior, and bond strength of lap-spliced rebar. Furthermore, adding EXA to SHCC matrix improved the tensile lap splice performance of rebar in SHCC materials. However, for controlling crack behavior, the performance of PE-SHCC was better than that of PESF-SHCC due to its mechanical properties. This study demonstrated an effective approach for reducing required development length of lap spliced rebar by using SHCC materials.

• Journal of the Korea Concrete Institute
• /
• v.21 no.6
• /
• pp.753-761
• /
• 2009

This paper presents the test results of total 24 beam-end specimens to investigate the effect of high-strength concrete and cover thickness on the development resistance capacity in tensile lap splice length regions. Based on bond characteristics that an increase in concrete strength results in higher bond stress and shortening of the transfer length, cracking behavior that thin cover thickness induced a splitting crack easily and brittle crack propagation, current design code that development length provisions as uniform bond stress assumption was investigated apply as it. The results showed that as higher strength concrete was employed, not only development resistance capacity was influenced by cover thickness, but also more sufficient safety factor reserved shorter than the lap splice length provision in current design code. From experimental research results, high-strength concrete development length was not inverse ratio of $\sqrt{f_{ck}}$ but directly inverse of $f_{ck}$, and it is also said that there is a certain limit length of the embedded steel over which the assumption of uniform bond stress distribution is valid specially for high-strength concrete not having a same embed length such as normal-strength concrete in current design criteria hypothesis.

• Journal of the Korea Concrete Institute
• /
• v.21 no.1
• /
• pp.65-74
• /
• 2009

Glass fiber reinforced polymer (GFRP) bars are sometimes used when corrosion of conventional reinforcing steel bar is of concern. In this study, a total of 36 beams and one-way slabs reinforced using GFRP bars were tested in flexure. Four different GFRP bars of 13 mm diameter were used in the test program. In most test specimens, the GFRP bars were lap spliced at center. All beams and slabs were tested under 4-point loads so that the spliced region be subject to constant moment. Test variables were splice lengths, cover thicknesses, and bar spacings. No stirrups were used in the spliced region so that the tests result in conservative bond strengths. Average bond stresses that develop between GFRP bars and concrete were determined through nonlinear analysis of the cross-sections. An average bond stress prediction equation was derived utilizing two-variable linear regression. A splice length equation based on 5% fractile concept was then developed. As a result of this study, a rational equation with which design splice lengths of the GFRP bars can be determined, was proposed.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.5
• /
• pp.135-142
• /
• 2022

In this study, lap spliced ultra-high strength reinforced concrete beams were tested and the code criteria for calculating the lap splice length which was affected by the transverse reinforcement and concrete covering performance were reviewed. The main variables for test were set as fiber volume fraction and transverse reinforcing bar arrangement to improve the confining performance of the concrete cover. The change of the confining performance of concrete cover according to the increase in the fiber mixing amount at 1% and 2% volume ratio was examined, and D10 stirrups with a spacing of 100 mm were placed in the lap spliced region. As a result of the test, the specimens confined by the stirrups showed a sudden drop of load bearing capacity with horizontal cracking at the position of tensile longitudinal reinforcement. However, horizontal cracks were not appeared at the location of longitudinal reinforcement for the specimens with steel fiber. And these specimens showed gradual decrease of load bearing capacity after experiencing peak load. In particular, it was found that the strain at the position of the tensile longitudinal reinforcements of the specimens to which the mixing ratio of 2% was applied exceeds the yield strain. As a result of measuring the strain on the concrete surface, it was found that the fiber was more effective in preventing damage to the concrete surface than the stirrups for short lap spliced region.