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

• Steel and Composite Structures
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• v.48 no.1
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• pp.43-57
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• 2023

The impacts of waste tire rubber (WTR) on the bending conduct of reinforced concrete beams (RCBs) are investigated in visualization of experimental tests and 3D finite element model (FEM) using both ANSYS and SAP2000. Several WTR rates are used in total 4 various full scale RCBs to observe the impact of WTR rate on the rupture and bending conduct of RCBs. For this purpose, the volumetric ratios (Vf) of WTR were chosen to change to 0%, 2.5%, 5% and 7.5% in the whole concrete. In relation to experimental test consequences, bending and rupture behaviors of the RCBs are observed. The best performance among the beams was observed in the beams with 2.5% WTR. Furthermore, as stated by test consequences, it is noticed that while WTR rate in the RCBs is improved, max. bending in the RCBs rises. For test consequences, it is clearly recognized as WTR rate in the RCB mixture is improved from 0% to 2.5%, deformation value in the RCB remarkably rises from 3.89 cm to 7.69 cm. This consequence is markedly recognized that WTR rates have a favorable result on deformation values in the RCBs. Furthermore, experimental tests are compared to 3D FEM consequences via using ANSYS software. In the ANSYS, special element types are formed and nonlinear multilinear misses plasticity material model and bilinear misses plasticity material model are chosen for concrete and compression and tension elements. As a consequence, it is noticed that each WTR rates in the RCBs mixture have dissimilar bending and rupture impacts on the RCBs. Then, to observe the impacts of WTR rate on the constructions under near-fault ground motions, a reinforced-concrete building was modelled via using SAP2000 software using 3-D model of the construction to complete nonlinear static analysis. Beam, column, steel haunch elements are modeled as nonlinear frame elements. Consequently, the seismic impacts of WTR rate on the lateral motions of each floor are obviously investigated particularly. Considering reduction in weight of structure and capacity of the members with using waste tire rubber, 2.5% of WTR resulted in the best performance while the construction is subjected to near fault earthquakes. Moreover, it is noticeably recognized that WTR rate has opposing influences on the seismic displacement behavior of the RC constructions.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.705-714
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• 2012

Precast reinforced concrete bridge columns with hollow rectangular section were tested under cyclic lateral load with constant axial force to investigate its seismic performance. After all the precast column segments were erected, longitudinal reinforcement was inserted in the sheath prefabricated in the segments, which were then mortar grouted. Main variables of the test series were column aspect ratio, longitudinal reinforcement ratio, amount of lateral reinforcement, and location of segment joints. The aspect ratios were 4.5 and 2.5, and the longitudinal steel ratios were 1.15% and 3.07%. The amount of lateral reinforcement were 95%, 55%, 50%, and 27% of the minimum amount for full ductility design requirements in the Korean Bridge Design Code. The locations of segment joints in plastic hinge region were 0.5 and 1.0 times of the section depth from the bottom column end. The test results of cracking and failure mode, axial-flexural strength, lateral load-displacement relationship, and displacement ductility are presented. Then, safety of the ductility demand based seismic design in the Korean Bridge Design Code is discussed. The column specimens showed larger ductility than expected, because buckling of longitudinal reinforcing bar was prevented due to confinement developed not only by transverse steel but also by sheath and infilling mortar.

• Magazine of the Korea Concrete Institute
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• v.7 no.6
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• pp.233-241
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• 1995

In this thesis, the fatigue tests were performed on a series of R /C beams repaired with co& crete-lmlyrner composites to investigate the fatigue bahavior. The three point loading system is used in the fatigue tests. In these tests, relations between the repeated loading cycles and mid-span deflections, number of repeated loading cycles when repaired beams were fractured, the bonding performance of repair materials were observed. On this basis, the mid-span deflections, the crack growth and failure mode of repaired R /C beams were studied. A S-N curve was drawn to present the fatigue strength of repaired beams. From the test results, it was shown that behavior of R /C beams repaired with polymer-cement series were very sirnillar to control beam about bonding performance, mid-span deflections and fatigue strength according to S-N curve drawn by the regression anlysis on the fatigue test results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.3
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• pp.139-148
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• 2015

The purpose of this paper is to induce the ductile behavior of the UHPFRC member after the peak load by using the bundle of longitudinal reinforcing bar as a substitute for steel fiber. Experiments on the flexural behavior of the Ultra High Performance Concrete rectangular beam with the combination of the steel fiber and longitudinal reinforcing bar were carried out. The volume fractions of steel fiber are 0%, 0.7%, 1%, 1.5%, 2% and the reinforcement ratios of longitudinal reinforcing bar which induce the ductile behavior are 0.0036, 0.016, 0.028 and 0.036. 15 UHPC beams were made with the combination of these test factors. Not only steel fiber but also bundle of longitudinal reinforcing bar has the effect to induce ductile behavior of UHPC structural member. The combination of 0.7% volume fraction of steel fiber and 0.028 reinforcement ratio showed the most economic combination. The relationship of load-deflection, strain variation of the concrete and the crack pattern indicate the usefulness of the bundle of the longitudinal bar which has small diameter with close arrangement each other.

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

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.1
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• pp.71-77
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• 2023

This study aims to investigate the structural performance of hollow-core slab (HCS) memebers with 400 mm thickness. To this end, a total of four HCS specimens were fabricated based on the individual mold method to provide shear reinforcement, unlike the extrusion method. The key variables were chosen as the presence of topping concrete, core-filling concrete, and shear reinforcements. The crack patterns and load-displacement responses of the test specimens were analyzed in detail. Test results showed that inclined shear cracking occurred all the specimens, and that the specimen with shear reinforcement on the web of HCS unit had higher strength and ductility than the specimen without shear reinforcement. In particular, shear reinforcements placed on the web of HCS unit effectively resisted not only to vertical shear force but also to horizontal shear force between the interface of HCS unit and topping concrete. In addition, it was discovered that the method in which shear reinforcements are placed on the web of HCS unit is more effective in improving structural performance than core-filling method.

• Journal of Korean Society of Steel Construction
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• v.29 no.3
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• pp.249-260
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• 2017

In order to investigate the structural performance of a novel prefabricated-SRC column using bolt-connected steel angles(PSRC column), eccentric axial loading tests were performed for six PSRC column specimens and two conventional SRC column specimens. The test parameters were the spacing and sectional configurations of lateral reinforcement, and eccentricity ratio of axial load. The test results showed that, due to high axial-stiffness of the angles located at the corners of the cross section, the compressive load-carrying capacity and deformation capacity of the PSRC specimens were greater than those of the SRC specimens in the large eccentricity ratio of axial load. Closely spaced lateral steel plates and Z-shaped lateral steel plates improved lateral confinement, which increased the load-carrying capacity of the PSRC specimens. The combined flexural and axial load-carrying capacity of the specimens by tests and nonlinear numerical analysis were greater than the predictions by current design codes. The numerical analysis agreed well with the test results including the initial stiffness, peak strength, and post-peak strength degradation.

• Journal of the Korea Concrete Institute
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• v.16 no.4 s.82
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• pp.493-500
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• 2004

FREP(Fiber Reinforced Epoxy Panel) are used for strengthening the damaged RC beams due to its good tensile strength, low weight, resistance to corrosion, and easy applicability. This study sets up structure equation for FREP bending reinforcement before and during the usage of RC beam. It finds the difference and finds the mechanical characteristics of rip-off failure that is caused by stress concentration in reinforcement material cutting part to estimate the performance of bending reinforcement. The result of this research can be summarized as two main consequences. The main failure of FREP reinforced concrete beam is rip-off failure and it evaluated rip-off failure of RC reinforcing bean based on the test and analytical conditions of this study. It found that stress was concentrated due to rapid change of bending rigidity in reinforced cutting part as a result of excessive reinforcement thickness of FREP. It resulted in rip-off failure. It means that it should evaluate the rip-off failure when designing reinforcement. It analyzed the reinforcement effect according to reinforced period for FREP. It found that reinforcement effect of P-Type that was reinforced during the usage decreased compared to I-Type that was reinforced before the usage. So when reinforcing a existing structure that is being used, it should consider the stress that is produced due to the fixed load.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.147-156
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• 1999

An investigation was conducted into the flexural behavior of earthquake damaged reinforced concrete columns repaired with carbon fiber sheets. Six column specimens were tested to failure under reversed cyclic loading. Two columns were specimens for control with no sheets and tested. These columns were repaired with carbon fiber sheets and retested to evaluate the effect of the confinement of the carbon fiber on the damaged column. Another two columns were repaired and tested with no pre-cyclic loading. The test specimens were designed to model single bent under a constant axial force with reversed cyclic lateral loading. Carbon fiber sheets were used to repair damaged concrete columns in the critically stressed areas near the column footing joint and the physical, mechanical properties of carbon fiber sheets are described. The performance of repaired columns in terms of their hysteretic response is evaluated and compared to those of the original columns. The results indicate that the repaire technique with carbon fiber sheets is highly effective. Both flexural strength and displacement ductility of repaired columns were higher than those of the original columns.