• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.6
• /
• pp.67-73
• /
• 2017

Recently, the demand for large diameter piles has been rapidly increased in order to secure the allowable bearing capacity of pile foundation due to the increase of large structures such as high rise buildings. In this study, to improve the shear capacity of a conventional PHC pile, a large diameter composite PHC pile strengthened by in-filled concrete and shear reinforcement was manufactured. All the piles were tested according to the shear strength test method of Korean Standard. As a result of the shear test, the F-type piles which are produced without shear reinforcement occurred abrupt horizontal cracks after flexural and inclined shear cracks occurred. On the contrary, the FT-type piles which are produced with shear reinforcement exhibited stable flexural and inclined shear cracks uniformly over the entire pile without abrupt horizontal cracks. Furthermore, the maximum load of the large diameter composite PHC pile improved to 2.9 times in the F series, and more than 3.3 times in the FT series compared to the conventional PHC pile. This result indicated that FT-type piles had excellent composite behavior due to the shear reinforcement and effectively prevented the unstable growth of inclined shear cracks.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.18 no.2
• /
• pp.201-211
• /
• 2005

Due to the complex mechanism and various parameters that affect shear behavior of reinforced concrete (RC) members, models on shear tend to be complex and difficult to utilize for design of structural members, and empirical relationships formulated with limited test data often work lot members having a specific range of influencing parameters on shear. As an alternative approach tot solving this problem, artificial neural networks have been suggested by some researchers. In this paper, artificial neural networks were used to predict shear strengths of RC beams without shear reinforcement. Especially, a large database that consists of shear test results of 398 RC members without shear reinforcement was used for artificial neural network analysis. Three well known approaches for shear strength of RC members, ACI 318-02 shear provision, Zsutiy's equation, and Okamura's relationship, are also evaluated with test results in the shear database and compared with neural network approach. While ACI 318-02 provided inaccurate predictions for RC members without shear reinforcement, the empirical equations by Zsutty and Okamura provided more improved prediction of Shear strength than ACI 318-02. The artificial neural networks, however provided the best prediction of shear strengths of RC beams without shear reinforcement that was closest to test results.

• Journal of the Korea Concrete Institute
• /
• v.24 no.4
• /
• pp.407-414
• /
• 2012

The purpose of this study is to experimentally investigate the shear behavior of reinforced concrete beams embedded with GFRP (glass fiber reinforced polymer) plate with openings. In this study, the parameters include the shape of reinforcement, reinforcement area, and thickness and width of reinforcements. The test was performed on 9 specimens with shear spanto-depth ratio of 2.8. When the reinforcement area was varied, the GFRP plate showed 3.6 times greater shear strength than steel stirrup. The test result showed that shear strength increased as reinforcement area increased. Also, when the shape of a parallelogram GFRP plate was used, it showed higher shear strength than that with rectangular shape. Effect of thickness and width of reinforcement showed that shear capacity increased as width increased. For a comparison study, a calculation of the shear strength of reinforced beams with GFRP plate based on the ACI 318M-08 was compared with the test results. The test results were compared with the maximum shear reinforcement areas required by ACI 318M-08, CSA-04, and EC2-02 provision.

• Journal of the Korea Concrete Institute
• /
• v.26 no.2
• /
• pp.189-199
• /
• 2014

Currently, in the precast concrete construction, Precast Concrete (PC) and Cast-In-Place (CIP) concrete with different concrete strengths are frequently used. However, current design codes do not specifically provide shear design methods for PC-CIP hybrid members using dual concrete strengths. In the present study, simply supported composite beams with shear reinforcement were tested. The test variables were the area ratio of the two concretes, spacing of shear reinforcement, and shear span-to-depth ratio. The shear strengths of the test specimens were evaluated by current design codes on the basis of the test results. The results showed that the shear strength of the composite beams was affected by the concrete strength of the compressive zone and also proportional to the flexural rigidity of un-cracked sections. Furthermore, the contribution of shear reinforcements varied according to the concrete strength of the compressive zone.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.5
• /
• pp.86-94
• /
• 2022

Replacement of FRP rod as steel reinforcement has been attracted significantly to prevent the degradation of the concrete structure due to corrosion. So, the technology development to extend the structure's service life by improving FRP properties has been proceeded worldwide. Accordingly, it is necessary to develop Korea's CFRP rod and CFRP grid, including the manufacturing techniques to improve the properties of high-strength and high-stiffness. Moreover, the research should be conducted to evaluate the structural behavior of the beams using the CFRP rod or grid. This study investigates the flexural and shear behavior of reinforced concrete beam using demonstrated CFRP rod as reinforcement according to the reinforcement ratio and shear span to depth ratio. From the results, when the reinforcement ratio is out of a specific range, it is seemed that the effect on performance improvement of the beam using CFRP rod is cancelled or not significant. Meanwhile, when the CFRP rod was used as reinforcement, the possibility of shear failure occurred, even steel stirrups were installed in the beam with CFRP rod as tensile reinforcement according to the Korean Design Standard. Therefore, when the CFRP rod is used as tensile reinforcement in a beam, it should be prepared that a specific limitation of reinforcement ratio and an investigation against shear failure. Also, the ductility of the beam using the CFRP rod is determined by the deformation energy evaluation method. So, the ductility should be investigated by applying the deformation energy evaluation method that reflects the structural behavior of the beam.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05a
• /
• pp.190-193
• /
• 2006

The definition of the Dual system is that the total seismic force resistance is to be provided by the combination of the moment frame and the shear walls or braced frames in proportion to their stiffness and the moment frame shall be capable of resisting at least 25% of the design force in Korean Building Code 2005 (KBC 2005). But, the definition of moment frame is ambiguous whether the moment frame include the imaginary columns in the shear wall (Case I) or include only the columns outside the shear wall (Case II). 60-story RC building was designed as dual system for Case I and Case II, and the required strength and reinforcement are compared. Moment and axial capacity of the shear wall of Case II decreased about 5% due to the absence of the column in the shear wall. The requirement of upper and bottom reinforcement of slab in Case II increased 13% and 40%, respectively, when compared to those of Case I. The required longitudinal reinforcement in columns for Case II is about 1.5 times larger than that of Case I.

• Journal of the Korea Concrete Institute
• /
• v.27 no.6
• /
• pp.603-613
• /
• 2015

In current design codes, minimum shear reinforcement is required for reinforced concrete flexural members, and the use of steel fiber reinforced concrete is permitted to replace the minimum shear reinforcements. In the present study, to estimate the effects of shear reinforcements and fibers on shear strength, simply supported beams were tested under transverse loading. The test results showed that the shear strength was significantly increased by the use of fibers. Particularly, the effect of fiber reinforced concrete was pronounced when high-strength concrete was used. The performance of fiber reinforced concrete for minimum shear reinforcement was evaluated using results of the present study and existing tests.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.11 no.4
• /
• pp.99-108
• /
• 2007

In the flat-plate slab design of the KCI and ACI building code, the punching shear strength of connections with shear reinforcement can increase one and half times to that of connections without shear reinforcement. And the ACI-ASCE committee 352 recommendations propose limiting the direct shear ratio $V_g$/$V_c$ on interior connections to 0.4 to insure adequate drift capacity. In this study, four interior column-slab connections were tested to look into the punching shear strength and the lateral displacement capacity of the flat-plate slab with and without shear reinforcement under cyclic lateral loading. Based on the test results, it is found that the provision about punching shear strength in the codes may appropriate for the gravity loading only whereas it is unconservative for the lateral loading and that the limit of ACI-ASCE committee 352 appears conservative.

• Journal of the Society of Naval Architects of Korea
• /
• v.54 no.3
• /
• pp.242-249
• /
• 2017

A design system for doubler reinforcement of the ship plate members subjected to in-plane shear and biaxial compressive loads was developed. This design system of doubler reinforcement on ship plate members established by design supporting system and this system was based on the buckling evaluation process of ship plate members for these in-plane loads. Each design parameters were suggested by equations as the form of influence coefficients for the doubler reinforcement subjected to the various in-plane loads including shear load. Strength of doubler plate member reinforced on the plate member could be suggested by the equivalent flat plate thickness after the consideration of corelation equations in the design system of doubler reinforcement. Level of strength recovery of ship plate members for these in-plane loads according to the local reinforcement by doubler could be suggested by use of this design system in the initial repair design stage of shipyards.

• Computers and Concrete
• /
• v.14 no.1
• /
• pp.1-18
• /
• 2014

The addition of steel fibers in concrete mixture is recognized as a non-conventional mass reinforcement scheme that improves the torsional, flexural, and shear behavior of structural members. However, the analysis of fiber reinforced concrete beams under combined torsion, bending, and shear is limited because of the complicated nature of the problem. Therefore, nonlinear 3D finite element analysis was conducted using the "ANSYS CivilFEM" program to investigate the behavior of fiber reinforced concrete L-beams. These beams were tested at different reinforcement schemes and loading conditions. The reinforcement case parameters were set as follows: reinforced with longitudinal reinforcement only and reinforced with steel bars and stirrups. All beams were tested under two different combined loading conditions, namely, torsion-to-shear ratio (T/V) = 545 mm (high eccentricity) and T/V = 145 mm (low eccentricity). Eight intermediate L-beams were constructed and tested in a laboratory under combined torsion, bending, and shear to validate the finite element model. Comparisons with the experimental data reveal that the program can accurately predict the behavior of L-beams under different reinforcement cases and combined loading ratios. The ANSYS model accurately predicted the loads and deformations for various types of reinforcements in L-beams and captured the concrete strains of these beams.