• Computers and Concrete
• /
• v.34 no.4
• /
• pp.503-517
• /
• 2024

This study presents an analysis model to estimate the shear strength of a reinforced concrete (RC) member with corroded tensile reinforcements. The thick-walled cylinder theory was modified to fit the dual potential capacity model to reflect interdependent failure mechanisms, including the degradation effect of bonds in corroded tensile reinforcement. In the proposed model, it is considered that the shear failure of corroded RC members with no proper anchorage detail is primarily dominated by the flexural-bond mechanism, where insufficient bond strength is provided owing to corrosion damage. However, when tensile reinforcements are properly anchored in the end regions using end hooks or mechanical devices, it is assumed that the tied-arch action can be developed as a secondary shear transfer mechanism, even under severe corrosion damage. The proposed model was verified by comparison with shear test results of corroded RC members collected from the literature, and it appeared that the proposed model can estimate their shear strengths with a good level of accuracy, regardless of various anchorage details and corrosion rates in tensile reinforcements.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.24 no.6
• /
• pp.495-512
• /
• 2022

Due to the concentration of population in the city center, the aboveground structures are saturated, and the development of underground structures becomes important. In addition, it is necessary to apply the reinforcement construction method for the pillar part of the adjacent tunnel that can secure stability, economy, and workability to the site. In this study, the tunnel pillar reinforcement method using prestress and grouting was reviewed. There are various reinforcement methods that can compensate for the problems of the side tunnel, but as the tunnel pillar construction method using prestress and grouting is judged to be excellent in field applicability, stability, and economic feasibility, it is necessary to review the theoretical and numerical analysis of the actual behavior mechanism. Therefore, a scaled-down model experiment was conducted. The reduced model experiment was divided into PC stranded wire + steel pipe reinforcement grouting + prestress (Case 1), PC strand + steel pipe reinforcement grouting (Case 2), and no reinforcement (Case 3), and the displacement of the pillar and the earth pressure applied to the wall were measured. Through experiments, it was confirmed that the PC stranded wire + steel pipe reinforcement grouting + prestress method is the most excellent reinforcement method among various construction methods. It was judged that it could be derived.

• Tunnel and Underground Space
• /
• v.17 no.4
• /
• pp.255-265
• /
• 2007

As the mechanism and effect range of subsidence are altered according to the various conditions (the ground condition, the earth pressure, the geometric condition of underground cavity and the structure load), the analysis and prediction of subsidence in abandoned mining area are very difficult. Also, as the geological characteristics and the mining methods are differed in each mines, the application of the pre-existing reinforcements without improvement has a lot of difficulties and limits. In this study, the various underground investigation such as long-depth core drilling, seismic tomography and BIPS (borehole image processing system) were performed, the distribution of underground cavity and coal seam and rock relaxation condition were analyzed. And we predicted the type of subsidence and estimated the subsidence by theories of mining subsidence. With these results, we analyzed the mechanism of subsidence occurrence in the research object area. Finally, we improved existing methods which were applied to the abandoned mining area and also we established the rational reinforcement for the ground and structure foundation against each subsidence cause.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.5 no.3
• /
• pp.23-30
• /
• 2002

In recently, using of steel reinforcements by reinforcing materials of the reinforced earth, micro-pile and root-pile etc,. is wide-spreading in the stabilizing control of cutting and embankment slopes, but the failure mechanism of reinforced earth as well as the effect of insert angles or types of reinforcement and others are not defined clearly. In this study, therefore heavy-duty direct shear tests were exercised on the reinforced soil and the non-reinforced soil, which was executed for research on the interaction of soil-reinforcement and theirs behavior. The hardness and softness and the standard sands were used for modeling of reinforced soil, the material constants for the computer simulation were estimated from the results of CD-Test. The effects of reinforcing and of friction increasing on the softness, area ratio of reinforcements is equal, were the better than them of the hardness, as well the reinforcing effects of shear strength without regard to the area ratio is much the same at $10^{\circ}$, insert angle of reinforced bar, differ from them of the existing study. Then, the results of numerical analysis showed that the behavior of reinforcements displayed bending resistance and shear resistance at $15^{\circ}$ and $30^{\circ}$, respectively. Also, the state of strain transfer was observed and the behavior of resistance mechanism on reinforcements presented almost the same them of landslides stabilizing pile.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.23 no.3
• /
• pp.133-149
• /
• 2021

This study aims to report the behavioral mechanism of steel pipe reinforcement grouting, which is being actively used to ensure the stability of the excavation surface during tunnel excavation, based on measurements taken at the actual site. After using a 12 m steel pipe attached with a shape displacement meter and a strain gauge to reinforce the actual tunnel surface, behavioral characteristics were identified by analyzing the measured deformation and stress of the steel pipe. Taking into account that the steel pipes were overlapped every 6 m, the measured data up to 7 m of excavation were used. In addition, the behavioral characteristics of the steel pipe reinforcement according to the difference in strength were also examined by applying steel pipes with different allowable stresses (SGT275 and SGT550). As a result of analyzing the behavior of steel pipes for 7 hours after the first excavation for 1 m and before proceeding with the next excavation, the stress redistribution due to the arching effect caused by the excavation relaxation load was observed. As excavation proceeded by 1 m, the excavated section exhibited the greatest deformation during excavation of 4 to 6 m due to the stress distribution of the three-dimensional relaxation load, and deformation and stress were generated in the steel pipe installed in the ground ahead of the tunnel face. As a result of comparing the behavior of SGT275 steel pipe (yield strength 275 MPa) and SGT550 steel pipe (yield strength 550 MPa), the difference in the amount of deformation was up to 18 times and the stress was up to 12 times; the stronger the steel pipe, the better it was at responding to the relaxation load. In this study, the behavior mechanism of steel pipe reinforcement grouting in response to the arching effect due to the relaxation load was identified based on the measured data during the actual tunnel excavation, and the results were reported.

• Journal of Korean Society of Steel Construction
• /
• v.23 no.1
• /
• pp.41-49
• /
• 2011

A long-span (more than 8m) plastic greenhouse is currently being used in farms due to its magnified benefits, such as the convenience of the farming equipment used, and the land usage efficiency. In this study, the reinforcing effects of the use of a pretension tie were shown. In a previous study, tests for a 6.5m single-span-type greenhouse announced by Rural Development Administration were carried out. The tests of symmetric and eccentrics now loading by the sun and wind were conducted for the 10.2m span with a ${\phi}48.1{\times}2.1$ section in this study, after which the load-deflection relationship was compared for the cases of reinforcement with a tie and without a tie. The results of the symmetric snow loading test showed that the strength increased by 68~93% in the case of the specimen with a tied arch. The failure mode of the specimen without a tie tended to be that with a sway failure mechanism, and that of the reinforcement specimens with a tie tended to be that with an arch buckling mechanism. The results of the eccentric snow loading test showed that the strength of the specimen with a tie increased by 10~20% compared to that of the specimen without a tie. For the failure mode of the latter, a combined failure mechanism was adapted, although the failure mode of the tied specimens tended to be that with an arch buckling mechanism.

• 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 Earthquake Engineering Society of Korea
• /
• v.12 no.4
• /
• pp.11-17
• /
• 2008

This study evaluates the seismic performance of post-tensioned flat plate structures with or without slab bottom reinforcement. For this purpose, 3 and 9 story frames were designed only considering gravity loads. This study conducts a nonlinear static pushover analysis. This study was an analytical model that is able to represent punching shear failure and fracture mechanism. The analytical results showed that the seismic performance of a post-tension flat plate is strongly influenced by the existence of slab bottom reinforcement through column. By placing slab bottom reinforcement in a PT flat plate frame, lateral strength and max drift capacity are significantly increased.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.18 no.3
• /
• pp.8-18
• /
• 2010

According to the needs of change to hybrid, fuel cell and electric vehicle, and to the increasing demand for safety and eco-friendliness, the necessity of Electro-Mechanical Brake(EMB) is being increased. But, one of the most important problems for realizing EMB to the practical use is that the required motor power for braking is too high. So the high braking efficient EMB is required. In recent years, the Electronic Wedge Brake(EWB) is noticeable for the high braking efficiency. In this research, we examine the improvable matter of the recent published EWB, and we propose the improved mechanism and the cost effective control method using this mechanism. And we test these feasibility by experiment and discuss these meaning and effect.

• Journal of the Korea Concrete Institute
• /
• v.12 no.3
• /
• pp.67-75
• /
• 2000

It was well recognized that the damages associated mainly with the aging of civil infrastructures were one of very serious problems for assurance of safety and reliability. Recently carbon fiber sheet(CFS) has been widely used for reinforcement and rehabilitation of damaged concrete beam. However, the fundamental mechanism of load transfer and its load-resistant for carbon fiber sheet reinforced concrete are not fully understood. In this study, three point bending test has been carried out to understand the damage progress and the micro-failure mechanism of CFS reinforced mortars. For this purpose, four different types of specimens are used, that is, mortar, steel bar reinforced mortar, CFS reinforced mortar, and steel bar and CFS reinforced morter. Acoustic Emission(AE) technique was used to evaluate the characteristics of damage progress and the failure mechanism of specimens. in addition, two-dimensional AE source location was also performed to monitor crack initiation and propagation processes for these specimens.