• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.505-510
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• 2008

FBG Sensor, which is smaller than strain gauge and has better durability and does not have a noise from electromagnetic waves, was adapted to develope a smart anchor. A series of pullout tests were performed to verify the feasibility of smart anchor and find out the load transfer mechanism around the steel wire fixed to rock with grout. Distribution of shear stresses at steel wire-grout interface is assessed from the measured strain distribution by the optical fiber sensors and compared with stress distributions predicted by Farmer's and Aydan's formulas. It was found that present theoretical formulas may underestimate the failure depth and magnitude of shear stresses when the pullout loads increase.

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.129-136
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• 1999

For the prediction of concrete-steel bond ability in reinforced concrete, many countries establish specifications for the pullout test. But these methods hardly to consider many parameters such as strength, shape, diameter and location of steel, concrete restrict condition by loading plate, strength of concrete and cover depth etc, and it is difficult to solve concentration and disturbance of stress. The purpose of this study is to propose a New Ring Test method which can be rational quantity evaluations of bond splitting mechanism. For this purpose, pullout test was carried out to assess the effect of several variables on bond splitting properties between reinforcing bar and concrete. Key variables are concrete compressive strength, concrete cover, bar diameter and rib spacing. Failure mode was examined and maximum bond stress-slip relationships were presented to show the effect of above variables. As the result, it appropriately expressed general characteristics of bond splitting mechanism, and it proved capability for standard test method.

• Coupled systems mechanics
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• v.7 no.2
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• pp.197-209
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• 2018

Fiber-reinforced concrete (FRC) is a material with increasing application in civil engineering. Here it is assumed that the material consists of a great number of rather small fibers embedded into the concrete matrix. It would be advantageous to predict the mechanical properties of FRC using nondestructive testing; unfortunately, many testing methods for concrete are not applicable to FRC. In addition, design methods for FRC are either inaccurate or complicated. In three-point bending tests of FRC prisms, it has been observed that fiber reinforcement does not break but simply pulls out during specimen failure. Following that observation, this work is based on an assumption that the main components of a simple and rather accurate FRC model are mechanical properties of the concrete matrix and fiber pullout force. Properties of the concrete matrix could be determined from measurements on samples taken during concrete production, and fiber pullout force could be measured on samples with individual fibers embedded into concrete. However, there is no clear relationship between measurements on individual samples of concrete matrix with a single fiber and properties of the produced FRC. This work presents an inverse model for FRC that establishes a relation between parameters measured on individual material samples and properties of a structure made of the composite material. However, a deterministic relationship is clearly not possible since only a single beam specimen of 60 cm could easily contain over 100000 fibers. Our inverse model assumes that the probability density function of individual fiber properties is known, and that the global sample load-displacement curve is obtained from the experiment. Thus, each fiber is stochastically characterized and accordingly parameterized. A relationship between fiber parameters and global load-displacement response, the so-called forward model, is established. From the forward model, based on Levenberg-Marquardt procedure, the inverse model is formulated and successfully applied.

• Journal of the Korean Geotechnical Society
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• v.30 no.2
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• pp.5-18
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• 2014

Depending on the underground load support mechanism, anchors are classified as friction anchors, bearing plate anchors and the recently developed combined friction-bearing plate anchors which combine the characteristics of both the friction and bearing plate type anchors. Even though numerous studies have been performed on bearing plate anchors, there were only few studies performed to observe the failure surface of bearing plate anchors. Furthermore most of the soil materials used on these tests were not real sand but carbon rods. In this study, sand was placed in the soil tank and laboratory tests were performed with bearing plate anchors installed with an embedment depth (H/h) ranging from 1~6. The variation in the pullout capacity and the behaviour of soil with the embedment depth (H/h) were observed. Ground deformation analysis program was also used to analyze soil displacement, zero extension direction, maximum shear strain contours. It was determined from the analysis of the results that at ultimate pullout resistance the deformation was 5 mm and the failure surface occurred in a narrower area when compared with results of the previous researches. It was also observed that the width of the fracture surface gradually becomes wider and expands up to the surface as the deformation increases from 10 mm to 15 mm.

• Journal of the Korea Concrete Institute
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• v.22 no.6
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• pp.777-786
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• 2010

This paper examines the flexural behavior of full-scale prestressed concrete girders that were constructed of steel fiber reinforced ultra high performance concrete (UHPC). This study is designed to provide more information about the bending characteristics of UHPC girders in order to establish a reasonable prediction model for flexural resistance and deflection for future structural design codes. Short steel fibers have been introduced into prestressed concrete T-girders in order to study their effects under flexural loads. Round straight high strength steel fibers were used at volume fraction of 2%. The girders were cast using 150~190 MPa steel fiber reinforced UHPC and were designed to assess the ability of steel fiber reinforced UHPC to carry flexural loads in prestressed girders. The experimental results show that steel fiber reinforced UHPC enhances the cracking behavior and ductility of beams. Moreover, when ultimate failure did occur, the failure of girders composed of steel fiber reinforced UHPC was observed to be precipitated by the pullout of steel fibers that were bridging tension cracks in the concrete. Flexural failure of girders occurred when the UHPC at a particular cross section began to lose tensile capacity due to steel fiber pullout. In addition, it was determined that the level of prestressing force influenced the ultimate load capacity.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.239-243
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• 2003

A reducing bearing angle theory for bond of ribbed reinforcing bars to concrete is proposed to simulate experimental observation. Analytical expressions to determine bond strength for splitting and pullout failure are derived, where the bearing angle is a key variable. As bearing angle is reduced, splitting strength decreases and shearing strength increases. The proposed reducing bearing angle theory is effective to simulate damage of the deformed bar-concrete interface and understand bond mechanism of ribbed reinforcing steel in concrete structures.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.132-135
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• 2003

Mechanical anchorage can substitute a standard hook. To enhance the workability and economical benefit of mechanical anchorage, the size of anchor plate should be optimized. In this paper, the pull-out behaviors such as strength, failure mode, and crack patterns of mechanically anchored reinforcement in concrete are investigated using nonlinear finite element analysis. The nonlinear finite element analysis results are consistent with the experimental results. These results show that the optimal anchor plates can be designed using the nonlinear finite element analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.11
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• pp.250-258
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• 2019

The seismic performance and stability of operating facilities installed in domestic power plants need to be verified because of the increased incidence of earthquakes resulting in power plant damage due to the overturning failure of electric operating facilities. In this study, a structural performance evaluation of the anchor bolts constructed to setup the operating facilities on concrete slabs was carried out through an on-site inspection of power plants, called Daechung-Dam. M10 J hook and M12 J hook anchor bolts were installed in the field unit. According to the ASTM E 488-96 specifications, anchor bolt pullout and shear tests were carried out and compared with the anchor-bolt design standards. The results from the tension and shear pullout tests showed that the M10 and M12 J hook anchor bolts had higher performance than the required design load. Thus, they were found to be safe enough. Nevertheless, more research in the field of analytical study will be needed in the near future.

• Journal of the Korea Institute of Building Construction
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• v.9 no.6
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• pp.141-149
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• 2009

The objective of this study was to propose a development length equation for bottom and top GFRP bars. Including the bottom and top GRPP bars, a total of 104 modified pullout tests were completed. The test variables were embedment length (15, 30, 45db), net cover thickness (0.5~2.0db), different GFRP bar types, and bar diameters (10, 13, 16mm). The average bond stresses were determined based on the modified pullout test results. Two variable linear regression analyses were performed on the results of the average bond stresses. Utilizing the 5% fractile concept, a conservative development length design equation was derived. The design equation of the development length for bottom and top GFRP bars was proposed and the design equation derived in this study was compared to the ACI 440.1R-06 committee equation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2469-2475
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• 2014

In 1990s, with the increase of domestic building renovation but also increase the amount of anchor. The 45-degree cone failure theory has been used in concrete anchor bolts design, but the CCD (concrete capacity design) method was adopted as a new design method since 2000. However, the method has some problems because it is based on the experimental results of pre-installed concrete anchor bolts. In this study, the objective is to investigate the effects of anchor edge distance, anchor interval and concrete strength on pullout characteristics of post-installed concrete set anchor embedded in plain concrete.