• Tunnel and Underground Space
• /
• v.20 no.5
• /
• pp.332-343
• /
• 2010

This study aims to evaluate the supporting effect of a spiral bolt that is superior to a rock bolt in terms of constructability, stability, environmental and economic aspects as a support system. This study thus analyzed the mechanical properties of a rock bolt which is widely used as a support and a spiral bolt. In addition, laboratory pull-out tests were conducted for the evaluation of properties of the supports such as displacement, pull-out load, confining pressure etc. Moreover, the differences between a rock bolt and a spiral bolt were drawn by comparing the two results of laboratory pull-out tests and in-situ pull-out tests. Then, the differences of the supporting effect of the two supports were analysed by comparing the results of the two pull-out tests with a numerical analysis using FLAC3D.

• Journal of the Korean Geotechnical Society
• /
• v.31 no.2
• /
• pp.27-37
• /
• 2015

The micropile is small diameter pile foundation of which diameter is below 300 mm. This system has been applied to reinforce the foundation structure. In the present study, the effects of embedded conditions of group micropiles were investigated from a series of uplift load tests. For the study, uplift load tests were performed using group micropiles in various pile spacing and installation angle. The increase of uplift resistance and the reduction of uplift displacement were investigated in the tests. As the result, the resistances were principally changed by embedded pile angle, the resistance increase were 33%, 59% and 5% for $15^{\circ}$, $30^{\circ}$ and $45^{\circ}$ of embedded pile angle. The uplift displacement reduction increases with lower pile spacing condition and the reduction ratios of uplift displacements in the same spacing condition were 50%, 53%, -45% for $15^{\circ}$, $30^{\circ}$ and $45^{\circ}$ of embedded pile angle.

• Journal of the Korea Concrete Institute
• /
• v.22 no.4
• /
• pp.575-583
• /
• 2010

This research investigated the influence of the number of twist on single fiber pullout behavior of Twisted steel (T-) fiber and tensile behavior of high performance cementitious composites reinforced with the (T-) fibers (HPFRCC). Micromechanical pullout model for T- fibers has been applied to analytically investigate the influence of various fiber parameters including the number of twist on single fiber pullout behavior; and, to optimize the number of twist to generate larger pullout energy during fiber pullout without fiber breakage. In addition, an experimental program including single fiber pullout and tensile tests has been performed to investigate the influence of twist ratio experimentally. Two types of T- fiber with different twisted ratios, T(L)- fiber (6ribs/30 mm) and T(H)- fiber (18ribs/30 mm), were tested. T(L)- fiber produced higher equivalent bond strength (larger pullout energy) although T(H)- fiber produced higher pullout stress during pullout since T(H)- fiber showed fiber breakage during pullout. Tensile test results confirmed that T(L)- fiber in high strength mortar generates better tensile performance of HPFRCC, e.g., load carrying capacity, strain capacity and multiple micro-cracking behavior.

• Journal of the Korean Geotechnical Society
• /
• v.39 no.12
• /
• pp.23-35
• /
• 2023

The Ministry of Agriculture, Food and Rural Affairs has announced design standards for disaster-resilient greenhouses capable of resisting wind speeds with a 30-year frequency to respond to the destruction of greenhouses caused by strong winds. However, many greenhouses are still being maintained or newly installed as conventional standard facilities for the supply type. In these supply-type greenhouses, a small pile called a steel peg is used as reinforcement to resist wind-induced damage. The wind resistance of steel pegs varies depending on the soil environment and installation method. In this study, a correlation analysis was performed between the wind resistance of steel pegs installed in loam and sandy loam, using a soil hardness meter. To estimate the pull-out force of steel pegs based on soil water content and compaction, soil compaction tests and laboratory soil box and field tests were performed. The soil compaction degree was measured using a soil hardness meter that could easily confirm soil compaction. This was used to analyze the correlation between the soil compaction degree in the tests. In addition, a correlation analysis was performed between the pull-out force of steel pegs in the soil box and field. The findings of this study will be useful in predicting the pull-out force of steel pegs based on the method of steel peg installation and environmental changes.

• Journal of the Korea Concrete Institute
• /
• v.23 no.4
• /
• pp.461-469
• /
• 2011

In this study, the effect of polyvinyl alcohol (PVA) fiber volume fraction on the pullout behavior of structural synthetic fiber in hybrid structural synthetic fiber and PVA fiber cement composites are presented. Pullout behavior of the hybrid fiber cement composites and structural synthetic fiber were determined by dog-bone bond tests. Test results found that the addition of PVA fiber can effectively enhance the structural synthetic fiber cement based composites pullout behavior, especially in fiber interface toughness. Pullout test results of the structural synthetic fiber showed the interface toughness between structural synthetic fiber and PVA fiber reinforced cement composites increases with the volume fraction of PVA fiber. The microstructural observation confirms the incorporation of PVA fiber can effectively enhance the interface toughness mechanism of structural synthetic fiber and PVA fiber reinforced cement composites.

• Journal of the Korean GEO-environmental Society
• /
• v.17 no.10
• /
• pp.55-62
• /
• 2016

The frequency slope over a year due to climate collapse is connected with huge casualties and property damage, but the situation rarely reduce the damage that gradually increases in size. In order to suppress this, engineers are improved better reinforcement and continued efforts to improve the shear force or withdrawal force. In this study, the GangWhaGu attached to the nail tip that improves the soil nail pullout resistance, and a method to increase the nail integral GangWhaGu maximize the contact area soil - by increasing the friction of the grout seems to increase the effect of slope stability. In order to validate the experiment to determine the effect of reinforcing the soil nail pullout tests of indoor and Behavior GangWhaGu nail and through field tests were conducted and applicability. Experimental results, the case of a pull-out test compared to the GangWhaGu nail through the tensile force of the nail were to increase by approximately 20%.

• Journal of the Korean Wood Science and Technology
• /
• v.41 no.3
• /
• pp.211-220
• /
• 2013

The nailed joints in wood construction are commonly designed to resist and carry the lateral load but also subject to withdrawal force like uplift load due to the wind. This research was conducted to evaluate the performance of nailed joint composed of dimension lumber and sheathing materials through the nail withdrawal and unsymmetric double shear joint test, and then compared to current design values. The withdrawal strength was greatly dependant on wood specific gravity, and the withdrawal strength of I-joist with OSB showed higher value in spite of low specific gravity. The maximum withdrawal loads were greater than that of derived current design values about 5 times. The lateral resistance of Japanese larch/OSB nailed joints was higher than that of SPF/OSB nailed joint, and derived allowable lateral strength of nailed joints in this study exceeded the current design values. The failure mode of nailed joints was primarily due to the nail bending and this tendency was notable in SPF/OSB nailed joint.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.18 no.2
• /
• pp.191-200
• /
• 2005

To develop composite bridge deck, comparative study on the flexural characteristics of deck fabricated with filament winding and pultrusion was performed. In this study, composite deck of triangular shape was fabricated with filament winding process and flexural tests were conducted along with pultruded 'Duraspan' deck. Failure load, maximum deflection and strains were compared with each other. Also finite element analysis for filament winding deck was carried out and the results were compared with those from experiments.

• Journal of the Korean Geotechnical Society
• /
• v.33 no.1
• /
• pp.67-77
• /
• 2017

In the present study, uplift load carrying behavior of micropiles with installation angle and pile spacing was investigated based on uplift load tests using single and group micropiles. In addition, evaluation methods of uplift load carrying capacity of group micropiles were proposed based on FHWA (2005) and Madhav (1987) and they were compared with test results to confirm the validity of proposed methods. From the test results, uplift load carrying capacities of single and group micropiles increased with the increase of the installation angle up to $30^{\circ}$, whose values also increased slightly with increasing pile spacing. For the proposed method based on FHWA (2005), the estimated values were similar to measured values up to $15^{\circ}$ of installation angle and 5D of pile spacing. For the proposed method based on Madhav (1987), on the other hand, it was observed that the estimated values were in good agreement with measured values in all installation conditions.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.7 no.3
• /
• pp.271-278
• /
• 2019

The corrosion of reinforcements embedded in concrete causes severe deterioration in reinforced concrete structures. As a countermeasure, epoxy coated reinforcements are used to prevent corrosion of reinforcements. When epoxy coated bars are used, the resistance of corrosion is excellent, but epoxy coating on the bars have a disadvantage of reduction in bond capacity comparing to that of normal bars. Therefore, it is necessary to confirm the bond performance of epoxy coated reinforcements through experimental and analytical methods. Bond behaviors of epoxy coated bars for various diameters of 13 and 19mm and thicknesses of cover concrete of 3 types(ratio of cover to bar diameter) are examined. As the diameters of the epoxy coated bars increase, the difference of bond strength between epoxy coated and uncoated bars also increases and damage patterns showed pull out failure. In addition, finite element analysis was performed based on the bond-slip relationship obtained by direct pullout test and compared with the flexural test results. It is considered that flexural member test is more useful than pullout test for simulating the behavior of actual structure.