• Journal of Korean Society of Steel Construction
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• v.15 no.6 s.67
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• pp.649-660
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• 2003

The paper presents an evaluation of the tensile strength of the expansion anchor that can cause failure in the concrete based on the design of the anchorage. Tests of the heavy-duty anchor and the wedge anchor that are domestically manufactured and installed in plain concrete members are conducted to probe the effects of the embedded depth, concrete strength, and anchors spacing. The design of post-installed steel anchors is presented using the Concrete Capacity Design (CCD) approach. The CCD method is applied to predict the concrete failure load of the expansion anchor in plain concrete under monotonic loading for important applications. The concrete tension capacity of the fastenings with heavy-duty anchors and wedge anchors in plain concrete predicted using the CCD method is compared with the test results. For the CCD method, a normalization coefficient of 9.94 is appropriale for the nominal concrete breakout strength of an anchor or a group of wedge anchors in tension. On the other hand, a normalization coefficient of 11.50 is appropriate for the nominal concrete breakout strength of an anchor or a group of heavy-duty anchors in tension.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.6
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• pp.675-689
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• 2019

Development of smart construction materials with both self-strain and self-damage sensing capacities is still difficult because of little information about the self-damage sensing source. Herein, we investigate the effects of the matrix strength, fiber geometry, and fiber content on the electrical resistivity of steel-fiber-reinforced cement composites by multi-fiber pullout testing combined with electrical resistivity measurements. The results reveal that the electrical resistivity of steel-fiber-reinforced cement composites clearly decreased during fiber-matrix debonding. A higher fiber-matrix interfacial bonding generally leads to a higher reduction in the electrical resistivity of the composite during fiber debonding due to the change in high electrical resistivity phase at the fiber-matrix interface. Higher matrix strengths, brass-coated steel fibers, and deformed steel fibers generally produced higher interfacial bond strengths and, consequently, a greater reduction in electrical resistivity during fiber debonding.

• Journal of Korea Water Resources Association
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• v.30 no.3
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• pp.211-223
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• 1997

This study was focused on the investigation of the distribution of trees which is an important factor for the improvement of the river environment, and the experimental examination of resistant force of trees to the external forces. The investigation of plant distribution performed in 11 major rivers in Korea showed that the willow family grows spontaneously over the whole country. The field experiments on the resistant force of trees were carried out on the 78 trees of 8 species in 3 different sites to estimate whether pulled out trees damage downstream hydraulic structure. The experiments were performed by the method that a backhoe drew trees and the forces were measured when the trees were overturned and pulled out. The analysis of the experimental results showed that there is a linear correlation between the resistant force and DHB (diameter at breast height).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3A
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• pp.251-260
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• 2011

In this study, the effect of natural jute fiber volume fraction on the bond characteristics of polyolefin based macro fiber in natural jute fiber reinforced cement composites, including bond strength, interface toughness, and microstructure analysis are presented. The experimental results on polyolefin based macro fiber pullout test of different conditions are reported. Natural jute fiber volume fractions ranging from 0.1% to 0.2% are used in the mix proportions. Pullout tests are conducted to measure the bond characteristics of polyolefin based macro fiber from natural jute fiber reinforced cement composites. Test results are found that the incorporation of natural jute fiber can effectively enhance the polyolefin based macro fiber-cement matrix interfacial properties. The bond strength and interface toughness between polyolefin based macro fiber and natural jute fiber reinforced cement composites increases with the volume fraction of natural jute fiber. The microstructural observation confirms the findings on the interface bond mechanism drawn from the fiber pullout test results.

• Journal of the Korean Geotechnical Society
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• v.29 no.11
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• pp.129-138
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• 2013

In this study, Anchor Pile Precast Retaining Wall (APC) with screw shape flange was investigated and the results were arranged for designing APC specifications. Since precast materials require special care when they are manufactured, carried or treated, more accurate design and analysis of optimized dimension are needed : thus moment distribution of front foot was checked. Through full-scale field test, form and optimal stiffening shape were obtained and through fracture test with real load, applicable load was reasonably calculated. Research result in this thesis could be used as guideline or standard of designing and constructing Anchor Pile Precast Retaining Wall with screw shape flange.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.211-220
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• 2004

This paper presents the evaluation of pullout strengths of expansion anchors and wedge anchors that can cause a failure of the concrete on the basis of the design for anchorage. Tests are conducted for heavy-duty anchors and wedge anchors domestically manufactured and to be installed in plain concrete member. The mainly testing parameters reflected the effects of edge distance. Design of post-installed steel anchors is presented by the Concrete Capacity Design(CCD) in European Organization for Technical Approval. This approach is compared to the well-known provisions, ACI 349-90 specification. The use of both methods to predict the concrete failure load of expansion anchor in uncracked concrete under monotonic loading for important applications is compared. In this study, the concrete tension capacity of fastenings with Heavy-duty Anchors and Wedge Anchors in plain concrete predicted by ACI 349-90 and the Concrete Capacity Design method has been compared with the results of tests.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.182-189
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• 2010

The strengthening performance of FRPs(Fiber Reinforced Polymers) is directly affected by the environmental conditions such as freezing-thawing and moisture because FRPs are usually bonded on the concrete surface. It is, therefore, strongly required to evaluate a durability of bond between FRPs and concrete as well as FRP materials itself. The freezing-thawing resistance of FRPs is evaluated in this study with the variables of freezing-thawing conditions, types of FRP and freezing-thawing cycles. From the test results, it is found that tensile strength and pull-off strength of CFRP are not affected by the freezing-thawing. On the other hands, those of GFRP show a little degradation because of continuous water immersion during thawing process. But, cautions are needed on the bond durability between FRPs and concrete in case of continuous water supplying from adjacent to the concrete.

• The Journal of Engineering Geology
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• v.31 no.3
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• pp.321-332
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• 2021

Though development of reinforced earth wall is on the rise recently, safety verification for various methods remains behind which has caused the problems including collapse after installation. This study aims to evaluate the field applicability of the shape of flexible strip reinforcement according to pullout resistance test and field damage test. The test specimens were 3 shape of reinforcement, the typical flexible band reinforcement, developed luged band reinforcement, and band type reinforcement made by cutting geogrid. It was found that reinforcement of type have strengths and weaknesses, respectively. The best type of flexible strip reinforcements can be selected, if the conditions are considered with the installation conditions of the reinforcing earth retaining wall and the particle size of the backfill materials.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.143-154
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• 1999

In this study, the load transfer mechanism of tendon-grout interface of rock anchors has been examined through a series of static pull-out tests conducted on the model rock anchors constructed in the natural and artificial rock masses of granite and concrete, respectively. Several rock masses with horizontal discontinuities have been prepared to study the effects of weak planes on the shear stress distribution in tendon-grout interface. As a result, for the rock anchors constructed in the rock mass without discontinuities, stress concentration occurs on the upper part of the tendon-grout interface. On the contrary, as the frequency or the number of discontinuities increases, the shear stress distribution along the depth tends to be uniform. Also, an experimental equation about shear stress distribution between tendon-grout interface can be made by the regression of test results. The shear stresses computed from the experimental results between the rock surface and the depth of 2~3 times the tendon diameter are smaller than those from theory. Below the depth, the reverse can be observed.

• Journal of Korean Society of Steel Construction
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• v.15 no.5 s.66
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• pp.519-529
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• 2003

In recent years, the use of cold-formed steel roof truss has been increased in the steel houses and high-rise apartments. The design of the roof truss anchor connections has been based on the experience and decision of designers. In this paper, the structural behavior of anchor connections based on experimental and decision is described. In the tests, truss members and connection members were jointed directly with self-drilling screw fasteners and the simple shaped connection member with excellent workability and structural capacity was used to connect roof truss and sub-structure. The connecting method was selected according to the construction material of sub-structure: chemical anchor for reinforced concrete structure and welding or DX-Pin for steel structures. The pull-out tests of various type anchor connection were executed to obtain the strength and the stiffness and the result have been compared with AISI(1996) and AlSC(1989) specifications, Simple formulas for the shear strength of screw connections have been propose and compared with tests.