• Advances in Computational Design
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• v.4 no.3
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• pp.251-272
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• 2019

This study performed lateral load testing on seventeen wood wall frames in two sections. Section one included eight tests studying structural foam sheathing of shear walls subjected to monotonic loads following the ASTM E564 test method. In this section, the wood frame was sheathed with four different types of structural foam sheathing on one side and gypsum wallboard (GWB) on the opposite side of the wall frame, with Simpson HDQ8 hold down anchors at the terminal studs. Section two included nine tests studying wall constructed with oriented strand board (OSB) only on one side of the wall frame subjected to gradually applied monotonic loads. Three of the OSB walls were tied to the baseplate with Simpson LSTA 9 tie on each stud. From the test results for Section one; the monotonic tests showed an 11 to 27 percent reduction in capacity from the published design values and for Section two; doubling baseplates, reducing anchor bolt spacing, using bearing plate washers and LSTA 9 ties effectively improved the OSB wall capacity. In comparison of sections one and two, it is expected the walls with structural foam sheathing without hold downs and GWB have a lower wall capacity as hold down and GWB improved the capacity.

• 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.25 no.5
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• pp.531-541
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• 2013

This paper investigated the structural capacity of the CT shear connectors, which is a kind of the perfobond rib and functions as an anchor transferring the tension force in the joint between a composite PHC wall pile and a bottom slab. The direct pull-out test was performed for various specimens. From failure modes and load-displacement curves, it was found that transverse rebars should be placed to holes in a web to restrict pull-out failure of CT shear connectors. The results of additional tests for specimens with transverse rebars and various support lengths indicated that all specimens were failed by the tension failure of PHC pile before pull-out failure of CT shear connector and concrete pull-out failure. Thus, the CT shear connector could endure the tension force between the PHC wall pile and the bottom slab.

• Journal of Korean Society of Steel Construction
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• v.27 no.1
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• pp.87-97
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• 2015

In this study, an experimental study was performed to evaluate the concrete breakout strength of cast-in-place(CIP) anchors in cracked concrete under static shear loading. The CIP anchors involved in this study were 30mm in diameter with an edge distance of 150mm and an embedment length of 240mm. The experiment was carried out for two specimens in uncracked concrete and three specimens in cracked concrete orthogonal and parallel to the direction of shear loading, respectively. Compared to the uncracked concrete specimen, cracked specimen orthogonal to the direction of shear loading showed no reduction in the concrete breakout strength and that parallel to the load direction about 91% strength which corresponds to 84% of uncracked concrete strength defined in ACI 318-11. Therefore, the experimental results showed smaller decrease in the shear resistance of CIP anchors in cracked concrete than that specified in ACI code which account for 71% strength of uncracked concrete in cracked concrete.

• Journal of the Korea Concrete Institute
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• v.12 no.1
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• pp.61-67
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• 2000

The strengthening method with CFS(Carbon Fiber Sheet) has some fatal defects that the beams strengthened with CFS is always failed far below its ultimated strenth due to rapid progress of horizontal delamination. The crack between beam and CFS are always started from the center of the beam and propagated to the end of the beam. The moment of the beam is always the largest in the middle of the beam, so is the tensile force of the CFS. The bumped surface of the CFS causes debonding force depending on the tensile force of CFS. In this study, two methods which delay early delamination are suggested and proved its validity, experimentally. The first method is using anchor bolt at the end of CFS, and the second method is using CFS wrap aroud at the center and the end of beam. The maximum load and ductility of the two methods are increased significantly. However, the maximum load is still far below the ultimate load. That's because the tensile strength of CFS is so large that its tensile strength can not be reached under normal loading condition. The ductility of the strengthened beam is improved more that twice before modiffication.

• Computers and Concrete
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• v.6 no.1
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• pp.41-57
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• 2009

This paper presents the details of a novel external prestressing technique for strengthening of concrete members. In the proposed technique, transfer of external force is in shear mode on the end block thus creating a complex stress distribution and the required transverse prestressing force is lesser compared to conventional techniques. Steel brackets are provided on either side of the end block for transferring external prestressing force and these are connected to the anchor blocks by expansion type anchor bolts. In order to validate the technique, an experimental investigation has been carried out on post-tensioned end blocks. Performance of the end blocks have been studied for design, cracking and ultimate loads. Slip and slope of steel bracket have been recorded at various stages during the experiment. Finite element analysis has been carried out by simulating the test conditions and the responses have been compared. From the analysis, it has been observed that the computed slope and slip of the steel bracket are in good agreement with the corresponding experimental observations. A simplified analytical model has been proposed to compute load-deformation of the loaded steel bracket with respect to the end block. Yield and ultimate loads have been arrived at based on force/moment equilibrium equations at critical sections. Deformation analysis has been carried out based on the assumption that the ratio of axial deformation to vertical deformation of anchor bolt would follow the same ratio at the corresponding forces such as yield and ultimate. It is observed that the computed forces, slip and slopes are in good agreement with the corresponding experimental observations.

• 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 Earthquake Engineering Society of Korea
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• v.23 no.5
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• pp.239-248
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• 2019

In this study, the out-of-plane seismic resistance of lightly-reinforced existing walls strengthened with thick RC jacket was investigated. The thick RC jacket with a thickness of 500 mm was placed at one side of the thin existing wall with a thickness of 150 mm. At the interface between the wall and RC jacket, a tee-shaped steel section with a number of anchor bolts and dowel bars was used as the shear connector. To investigate the connection performance and strengthening effects, the cyclic loading tests of four jacketed wall specimens were performed. The tests showed that the flexural strength of the jacketed walls under out-of-plane loading was significantly increased. During the initial behavior, the tee shear connector transferred forces successfully at the interface without slip. However, as the cracking, spalling, and crushing of the concrete increased in the exiting walls, the connection performance at the interface was significantly degraded and, consequently, the strength of the jacketed walls was significantly decreased. The flexural strength of the jacketed walls with tee shear connector was estimated considering the full and partial composite actions of the tee shear connector.

• Journal of the Korean Geotechnical Society
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• v.22 no.5
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• pp.47-57
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• 2006

The shear wave velocity is related with the stiffness of granular skeleton and mass density. The shear stiffness of the granular skeleton remains unaffected by the presence of the fluid. Bender elements are convenient shear wave transducers for instrumenting soil cells due to optimal soil-transducer coupling. This study addresses the principles of the shear wave, the design and implementation of bender elements including electromagnetic coupling prevention, directivity, resonant frequency, detection of first arrival, and near field effects. It is shown that electromagnetic coupling effects can be minimized using parallel-type bender elements. Thus, the in-plane S-wave directivity is quasi-circular. The resonant frequency of bender element installations depends on the geometry of the bender element, the anchor efficiency and the soil stiffness. One of the most cumbersome parts in the bender element test is near field effects, which affect the selection of arrival time. The selection of the first arrival within the near field Is effectively solved by the multiple reflection technique and signal matching technique. Bender elements, which requires several considerations, may be effective tools for the subsurface characterization by using S-wave.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.105-117
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• 2015

The purpose of this study is to develop a new seismic resistant method by using precast concrete wall panels for existing low-rise, reinforced concrete beam-column buildings such as school buildings. Three quasi-static hysteresis loading tests were experimentally performed on one unreinforced beam-column specimen and two reinforced specimens with L-type precast wall panels. The results were analyzed to find that the specimen with anchored connection experienced shear failure, while the other specimen with steel plate connection principally manifested flexural failure. The ultimate strength of the specimens was determined to be the weaker of the shear strength of top connection and flexural strength at the critical section of precast panel. In this setup of L-type panel specimens, if a push loading is applied to the reinforced concrete column on one side and push the precast concrete panel, a pull loading from upper shear connection is to be applied to the other side of the top shear connection of precast panel. Since the composite flexural behavior of the two members govern the total behavior during the push loading process, the ultimate horizontal resistance of this specimen was not directly influenced by shear strength at the top connection of precast panel. However, the RC column and PC wall panel member mainly exhibited non-composite behavior during the pull loading process. The ultimate horizontal resistance was directly influenced by the shear strength of top connection because the pull loading from the beam applied directly to the upper shear connection. The analytical result for the internal shear resistance at the connection pursuant to the anchor shear design of ACI 318M-11 Appendix-D except for the equation to predict the concrete breakout failure strength at the concrete side, principally agreed with the experimental result based on the elastic analysis of Midas-Zen by using the largest loading from experiment.