• Steel and Composite Structures
• /
• v.44 no.3
• /
• pp.339-351
• /
• 2022

A mortar-filled rectangular hollow structural section (RHS) can increase a structural section property as well as a compressive buckling capacity of a RHS member. In this study, the tensile performance of newly developed mortar-filled RHS members was experimentally evaluated with various connection details. The major test parameters were the type of end connections, the thickness of cap plates and shear plates, the use of stud bolts, and penetrating bars. The test results showed that the welded T-end connection experienced a brittle weld fracture at the welded connection, whereas the tensile performance of the T-end connection was improved by additional stud bolts inserted into the mortar within the RHS tube. For the end connection using shear plates and penetrating stud bolts, ductile behavior of the RHS tube was achieved after yielding. The penetrating bars increased load carrying capacity of the RHS. Based on the analysis of the load transfer mechanism, the current design code and test results were compared to evaluate the tensile capacity of the RHS tube according to the connection details. Design considerations for the connections of the mortar-filled RHS tubes were also recommended.

• Journal of the Korea Concrete Institute
• /
• v.19 no.4
• /
• pp.475-482
• /
• 2007

The property and applicability of the organic-inorganic synthesized penetrating and reinforcing agent, which is developed in order to improve durability of concrete structures and prevent deterioration that may occur as service years increased, are researched with experimental works. TEOS (tetra-ethoxyorthosilicate) and acrylate monomer are synthesized by the solution polycondensation method in order to formulate silicate with sol-gel process and improve durability of concrete. Additional substances such as isobutyl-orthosilicate is supplemented in order to improve the performance of the agent. After the developed organic-inorganic penetrating reinforcing agent penetrates, a flexible impact alleviating layer is formed with organic monomers as well as the agent strengthens concrete by filling up the internal pore of concrete with stable compounds after penetration. Penetrating and reinforcing agent can be applied as an effective life management method because it makes concrete more durable against the aging factors, such as chloride ion, carbonation, freezing-thawing, and compound aging.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.7 no.2
• /
• pp.177-184
• /
• 2003

A series of experimental work has been conducted to evaluate the capability of Ground Penetrating Radar (GPR) system in detecting delamination inside concrete. Three antenna at 900 MHz, 1000 MHz, and 1500 MHz frequency are used in the experiments for laboratory size specimens, and 400 MHz antenna has been used for a large size specimen. The laboratory size specimens have the dimensions of 1,000 mm (length) ${\times}$ 600 mm (width) ${\times}$ 140 mm (thickness) with a delamination of 200 mm (length) ${\times}$ 600 mm (width) ${\times}$ 140 mm (thickness). The cover depth of the delamination is varied as follows: 20 mm, 30 mm, 60 mm, and 70 mm. In all cases, the delamination has been successfully identified. The property of three frequencies was seized about detecting delamination. Also, it was shown that the image results in GPR were improved by signal processing.

• Economic and Environmental Geology
• /
• v.57 no.1
• /
• pp.17-23
• /
• 2024

Ground penetrating radar (GPR) survey is a geophysical method that utilizes electromagnetic waves reflecting from a boundary where the electromagnetic property changes. As the frequency of the antenna is about 25 MHz ~ 1 GHz, it is effective to acquire high resolution images of underground pipe, artificial structure, underground cavity, and underground structure. In this study, we analyzed the change of signals reflected from the same underground objects according to the arrangement of transceiver antennas used in ground penetrating radar survey. The antenna used in the experiment was 200 MHz, and the survey was performed in the vertical direction across the sewer and the parallel direction along the sewer to the sewer buried under the road, respectively. A total of five antenna array methods were applied to the survey. The most used arrangement is when the transmitting and receiving antennas are all perpendicular to the survey line (PR-BD). The PR-BD arrangement is effective when the object underground is a horizontal reflector with an angle of less than 30°, such as the sewer under investigation. In this case study, it was confirmed that the transmitter and receiver antennas perpendicular to the survey line (PR-BD) are the most effective way to show the underground structure. In addition, in the case where the transmitting and receiving antennas are orthogonal to each other (XPOL), no specific reflected wave was observed in both experiments measured across or parallel to the sewer. Therefore, in the case of detecting undiscovered objects in the underground, the PR-BD array method in which the transmitting and receiving antennas are aligned in the direction perpendicular to the survey line taken as a reference and the XPOL method in which the transmitting and receiving antennas are orthogonal to each other are all used, it can be effective to apply both of the above arrangements after setting the direction to 45° and 135°.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.05a
• /
• pp.664-667
• /
• 2004

It may have to establish the definite standard for performance evaluation basis about cementitious waterproofing material in job site that applied the method of construction formed cement waterproof course on concrete surface In present paper shows the effective selection method of waterproof layer of optimum thickness for economic performance as evaluating of the need thickness on waterproof property of penetrating waterproofing material.

• Proceedings of the Korean Biophysical Society Conference
• /
• 1996.07a
• /
• pp.27-27
• /
• 1996

SecA protein which has a pivotal role in the preprotein cranslocation across the inner membrane of Escherichia coli is a water-soluble protein with an unusual property of penetrating the membrane readily. An interesting and important question is what structural characteristics of SecA enables its ready penetration of lipid bilayer. The conformational properties of SecA in solution at 3$0^{\circ}C$, pH 7.5 were observed by hydrogen-tritium (HT) exchange, and denaturant-induced denaturation/renaturation and thermal unfolding. (omitted)

• Fibers and Polymers
• /
• v.5 no.4
• /
• pp.316-320
• /
• 2004

Waterproof fabrics are seamed and sealed by waterproof sealing tape to prevent water from penetrating through the stitch holes. As this process may change the mechanical properties of breathable waterproof fabric related to its deformation with human body, the changes in mechanical properties were investigated. In both of parallel and perpendicular directions, tensile characteristics were remarkably changed with seaming and sealing processes. The increase of LT and WT means that the clothing sealed by waterproofing tape may produce somewhat discomfort feeling. On the other hand, the bridge of the sewing thread seemed to be reinforced by waterproofing tape. Shear characteristics such as G, 2HG, and 2HG5 gradually increased with seaming and sealing processes in parallel direction. However, they decreased with sealing process in perpendicular direction because the seam line would work as an axis located at the center of the testing range.

• Proceedings of the KSR Conference
• /
• 2007.11a
• /
• pp.494-499
• /
• 2007

The ballast, one of a track components, plays an essential role as intermedium in transmitting train traffic-load to subgrade safely, and deterioration of ballast caused by cumulative load effects growth of track irregularity. Especially in the case of Gyeongbu high-speed railway, the deteriorating speed of ballast by dynamic vibration is faster than conventional line because KTX is longer than normal trains in length and it's velocity is very fast with high speed of 300km/h as well. In addition, ballast is a nonlinear material contrary to ordinary metal which has homogeneous property and this property of ballast may cause transformation of ballast. Therefore the theoretical modeling of ballast is quite complicated and it is hard to ensure the reliability of the result. The objective of this paper is to examine the availability of GPR(Ground Penetrating Radar) in estimating the thickness and the degree of deterioration of ballast. First, We figured out the principle of GPR which is the technique of evaluating the condition of ballast and then analyzed data which were measured at Gyeongbu high-speed railway where KTX is running now.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2009.04a
• /
• pp.151-156
• /
• 2009

Forward modelling of ground penetrating radar (GPR) data is implemented using a new finite element ray tracing technique. The method is different from conventional ray tracing techniques in that the radar cross section of buried targets, the effective area of the receiving antenna, and the attenuation along the raypath are computed. The forward models are used to understand radar signatures measured across various ground structures which are important in detecting engineering hazards at construction sites, void spaces beneath simulated road beds, as well as a learning tool to avoid pitfalls in radargram interpretation. Forward modelling of radar data also can be used in predicting possible structures present at cultural property sites.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.1239-1240
• /
• 2006

Effects of $Ag_2O$ doping on the electromagnetic properties in the BiSrCaCuO superconductors. The electromagnetic properties of $Ag_2O$ doped and undoped BiSrCaCuO superconductor were evaluated to investigate the contribution of the pinning centers to the magnetic effect. It was confirmed experimentally that a large amount of magnetic flux was trapped in the $Ag_2O$ doped sample than that in the undoped one, indicating that the pinning centers of magnetic flux are related closely to the occurrence of the magnetic effect. It is considered that the area where normal conduction takes place increases by adding $Ag_2O$ and the magnetic flux penetrating through the sample increases. The results suggested that Ag acts to increase pinning centers of magnetic flux, contributing to the occurrence of the electromagnetic properties.