• Journal of the Korean Society for Nondestructive Testing
• /
• v.24 no.2
• /
• pp.158-162
• /
• 2004

Reliability of welded structures in power plant facilities is very important, and their reliability evaluation requires exact materials properties. But, the conventional PQR (Procedure Qualification Record) can hardly reflect the real material properties in the field because the test is only done on specimens with simulated welding. Therefore, a continuous indentation technique is proposed in this study for simple and non-destructive testing of in-field structures. This test measures the indentation load-depth curve during indentation and analyzes the mechanical properties such as the yield strength, tensile strength and work hardening index. This technique has been applied to evaluate the tensile properties of the weldment in the main steam pipe and hot reheater pipe in power plants under construction and in operation.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.21 no.5
• /
• pp.532-541
• /
• 2001

Developments of nondestructive evaluation techniques for reduction of strength or toughness by aging of material have been carried out, and the method using electrical resistivity is one of them. In this study, to examine the application of electrical resistivity to the evaluation of degradation of metallic alloy, ten different non-magnetic materials were selected as test materials. Electrical resistivities measured by DC two-point probe method and those measured by non-contact type eddy current method were compared with each other. In addition, to examine the application possibility of four-point probe technology in field, the electrical resistivities for 1Cr-lMo-0.25V steel measured by DC two-point probe method and four-point probe method were compared with each other Differences between two measured values for the 1Cr-1Mo-0.25V steel were 0.6%. Therefore, the four-point probe method can be applied to the estimation of the degradation of metallic alloy. ect.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.941-944
• /
• 2008

Various ductile fiber reinforced cement composite(DFRCC) including large quantities of PVA fiber or steel fiber have been developed recently and studies to find applications in diverse domains are currently conducted actively. Regard to economical efficiency, DFRCC becomes competitive when applied as special elements and repair material with small quantities rather than the casting of large volume for the main body of structures in field. The authors have developed FRP-DFRCC composite slab for bridges and a wet spraying repair technique using DFRCC. In case of the application on FRP-DFRCC composite slab, it was found that there was no problems the structure and durability of it after passed 3 months. And in case of the application on the application of the deteriorated sewage box that passed 20 years, it was found that there was no difference the repair performance between domestic PVA fiber and the Japan. Therefore, DFRCC using PVA fiber, the concrete structures can be increased to performance and secured the economical efficiency.

• Journal of the Korean Geotechnical Society
• /
• v.20 no.9
• /
• pp.65-75
• /
• 2004

In this paper, a mechanism of the soil structure reinforced by geosynthetics is discussed. The reinforcing mechanism is interpreted as an effect arising from the reinforcement works preventing the dilative deformation (negative dilatancy) of soil under shearing. A full-scale in-situ model test was carried out in Kanazawa of Japan (1994), and in the laboratory test the strength and the characteristics of deformation conducting a constant volume shear test are examined. The parameters needed in the FEM are also applied by using the experimental data. The elasto-plastic finite element simulation is carried out, and the results are quantitatively compared with that of experiment. As a results, it is known that the theoretical predictions could explain effectively the experimental results which are obtained by a full-scale in-situ model test.

• Resources Recycling
• /
• v.18 no.3
• /
• pp.20-26
• /
• 2009

The objective of this study is to investigate the properties of fresh concrete with recycled coarse and fine aggregates. Four different kinds of aggregate with natural, recycled aggregates were prepared. The concrete mixtures were produced with test parameters of replacement ratio of recycled aggregate. The properties of the fresh concrete were measured by means of slump and air content according to elapsed time. Quality control method to maintain the constant total mixing water for recycled aggregate concrete was suggested. The all concrete mixtures were produced with approximately the same slump on the job site after an hour. Test results indicated that compressive strength of concrete with constant slump is not affected by the replacement ratio of recycled aggregate. Also the practical way for the quality control of recycled aggregate concrete is to maintain the constant total mixing water.

• Journal of the Korea Concrete Institute
• /
• v.13 no.4
• /
• pp.406-413
• /
• 2001

Up to this day, reinforced spun concrete pipes have been widely used as drain pipes. However, many reinforced spun concrete pipes are exposed to the deteriorated environment such as freezing-thawing damage and chemical attack by the growth of a sulfur-oxidizing bacterium isolated from corroded concrete. The purpose of this study is to evaluate the effects of lining by polymer-modified mortar using polymer dispersions as cement modifier on the development in durability of reinforced spun concrete pipe. The polymer-modified mortars were prepared with various polymer types and polymer-cement ratios, and tested for compressive and flexural strengths, acid, freezing-thawing, and heat resistances. And then, the reinforced spun concrete pipe product lined by polymer-modified mortars was tested for adhesion in tension and surface conditions according to curing temperatures in the field. From the test results, it is apparent that the polymer-modified mortars have good mechanical properties and durability as a lining material. In practice, all polymers can be used as lining the materials for reinforced spun concrete pipe, and types of polymer, and polymer-cement ratio and curing conditions are controlled for a good lining product.

• Journal of the Korean Geosynthetics Society
• /
• v.3 no.4
• /
• pp.3-12
• /
• 2004

In this paper, a mechanism of the soil structure reinforced by geosynthetics is discussed. The reinforcing mechanism is interpreted an effect arising from the reinforcement works so as to prevent the dilative deformation (negative dilatancy) of soil under shearing. A full-scale in-situ model test was carried out in Kanazawa of Japan(1994) and in the laboratory test the strength and the characteristics of deformation conducting a constant volume shear test are examined. The parameters needed in the FEM are also applied by using the experimental data. The elasto-plastic finite element simulation is carried out, and the results are quantitatively compared with that of experiment. As a results, it is known that the theoretical predictions could be explained effectively the experimental results which are obtained by a full-scale in-situ model test.

• Journal of the Korean Geotechnical Society
• /
• v.26 no.9
• /
• pp.59-69
• /
• 2010

This study is experimentally investigated for characteristics of lightweight air-trapped soils with uniform quality. Previously, EPS (Expanded PolyStyrene) blocks are often used as lightweight embankment, but many problems such as the level difference and cracks were caused by plastic (creep) deformation. So, a new material development is urgent. By means of alternatives, lightweight air-mixed soil using in-situ soils has been developed and applied to fields. In comparison with EPS block, lightweight air-mixed soil has less plastic (creep) deformation in long period, but the strength characteristics are different according to the soils where they are obtained. Therefore, the quality management of lightweight air-mixed soil is very difficult. Therefore in this study, characteristics of lightweight air-trapped soil using a manufactured sand with uniform quality are investigated. To found out the compression and tensile characteristics of lightweight air-tapped soils, unconfined compression test and splitting tensile test are conducted on the specimens prepared with different unit weight, cement-sand ratio and air-pore.

• Geotechnical Engineering
• /
• v.4 no.3
• /
• pp.35-42
• /
• 1988

A series of consolidated-undrained cubical triaxial tests was performed to investigate the three- dimensional strength characteristics of anisotropic overconsolidated clay. All specimens sampled in field were loaded under conditions of principal stress directions fixed and aligned with the directions during sampling. A sufficient number of tests It was performed to deter.mine the three- dimensional failure surface in the octahedral plane. The adjusted effective friction angles obtained by the stress state projected on the same octahedral plane did not show anisotropy, while the measured effective friction angles showed considerally difference according to the axes of speccimens. Therefore, Lade failure criterion proposed fort isotropic materials could be also used practically for anisotropic overconsolidated clay. The direction of the plastic strain increment wrectors superimposed on the principal stress space was nearly perpendicular to the traces of the failure surface in the octahedral plane.

• Journal of the Society of Naval Architects of Korea
• /
• v.51 no.3
• /
• pp.254-258
• /
• 2014

Field trial in ice-covered sea is one of the most important tasks in the design of icebreaking ships. To correctly estimate ice load and ice resistance on ship's hull, It is essential to understand the material properties of sea ice during ice field trials and to perform the proper experimental procedure by gathering sea ice data. A measurement of sea ice properties was conducted during February and March of 2012 with the Korean Icebreaking research vessel "ARAON" in the Amundsen Sea, Antarctica. This paper describes a test procedure to obtain sea ice data which provide basic information to estimate ice loads and icebreaking performance of the ship. The data gathered from sea ice field trials during the 2012 Antarctic voyage of the ARAON includes ice temperature/salinity/density and the compressive/flexural strength of sea ice. This paper analyses the gathered Antarctic sea ice material properties comparing with the previous data obtained during ARAON's Arctic and Antarctic voyages in 2010.