• Smart Structures and Systems
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• v.22 no.6
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• pp.699-709
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• 2018

With increasing traffic volumes and rising vehicle traffic, especially in cities, the number of pedestrian bridges has also increased significantly. Like all other structures, pedestrian bridges also suffer damage. In order to increase the safety of pedestrians, it is necessary to identify existing damage and to repair them to ensure the safety of the bridge structures. Owing to the shortcomings of local methods in identifying damage and in order to enhance the reliability of detection and identification of structural faults, signal methods have seen significant development in recent years. In this research, a new methodology, based on cone-shaped kernel distribution with a new damage index, has been used for damage detection in pedestrian truss bridges. To evaluate the proposed method, the numerical models of the Warren Type steel truss and the Arregar steel footbridge were used. Based on the results, the proposed method and damage index identified the damage and determined its location with a high degree of precision. Given the ease of use, the proposed method can be used to identify faults in pedestrian bridges.

• Agricultural and Biosystems Engineering
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• v.6 no.2
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• pp.59-64
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• 2005

In the study, the cone index, the cohesion and the internal resistant angle of soil were measured before and after tillage in order to suggest relative improvement in soil properties. The tillage methods tested in the study were five combinations of plow and rotary tillage operation and the experiments were performed on five selected test fields. The maximum tillage depth was 20 cm under the ground. The CIs for all the tillage operations were improved in comparison with those before tillage. The best combination of tillage operations for improving the CIs of soil was one plow operation followed by one rotary. After applying the tillage operations, the internal resistance angle reduced by 7-8 degree and the cohesion decreased up to about $1N/cm^2$ in comparison with those before tillage. We concluded that the cone index, the cohesion and the internal resistant angle of soil could be used as measures for representing the relative degree of tillage for a specific tillage operation. In addition, the study was useful as a basic research tool for developing an decision making system that determines an optimal tillage method with soil properties.

• Polymer(Korea)
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• v.24 no.6
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• pp.777-786
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• 2000

Fire resistance and thermal stability of polypropylene composite systems were investigated by using several halogenated fire-retardants such as decabromodiphenyl oxide (DBDPO) and chlorinated paraffin wax (CPW). The fire resistance of composite systems was thoroughly examined by measuring limited oxygen index (LOI, ASTM D2863, ISO 4589) and characteristic properties of cone calorimetry(ASTM E1354, ISO 5660) heat release rates (HRR), time to ignition (TTI), total heat release (THR), effective heat of combustion (EHC), mass loss rates, etc. Comparing the cone calorimetry experimental results of the halogen flame retardants, DBDPO exhibited twice higher efficiency than CPW in polypropylene systems, and the LOI also showed similar trends to cone calorimetry. The thermo-oxidative stability of the composite systems was increased about 30-5$0^{\circ}C$ in thermogravimetry analysis.Collectively, the combustion, extinction and thermally-stable characteristics of flame retardants were identified in this study.

• The Journal of the Petrological Society of Korea
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• v.25 no.2
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• pp.143-149
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• 2016

Eruptive volumes of three monogenetic volcanoes (Songaksan tuff ring, Biyangdo scoria cone, and Ilchulbong tuff cone) with the youngest eruption age are calculated using the model, applied to Auckland Volcanic Field in New Zealand, to investigate the volcanic eruption scale and to evaluate volcanic hazard of Jeju Island. Calculated eruptive volumes of the volcanoes are $24,987,557m^3$, $9,652,025m^3$, and $11,911,534m^3$, respectively, and the volumes include crater infill, tuff ring (tuff cone), scoria cone, and lava flow. Volcanic explosivity indices of Songaksan tuff ring, Biyangdo scoria cone, and Ilchulbong tuff cone are estimated based on the eruptive volumes to be 3, 2, and 3 respectively, and eruption type is Strombolian to Surtseyan. It is assumed that the amount of emitted sulfur dioxide gas is $2-8{\times}10^3kt/y$ according to the correlation between volcanic explosivity index and volcanic sulfur dioxide index. Recent age dating researches reveal evidences of several volcanic activities during the last 10,000 years indicating the possible volcanic eruption in Jeju Island in the near future. Therefore, it is necessary for appropriate researches regarding volcanic eruption of the island to be accomplished. In addition, establishment of the evaluation and preparation system for volcanic hazard based on the researches is required.

• Journal of the Korean Geosynthetics Society
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• v.21 no.4
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• pp.1-12
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• 2022

Generally, the plate load test and the field density test are conducted for compaction quality control in earthwork, and then additional analysis. Recently developed that the DCPT (Dynamic Cone Penetration Test) equipment for smart compaction quality control its the system are able to get location and real-time information about worker history management. The IoT-based the DCPT system improved the time-cost in the field compared traditional test, and the functions recording and storage of the DPI (Dynamic Cone Penetration Index) were automated. This paper describes using these DCPT equipment on in-situ and compared to the standards of the DCPT, and the compaction trend had be confirmed with DPI as the field test data. As a result, the DPI of the final compaction decreased by 1.4 times compared to the initial compaction, confirming the increase in the compaction strength of the subgrade compaction layer 10 to 14 cm deep from the surface. A trend of increasing compaction strength was observed. This showed a tendency to increase the compaction strength of the target DPI proposed by MnDOT and the results of the existing plate load test, but there was a difference in the increase rate. Therefore, additional studies are needed on domestic compaction materials and laboratory conditions for target DPI and correlation studies with the plate load tests. If this is reflected, it is suggested that DCPT will be widely used as smart construction equipment in earthworks.

• Journal of the Korean GEO-environmental Society
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• v.17 no.1
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• pp.5-12
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• 2016

Investigation of in-situ ground in cold region is difficult due to low accessibility and environmental factors. In this study, correlation between dynamic cone resistance and shear strength is suggested to estimate the strength of frozen soils by using instrumented dynamic cone penetrometer. Tests were conducted in freezing chamber after preparing sand-silt mixture with 2.3% water content. Vertical stresses of 5 kPa and 10 kPa were applied during freezing, shearing, and penetration phase to compare the dynamic cone resistance and shear strength. The dynamic cone resistance, additionally, is calculated to minimize the effect of energy loss during hammer impact. Experimental results show that as the shear strength increases, the dynamic cone penetration index (DCPI) decreases nonlinearly, while the dynamic cone resistance increases linearly. This study provides the useful correlation to evaluate strength properties of the frozen soils from the dynamic cone penetration and direct shear tests.

• Journal of Biosystems Engineering
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• v.41 no.4
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• pp.304-312
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• 2016

Purpose: Soil strength has been measured using a cone penetrometer, which is making it difficult to obtain the spatial data required for precision agriculture. Our objectives were to evaluate real-time horizontal soil strength (RHSS) to measure soil strength in real time while moving across the field. Using the RHSS data, the tillage depth was determined, and the power consumption of a tractor and rotavators were compared. Methods: The horizontal soil-strength index (HSSI) obtained by the RHSS was compared with the cone index (CI), which was measured using a cone penetrometer. Comparison analysis in accordance with the measurement depth that increased at 5-cm interval was conducted using kriged maps at six sensing depths. For tillage control and evaluation of the power consumption, the system was installed with a potentiometer for tillage depth, a torque sensor from the rear axle, and a power take-off (PTO) shaft. Results: The HSSI was lower than the CI, but they were the same at 54.81% of the total grids for the 5-cm depth and at 3.85% for the 10-cm depth. In accordance with the recommended tillage map, tillage operations between 0 and 15 cm left 2.3% and 7% residue cover on the soil, and that between 20 and 10 cm covered a wider utilization of 3% and 18.4%, respectively. When the tillage depth was 15 cm, the comparison result of the power requirements between the PTO and rear axle in terms of control performance revealed that the maximum power requirements of the axle and PTO were 44.63 and 23.24 kW, respectively. Conclusions: An HSSI measurement system was evaluated by comparison with the conventional soil strength measurement system (CI) and applied to a tractor to compare the tillage power consumption. Further study is needed on its application to various farm works using a tractor for precision agriculture.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.320-325
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• 2009

The constrained modulus, representative property to evaluate compressibility of soil, is needed to estimate the settlement of ground structure. A series of lab and field cone penetration tests for clayey soil of Busan new-port and Noksan industrial area were conducted to evaluate the estimation method of constrained modulus. Since CPT generates large deformation of ground, it is difficult to correlate the cone resistance with the constrained modulus. Therefore, appropriate correlation between them is essential to estimate the constrained modulus based on CPT results. The test results show that the ratio of the constrained modulus to the cone resistance is inversely proportional with plasticity index. Based on this result, the estimation method of constrained modulus for Busan clay is suggested.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1999.12a
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• pp.99-106
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• 1999

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.730-739
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• 2010

Stress history increases in penetration resistance due to the increase in residual horizontal stress of granular soil. This study analyzes the effect of stress history on the results of CPT and DMT from calibration chamber specimen in OC as well as NC state. Test results show that the normalized cone resistance by mean effective stress correlates well with the relative density and the state parameter, whereas the normalized cone resistance with regard to vertical effective stress is a little affected by stress history. The horizontal stress index($K_D$) in DMT more reflects the influence of stress history on granular soil than the dilatometer modulus($E_D$) and cone resistance($q_c$). The $K_D/K_0$, in which the effect of stress history on $K_D$ is compensated by the at-rest coefficient of earth pressure, $K_0$, is related to relative density, state parameter and the normalized cone resistance by mean effective stress. It is also observed that the normalized dilatometer modulus by mean effective stress($E_D/{\sigma_m}'$) is unique correlated with the state parameter, regardless of stress history.