• Journal of the Korean Geotechnical Society
• /
• v.16 no.1
• /
• pp.5-17
• /
• 2000

The physical and mechanical properties of the sedimentary rocks deposited in Taegu and Kyongbuk region have been measured in the laboratory and at the field. Four kinds of rocks such as the shale, the mudstone, the siltstone and the sandstone were the object of this study. In sedimentary rock joint, bedding made it impossible to extract cores for uniaxial compressive test. Some correlations between the uniaxial compressive strength and the other characteristic values such as Point load index, Schmidt hammer rebound, Brazilian strength, P-wave velocity and Absorption ratio are made. The chemical and mineral compositions are also investigated by the XRF and XRD analysis. In addition, the weathering grade of rocks are classified by the quantitative indices of Point load index, Schmidt hammer rebound and Absorption ratio.

• Computational Structural Engineering : An International Journal
• /
• v.3 no.1
• /
• pp.9-17
• /
• 2003

This paper aims at investigating the damage process of steel members leading to the failure under strong repeated loading, proposing the damage index using various factors related to the damage, and developing the analysis method for evaluating the damage state. Cantilever-type steel members were analyzed under uniaxial load and combined with a constant axial load, considering a horizontal displacement history. In analyzing the models, loading patterns and steel types (SS400, SM570, Posten80) were considered as main parameters. From the analysis results, the effects of parameter on the failures mode, the deformation capacity, the damage process are also discussed. Each failure process was compared as steel types. Consequently, the failure of steel members under strong repeated loading was determined by loading. Especially it was seen that the state of the failure is closely related to the local strain.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.31 no.6
• /
• pp.351-355
• /
• 2019

Load resistance factors for the limit state design of vertical caisson breakwaters are presented. Reliability analysis of 16 breakwaters in nationwide ports was conducted to calculate the partial safety factors and they were converted into load and resistance factors. The final load resistance factor was calibrated by applying the optimization technique to the individually calculated load resistance factors. Finally, the breakwater was redesigned using the optimal load resistance factor and verified whether the target level was met. The load resistance factor according to the change of the target reliability level is presented to facilitate the limit state design of breakwater.

• Journal of Korean Neurosurgical Society
• /
• v.54 no.3
• /
• pp.232-235
• /
• 2013

Objective : Major complaints of carpal tunnel syndrome (CTS) are sensory components. However, motor deficit also impedes functional status of hand. Contrary to evaluation of sensory function, the objective, quantitative evaluation of median nerve motor function is not easy. The motor function of median was evaluated quantitatively using load cell and its correlation with findings of electrodiagnostic study (EDS) was evaluated. Methods : Objective motor function of median nerve was evaluated by load cell and personal computer-based measurement system. All of the measurement was done in patients diagnosed as having idiopathic CTS by clinical features and EDS findings. The strength of thumb abduction and index finger flexion was measured in each hand three times, and the average value was used to calculate thumb index ratio (TIR). The correlation of TIR with clinical, EDS, and ultrasonographic findings were evaluated. Results : The TIR was evaluated in 67 patients (119 hands). There were 14 males and 53 females, mean age were 57.6 years (range 28 to 81). The higher preoperative nerve conductive studies grade of the patients, the lower TIR was observed [p<0.001, analysis of variance (ANOVA)]. TIR of cases with thenar atrophy were significantly lower than those without (p<0.001, t-test). TIR were significantly lower in patients with severe median nerve swelling in ultrasonography (p=0.042, ANOVA). Conclusion : Measurements of median nerve motor function using load cell is a valuable evaluation tool in CTS. It might be helpful in detecting subclinical motor dysfunction before muscle atrophy develops.

• Structural Engineering and Mechanics
• /
• v.75 no.6
• /
• pp.643-657
• /
• 2020

This study presents experimental and numerical investigations on circular steel tube confined ultra high performance concrete (UHPC) columns under axial compression. The plain UHPC without fibers was designed to achieve a compressive strength ranged between 150 MPa and 200 MPa. Test results revealed that loading on only the UHPC core can generate a significant confinement effect for the UHPC core, thus leading to an increase in both strength and ductility of columns, and restricting the inherent brittleness of unconfined UHPC. All tested columns failed by shear plane failure of the UHPC core, this causes a softening stage in the axial load versus axial strain curves. In addition, an increase in the steel tube thickness or the confinement index was found to increase the strength and ductility enhancement and to reduce the magnitude of the loss of load capacity. Besides, steel tube with higher yield strength can improve the post-peak behavior. Based on the test results, the load contribution of the steel tube and the concrete core to the total load was examined. It was found that no significant confinement effect can be developed before the peak load, while the ductility of post-peak stage is mainly affected by the degree of the confinement effect. A finite element model (FEM) was also constructed in ABAQUS software to validate the test results. The effect of bond strength between the steel tube and the UHPC core was also investigated through the change of friction coefficient in FEM. Furthermore, the mechanism of circular steel tube confined UHPC columns was examined using the established FEM. Based on the results of FEM, the confining pressures along the height of each modeled column were shown. Furthermore, the interaction between the steel tube and the UHPC core was displayed through the slip length and shear stresses between two surfaces of two materials.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.19 no.4
• /
• pp.529-538
• /
• 2010

This paper presents a reliability-based topology optimization (RBTO) based on bidirectional evolutionary structural optimization (BESO). In design of a structure, uncertain conditions such as material property, operational load and dimensional variation should be considered. Deterministic topology optimization (DTO) is performed without considering the uncertainties related to the design variables. However, the RBTO can consider the uncertainty variables because it can deal with the probabilistic constraints. The reliability index approach (RIA) and the performance measure approach (PMA) are adopted to evaluate the probabilistic constraints in this study. In order to apply the BESO to the RBTO, sensitivity number for each element is defined as the change in the reliability index of the structure due to removal of each element. Smoothing scheme is also used to eliminate checkerboard patterns in topology optimization. The limit state indicates the margin of safety between the resistance (constraints) and the load of structures. The limit State function expresses to evaluate reliability index from finite element analysis. Numerical examples are presented to compare each optimal topology obtained from RBTO and DTO each other. It is verified that the RBTO based on BESO can be effectively performed from the results.

• Journal of Korean Society on Water Environment
• /
• v.37 no.4
• /
• pp.296-305
• /
• 2021

This work investigated heavy metal pollution in surface sediments of rivers in Busan, Korea. Surface sediments were analyzed in order to conduct contamination assessment of organic matter, nutrients, and heavy metal concentrations. Contamination assessment of heavy metals was conducted using geoaccumulation index (I_geo), pollution load index (PLI), and potential ecological risk index (RI). Accumulation of organic matter and nutrients were affected by water discharged from sewage treatment plant. The concentrations of organic matter and nutrients were found to be greater in points which were close to the sewage treatment plant more than points furthest. The concentrations of Pb, Zn, Cu, Cd, Hg, As, Cr, and Ni were found to be greater in surface sediment more than in the background. The mean concentrations of heavy metals were in the order of Zn (323.5 mg/kg) > Cu (70.5 mg/kg) > Pb (39.8 mg/kg) > Cr (33.4 mg/kg) > Ni (13.5 mg/kg) > As (9.4 mg/kg) > Cd (0.84 mg/kg) > Hg (0.092 mg/kg). The result of geoaccumulation indices indicated that Hg > Cr > Cu > Ni > Zn > As > Pb > Cd were found in order of severe contamination by heavy metals. From PLI and RI analysis, it was evident that the Suyeonggang 2 was the most contaminated river.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.22 no.2
• /
• pp.107-120
• /
• 2019

In this study, the characteristics of watershed and pollution source were investigated in SoOakcheon located in the upper stream of Daecheong Lake. The Dimension Index method was applied to index various watershed and pollution source data. The influence factors of each pollutant source were derived through correlation analysis between selected index and water quality monitoring data. BOD and COD were significantly influenced by population density and land area ratio, T-N by CN and rice area ratio, and T-P by population density and land area ratio, respectively. The discharge load is often used to establish non-point source countermeasures, but there is a difference between the water load and the water load in the lake or river. Therefore, in order to manage non-point pollution efficiently, it is necessary to analyze influential factors with high correlation with water quality and to manage the relevant factors with priority.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.23 no.9
• /
• pp.610-619
• /
• 2011

This paper investigates the simplified comfort index and control logic for VRF (Variable Refrigerant Flow) system by using 3 environmental factors such as temperature, humidity and air flow. Indoor test under thermal load was conducted to explore relationship of each environment factors that is related to simplified comfort index. Simplified comfort function that has 3 environmental variables was proposed based on survey results. Each factor is measured and comfort preference was surveyed by more than 30 subjects in the indoor comfort test. Moreover, control logic for VRF system was developed and then simulated by using thermal load calculation method and verified with test. The proposed comfort function was in good agreement with survey results, and also verification test trend of comfort change and maintenance are quite similar with survey. Furthermore, through the additional test data analysis some differences of comfort according to position of people staying in the test room were additionally investigated by air flow. People being under an exit of air in the indoor air-conditioner feel more comfortable condition and speed of response to comfort change is relatively fast.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.03a
• /
• pp.863-874
• /
• 2008

We have to judge engineering properties of rock accurately in order to design and construct rock structure safely and economically. Among the rock tests, the test result of UCS(Uniaxial Compressive Strength) is very important factor used in the variety ways for designing and construction of underground structures, rock slope and foundation analysis. But the UCS test has some disadvantages of intact sample preparation such as because the shape of sample has to be regular cylindrical, cube or rectangular. In order to solve those problem, indirect tests are used such as point load test, schmidt hammer test, absorption test, dry density to predict UCS of rock. Those tests are easy to prepare sample and convenient to carry out the tests, so it is simple and costs less. Schmidt hammer test are frequently used in the construction site, because it is handy and easy to use, but there is concern of misuse without classifying the specification of each schmidt hammer. Thus, this study suggested presumptive numerical formula related on each specification of schmidt hammer test, point load test, absorption test and dry density also. We compared presumptive numerical formula and R-square through schmidt rebound assessment method already brought up. Also, through the test we offer the extent of weathering index according to the weathering grade.