• Journal of Environmental Science International
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• v.14 no.12
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• pp.1185-1194
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• 2005

The runoff characteristics of non-point source pollutions in the municipal area of Jeonju were investigated and analyzed by using the SWMM (Storm Water Management Model). The flow rates and water qualities of runoff from two types of drainage conduits were measured respectively. One was a conventional combined sewer system and the other was a separated sewer system constructed recently From August to November in 2004, investigations on two rainfall events were performed and flow rate, pH, BOD, COD, SS, T-N and T-P were measured. These data were also used for model calibration. On the basis of the measured data and the simulation results by SWMM, it is reported that $80-90\%$ of pollution load is discharged in the early-stage storm runoff. Therefore, initial 10-30 mm of rainfall should be controlled effectively for the optimal treatment of non-point source pollution in urban area. Also, it was shown that the SWMM model was suitable for the management of non-point source pollution in the urban area and for the analysis of runoff characteristics of pollutant loads.

• Journal of Korean Society of Steel Construction
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• v.22 no.5
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• pp.465-475
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• 2010

In the horizontally curved bridges, girders are subjected to the combined action of vertical bending and torsion due to their curvatures without any eccentric loads. As subjected to bending and torsion, the ultimate strength of steel/concrete composite box girders are limited by the diagonal tensile stress in the deck concrete induced by the St. Venant torsion. To determine the ultimate strength of composite box girders in bending and torsion and their interactions, this study conducted a 3-dimensional FEA and classical strength of materials investigation. Using ABAQUS, the FEA fully utilized advanced nonlinear analysis techniques simulating material/geometrical nonlinearity and post-cracking behaviors. The ultimate strength from numerical data were compared with theoretically derived values. Concurrent compressive stresses in the concrete deck improve the shear-resisting capacity of concrete, thereby resulting in an increased torsional resistance of the composite box girder in positive bending. The proposed interaction equation is very simple yet it provides a rational lower bound in determining the ultimate strength of concrete/steel composite box girders.

• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.113-121
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• 2004

A test program was conducted on full-scale steel moment connections constructed using a T-stiffener. In the T-stiffener connection, the beam-to-column connection was reinforced with the horizontal and vertical element of the T-stiffener to resist moment under severe cyclic loads. A total of five specimens were tested in this study together with a concrete-filled tubular(CFT) column(${\sqsubset}-500{\times}500{\times}12$) and a steel beam($H-506{\times}201{\times}11{\times}19$). For the specimens, the T-stiffener was combined with RBS (also known as "Dog-bone") detail or Horizontal Element Hole(HEH) detail constructed to enhance deformation capacity. The test program showed excellent seismic performance for specimens constructed with an RBS or an HEH. except the specimens had brittle failure of VE. The test results also showed that the connections all developed maximum moments at the face of the column. Such moments were at least 15% and as much as 36% larger than the plastic moment capacity of the beam. based on the actual yield stress of the beam steel.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.101-108
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• 2004

A FEM-based efficient method is developed for the shape optimization of 2-D structures. The combined SLP and Simplex method are coupled with finite element analysis. Selected set of master nodes on the design boundaries are employed as design variables and assigned to move towards their normal directions. The other nodes along the design boundaries are grouped into the master node. By interpolating the repositioned master nodes, the B-spline curves are formed so that the rest mid-nodes efficiently settle down on the B-spline curves. Mesh smoothing scheme is also applied for the nodes on the design boundary to maintain most finite elements in good quality. Finally, a numerical implementation of optimum design of an automobile torque converter piston subjected to pressure and centrifugal loads is presented. The results shows additional weight up to 13% may be saved after the shape optimization.

• The Journal of Engineering Geology
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• v.18 no.1
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• pp.93-102
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• 2008

The use of lattice girder is increased at the tunnel site in Korea because of the several advantages over the traditional H-steel rib. The lattice girder supports the ground with shotcretes, forming a combined support system. Therefore, stress measurements at the lattice girder are necessary to calculated the ground loads. However, field measurements at the lattice girder are rarely performed at the tunnel site. The proper way of stress measurements for the lattice girder is not fully established in Korea. The correction of stress measurements at the shotcretes is often disregarded even though the measured stresses include non-stress related strains. Results of the stress measurements obtained from the lattice girder and non-stress shotcretes are used to improve the credibility of the stress measurements at the primary lining.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.12
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• pp.92-100
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• 2005

An aircraft wing or fuselage panel of skin-stringer assembly can fail in a variety of instable modes under compression loads. Instability modes can be buckling of the panel, local buckling of the stringer, flexure, torsion, wrinkle and combined flexural/torsional buckling of the panel assembly. Although researches on these buckling behaviors have been carried out for a long time, there are some difficulties to apply to the practice because of complex theoretical and empirical equations. Accordingly, It is well known that leading aerospace companies are using their own in-house programs for the convenience of practical usage, but our domestic situation is that no such program has been ever developed. In this study a comprehensive program has been developed, which can identify the instability modes and the magnitude of reserve factor of the modes for the skin/stringer panel assembly under compression load. The developed program is based on the theory manual of the Airbus program APA114. For the verification, calculation of the instable reserve factors for the A320 wing panel and A380 low wing panel sections were carried out and compared with results by APA114.

• Journal of KIISE:Information Networking
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• v.36 no.2
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• pp.118-129
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• 2009

The ISO 18000-7 Active RFID standard, a single channel system operating in the 433Mhz, faces technical difficulties in supporting some recently introduced application demands because of its low transmission rates and radio interference between readers. We propose a new multi-channel active RFID system operating in the 2.4Ghz. The special feature of the proposed system is that a reader makes use of multiple interfaces to improve its performance like a multi-core processor. However if only a small part of interfaces are actually used, the performance improvement would not meet the expectation. To overcome this problem, a new multi-channel multi-interface active RFID protocol, which balances communication loads among all available interfaces, is necessary. 3 protocols, named as "Aggregated", "LP-Combined", "AP-Balanced", are proposed. Through simulation, we compare them for various conditions by changing number of tags, number of interfaces, tag data size. AP-Balanced shows the best performance and its performance increases almost linearly as the number of interface increases, which meets our expectation.

• Steel and Composite Structures
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• v.18 no.6
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• pp.1369-1389
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• 2015

In order to investigate the behaviour of lying multi-stud connectors in cable-pylon anchorage zone, twenty-four push-out tests are carried out with different stud numbers and diameters. The effect of concrete block width and tensile force on shear strength is investigated using the developed and verified finite element model. The results show that the shear strength of the lying multi-stud connectors is reduced in comparison with the lying single-stud connector. The reduction increases with the increasing of the number of studs in the vertical direction. The influence of the stud number on the strength reduction of the lying multi-stud connectors is decreased under combined shear and tension loads compared with under pure shear. Yet, due to multi-stud effect, they still can't be ignored. The concrete block width has a non-negligible effect on the shear strength of the lying multi-stud connectors and therefore should be chosen properly when designing push-out specimens. No obvious difference is observed between the strength reductions of the studs with 22 mm and 25 mm diameters. The shear strengths obtained from the tests are compared with those predicted by AASHTO LRFD and Eurocode 4. Eurocode 4 generally gives conservative predictions of the shear strength, while AASHTO LRFD overestimates the shear strength. In addition, the lying multi-stud connectors with the diameters of 22 m and 25 mm both exhibit adequate ductility according to Eurocode 4. An expression of load-slip curve is proposed for the lying multi-stud connectors and shows good agreement with the test results.

• Steel and Composite Structures
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• v.23 no.3
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• pp.273-283
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• 2017

In this paper, it is aimed to present a detail investigation related to structural behavior of laterally unrestrained steel cantilever roof of tribune with slender cross section. The structure is located in Tutak town in $A{\breve{g}}r{{\i}}$ and collapsed on October 25, 2015 at eastern part of Turkey is considered as a case study. This mild sloped roof structure was built from a variable I beam, and supported on steel columns of 5.5 m height covering totally $240m^2$ closed area in plan. The roof of tribune collapsed completely without any indication during first snowfall after construction at midnight a winter day, fortunately before the opening hours. The meteorological records and observations of local persons are combined together to estimate the intensity of snow load in the region and it is compared with the code specified values. Also, the wide/thickness and height/thickness ratios for flange and web are evaluated according to the design codes. Three dimensional finite element model of the existing steel tribune roof is generated considering project drawings and site investigations using commercially available software ANSYS. The displacements, principal stresses and strains along to the cantilever length and column height are given as contour diagrams and graph format. In addition to site investigation, the numerical and analytical works conducted in this study indicate that the unequivocal reasons of the collapse are overloading action of snow load intensity, some mistakes made in the design of steel cantilever beams, insufficient strength and rigidity of the main structural elements, and construction workmanship errors.

• Geomechanics and Engineering
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• v.12 no.4
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• pp.611-626
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• 2017

The research reported herein is concerned with the model testing of piles socketed in soft rock which was simulated by cement, plaster, sand, water and concrete hardening accelerator. Model tests on a single pile socketed in simulated soft rock under axial cyclic loading were conducted and the bearing capacity and accumulated deformation characteristics under different static, and cyclic loads were studied by using a device which combined oneself-designed test apparatus with a dynamic triaxial system. The accumulated deformation of the pile head, and the axial force, were measured by LVDT and strain gauges, respectively. Test results show that the static load ratio (SLR), cyclic load ratio (CLR), and the number of cycles affect the accumulated deformation, cyclic secant modulus of pile head, and ultimate bearing capacity. The accumulated deformation increases with increasing numbers of cycles, however, its rate of growth decreases and is asymptotic to zero. The cyclic secant modulus of pile head increases and then decreases with the growth in the number of cycles, and finally remains stable after 50 cycles. The ultimate bearing capacity of the pile is increased by about 30% because of the cyclic loading thereon, and the axial force is changed due to the applied cyclic shear stress. According to the test results, the development of accumulated settlement is analysed. Finally, an empirical formula for accumulated settlement, considering the effects of the number of cycles, the static load ratio, the cyclic load ratio and the uniaxial compressive strength, is proposed which can be used for feasibility studies or preliminary design of pile foundations on soft rock subjected to cyclic loading.