• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.1-8
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• 2017

Three small scale hollow circular reinforced concrete columns with aspect ratio 4.5 were tested under cyclic lateral load with constant axial load. Diameter of section is 400 mm, hollow diameter is 200 mm. The selected test variable is transverse steel ratio. Volumetric ratios of spirals of all the columns are 0.302~0.604% in the plastic hinge region. It corresponds to 45.9~91.8% of the minimum requirement of confining steel by Korean Bridge Design Specifications, which represent existing columns not designed by the current seismic design specifications or designed by seismic concept. The longitudinal steel ratio is 2.017%. The axial load ratio is 7%. This paper describes mainly crack behavior, load-displacement hysteresis loop, seismic performance such as equivalent damping ratio, residual displacement and effective stiffness and flexural over-strength of circular reinforced concrete bridge columns with respect to test variable. The regulation of flexural over-strength is adopted by Korea Bridge Design Specifications (Limited state design, 2012). The test results are compared with nominal strength, result of nonlinear moment-curvature analysis and the design specifications such as AASHTO LRFD and Korea Bridge Design Specifications(Limited state design).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.3
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• pp.238-244
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• 1990

The behavior of conger eel, Astroconger myriaste(Brevoort), to the net pots with baits was investigated alternately in two experimental water tanks. One of the pots being dropped on the tank bottom, the eels increased rapidly in number of touching the pot to show a maximum whithin 30 minutes and then decreased gradually. The enterings of eels into the pots were also made mainly within 30 minutes and easier in pots with lower entrances. But the complete enterings were decided by the passage of eel tails through the pot entrances and so the eels retreated frequently after attemping to enter the pots, especially in pots small in the interval between the entrances and the baits or in pots with flappers. However, most of enterings encouraged the touches and earlier enterings ascribed earlier production of maximum touch. The eels, if entered the pots without flappers, got out of the pots relatively easily and the getting-out was easier in pots with lower entrances. On the other hand, the eels entered the pot with flappers could not get out of the pots. A comparison between the circular and square pots gave that the guidance of eels to the entrances was easier in the former and the passing of eels through the entrances in the latter, not only at the inside of pots but also at the outside. The general behavior of eels in touching or entering the net pots in the above results was almost equal to that on the bamboo and plastic pots in the previous paper.

• The Journal of Society for e-Business Studies
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• v.21 no.3
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• pp.79-99
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• 2016

Supply network of automobile part is addressed with the e-invoices generated at real time. Automobile is composed of 8 modules. Firms which produce these modules are defined as the first outsourcing firm. Brake is the part of power control module and so, brake manufacturing firm is called the second outsourcing firm. In this paper, the third supply networks of brake manufacturing firms is analyzed with e-invoices and social network method. At the node-level, the third outsourcing firms are classified into 3 categories, interator, allocator and hub with respect to their role at the ego-network of each brake manufacturing firm. At the network level, A2, one of 3 brake manufacturing firms have more outsourcing firms and bigger centrality than the other brake manufacturing firms. Intre-firms trade patterns are, also, analyzed by using the degree of trade dedication with respect to the modes of business. It is shown that trade pattern of retail, commodity brokerage firm, rubber and plastic manufacturing firm are hierarchical trade because their degree of trade dedication is almost near to 1.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.2
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• pp.141-154
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• 1993

In this paper, a method to calculate the ultimate compressive strength of welded one-sided stiffened plates simply supported along all edges is proposed. At first initial imperfections such as distortions and residual stresses due to welding are predicted by using simplified methods. Then, the collapse modes of the stiffened plate are assumed and collapse loads for each mode are calculated. Among these loads, the lowest value is selected as the ultimate strength of the plate. Collapse modes are assumed as follows ; (1) Overall buckling of the stiffened plate$\rightarrow$Overall collapse due to stiffener bending (2) Local buckling of the plate part$\rightarrow$Local collapse of the plate part$\rightarrow$Overall collapse due to stiffener yielding (3) Local buckling of the plate part$\rightarrow$Overall collapse due to stiffener berthing (4) Local buckling of the plate part$\rightarrow$Local collapse of the plate part$\rightarrow$Overall collapse due to stiffener tripping. The elastic large deflection analysis based on the Rayleigh-Ritz method is carried out, and plastic analysis assuming hinge lines is also carried out. Collapse load is defined as the cross point of the two analysis curves. This method enables the utimate strength to be calculated with small computing time and a good accuracy. Using the present method, characteristics of the stiffener including torsional rigidity, bending and tripping can also be clarified.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3A
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• pp.161-169
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• 2012

This paper presents the safety and strength of simplified composite H-beam panel bridges (SCHPBs) using 3-dimentional finite-element program, ABAQUS (2007) and experimental tests. Two finite-element models (one-steel-girder-and-composite-deck model and four-steel-girder-and-wide-composite-deck model) were reviewed to predict the strength and load distribution factor (LDF) values of the composite bridges. Based on the results of the finite-element analyses, the behaviors of the two models were investigated, and deflection and strain gauges for the experimental specimens were set up to obtain the ultimate strengths and the LDF values. The ultimate strength of the one-steel-girder-and-composite-deck specimen was estimated to be 840 kN. The yield and plastic moments of the four-steel-girder-and-wide-composite-deck specimen were obtained to be 2.4 and 4.1 times the design moment based on the live loading condition of the Korea Bridge Design Specifications (2005). The SCHPB were found to have enough strength for safety under and after construction.

• Composites Research
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• v.33 no.3
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• pp.161-168
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• 2020

In this paper, we have studied the mechanical properties of thermoplastic carbon fiber fabric composites with spread technology and compression molding temperature were investigated. Carbon fiber reinforcement composites were fabricated using commercial carbon fiber fabrics and spread carbon fiber fabrics. Mechanical properties of the commercial carbon fiber composites (CCFC) and spread carbon fiber composites (SCFC) according to compression molding temperatures were investigated. Thermal properties of the polypropylene film were examined by rheometer, differential scanning calorimetry, thermal gravimetric analysis. Tensile, flexural and Inter-laminar shear test. Commercial carbon fiber reinforcement composites and spread carbon fiber composites were fabricated at 200~240℃ above the melting temperature of the polypropylene film. Impregnation properties according to compression molding temperature of the polypropylene film were investigated by scanning electron microscopy. As a result, as the compression molding temperature was increased, the viscosity of the polypropylene film was decreased. The mechanical properties of the compression molding temperature of 230℃ spread carbon fiber composite was superior.

• Resources Recycling
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• v.22 no.5
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• pp.20-28
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• 2013

This study was carried out to evaluate the possibility of resource recovery for municipal solid waste(MSW) that sorted by a MBT system. First, physical property of MSW was similar to wastes carried into Sudokown landfill site. However, moisture of MSW was little higher than that. As a result of BMP test using organic fraction of MSW(OFMSWs), approximately 60 ~ 80 mL $CH_4/g$-VS of methane was occurred. Compared to the other studies, the value of methane is lower. It seems to be caused that high ratio of vinyl/plastic in OFMSWs. The other BMP test using sample of MBT system located in Sudokwon landfill was conducted each physical properties. According to the result of experiment, food waste makes 193 mL $CH_4/g$-VS, and paper is 102 mL $CH_4/g$-VS. However, there was not methane production in vinyl and rubber. Additionally, others that can't sort no more show 30 m $CH_4L/g$-VS of methane production. From the result of experimental data OFMSWs has high fraction of vinyl, rubber and other substance that difficult for biodegradation. Therefore it is need to sort of them.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.6
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• pp.531-539
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• 2017

This paper deals with the development of bonded joints for fibre reinforced plastic (FRP) hull structures using moulding-in concept. Focus is placed on bonded in-plane connections between two adjacent panels that could form the boundaries of hull structural module. Traditional construction in FRP hull structures requires the construction of a mould, usually from steel or aluminium. In this construction the FRP materials are laid in the mould, and resin is saturated, and then the structural member is cured. This is expensive since it involves the fabrication of metal hull mould for every different hull type, which is sacrificed after the production of the FRP ship. One way of encouraging greater use of FRP in ship construction is to investigate the possible construction of FRP hull structures in a similar manner to metallic ships, that is in terms of blocks or modules. Such a manner of construction would eliminate the need for expensive hull moulds permitting greater flexibility in the construction of FRP ships. The main issue then would be the design and construction of adequate bonded connections between adjacent panels. To fulfill this object, the simplified and automated way of manufacturing joint edge shapes for bonded joints is developed, and their structural assessment is performed in both experimentally and numerically.

• Steel and Composite Structures
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• v.13 no.3
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• pp.239-258
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• 2012

In this paper, experimental investigations on high strength steel (HSS) stud connected steel-concrete composite (SCC) girders to understand the effect of shear connector density on their flexural behaviour is presented. SCC girder specimens were designed for three different shear capacities (100%, 85%, and 70%), by varying the number of stud connectors in the shear span. Three SCC girder specimens were tested under monotonic/quasi-static loading, while three similar girder specimens were subjected to non-reversal cyclic loading under simply supported end conditions. Details of casting the specimens, experimental set-up, and method of testing, instrumentation for the measurement of deflection, interface-slip and strain are discussed. It is found that SCC girder specimen designed for full shear capacity exhibits interface slip for loads beyond 25% of the ultimate load capacity. Specimens with lesser degree of shear connection show lower values of load at initiation of slip. Very good ductility is exhibited by all the HSS stud connected SCC girder specimens. It is observed that the ultimate moment of resistance as well as ductility gets reduced for HSS stud connected SCC girder with reduction in stud shear connector density. Efficiency factor indicating the effectiveness of high strength stud connectors in resisting interface forces is estimated to be 0.8 from the analysis. Failure mode is primarily flexure with fracturing of stud connectors and characterised by flexural cracking and crushing of concrete at top in the pure bending region. Local buckling in the top flange of steel beam was also observed at the loads near to failure, which is influenced by spacing of studs and top flange thickness of rolled steel section. One of the recommendations is that the ultimate load capacity can be limited to 1.5 times the plastic moment capacity of the section such that the post peak load reduction is kept within limits. Load-deflection behaviour for monotonic tests compared well with the envelope of load-deflection curves for cyclic tests. It is concluded from the experimental investigations that use of HSS studs will reduce their numbers for given loading, which is advantageous in case of long spans. Buckling of top flange of rolled section is observed at failure stage. Provision of lips in the top flange is suggested to avoid this buckling. This is possible in case of longer spans, where normally built-up sections are used.

• Steel and Composite Structures
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• v.34 no.1
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• pp.1-15
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• 2020

This paper presents experimental and numerical studies on effects of local damages on the in-plane elastic-plastic buckling and strength of a fixed parabolic steel tubular arch under a vertical load distributed uniformly over its span, which have not been reported in the literature hitherto. The in-plane structural behaviour and strength of ten specimens with different local damages are investigated experimentally. A finite element (FE) model for damaged steel tubular arches is established and is validated by the test results. The FE model is then used to conduct parametric studies on effects of the damage location, depth and length on the strength of steel arches. The experimental results and FE parametric studies show that effects of damages at the arch end on the strength of the arch are more significant than those of damages at other locations of the arch, and that effects of the damage depth on the strength of arches are most significant among those of the damage length. It is also found that the failure modes of a damaged steel tubular arch are much related to its initial geometric imperfections. The experimental results and extensive FE results show that when the effective cross-section considering local damages is used in calculating the modified slenderness of arches, the column bucking curve b in GB50017 or Eurocode3 can be used for assessing the remaining in-plane strength of locally damaged parabolic steel tubular arches under uniform compression. Furthermore, a useful interaction equation for assessing the remaining in-plane strength of damaged steel tubular arches that are subjected to the combined bending and axial compression is also proposed based on the validated FE models. It is shown that the proposed interaction equation can provide lower bound assessments for the remaining strength of damaged arches under in-plane general loading.