• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.271-280
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• 2011

This study intends to analytically evaluate the vibration serviceability of the bridges for each long-span type having the same span length and road width using the Meister vibration sensation curve. With MIDAS, a structural analysis program, bridges were modeled using the girders as the frame element and slabs as the plate element. The transient analysis was performed using the moving loads of the design vehicles. This study presents the analytical process of reviewing the vibration serviceability during the design of long-span bridges. It involves the comparison of the vibration serviceability of different bridge types by applying the lagging-behind and acceleration amplitude from transient analysis to Meister curve. The result confirms that the process is appropriate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.6
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• pp.1271-1276
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• 2006

Vertical loads acting on corrugated metal culverts under negative arching condition were investigated through numerical analyses. Four kinds of corrugated metal culverts with span of 3m were considered in numerical analyses. Also, depths of cover were varied from 1m to 6m with increment of 1m. According to numerical analyses, magnitudes of vertical loads acting on culverts under the condition of negative arching were similar as overburden load on culvert. Furthermore, magnitudes of vertical loads acting on culverts supported by pile foundation were similar as those without pile foundation when depths of cover were less than about 2m. For larger depths of cover which are greater than about two times of span of culvert, magnitudes of vertical loads were slightly larger than those without pile foundation and its tendency becomes more clear as flexural rigidity of corrugated metal increases.

• Journal of Korean Society of Steel Construction
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• v.10 no.1 s.34
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• pp.125-135
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• 1998

This study presents a design method for three-span continuous preflex composite girder bridges (3S-PCB) which imposes prestresses in the negative moment region by lifting or lowering interior supports and the design method is automated by a computer program which incorporates optimal design procedure. The objective function for the design of 3S-PCB minimizes the cost of construction materials and the constraint functions represent the limited dimensions of the design section and the allowable stress for each structural member as given in the specifications. Optimal design procedure used in this study is a modification of existing sequential unconstrained minimization technique (SUMT), a numerical analyses procedure for two-span continuous preflex composite bridges. The optimized design sections determined for each span length are compared with those of simple preflex composite beams (SPCB) and the optimal girder depth is determined by defining the relationship between girder depth and construction material costs.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.1-8
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• 2008

This research carried out to optimize crossbeams and stringers of steel box girder bridges, which are parts of floor system and support loading from the bridge deck. In the current design practice, the crossbeam is densely deployed with a spacing of 6 meters, and the stringer is placed between the crossbeams. The crossbeams and stringer are connected to the deck through slab anchors but the allowable stress of the compression flange is determined by the lateral-torsional buckling. To increase economic efficiency of the steel box girder bridges. the increased spacing of the crossbeam was studied. The study shows that the spacing can be increased up to 10 meters. However, higher strength steel plates are necessary. Shear studs rather than slab anchors are also recommended to prevent lateral-torsional buckling strength of the crossbeams and stringer.

• Journal of Korean Society of Transportation
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• v.28 no.5
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• pp.107-116
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• 2010

The vehicle travel time between locations in a downtown is greatly influenced by both complex road conditions and traffic situation that changes real time according to various external variables. The customer's demands also stochastically change by time period. Most vehicle routing problems suggest a vehicle route considering travel distance, average vehicle speed, and deterministic demand; however, they do not consider the dynamic external environment, including items such as traffic conditions and stochastic demand. A realistic vehicle routing problem which considers traffic (smooth, delaying, and stagnating) and stochastic demands is suggested in this study. A mathematical programming model and hybrid genetic algorithm are suggested to minimize the total travel time. By comparing the results considering traffic and stochastic demands, the suggested algorithm gives a better solution than existing algorithms.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.2
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• pp.125-133
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• 2017

This paper presents the inter-rater reliability of finger spasticity assessment tested realized by using finger simulator that mimics finger spasticity of patients after a stroke. For controlling the simulator torque, finger spasticity was modeled, and the model parameters were obtained by measuring quantitative data while grading based on Modified Ashworth Scale (MAS). A robotic finger simulator was designed for mimicking finger spasticity. Evaluation of this simulator with the help of seven rehabilitation doctors showed that the simulator had a Cohen's kappa value of 0.619 for Metacarpophalangeal Joint and 0.514 for Proximal Interphalangeal Joint. Fleiss' kappa between raters is 0.513 for Metacarpophalangeal Joint and 0.486 for Proximal Interphalangeal Joint. Therefore, the spasticity assessment made by MAS grade system is not reliable owing to the subjectivity of the assessment. The proposed robotic simulator can be used as a training tool for improving the reliability of the spasticity assessment.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.1
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• pp.65-71
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• 2009

In this study, dynamic serviceability of PSC, PreStressed Concrete, simple railway bridge with 25m span was estimated. All of the high speed and general train loads were considered at estimation. Natural frequency is estimated about 8Hz and includes within optimum natural frequency extent of the railway bridge. Also, the bridge was detected that resonance occurrence possibility does not exist. When travel the Moogunghwa train, acceleration response was measured to 0.43g that exceed limitation value 0.35g. Also, rotation angle of girders end did not satisfy design standard of railway bridge for high speed train, but impact coefficient and deflection satisfied design standard. As a result, that railway bridge was detected that is securing dynamic safety and serviceability partially, but methods to decrease vibration acceleration response are required.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1A
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• pp.39-49
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• 2008

Dynamic responses of steel plate girder bridges considering road surface roughness of bridge and bridge-vehicle interaction are investigated by numerical analysis. Simply supported steel plate girder bridges with span length of 20 m, 30 m, and 40 m from "The Standardized Design of Highway Bridge Superstructure" published by the Korean Ministry of Construction are used for bridge model and the road surface roughness of bridge decks are generated from power spectral density(PSD) function for different road. Three different vehicles of 2- and 3-axle dump trucks, and 5-axle tractor-trailer(DB-24), are modeled three dimensionally. For the bridge superstructure, beam elements for the main girder, shell elements for concrete deck, and rigid links between main girder and concrete deck are used. Impact factor and DLA of steel plate girder bridges for different spans, type of vehicles and road surface roughnesses are calculated by the proposed numerical analysis model and compared with those specified by several bridge design codes.

• International Area Studies Review
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• v.15 no.1
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• pp.571-583
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• 2011

We use the properties of competitive location equilibrium to study the relationship between the demand for education and the choice of primary residential location. Consumers can work and live in a comparatively high wage place where there are few education opportunities, or live in a place where education is available and commute to work. If education and employment are each location-specific, there are pooling equilibria in which consumers locate according to their preference for education. In general, the stronger the taste for education, the greater the attraction of living close to the education site and the lower the demand for other goods, including housing. Exploring the effects of the model parameters on the spatial distribution of consumers, we find that a higher frequency of trips taken to the education site, a shorter distance between the work place and the education site, or a greater out-of-pocket education cost each leads to a wider range of consumer types selecting to reside at the education location. We also find that a higher wage lowers the range of consumers who select to live near the education site.

• Journal of the Korean Orthopaedic Association
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• v.56 no.6
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• pp.484-490
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• 2021

Purpose: A rheumatoid forefoot deformity includes severe hallux valgus and claw toe of the four lateral toes. The authors intended to analyze the mid-term results of the modified Hoffman procedure for a rheumatoid forefoot deformity. Materials and Methods: Twenty-two feet of eighteen patients were followed up for more than two years after the modified Hoffman procedure. The mean age was 54.7 years, and the mean follow-up period was three years and four months. Clinically visual analogue scale (VAS) and American Orthopaedic Foot and Ankle Society (AOFAS) MP-IP score were analyzed preoperatively and postoperatively. The postoperative complications, the satisfaction of patients, and the presence of plantar callosity were also analyzed. Radiographically, the hallux valgus angle, the 1st intermetatarsal angle, the 1st interphalangeal angle, the 1st interphalangeal joint arthritic change after the operation, and the dorsiflexion angle and the time to union of the 1st metatarsophalangeal joint were analyzed. Results: Clinically, the VAS and AOFAS score were respectively improved from 7.1 points and 30.3 points preoperatively to 1.5 points and 83.1 points postoperatively (p<0.001). All patients were satisfied with the results. Plantar callosity disappeared in all cases. Radiographically, the mean hallux valgus angle, the 1st intermetatarsal angle, and the 1st interphalangeal angle changed from 52.8°, 13.3°, and 7.5° preoperatively to 16.2°, 8.7°, and 14.6° postoperatively (p<0.001). The mean dorsiflexion angle of the 1st metatarsophalangeal joint was 17.2° postoperatively. The mean time to radiographic union of the 1st metatarsophalangeal joint was 11.1 weeks. There were two cock-up deformities of the lesser toe, one wound problem, and two hallux interphalangeal joint arthritis as a complication. There were no cases of nonunion of the 1st metatarsophalangeal joint. Conclusion: The modified Hoffman procedure appears to be a safe and satisfactory procedure for a rheumatoid forefoot deformity.