• The Journal of the Korea Contents Association
• /
• v.14 no.7
• /
• pp.511-517
• /
• 2014

The superstructure type of the railway bridge in our country, is mainly classified into the box girder and the I-type girder. The box girder is widely used in the high speed railway bridge because of the safety due to dynamic behavior. The I-type girder is used in the conventional railway bridge, and is also divided into the general type and the composite type, and the newly modified types have been developed. According to the current railway bridge design code, the girder design by the span length in various railway bridge types are performed in this study. The suitable girder height by the span length are analyzed, and the comparative analysis of the structural efficiency and the economical efficiency is carried out. From this study, the composite type girder is appeared the good result in respect of the structural efficiency. However, in the economical aspect, the general I-type girder is required less cost than the other types.

• Journal of the Society of Disaster Information
• /
• v.13 no.4
• /
• pp.455-464
• /
• 2017

Static loading test was performed on a composite girder with an I-shaped steel girder and SUPER concrete on the top of the steel in order to evaluate flexural behavior characteristics. Total length of the test specimen was 25m long and the depth was 786mm including compressive concrete section('casing' hereafter) with 80MPa strength. 4-point loading on simply-supported beam was applied up to 2,010kN. Results showed that yield strength at tensile steel was 2.7 times greater than service load and the ratio of ductility was 1.481. No cracks were found on the casing surface and the relative slip between different sections was insignificant.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.3A
• /
• pp.241-256
• /
• 2010

This study intends to develop an aerodynamic girder for suspension bridge with width corresponding to 1/70 of the main span length. In the first step of present study, parametric study for the effects of major structural properties on aerodynamic stability of bridges was performed. The span length and natural frequency of bridges were found to be free from girder width, girder height, and aspect ratio of width to height. The empirical equation according to confidence interval was proposed to estimate the natural frequencies of bridges from span length. From the sensitivity analysis, it was revealed that the torsional frequency was dominant parameter among various structural properties that affected flutter velocity mostly. The final aerodynamic bridge section which satisfied the flutter criteria was found from section wind tunnel tests for 30 cross sectional models. The aerodynamic stability of the developed cross section was verified by multimode flutter analysis. The present economical cross section can be used for long span suspension bridge.

• 대한공업교육학회지
• /
• v.43 no.1
• /
• pp.76-93
• /
• 2018

The purpose of this study is to analyze job of management teacher of industry-academy cooperation of specialized high school using DACUM method. The contents of this study are to identify the duties, tasks and the level of importance, difficulty, frequency and entry level on each task. Finally, based on the job analysis results, the DACUM chart of management teacher of industry-academy cooperation of specialized high school was developed. The workshop for DACUM job analysis consisted of one DACUM facilitator who acquired Level-I license, eight members of DACUM who had more than five years experience, one clerk and one practitioner for two days. The results of the study are as follows. First, this study defines management teacher of industry-academy cooperation as 'a person who career teachers in charge of career guidance, NCS-based field practice, establishment of industry-academia-government relations, external business administration, industry-academia cooperation administration, teaching subject class'. Second, the job of management teacher of industry-academy cooperation were total 7 duties and 80 tasks. Third, the importance, difficulty, and frequency of each task are classified into high (A), normal (B), and low (C) according to degree. Finally, this study make out a DACUM chart of management teacher of industry-academy cooperation of specialized high school based on the results of DACUM job analysis. And knowledge, skills, tools, and positive behaviors, future trends/concerns about management teacher of industry-academy cooperation of specialized high school were presented.

• Journal of Korean Society of Steel Construction
• /
• v.15 no.1
• /
• pp.77-85
• /
• 2003

The lifting and lowering supports method makes up for the weak points in the classical method and provides makes construction economical effect to construction. The application of pre-compression to continuous steel box girder bridges makes it possible to reduce the amount of steel, the height of girders and consequently, the cost consequentlyof the bridges' construction by through the process of concrete filling- up and the lifting-lowering of the inner supports. The lifting and lowering supports method is apt to cause local buckling in the lower flange and web plates by due to the process of the lifting of the inner supports. Therefore iln this study, therefore, the possibility of local buckling could be decreased, in consideration of the lifting force and the buckling strength of stiffened plates, by increasing the number of longitudinal stiffeners and the installation of extended longitudinal stiffeners on the lower flange and the web plates in the range of positive moment.

• Journal of Korean Society of Steel Construction
• /
• v.18 no.6
• /
• pp.793-804
• /
• 2006

Various PSC and steel-concrete composite railway bridges are being developed for short-medium spans with structural and economic efficiency. According to the design concept, the prestressed composite girder bridge has the advantages of being lightweight and having low girder depth, with the capacity for long spans. However, the dynamic behavior under a passing train is one of the critical issues concerning these railway bridges designed with more flexibility. Therefore, it is very important to evaluate the modal parameters before performing dynamic analyses. In this paper, real-scale prestressed composite girders were fabricated as a test model and modal testing was carried out to evaluate modal parameters including natural frequency and modal damping ratio. During the modal testing, a digitally controlled vibration exciter as well as an impact hammer was applied to obtain frequency-response functions, and the modal parameters were also evaluated after the fracture of test models. With application of reliable properties from modal tests, the estimation of dynamic performances of prestressed composite girder railway bridges can be obtained from various parametric studies on dynamic behavior under the passage of a moving train.

• Journal of Korean Society of Steel Construction
• /
• v.9 no.4 s.33
• /
• pp.697-705
• /
• 1997

The conventional preflex beams are designed by the method of paritial prestressing and allow the tensile stresses at the lower concrete of beams. As a consequence, most of preflex beams experience the tensile cracks under the service loads. This study was conducted to develop the most effective preflex beams, which do not allow tensile stress under the service load, by introducing additional prestressing called 'represtressing' at the lower concrete of beams. The objective of the study was accomplished by developing a computer analysis and design program and conducting experiments. Using the developed computer program, standard sections of the represtressed preflex beams were determined by computer modeling. In the experiment, two actual size of represtressed beams were tested under the imitated service loads. The results of test have shown that the performance of the represtressed preflex beams is generally excellent. A remarkable improvement was made in the design of preflex composite beams. Since the represtressed preflex beams(RPF) do not experience the tensile cracks under the service loads, the use of this beam for the bridge structures will lead to easy bridge maintenance and management. Furthermore, due to the low beam depth, high clearance and economical design can be realized in the bridge design using RPF.

• 대한공업교육학회지
• /
• v.44 no.1
• /
• pp.114-140
• /
• 2019

The purpose of this research is to analyze a principal's job at a Vocational High School using DACUM Task Analysis Method. The contents of this research are to set the order after deriving the duties and tasks of the principal., then to verify as the importance, difficulty, and frequency of each task, and also to indicate whether it is an essential capability to have in the early stages of one's duty. Finally, based on the job analysis results, a DACUM chart was developed by the principal of the Vocational High School. The DACUM Task Analysis Workshop was attended by one DACUM analyst with LEVEL - 1 license, seven DACUM members with more than four years experience, one secretary and two administrative assistants for a two-day period. The results of the research are as follows; First, the Vocational High School Principal is defined as a school administrator who operate the vocational education curriculum of in the specialized and customized high schools of industrial demand development and the job area. The analysis derived 11 duties and 95 tasks of the Principal. Second, the importance, difficulties, and frequency of each task were divided respectively into high (A), moderate (B), and low (C), and the consensus of the experts was made to determine whether the core capabilities are acquired early on the job. Third, based on the analysis results, a DACUM Task Analysis chart of the Vocational High School principals was presented. In addition, while engaged on the job of the vocational high school principal, a list of 49 general knowledge and abilities, 16 tools, Integrated data and fixtures are required. Along with 28 attitudes 33 future prospects and characteristics of the Vocational High School principal was presented.