• 한국음향학회지
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• 제38권3호
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• pp.340-343
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• 2019

본 논문은 동력차에서 견인전동기 기진 주파수와 견인전동기 강체 모드 공진 문제로 인해 발생할 수 있는 현상에 대해 소개하고, 이를 제어하는데 효과적인 설계인자를 해석적으로 검토해보았다. 회전 속도가 변하는 회전기기의 경우, 공진 문제를 해결하기 위해서는 공진주파수 대역을 상용 운전 범위 바깥으로 이동시키거나 동강성을 크게 하는 등의 방법을 통하여 공진 응답이 낮아지도록 하는 방안이 있다. 견인전동기의 운전 범위는 일반적으로 0 r/min ~ 4800 r/min으로 대차모드가 이 운전 영역대를 벗어나게 설계하는 것은 현실적으로 불가능 하다. 따라서 공진 응답에 영향을 주는 설계 인자를 찾아 이를 적절하게 조정하여야 한다. 유한요소 해석 검토 결과, 견인전동기 강체모드 공진 응답에 영향을 주는 설계인자는 트랜섬파이프 간격으로 간격이 지나치게 넓게 설계될 경우 견인전동기 기진력과 강체 모드 간 공진 시 과도한 진동이 발생될 수 있음을 파악하였다.

• 한국안전학회지
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• 제35권5호
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• pp.49-58
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• 2020

In domestic construction sites, when installing steel pipe scaffolding and system scaffolding, the guardrails are installed after the installation of the work platforms. This conventional guardrail system (CGS) is always exposed to the risk of falls because the safety railing is installed later. In order to prevent fall disasters during erecting and dismantling scaffolds, it is necessary to introduce the advanced guardrail system (AGS) which installs railings in advance of climbing onto a work platform. For the introduction of the AGS, the structural performance of the system scaffolding applying the CGS and the AGS was compared and evaluated. The structural analysis of the system scaffold (height: 31 m and width: 27.4 m) with AGS confirmed that structural safety was ensured because the maximum stress of each element of the system scaffolding satisfies the allowable stress of each element. As a result of performance comparison of CGS and AGS for each element, the combined stress ratio of vertical posts in AGS was 6.4% lower than that of CGS. In addition, in the case of ledger and transom, the combined stress ratios of AGS and CGS were almost the same. The compression test of the assembled system scaffolding (three-storied, 1 bay) showed that the AGS had better performance than the CGS by 9.7% (8.91 kN). The cross bracing exceeds the limit on slenderness ratio of codes for structural steel design. But the safety factor for the compressive load of the cross bracing was evaluated as meeting the design criteria by securing 3 or more. In actual experiments, it was confirmed that brace buckling did not occur even though the overall scaffold was buckled. Therefore, in the case of temporary structures, it was proposed to revise the standards for limiting on slenderness ratio of secondary or auxiliary elements to recommendations. This study can be used as basic data for the introduction of AGS for installing guardrails in advance at domestic construction sites.