In this article, improvement of heat screen failure for battle tank is proposed. The heat screen applied to protect a cam sensor from engine heat was cracked by vibrations generated in the engine. To solve this problem, the configuration of the heat screen was changed to a structure that can avoid engine vibration levels. The improved heat screen has first mode frequency at 4,000 RPM band outside the main operating range of the engine, and heat dissipation is at the same level as conventional heat screen. As a result, the improved heat screen secured reliability by improving vibration effects by approximately 163% while maintaining heat dissipation performance.

Following the earthquake that shook the city of Gyeongju, Korea, in 2016, it became apparent that research on the safety of cultural heritages against the seismic hazards is necessary in Korea. Predictions of how historically significant stone pagodas would behave the earthquakes anticipated in near future, which are the subject of this study, is also required. In this study, the dynamic characteristics of 15 cultural heritage designated stone pagodas of Korea were investigated, including natural frequency and damping ratio, and the stiffness of the stone material and its contact area were determined using eigenvalue analysis by assuming the stone pagodas to be multi-degree-of-freedom structures. The results of this study enable the structural modeling of stone pagodas using a finite element analysis program and the method is expected to be useful in assessing the structural safety of stone pagodas against vertical loads as well as lateral forces, including earthquakes. Also, by identifying the dynamic characteristics of the structures, the results of this study can be utilized as a nondestructive testing method to determine the rigidity of cultural heritage structures and to identify inherent problems. The natural frequencies of the Korean stone pagodas were measured to be within 3.5~8.3㎐, excluding cases with distinct natural frequency results, and it was determined that the natural frequencies of the stone pagodas are influenced by various parameters including the height and joint stiffness of the structures.

Theories for composite structures are too difficult for design engineers for construction. The purpose of this paper is to demonstrate to the practicing engineers, how to apply the advanced composite materials theory to the structures. In this study, the natural frequency of a laminated cantilever beam was studied. An ultrasonic testing platform was employed to resonate the beam, and its time domain signal was optically measured. The natural frequency was quantified through the fast Fourier transform of the waveform, and the result showed good agreement with a theoretical estimation from the Euler-Bernoulli beam theory. This study is expected to provide a dynamic evaluation technique for laminated cantilever beam structures.

오늘날까지 적층 마이크로 외팔보의 고유진동수에 대하여 연구가 진행되었다. 마이크로 보는 실리콘 재질로 만들어 지지만, 그것의 상하 표면은 얇은 금 박막층(~30nm)이 증착되어 있다. 초음파 검사를 위해 초음파 테스트 플랫폼을 사용했으며, 시간영역 신호는 광학적으로 측정되었다. 고유진동수는 파형을 고속 Fourier 변환을 통해 정량화하였으며, 결과적으로 고전적인 보 이론과 일치하는 결과를 보여 주었다. 본 연구는 마이크로/나노스케일 재료와 마이크로 구조에 대한 동적평가기법 을 제공할 것으로 기대된다.

본 연구에서는 5층에 설치된 능동질량감쇠기를 사용하여 5층 철골구조물의 처음 세 개 모드의 모드 특성을 식별하였다. 이 건물은 병진모드와 비틀림모드의 고유진동수가 매우 근접하며, 이 경우 정확한 모드 분리와 모달 파라미터 식별은 매우 어렵다. 사인 하중 가진실험을 수행하여 모드 진동수, 감쇠비, 질량, 모드형상을 식별하였고, 근접한 모드 응답을 분리하였다. 식별된 시스템은 동일 한 입력신호를 사용하여 측정된 구조물의 응답과 매우 근접한 응답을 추정할 수 있다.

In this paper, the method of vibration analysis for calculating the natural frequency is presented. This method is a simple but exact method of calculating natural frequencies corresponding to the modes of vibration for the cantilevered composite materials conical beam. The influence of natural frequency of the cantilevered composite materials conical beam is presented. This method may be extended to stability analysis of complex structureal elements.

Theories of advanced composite structures are too difficult for such field engineers and some simple methods are necessary. In this paper, Simple method of vibration analysis is presented. This method presented in this paper is studied self-weight and other loads. The result of the 2~3 times iteration is good enough for field engineering purposes. In the case of cantilevered composite materials beams with different cross section, increase of mass near the support does not significantly affect the vibration characteristics. As a calculations of the simple method of vibration analysis for cantilevered composite materials beams with different cross section, it is noted that the result of the second cycle at the point of free end (actually 5L/6 span) is only 2.2% away from the ‘exact’ solution.

In this paper. the effects of the aspect ratio on the natural frequency of the advanced composite road structures is studied. The advanced composite structures are too difficult for such design engineers for construction and some simple but accurate enough methods are necessary. Some laminate orientations have decreasing values of  ,  ,  and  stiffnesses as the ply number increases. The plate aspect ratio considered is from 1 to 5. Most of the road structures have large aspect ratios, for such cases further simplification is possible by neglecting the effect of the longitudinal moment terms.

Wind turbine tower has a very important role in wind turbine system as one of the renewable energy that has been attracting attention worldwide recently. Due to the growth of wind power market, advance and development of offshore wind system and getting huger capacity is inevitable. As a result, the vibration is generated at wind turbine tower by receiving constantly dynamic loads such as wind load and wave load. Among these dynamic loads, the mechanical load caused by the rotation of the blade is able to make relatively periodic load to the wind turbine tower. So natural frequency of the wind turbine tower should be designed to avoid the rotation frequency of the rotor according to the design criteria to avoid resonance. Currently research of the wind turbine tower, the precise research does not be carried out because of simplifying the structure of the other upper and lower. In this study, the effect of blade modeling differences are to be analyzed in natural frequency of wind turbine tower.

Natural frequency characteristic of Wind turbine tower is important for designing of tower due to guarantee of structural safety of tower. In GL specification, natural frequency of tower should be designed by consideration of blade rotational frequency. Natural frequency characteristic of tower could be changed by mass ratio of RNA-tower, modeling method of blade and angle of blade in idling condition. In this research, natural frequency of tower is analysed by ABAQUS and compared it result according to tower dimension.

According to natural frequency of soil, characteristics of earthquake responses of an isolated containment building in nuclear power plants are examined. For this, earthquake response analysis of seismically isolated containment buildings in nuclear power plants is carried out by strictly considering soil-structure interactions. The structure and near-field soil are modeled by the finite element method while far-field soil by consistent transmitting boundary. The equation of motion of a soil-structure interaction system under incident seismic wave is derived. The derived equations of motion are solved to carry out earthquake analysis of a seismically isolated soil-structure system. Generally, the results of this analysis show that seismic isolation significantly reduces the responses of the soil-structure system. However, if the natural frequency of the soil is similar to that of the soil-structure system, the responses of the containment buildings in nuclear power plants rather increases due to interactions in the system.

PURPOSES: This paper aims to give a guideline and the way to apply the advanced composite materials theory to the road structures with different cross sections to the practicing engineers. METHODS: To simple but exact method of calculating natural frequencies corresponding to the modes of vibration of road structures with different cross sections and arbitrary boundary conditions. The effect of the D22 stiffness on the natural frequency is rigorously investigated. RESULTS: Simple method of vibration analysis for calculating the natural frequency of the different cross sections is presented. CONCLUSIONS: Simple method of vibration analysis for calculating the natural frequency of the different cross sections is presented. This method is a simple but exact method of calculating natural frequencies of the road structures with different cross sections. This method is extended to be applied to two dimensional problems including composite laminated road structures.

PURPOSES: Current theories for composite structures are too difficult for design engineers for construction. The purpose of this paper is to demonstrate to the practicing engineers, how to apply the advanced composite materials theory to the road structures. METHODS: Some laminate orientations have decreasing values of D16, B16, D26 and B26 stiffnesses as the ply number increases. The plate aspect ratio considered is from 1 to 5. In order to study the effect of Mx on the equilibrium equations, two cases are considered. Mx term is considered or neglected. RESULTS: Most of the road structures have high aspect ratios, for such cases further simplification is possible by neglecting the effect of the longitudinal moment terms. CONCLUSIONS: Most of the road structures have plate aspect ratios higher than 2. It is concluded that, for all boundary conditions, neglecting the longitudinal moment(Mx) terms is acceptable if the aspect ratio (a/b) is equal to or higher than 2. This conclusion gives good guide line for design of the road structures.

In this paper, the relation between the applied load distribution and the natural frequency of vibration of some structural elements is presented. In this paper, the effects of the loading sizes on the natural frequency of vibration of some structural elements is presented. Many junior engineers get confused on such relations. This method extended to two dimensional problems including advanced composite laminated structures. It is hoped that this paper gives some guideline to such junior engineers.

본 연구진은 최근 U자 형태인 액체댐퍼의 수직관을 다수의 셀(사각 기둥)로 나누어 셀 상부를 개폐함에 따라 다양한 고 유진동수를 쉽게 재현하는 새로운 멀티셀 액체댐퍼를 제시하였다. 이러한 댐퍼를 1층 건물 모형에 설치하여 진동대 실험을 수행하여 건물응답이 감소되는 것을 검증하였다. 64층의 풍응답인 가속도를 제어할 수 있도록 댐퍼를 설계하기 위하여 건 물을 1자유도계로 축소하였다. 가속도 기반 상사비인 1/20를 적용하여 1층 건물 모형과 새로운 댐퍼를 제작하였다. 설계 진 동수인 0.65Hz가 구현되도록 모형건물의 질량과 강성을 쉽게 조절할 수 있도록 탈부착식으로 제작하였다. 모형건물은 중량 을 부담하는 질량부와 하부에 스프링과 LM guide가 설치된 구동부로 나누어서 제작되었다. 18개의 셀을 가지는 액체댐퍼 를 제작하여 고유진동수 조절 범위가 0.65Hz～0.81Hz인 것을 파악하였다. 대형 진동대에 설치한 모형건물의 일방향 가진을 통하여 모형의 응답을 측정하고 모형상부에 멀티셀 액체댐퍼가 설치되었을 경우 모형의 응답을 측정하여 비교하였다. 진동 대 가속도를 입력과 모형건물의 가속도를 출력으로 하는 전달함수를 통해 결과를 나타내었다. 예상한 바와 같이 멀티셀 액 체댐퍼의 고유진동수를 건물의 진동수에 동조시켰을 경우 건물의 가속도 응답이 감소함을 알 수 있었다.

본 논문에서는 고유진동수 조절이 가능한 멀티셀 액체댐퍼를 개발하여 특성을 평가하였다. 본 연구에서 제안한 댐퍼의 기본적인 형태는 기존의 Liquid Column Vibration Absorber(LCVA)와 같다. 그러나 이번에 제안한 액체댐퍼는 기존 LCVA의 수직관을 일정한 면적의 독립된 셀로 나누었으며 이 셀을 각각 밀폐시킬 수 있게 하여 수직관의 면적을 조절하는 방식으로 댐퍼의 고유진동수를 변화시킬 수 있도록 하였다. 이렇게 제작된 액체댐퍼는 밀폐된 셀 개수를 조절하여 진동대 실험을 통해 댐퍼의 고유진동수 특성을 파악하였다. 진동대 실험에서 나온 고유진동수와 이론적으로 산정한 고유진동수를 비교하여 댐퍼의 사용성을 평가하였다. 개발된 액체 댐퍼의 수직관의 면적 조절을 통해 고유 진동수 조절이 용이하여 실제로 사용이 가능함을 확인할 수 있었다.

임의의 단면과 지점을 갖고 임의의 하중을 받는 보나 탑의 진동해석 방법이 발표된 바가 있다. 이러한 진동해석을 위하 여 처짐의 영향을 고려한 다양한 방법이 검토되었다. 본 연구에서 얻은 결과를 보 이론과 비교하였다. 이러한 목적으로 본 논문에서는 유한차분법을 사용하였다. 고유진동수에 대한 D 22 탄성계수의 영향을 철저히 검토하였다. 본 논문에서는 구조부재의 고유진동수와 적용 하중의 크기에 대한 관련성을 연구하였으며 그 결과를 제시하였다. 본 논문에서는 특별 직교이방성 판이론 이용하여 강교량과 철근콘크리트 슬래브 교량에 적용하여 을 해석하였으며 그 결과를 제시하였다.

건설관련 설계기술자들에게는 첨단 복합신소재 구조에 대한 이론이 너무 어려워서 간단하면서도 쉽게 적용할 수 있는 정확한 방법을 필요로 하고 있다. 몇 가지 섬유 배향각을 가진 적층판은 층수가 증가하면 D16, B16, D26 및 B26 강성이 감소하게 되어 특별직교이방성 판처럼 거동함을 밝히고, 간단한 공식들을 개발하여 발표한 바 있다. 대부분의 교량이나 건물의 상판은 형상 비가 큰 경우가 많은데, 이런 구조물의 평형방정식에 대한 종방향모멘트항(Mx)의 영향은 매우 작아서, 더욱 간단한 해석이 가능하다. 본 논문에서는 복합적층판의 고유진동수에 대한 형상비의 영향을 연구하였으며 이 방법을 사용하면 충분히 정확한 값을 쉽게 산출할 수 있다.