• Structural Engineering and Mechanics
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• 제87권1호
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• pp.57-68
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• 2023

Response spectrum method is still an effective approach for the design of buildings with supplemental dampers. In practice, complex complete quadratic combination (CCQC) rule is always used in the response spectrum method to consider the effect of non-classical damping. The conventional CCQC rule is based on exact complex mode vectors. Sometimes the calculated complex mode vectors may be not excited by the external loading and errors in the structural responses always arise due to the mode truncation. Load-dependent Ritz (LDR) vectors are associated with the external loading and LDR vectors not excited can be automatically excluded. Also, contributions of higher modes are implicitly contained in the LDR vectors in terms of static responses. To improve the calculation efficiency and accuracy, LDR vectors are introduced in the CCQC rule in the present study. Firstly, the generation procedure of LDR vectors suitable for non-classical damping system is presented. Compared to the conventional LDR vectors, the LDR vectors herein are complex-valued and named as complex LDR (CLDR) vectors. Based on the CLDR vectors, the CCQC rule is then rederived and an improved response spectrum method is developed. Finally, the effectiveness of the proposed method in this paper is verified through three typical non-classical damping buildings. Numerical results show that the CLDR vector is superior to the complex mode with the same number in the calculation. Since the generation of CLDR vectors requires less computational cost and storage space, the method proposed in this paper offers an attractive alternative, especially for structures with a large number of degrees of freedom.

• 대한기계학회논문집A
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• 제39권5호
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• pp.491-497
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• 2015

본 논문은 필라멘트 와인딩 공법으로 제작된 구배 단면을 갖는 돔 분리형 복합재 압력용기 접착체결부의 온도영향에 따른 층간파괴인성 평가를 위해 모드 I, II 그리고 혼합모드의 시험적 평가를 수행하였다. 모드 I과 혼합모드 층간파괴인성은 DCB 시편을 사용하였으며, 모드 II 층간파괴인성은 ENF 시편을 사용하여 평가하였다. 와인딩 각도는 $[{\pm}10^{\circ}]_6$, $[{\pm}27^{\circ}]_6$ 그리고 ($[{\pm}10^{\circ}]_3/FM73/[{\pm}10^{\circ}]_3$)이며 곡면 단면을 고려하였다. 시험 평가에 적용된 온도 환경은 환경 챔버와 전기로를 이용하여 $-30^{\circ}C$에서 $60^{\circ}C$로 조성하였다. 층간파괴인성에 온도가 미치는 영향을 평가한 결과, 층간파괴인성은 저온에서 높게 나타났으며, 온도가 증가함에 따라 감소하는 경향을 확인하였다. 시편 종류별 결과에서는, 돔부와 헬리컬부가 접착체결된 $[{\pm}10^{\circ}]_3/FM73/[{\pm}10^{\circ}]_3$ 와인딩 시편이 가장 높은 층간파괴인성을 가짐을 확인하였다.

• Computers and Concrete
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• 제15권2호
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• pp.141-166
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• 2015

In the present study, a Finite Element Model has been developed and used to study the effect of diameter to wall thickness ratio (D/t) of steel tube filled with concrete under axial loading on its behavior and load carrying capacity. The model is verified by comparing its findings with available experimental results. Influence of thickness and area of steel tube on strength, ductility, confinement and failure mode shapes has been studied. Strength enhancement factors, load factor, confinement contribution, percentage of steel and ductility index are defined and introduced for the assessment. A parametric study by varying length and thickness of tube has been carried out. Diameter of tube kept constant and equals to 140 mm while thickness has been varied between 1 mm and 6 mm. Equations were developed to find out the ultimate load and confined concrete strength of concrete. Variation of lateral confining pressure along the length of concrete cylinder was obtained and found that it varies along the length. The increase in length of tubes has a minimal effect on strength of tube but it affects the failure mode shapes. The findings indicate that optimum use of materials can be achieved by deciding the thickness of steel tube. A better ductility index can be obtained with the use of higher thickness of tube.

• 토지주택연구
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• 제3권2호
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• pp.169-175
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• 2012

최근, 지열 냉난방 시스템의 초기 공사비를 절감하기 위해 연구되고 있는 에너지 파일의 열교환량을 산정하기 위해 2종류(부속연결형, 슬링키형)의 현장타설말뚝형(PRD, 시공심도 4.5m, 직경 1,200mm) 에너지 파일을 시험시공하고 수치 시뮬레이션에 의해 효율을 상호 비교하였다. 상호 비교결과에 의하면 지중 교환량은 운전시작과 함께 채열에 의한 지중온도의 저하에 의해 점점 감소하였고 부속연결형의 평균 열원수의 온도차는 난방운전에서 $0.37^{\circ}C$, 냉방운전에서 $0.34^{\circ}C$로 나타났다. 또, 부속연결형의 난방운전시 열교환량 231.4W/m보다 냉방운전의 방열량은 252.2W/m로서 9% 높았고 슬링키형은 난방 기간 평균 열교환량이 168.0W/m로 부속연결형에 비해 약 27% 낮은 열교환량을 얻었다.

• 한국통신학회논문지
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• 제29권7A호
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• pp.814-827
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• 2004

WCDMA 시스템에서는 다른 주파수 또는 다른 시스템의 신호 세기를 측정하기 위하여 압축 모드(Compressed Mode)를 사용한다. 압축 모드로 동작하는 동안에는 처리 이득(Processing Gain)이 낮아지기 때문에 단말의 QoS(Quality of Service)에 영향을 끼친다. 그러므로 기지국은 단말이 요구하는 QoS를 만족시키기 위해서 전송 전력량을 증가시킨다. 한편 압축 모드의 전송 간격(Transmission Gap) 동안에는 내부 회로 전력 제어가 동작하지 않고 인터리빙(Interleaving)의 영향도 줄어들기 때문에 단말은 더 높은 Eb/No을 요구하게 된다. 따라서 시스템의 전체적인 성능 저하를 초래하게 된다. 성능에 미치는 영향 때문에, 압축 모드는 RNC(Radio Network Controller)에 의해서 다른 주파수 또는 다른 시스템의 신호 측정이 필요한 경우에만 동작하여야 한다. 그러나 3GPP는 압축 모드 동작을 결정할 수 있는 방법을 정의하지 않았다. 그러므로 성능 저하를 줄이기 위해서 압축 모드 동작을 결정할 수 있는 방법이 필요하다. 본 논문에서는 서비스 셀과 같은 주파수를 사용하는 인접 셀과 다른 주파수 또는 다른 시스템을 사용하는 인접 셀로 구성된 셀 환경에서 압축 모드가WCDMA 순방향 링크의 성능에 미치는 영향을 수식적으로 분석하고 압축 모드 사용에 따른 성능 저하를 줄이기 위하여 압축 모드가 필요하지 않은 단말의 압축모드 동작을 제한할 수 있는 단말 측정에 의한 압축 모드 방법을 제안한다. 수치적 분석 결과, 압축 모드를 사용할 때의 성능은 압축 모드를 사용하지 않을 때의 성능에 비해 급격하게 감소하는 것을 확인하였다. 그리고 제안하는 방법을 적용하였을 때, 압축 모드 사용에 따른 성능 감소를 크게 줄임을 확인하였다.

• Structural Engineering and Mechanics
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• 제51권1호
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• pp.131-140
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• 2014

This study focuses on seismic behaviour of tall piers characterized by high slender ratio. Two analysis models were developed based on elastic-plastic hinged beam element and elastic-plastic fiber beam element, respectively. The effect of the division density of elastic-plastic hinged beam element on seismic demand was discussed firstly to seek a rational analysis model for tall piers. Then structural seismic behaviour such as the formation of plastic hinges, the development of plastic zone, and the displacement at the top of the tall piers were investigated through incremental dynamic analysis. It showed that the seismic behaviour of a tall pier was quite different from that of a lower pier due to higher modes contributions. In a tall pier, an additional plastic zone may occur at the middle height of the pier with the increase of seismic excitation. Moreover, the maximum curvature reaction at the bottom section and maximum lateral displacement at the top turned out to be seriously out of phase for a tall pier due to the higher modes effect, and thus pushover analysis can not appropriately predict the local displacement capacity.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 가을 학술발표회 논문집
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• pp.267-272
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• 1993

Currently about 60 contries in the world require earthquake resistant structural design in case of multistory building constructions. In these cases the equivalent lateral force procedure is commonly adopted because of its simplicity and convenience. This procedure, however, is developed based mainly on the first vibration mode response of building structure. The dynamic analysis of tall building shows that the effect of higher modes of vibration on the response of the building can not be neglected. In this paper, the effect of higher modes of vibration on seismic response is evaluated through modal analysis of tall building structures. On the basis of evaluation results, an improved procedure is to be proposed for the extended application of the equivalent lateral force procedure.

• Structural Engineering and Mechanics
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• 제75권2호
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• pp.133-144
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• 2020

This investigation is to study the effect of gravitational field and diffusion on a microstretch thermoelastic medium heating by a non-Gaussian laser beam. The problem was studied in the context of the dual-phase-lag model. The normal mode analysis is used to solve the problem to obtain the exact expressions for the non-dimensional displacement components, the micro-rotation, the stresses, and the temperature distribution. The effect of time parameter, heat flux parameter and gravity response of three theories of thermoelasticity i.e. dual-phase-lag model (DPL), Lord and Shulman theory (L-S) and coupled theory (CT) on these quantities have been depicted graphically for a particular model.

• 한국지진공학회논문집
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• 제19권3호
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• pp.85-92
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• 2015

Response spectra of a building are made with a SDOF system taking into account a first mode shape, even though higher modes may affect on the dynamic responses of a high-rise building. A soft soil layer under a building also affects on the responses of a building. In this study, seismic responses of a MDOF system were investigated to examine the effects of higher modes on the response of a tall building by comparing them with those of a SDOF system including the kinematic interaction effect. Study was performed using a pseudo 3D finite element program with seven bedrock earthquake records downloaded from the PEER database. Effects of higher modes on the seismic responses of a tall building were investigated for base shear force and base moment of a MDOF system including story shear forces and story moments. Study results show that higher modes of a MDOF system contribute to a reduction of base shear force up to 1/4-1/5 of KBC and base moment. The effect of higher modes is more significant on the base shear force than on the base moment. Maximum story shear force and moment occurred at the top part of a building rather than at a base in the cases of tall buildings differently from short buildings, and higher modes of a tall building affected on the base forces making them almost constant at the base. A soft soil layer also affects some on the base shear force of a high-rise building independently on the soft soil type, but a soft soil effect is prominent on the base moment.

• 한국자동차공학회논문집
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• 제22권3호
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• pp.42-49
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• 2014

The gasoline direct injection (GDI) system is considerably spreading in automotive market due to its advantages. Nevertheless, since GDI system emit higher particle matter (PM) due to its combustion characteristics, it is difficult to meet strengthened emission regulation in near future. For this reason, a combined GDI with MPI system, so-called, dual injection (DUI) system is being investigated as a supplemental measure for the GDI system. This paper focused on power and fuel consumption effect by injection mode strategy of DUI system in part load and idle engine operating condition. In this study, port fuel injectors are installed on 2.4 liters GDI production engine in order to realize DUI system. And, at each injection mode, DOE (design of experiment) method is used to optimize engine control parameters such as dual injection ratio, start of injection timing, end of injection timing, CAM position and so on. As a consequence, DUI mode shows slightly better or equivalent fuel efficiency compared to conventional GDI engine on 9 points fuel economy mode as well as MPI mode shows less fuel consumption than GDI mode during idle operation. Furthermore, DUI system shows improvement potential of maximum 2.0% fuel consumption and 1.1% performance compared to GDI system in WOT operating condition.