• Wind and Structures
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• 제1권2호
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• pp.183-199
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• 1998

This paper discusses some of the findings arising from long-term monitoring of the wind effects on a transmission tower located on an exposed site in South-West England. Site wind speeds have been measured, together with the foundation loads at the base of each of the four legs. The results show good correlation between the wind speeds and leg strains (loads) for a given wind direction, as expected, for wind speeds in excess of 10 m/s. Comparisons between the measured strains and those determined from the UK Code of Practice for lattice towers (BS8100), for the same wind speed and direction, show that the Code over-estimates most of the measured foundation loads by a moderate amount of about 14% at the higher wind speeds. This tends to confirm the validity of the Code for assessing design foundation loads. A finite element analysis model has been used to examine the dynamic behaviour of the tower and conductor system. This shows that, in the absence of the conductor, the tower alone has similar natural frequencies of approximately 2.2 Hz in the both the first (transversal) and second (longitudinal) modes, whilst for the complete system and conductor oscillations dominate, giving similar frequencies of approximately 0.1 Hz for both the first and second modes.

• Advances in concrete construction
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• 제4권4호
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• pp.319-332
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• 2016

In most cases strengthening reinforced concrete columns exposed to high strain rate is to be expected especially within weak designed structures. A special type of loading is instantaneous loading. Rapid loading can be observed in structural columns exposed to axial loads (e.g., caused by the weight of the upper floors during a vertical earthquake and loads caused by damage and collapse of upper floors and pillars of bridges).Subsequently, this study examines the behavior of reinforced concrete columns under rapid loading so as to understand patterns of failure mechanism, failure capacity and strain rate using finite element code. And examines the behavior of reinforced concrete columns at different support conditions and various loading rate, where the concrete columns were reinforced using various counts of FRP (Fiber Reinforcement Polymer) layers with different lengths. The results were compared against other experimental outcomes and the CEB-FIP formula code for considering the dynamic strength increasing factor for concrete materials. This study reveals that the finite element behavior and failure mode, where the results show that the bearing capacity increased with increasing the loading rate. CFRP layers increased the bearing capacity by 20% and also increased the strain capacity by 50% through confining the concrete.

• 한국항공우주학회지
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• 제37권2호
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• pp.131-138
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• 2009

해석용 모델의 검증이란 완성된 모델이 실제 제품의 특성을 반영하고 있는지에 대한 확인절차이다. 일반적으로 해석모델작성 시 형상의 단순화 및 비선형특성의 반영에 대한 한계 등으로 공학적 가정을 이용하므로 실제 구조와는 다른 물리적, 기계적 특성을 갖게 된다. 본 연구에서는 순차적 2차계획법(Sequential Quadratic Programming, SQP)을 이용하는 목표달성기법(Goal-Attainment Method)의 다목적 최적화 기법을 이용하여 활공체 날개의 정적 처짐과 고유진동수 차이를 최소화하는 방법으로 구조모델의 최신화를 수행하였으며, 모드형상의 일치성을 정량적으로 판단하기 위하여 Modal Assurance Criterion(MAC)를 이용하였다.

• 한국실내디자인학회논문집
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• 제18권1호
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• pp.27-34
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• 2009

Architect Bernard Tschumi had explored a new architectural conception through his own notional devices such as space, event and movement during 1970s. But, among these notions, the concept of movement was ambiguous and difficult to adopt it for architectural design strategy. Because the movements in everyday's behaviour or in dancing art are significantly different from architectural thought. However he had succeeded in coining the creative notion of movement as almost real body's and of living flesh. He invented an acute methodology and bold interpretation for his early experimental works. So, this paper tried to understand and analyse his concept of movement focused on his early works. The results of this paper's discussion are as follows; First, Tschumi's movement concept Is dynamic one operated by desire and can violate space in physical level as well as metaphysical level. Next, the movement performs the role of generator which deforms space or even generate it. Third, his movement can be readable only when you go down and bring it in practice. Also it Is unblocked potentiality, undetermined sequential material and unfinished practice. Fourth, when Tschumi's movement could be thought as walking, this walking movement makes up a story through rhetorical speech acts that are presented by turns and detours.

• 한국안전학회지
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• 제23권6호
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• pp.21-27
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• 2008

Polypropylene(PP) foams are widely used as protective materials such as automotive bumper and safety helmet, but whose dynamic behaviour are not well defined. In this paper, the compression tests by Split Hopkinson Pressure Bar were conducted to obtain the stress-strain curve and to investigate the effect of density on the absorption of impact energy in the PP foams. Three kinds of foams were chosen depending upon the density. The result of the experiment has revealed that the stiffness of the low-density PP foam is remarkably increased at high strain rate compared with that of the high-density PP foam. And it is also shown that the absorption of impact energy are greatly influenced by the density of PP foam. These results are expected to be utilized for the development of a protective structure with polymer foams.

• Geomechanics and Engineering
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• 제13권5호
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• pp.809-823
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• 2017

This paper describes lab test results of artificial rock-like material samples having a plane joint. Cyclic shear tests were performed under different normal loads and different shear displacement amplitudes. For this purpose, multi-stage normal loading tests (30 kN, 60 kN, 90 kN, 180 kN, 360 kN and 480 kN) with cyclic excitation at frequency of 1.0 Hz and different shear displacement amplitudes (0.5 mm, 1.0 mm, 2.0 mm, 4.0 mm, 5.0 mm, and 8.0 mm) were conducted using the big shear box device GS-1000. Experimental results show, that shear forces increase with the increase of normal forces and quasi-static friction coefficient is larger than dynamic one. With the increase of normal loads, approaching the peak value of shear forces needs larger shear displacements. During each cycle the normal displacements increase and decrease (rotational behavior in every cycle). Peak angle of inclination increases with the increase of normal load. A phase shift between maximum shear displacement and maximum shear force is observed. The corresponding time shift decreases with increasing normal load and increases with increasing shear displacement amplitudes.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.133-136
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• 2008

본 연구는 추진제를 공급하는 터보펌프와 연계한 연료 과농 가스발생기의 연소 특성에 관한 것이다. 총 5회의 연소시험이 안정적으로 실시되었다. 가스발생기의 압력 형성은 터보펌프로부터 추진제 공급유량에 따라 연동하였다. 터보펌프를 가스발생기 가스로 직접 구동하는 폐회로 시험에서도 안정적인 작동 성능을 보여주었다. 연소 가스의 온도 형성은 이전 시험 결과와 비슷한 양상을 보였다. 실제 작동 연소 압력 변경을 위해 장착한 오리피스는 압력 섭동 저감에 효과적이었으나 45 bar 이하의 저압에서는 단품 시험 시와 동일한 압력 섭동 특성을 보여주었다.

• Wind and Structures
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• 제1권1호
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• pp.1-23
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• 1998

This paper describes wind investigations for the Leaning Tower of Pisa which were conducted as part of an overall evaluation of its behaviour. Normally a short, stiff and heavy building would not be a candidate for detailed wind analyses. However, because of extremely high soil pressures developed from its inclination, there has been increasing concern that environmental loading such as wind actions could combine with existing conditions to cause the collapse of the tower. The studies involved wind assessment at the site as a function of wind direction, analysis of historical wind data to determine extreme wind probabilities of occurrence, estimation of structural properties, analytical and boundary layer wind tunnel investigations of wind loads and evaluation of the response with special concern for loads in the direction of inclination of the tower and significant wake effects from the neighboring cathedral for critical wind directions. The conclusions discuss the role of wind on structural safety, the precision of results attained and possible future studies involving field measurements aimed at validating or improving the analytical and boundary layer wind tunnel based assessments.

• Structural Engineering and Mechanics
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• 제20권1호
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• pp.21-43
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• 2005

Masonry is a composite non-homogeneous structural material, whose mechanical properties depend on the properties of and the interaction between the composite components - brick and mortar, their volume ratio, the properties of their bond, and any cracking in the masonry. The mechanical properties of masonry depend on the orientation of the bed joints and the stress state of the joints, and so the values of the shear modulus, as well as the stiffness of masonry structural elements can depend on various factors. An extensive testing programme in several countries addresses the problem of measurement of the stiffness properties of masonry. These testing programs have provided sufficient data to permit a review of the influence of different testing techniques (mono and bi-axial tests), the variations caused by distinct loading conditions (monotonic and cyclic), the impact of the mortar type, as well as influence of the reinforcement. This review considers the impact of the measurement devices used for determining the shear modulus and stiffness of walls on the results. The results clearly indicate a need to re-assess the values stated in almost all national codes for the shear modulus of the masonry, especially for masonry made with lime mortar, where strong anisotropic behaviour is in the stiffness properties.

• 한국철도학회논문집
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• 제10권5호
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• pp.600-606
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• 2007

복부 파형강판 거더와 복합 트러스 거더의 정적 및 동적거동 특성을 분석하기 위해 3차원 유한요소해석을 수행하였고, 이 결과를 등가보 이론에 의한 해석결과와 비교하였다. 등가보 이론은 트러스 구조의 모든 단면제원을 등가의 보로 치환함과 동시에 전단계수 등의 단면특성을 고려한 이론이다. 등가보 이론 적용 시 복부 파형강판 거더의 전단계수는 복부 단면적에 대한 전체 단면적의 비로 산정하였고, 복합 트러스 거더의 전단계수는 Abdel의 계산식을 사용하여 산정하였다. 정적해석 및 자유진동해석 결과 3차원 유한요소모델을 이용한 해석결과가 전단변형을 고려한 등가보 이론에 의한 해석결과와 잘 일치하였다.