• 한국기계가공학회지
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• 제21권5호
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• pp.16-21
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• 2022

This study investigates the effect of the deformation on the sensitivity of a flexible polydimethylsiloxane (PDMS) membrane sensor. A PDMS membrane sensor was developed to measure the impact force of a water droplet using a silver nanowire (AgNW). The initial deformation of the membrane was confirmed with the application of a tensile force (i.e., tension) and fixing force (i.e., compressive force) at the gripers, which affects the sensitivity. The experimental results show that as the tension applied to the membrane increased, the sensitivity of the sensor decreased. The initial electrical resistance increased as the fixing force increased, while the sensitivity of the sensor decreased as the initial resistance increased. The movement of the membrane due to the impact force of the water droplet was observed with a high-speed camera, and was correlated with the measured sensor signal. The analysis of the motion of the membrane and droplets after collision confirmed the periodic movement of not only the membrane but also the change in the height of the droplet.

• 한국구조물진단유지관리공학회 논문집
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• 제11권5호
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• pp.123-134
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• 2007

본 논문은 기존 강합성 교량의 내하력 향상을 목적으로 외부 긴장재의 초기 긴장력 결정 방법을 제시하였다, 외부 긴장력은 콘크리트 슬래브 재시공 전과 후에 각각 적용하였다. 활하중에 의하여 발생하는 증가 프리스트레스력을 고려한 내하율식을 제안하여 긴장재 개수와 초기 긴장력의 결정 과정을 제시하였다. 기존 강합성 교량의 내하율 향상에 적용하여 그 타당성을 입증하였다.

• 한국공간정보시스템학회:학술대회논문집
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• 한국공간정보시스템학회 2004년도 춘계 학술발표회 논문집 제1권1호(통권1호)
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• pp.131-138
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• 2004

The cable structure is a kind of ductile structural system using the tension cable and compression column as a main element. From mechanical characteristics of the structural material, it is profitable to be subjected to the axial forces than bending moment or shear forces. And we haweto consider the local buckling when it is subjected to compression forces, but tension member can be used until the failure strength. So we can say that the tension member is the most excellent structural member. Cable dome structures are made up of only the tension cable and compression column considering these mechanical efficiency and a kind of structural system. In this system, the compression members are connected by using tension members, not connected directly each other. Also, this system is lightweight and easy to construct. But, the cable dome structural system has a danger of global buckling as external load increases. That is, as the axisymmetric structure is subjected to the axisymmetric load, the unsymmetric deformation mode is happened at some critical point and the capacity of the structure is rapidly lowered by this reason. This phenomenon Is the bifurcation and we have to reflect this in the design process of the large space structures. In this study, We investigated the nonlinear unstable phenomenon of the Geiger, Zetlin and Flower-type cable dome.

• Ocean Systems Engineering
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• 제8권3호
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• pp.345-360
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• 2018

Increasing demand for large-sized Floating, Storage and Regasification Units (FSRUs) for oil and gas industries led to the development of novel geometric form of Buoyant Leg Storage and Regasification Platform (BLSRP). Six buoyant legs support the deck and are placed symmetric with respect to wave direction. Circular deck is connected to buoyant legs using hinged joints, which restrain transfer of rotation from the legs to deck and vice-versa. Buoyant legs are connected to seabed using taut-moored system with high initial pretension, enabling rigid body motion in vertical plane. Encountered environmental loads induce dynamic tether tension variations, which in turn affect stability of the platform. Postulated failure cases, created by placing eccentric loads at different locations resulted in dynamic tether tension variation; chaotic nature of tension variation is also observed in few cases. A detailed numerical analysis is carried out for BLSRP using Mathieu equation of stability. Increase in the magnitude of eccentric load and its position influences fatigue life of tethers significantly. Fatigue life decreases with the increase in the amplitude of tension variation in tethers. Very low fatigue life of tethers under Mathieu instability proves the severity of instability.

• Steel and Composite Structures
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• 제24권4호
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• pp.455-465
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• 2017

This paper presents a series of ultimate and fatigue experimental investigation on concrete-filled rectangular hollow section (CRHS) X joints with Perfobond Leister rib (PBR) under tension. A total of 15 specimens were fabricated, in which 12 specimens were tested under ultimate tension and 3 specimens were investigated in fatigue test. Different parameters including PBR stiffening, brace-to-chord ratio (${\beta}$) and inclined angle (${\theta}$) were considered in the test. Each joint was tested to failure under tension load. Obtained from test result, PBR was found to improve the tension strength and fatigue durability of CRHS joint substantially. Concrete dowel consisted by PBR and concrete inside the chord stiffened the joint, which leaded to a combination failure mode of punching shear and chord plastification of CRHS joint under tension. Finite element analysis validated the compound failure mode. Stress concentration on typical spot of CRHS joint was mitigated by PBR which was observed from fatigue test. Initial fatigue crack presented in CRHS joint with PBR also differentiated with the counterpart without PBR.

• 대한치과교정학회지
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• 제16권2호
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• pp.53-67
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• 1986

The physical tooth movement by orthodontic force is based upon alveolar bone resorption at compression site and new bone formation at tension site of the alveolar socket. The function of the cyclic AMP is to participate not only in initial action of bone cells by mechanical forces but also in the continuous cellular response leading to bone remodelling. This experiment was performed to clarify the role of cyclic AMP in bone remodelling by mechanical force in the NORMAL group, the DIABETES group and the INSULIN TREATED group. The 72 rats were divided into the NORMAL group, the DIABETES group and the INSULIN TREATED group. The same orthodontic forces were applied to the rats of 3 groups. These rats were treated for periods of time ranging from 1 hour, 1 day, 7 days, 14 days, 21 days and 28 days. The samples of alveolar bones were obtained from compression and tension sites surrounding the tipping teeth from NORMAL, DIABETE and INSULIN TREATED rats. The samples were assayed for cyclic AMP by the cyclic AMP RIA kit. The results were as follows: 1. The cyclic AMP levels of alveolar bone in compression and tension sites showed initial decrease, then increased and .remained elevated by the time consuming. 2. The highest cyclic AMP level showed in the DIABETES group and the lowest level was in the NORMAL group. 3. The cyclic AMP levels in the INSULIN TREATED group was similar with the NORMAL group in control and tension sites, but in the compression sites it was similar with the DIABETES group.

• 한국해안·해양공학회논문집
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• 제21권4호
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• pp.290-300
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• 2009

연직 막체방파제에 대한 기존의 수치해석에서는 막체의 운동 중 발생하는 변동장력성분이 초기장력에 비하여 미미하다는 가정 하에 운동 중의 막체 장력을 초기장력으로 대체하는 선형해석을 수행하였다. 본 수치해 석에서는 막체장력의 비선형 변화를 한 주기 동안의 평균장력으로 대체하며 이 평균장력을 반복계산을 통하여 구해나가는 준 비선형 해석을 수행하였다. 상기 선형해석 결과와 비교하여 입사파 주기가 증가할수록 반사율은 증가하며 전달율은 감소하는 것으로 나타났다. 아울러, 본 준 비선형해석을 계류형태를 달리하는 두 구조물에 적용한 결과, 막체의 수평변위의 제어가 방파성능에 밀접한 효과가 있는 것으로 나타났다. 막체의 수평변위를 억제하기 위해서는 막체의 초기장력을 증가시키거나 막체의 중간부에 계류라인을 추가 결속시키는 방법들이 있으나 이를 위해서는 연직 하향 계류력을 지지하기 위한 대형 수면 부표의 설치가 요구된다.

• 대한기계학회논문집
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• 제15권1호
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• pp.41-48
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• 1991

본 연구에서는 Kim등이 제안한 다공질금속을 위한 특수 구성방정식을 바탕으 로 하여 인장/비틀림 조합하중하의 다공질금속의 탄성-소성변형을 위한 구성방정식을 제시하였다. 탄성거동에서는 기공의 영향을 고려한 일반화된 Hooke의 법칙을 사용하 였고, 탄성-소성거동은 변형률공간을 주공간으로 하여 Naghdi등에 의해 개발된 탄성- 소성변형의 구성이론을 수정하여 다공질고체에 적용하였다. 끝으로, 본 논문에서 제 안된 구성이론은 Kim등과 본 연구에서 구한 인장/비틀림의 조합하중하에서의 다공질 철 소결체의 소성 항복조건 및 탄성-소성 거동의 실험치와 비교하였다.

• 한국공간구조학회:학술대회논문집
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• 한국공간구조학회 2005년도 춘계학술발표회 및 정기총회 2권1호(통권2호)
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• pp.108-115
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• 2005

Maintenance and reinforcement are very important especially in the case of the hybrid structures. In this paper, we introduce the maintenance and reinforcement design method of cable dome structures. In the case of the Olympic fencing stadium structural system has the stiffness in dependence of the initial tension force. Therefore, the verification of this phenomenon is very important. The result shows that the final tension force which is measured is almost reached to the calculated aim tension force after the maintenance ana reinforcement works is confirmed.

• Structural Engineering and Mechanics
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• 제60권2호
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• pp.301-312
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• 2016

In a concrete member under pure tension, the stress in concrete is uniformly distributed over the whole concrete section. It is supposed that a local bond failure occurs at each crack, and there is a relative slip between steel and surrounding concrete. The compatibility of deformation between the concrete and reinforcement is thus not maintained. The bond transfer length is a length of reinforcement adjacent to the crack where the compatibility of strain between the steel and concrete is not maintained because of partially bond breakdown and slip. It is an empirical measure of the bond characteristics of the reinforcement, incorporating bar diameter and surface characteristics such as texture. Based on results from a series of previously conducted long-term tests on eight restrained reinforced concrete slab specimens and material properties including creep and shrinkage of two concrete batches, the ratio of final bond transfer length after all shrinkage cracking, to THE initial bond transfer length is presented.