• 한국해양공학회지
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• 제21권6호
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• pp.7-15
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• 2007

A mechanical model was developed to predict the behavior of point-loaded RC slender beams (a/d > 2.5) without stirrups. It is commonly accepted by most researchers that a diagonal tension crack plays a predominant role in the failure mode of these beams, but the failure mechanism of these members is still debatable. In this paper, it was assumed that diagonal tension failure was triggered by the concrete cover splitting due to the dowel action at the initial location of diagonal tension cracks, which propagate from flexural cracks. When concrete cover splitting occurred, the shape of a diagonal tension crack was simultaneously developed, which can be determined from the principal tensile stress trajectory. This fictitious crack rotates onto the crack tip with load increase. During the rotation, all forces acting on the crack (i.e, dowel force of longitudinal bars, vertical component of concrete tensile force, shear force by aggregate interlock, shear force in compression zone) were calculated by considering the kinematical conditions such as crack width or sliding. These forces except for the shear force in the compression zone were uncoupled with respect to crack width and sliding by the proposed constitutive relations for friction along the crack. Uncoupling the shear forces along the crack was aimed at distinguishing each force from the total shear force and clarifying the failure mechanism of RC slender beams without stirrups. In addition, a proposed method deriving the dowel force of longitudinal bars made it possible to predict the secondary shear failure. The proposed model can be used to predict not only the entire behavior of point-loaded RC slender shear beams, but also the ultimate shear strength. The experiments used to validate the proposed model are reported in a companion paper.

• Computers and Concrete
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• 제33권2호
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• pp.217-240
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• 2024

The purpose of this study is to propose new hysteretic characteristics of medium- to low-rise RC structures controlled by both shear and flexure. Through previous study, the dual lateral force-resisting system composed of shear and flexural failure members has a new failure mechanism that cooperates to enhance the flexural capacity of the flexural failure member even after the failure of the shear member, and the existing theoretical equation significantly underestimates the ultimate strength. In this study, the residual lateral strength mechanism of the dual lateral force-resisting system was analyzed, and, as a result, an equation for estimating the residual flexural strength of each shear-failure member was proposed. The residual flexural strength of each shear-failure member was verified in comparison with the structural testing results obtained in previous study, and the proposed residual flexural strength equation for shear-failure members was tested for reliability using FEA, and its applicable range was also determined. In addition, restoring-force characteristics for evaluating the seismic performance of the dual lateral force-resisting system (nonlinear dynamic analysis), reflecting the proposed residual flexural strength equation, were proposed. Finally, the validity of the restoring-force characteristics of RC buildings equipped with the dual lateral force-resisting system proposed in the present study was verified by performing pseudo-dynamic testing and nonlinear dynamic analysis based on the proposed restoring-force characteristics. Based on this comparative analysis, the applicability of the proposed restoring-force characteristics was verified.

• 한국터널지하공간학회 논문집
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• 제20권2호
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• pp.235-253
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• 2018

지하관거 균열로 인한 지하수의 흐름은 주변 지반의 토사유실을 야기하여 관거 인접 지반에서의 공동발생, 나아가 지반함몰(싱크홀) 원인이 된다. 본 연구는 관거의 균열을 모사하는 모형시험을 통해 비점착성 지반에 위치한 지중 비압력 관거의 균열로부터 비롯되는 지반함몰 메커니즘과 이로 인한 파괴모드를 조사하였다. 토사유실 및 함몰 영향인자로서 균열크기, 관거유속, 지하수위, 토피고 그리고 지반구성재료 등을 채택하여 이들 인자들이 함몰거동에 미치는 영향을 조사하였다. 각 인자들에 따른 지반파괴의 형상(파괴모드)과 지반유실량을 분석한 결과, 토피고와 지하수위가 일치하는 경우 최종파괴모드는 침식각이 불연속적으로 변화하는 'Y'형으로 관찰되며, 지하수위가 더 높게 위치하는 경우 침식각이 일정한 파괴면 형상인 'V'형으로 나타난다. 토피고가 증가하는 경우의 파괴형상에서 토피고 영향에 무관한 길이와 토피고에 따라 점진적으로 증가하는 폭을 갖는 수직함몰구간이 형성되는 결과를 얻었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
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• pp.677-682
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• 1998

Concrete is an inhomogeneous material consisting of larger aggregates and sand embedded in a cement paste matrix. In this study, an acoustic emission technique has been used to clarify the microscope failure mechanisms of concrete under three point bending test. AE source location has also been done to monitor the activities of internal damage and the progress of microscopic failure path during the loading. The relationship between AE characteristic and microscopic and microscopic failure mechanism is discussed.

• 한국시스템다이내믹스연구
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• 제8권1호
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• pp.187-209
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• 2007

This paper deals with the policy failure in housing markets. In order to understand basic mechanism leading to policy failure, systems thinking and system dynamics modeling is applied to housing markets and housing policy. This paper will show different set of causal maps on housing policy, and compare causal reasons of housing policy and its critics.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.355-358
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• 2003

The strengthening method with CFS(Carbon Fiber Sheet) to reinforced concrete structures has a fatal defect. Strengthened beams have been almost failed far below their ultimate strength due to interface debonding failure between the surface of concrete and CFS. The purpose of this study is to investigate the failure mechanism and failure behavior of strengthened RC beam using CFS.

• 항공우주기술
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• 제7권2호
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• pp.95-102
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• 2008

2009년에 발사될 통신해양기상위성은 다중화 구조설계를 통해 발생 가능성이 있는 고장으로부터 자동 회복을 수행할 수 있도록 자동조치기능이 탑재되어 있다. 본 연구에서는 자이로 센서의 고장이 COMS 임무에 미치는 영향을 살펴보고 장치 레벨의 자이로 센서 고장 처리를 위한 고장감지 방법과 기준, 고장고립과 회복 동작에 대한 메커니즘을 분석하였다 또한 시뮬레이터를 이용하여 고장 발생에 대한 자동조치 동작검증 결과를 확인하였다.

• 한국암반공학회:학술대회논문집
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• 한국암반공학회 2011년도 추계 총회 및 창립 30주년 기념 심포지엄
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• pp.3-21
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• 2011

Laboratory experiments and numerical simulations using Particle Flow Code (PFC2D) were performed to study the effects of joint separation and joint overlapping on the full failure behavior of rock bridges under direct shear loading. Through numerical direct shear tests, the failure process is visually observed and the failure patterns are achieved with reasonable conformity with the experimental results. The simulation results clearly showed that cracks developed during the test were predominantly tension cracks. It was deduced that the failure pattern was mostly influenced by both of the joint separation and joint overlapping while the shear strength is closely related to the failure pattern and its failure mechanism. The studies revealed that shear strength of rock bridges are increased with increasing in the joint separation. Also, it was observed that for a fixed cross sectional area of rock bridges, shear strength of overlapped joints are less than the shear strength of non-overlapped joints.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.84-87
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• 2004

Nominal flexural strength of RC members strengthened with FRP sheets is generally based on the tensile strength of composite materials obtained from coupon tests. This method is based on the assumption that bond failure does not occur until the FRP sheet reaches its rupture strength. According to the previous researches, however, bond failure often occurs before the FRP sheet reaches its rupture strength. Some attempts were made to control debonding failure by increasing the bonded length of sheet or wrapping the section around their side of the member(U-wrap). In this study, the flexural failure mechanism of RC beams strengthened with AFRP sheets with different bond lengths is investigated. Their strengthening details to prevent the premature debonding failure are also suggested and its effectiveness is verified.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1792-1797
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• 2007

This paper try to find root-cause of failure in a connector used in transmitting signals for throttle body control in automotives by analyzing possible failure causes and performing experiments to simulate the cable failure in field. The connector comprises fins, wires, and case moldings. The failure is due to degradation of initial clamping force required fixing fins and wires in the connector. Expansion and compression of the case molding material surrounding fins would cause the degradation. Investigations of strict initial claming force and control of thermal expansion property of the molding are required to prevent the failure.