• 한국전산구조공학회논문집
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• 제27권6호
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• pp.573-580
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• 2014

본 논문에서는 현재 시공중인 58층의 철근콘크리트조 고층건물에서 진동현식게이지를 통해 계측된 기둥의 축방향 변형률과 레이져 스캐닝을 통해 구한 횡변위를 3차원 시공단계해석에 의한 예측치와 비교하였다. 예측치는 ACI 209와 PCA의 재료모델식, PCA report의 축소량 산정알고리즘을 3차원 구조해석 프로그램으로 개발한 ASAP을 사용하여 구하였다. 비교결과 평면의 중앙부 기둥의 축방향 변형율 계측치는 시공단계 해석치와 거의 유사한 결과를 나타내었으나 각 모서리에 두 개씩 배치된 기둥의 경우 비교적 큰 오차를 나타내었다. 레이져 스캐닝에 의한 횡변위 계측결과는 해석결과와 유사한 경향을 보였으나 층당 계측치가 큰 변동을 나타내므로 향후 이를 해결하기 위한 계측 및 데이터 처리기법이 요구된다.

• Smart Structures and Systems
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• 제15권3호
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• pp.665-682
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• 2015

Structural identification or St-Id is 'the parametric correlation of structural response characteristics predicted by a mathematical model with analogous characteristics derived from experimental measurements'. This paper describes a St-Id exercise on Humber Bridge that adopted a novel two-stage approach to first calibrate and then validate a mathematical model. This model was then used to predict effects of wind and temperature loads on global static deformation that would be practically impossible to observe. The first stage of the process was an ambient vibration survey in 2008 that used operational modal analysis to estimate a set of modes classified as vertical, torsional or lateral. In the more recent second stage a finite element model (FEM) was developed with an appropriate level of refinement to provide a corresponding set of modal properties. A series of manual adjustments to modal parameters such as cable tension and bearing stiffness resulted in a FEM that produced excellent correspondence for vertical and torsional modes, along with correspondence for the lower frequency lateral modes. In the third stage traffic, wind and temperature data along with deformation measurements from a sparse structural health monitoring system installed in 2011 were compared with equivalent predictions from the partially validated FEM. The match of static response between FEM and SHM data proved good enough for the FEM to be used to predict the un-measurable global deformed shape of the bridge due to vehicle and temperature effects but the FEM had limited capability to reproduce static effects of wind. In addition the FEM was used to show internal forces due to a heavy vehicle to to estimate the worst-case bearing movements under extreme combinations of wind, traffic and temperature loads. The paper shows that in this case, but with limitations, such a two-stage FEM calibration/validation process can be an effective tool for performance prognosis.

• 한국강구조학회 논문집
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• 제15권6호통권67호
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• pp.701-709
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• 2003

이 논문은 모멘트 저항골조의 접합부에 이용하기 위한 T-스티프너로 보강된 접합부의 내진성능에 관해 나타냈다. 접합부는 보플랜지와 기둥플랜지에 T-스티프너의 수평 및 수직요소가 용접되어 보강되었다. T-스티프너 접합부의 거동을 명확히 파악하기 위해 유한요소해석과 실험이 수행되었다. 유한요소해석결과, T-스티프너의 수평요소의 길이가 길어짐에 따라 T-스티프너는 보플랜지와 수평요소사이의 응력집중을 줄이는데 효과적임을 나타냈다. 또한, 접합부의 이력 거동을 파악하기 위해 실대형 접합부 실험을 실시하였다. 주요 변수는 보에 대한 T-스티프너의 강도비와 수평요소의 형상이다. 수평요소의 길이가 길수록 접합부의 변형능력은 증가하였고, 모든 실험체는 방추형의 안정된 이력거동을 나타내었다.

• 한국해안·해양공학회논문집
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• 제33권4호
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• pp.160-167
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• 2021

단층파괴에 의한 해저지형변화는 공간적으로 시간차를 가진다. 특정 지점에서 파괴가 발생하면 이웃지점으로 단층파괴가 전파하면서 시간차에 따른 단층파괴가 발생하며, 단층파괴시 연직방향으로 상승하면서 지진해일을 야기한다. 해저 지형의 상승속도는 지진해일 초기파형에 영향을 주며 결과적으로 지진해일의 도달시간 및 크기에 영향을 준다. 본 연구에서는 단층파괴에 의한 해저 지형의 수평적 및 수직적 변화를 능동적 및 동적으로 고려하여 지진해일의 생성 및 전파를 모의할 수 있는 수치모형을 개발하였다. 모델의 검증을 위하여 2011년 동일본대지진에 대해 적용하였으며 기존의 수동적 및 정적 모형에 비해 정확성이 개선되는 것을 확인하였다.

• 센서학회지
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• 제31권6호
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• pp.411-417
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• 2022

In this paper, we propose a sensor with a C-shaped load cell to detect force change when a person sitting on the chair in an electrical transport-convenience vehicle is pushing ground by both heels. The load cell built in the vehicle is mechanically deformed by the vertical force owing to the human weight and the horizontal force by ground-pushing feet. The deformation rate of the load cell and its distribution are simulated using finite element analysis. In the simulation, the applied loads are preset in the range of 10 kg - 100 kg with a step size of 10 kg, and the ground-pushing force by feet is increased to 40 N with a step size of 5 N with respect to each applied load level. The resistance change of the load cell was observed to be linear in simulation as well as in measurement. the maximum difference between simulation and measurement was 0.89 % when the strain gauge constant was 2.243. The constant has a large influence on the difference. The proposed sensor was fabricated by connecting an instrument amplifier and a microcontroller to a load cell and used to detect the force by ground-pushing feet. To detect foot driving, the reference signal was set to 130% of the load, and the duration of the sensor output signal exceeding the reference signal was set to 0.6 s. In a test of a vehicle built with the proposed sensor, the footpushing force by the worker could be successfully detected even when the worker was working.

• 한국지반공학회논문집
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• 제25권5호
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• pp.17-28
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• 2009

연약지반상 성토시, 성토하중은 연약지반에 편재하중으로 작용하게 되어 기초 연약지반의 과도한 침하와 측방유동을 야기할 수 있다. 연약지반의 과도한 변형은 결국 성토체 자체와 인접 지반 및 구조물의 안전을 위협하게 된다. 연약지반의 변형거동에 영향을 미치는 요인은 크게 성토하중 조건과 지반조건으로 구분할 수 있다. 따라서 본 연구에서는 이들 조건을 달리한 5회의 모형실험을 수행하여, 성토하중 재하가 기초 연약지반의 변형거동에 미치는 영향을 평가하였다. 모형실험 결과, 성토하중 재하가 지중 측방변위 발생에 영향을 미치는 영향거리는 성토체 선단부로부터 재하폭의 2배까지인 것으로 나타났다. 또한 모형실험 결과를 근거로, 성토속도(v, kPa/day)와 일평균 침하량(${\Delta}s$, mm/day) 사이의 관계식과 성토속도와 일평균 지중 최대수평변위(${\Delta}y_m$, mm/day) 사이의 상관관계식을 제안하였다.

• Geomechanics and Engineering
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• 제33권3호
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• pp.301-315
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• 2023

Adopting cohesive soil as geocell-pocket infill materials is not fully accepted by researchers in the field of road engineering. The cohesion that may inhibit the lateral limitation of geocells is a common vital idea that exists within every researcher. However, the influence of infill materials' cohesion on geocell-reinforced performance is still not thoroughly determined. The mechanism behind this still needs to be studied in depth. This study initially discussed the relationship between subgrade bearing capacity, geocells' contribution to reinforced performance, and infill materials' cohesion (IMC). A law was proposed that adopting the soil with high cohesion as infill materials benefited the subgrade bearing capacity, but this was attributed to the superior mechanical properties of infill materials rather than geocells' contribution. Moreover, the vertical and lateral deformation of subgrade, coupling shear stress and confining stress of geocells, and deformation of geocells were deeply studied to analyze the mechanism that high cohesion can inhibit the geocells' contribution. The results indicate that the infill materials with high cohesion result in the total displacement of the subgrade toward to deeper depth, not the lateral direction. These responses decrease the vertical coupling shear stress, confining stress, and normal displacement of geocell walls, which weaken the lateral limitation of geocells.

• Geomechanics and Engineering
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• 제14권6호
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• pp.589-600
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• 2018

For foundations in permafrost regions, the displacement characteristics are uncertain because of the randomness of temperature characteristics and mechanical parameters, which make the structural system have an unexpected deviation and unpredictability. It will affect the safety of design and construction. In this paper, we consider the randomness of temperature characteristics and mechanical parameters. A stochastic analysis model for the uncertain displacement characteristic of foundations is presented, and the stochastic coupling program is compiled by Matrix Laboratory (MATLAB) software. The stochastic displacement fields of an embankment in a permafrost region are obtained and analyzed by Neumann stochastic finite element method (NSFEM). The results provide a new way to predict the deformation characteristics of foundations in permafrost regions, and it shows that the stochastic temperature has a different influence on the stochastic lateral displacement and vertical displacement. Construction disturbance and climate warming lead to three different stages for the mean settlement of characteristic points. For the stochastic settlement characteristic, the standard deviation increases with time, which imply that the results of conventional deterministic analysis may be far from the true value. These results can improve our understanding of the stochastic deformation fields of embankments and provide a theoretical basis for engineering reliability analysis and design in permafrost regions.

• 한국철도학회논문집
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• 제17권1호
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• pp.52-58
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• 2014

노반 성토체에서 발생하는 소성 변형은 콘크리트 궤도의 안정성과 유지보수에 영향을 미친다. 철도 노반에서의 장기적인 소성 변형은 주로 반복적인 열차 통과로 발생하는 누적된 비탄성적 변형률에 의해 발생한다. 누적 소성 변형의 예측은 궤도의 유지보수와 열차의 안전한 운영을 위해서 중요하다. 본 연구에서는 서로 다른 강화노반 두께를 가진 철도노반에서 발생하는 연직 변위를 계산하였다. 누적 소성 변형률을 계산하기 위한 멱함수의 상수는 삼축 실험과 실대형 재하 실험의 결과로부터 구하였다. 표준 노반 단면에 대한 3차원 유한요소해석 결과로부터 강화노반의 두께를 선정하는 가이드라인을 제시하였다.

• Structural Engineering and Mechanics
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• 제59권6호
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• pp.1139-1153
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• 2016

Elastic constraints are usually simplified as "spring forces" exerted on beam ends without considering the "spring deformation". The partial differential equation governing the free vibrations of a cantilever Bernoulli-Euler beam considering the deformation of elastic constraints is firstly established, and is nondimensionalized to obtain two dimensionless factors, $k_v$ and $k_r$, describing the effects of elastically vertical and rotational end constraints, respectively. Then the frequency equation for the above Bernoulli-Euler beam model is derived using the method of separation of variables. A numerical analysis method is proposed to solve the transcendental frequency equation for the continuous change of the frequency with $k_v$ and $k_r$. Then the mode shape functions are given. Finally, effects of $k_v$ and $k_r$ on free vibration characteristics of the beam with different slenderness ratios are calculated and analyzed. The results indicate that the effects of $k_v$ are larger on higher-order free vibration characteristics than on lower-order ones, and the impact strength decreases with slenderness ratio. Under a relatively larger slenderness ratio, the effects of $k_v$ can be neglected for the fundamental frequency characteristics, while cannot for higher-order ones. However, the effects of $k_r$ are large on both higher- and lower-order free vibration characteristics, and cannot be neglected no matter the slenderness ratio is large or small.