• Earthquakes and Structures
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• 제13권2호
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• pp.137-150
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• 2017

This paper focuses on the post-earthquake serviceability of steel arch bridges installed with three types of seismic dampers suffered mainshock-aftershock sequences. Two post-earthquake serviceability verification methods for the steel arch bridges are compared. The energy-absorbing properties of three types of seismic dampers, including the buckling restrained brace, the shear panel damper and the shape memory alloy damper, are investigated under major earthquakes. Repeated earthquakes are applied to the steel arch bridges to examine the influence of the aftershocks to the structures with and without dampers. The relative displacement is proposed for the horizontal transverse components in such complicated structures. Results indicate that the strain-based verification method is more conservative than the displacement-base verification method in evaluating the post-earthquake serviceability of structures and the seismic performance of the retrofitted structure is significantly improved.

• 한국안전학회지
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• 제30권4호
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• pp.99-105
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• 2015

In this study, displacement estimation algorithm, which is not requiring an absolute reference point unlike the conventional displacement measurement method, is developed using the geophone. To estimate displacement of the bridge, measured velocity time signal is integrated in the frequency domain. And, the estimated displacement is compared with the measured result using a conventional method. Based on the dynamic field test results, it was found that the estimated displacement by the present algorithm is similar to that of a conventional method. The displacement estimation algorithm proposed in this paper can be effectively applied to measure the displacement of a structure, which is difficult to install a displacement transducer at the fixed point.

• Smart Structures and Systems
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• 제29권4호
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• pp.599-616
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• 2022

Bridge displacement contains vital information for bridge condition and performance. Due to the limits of direct displacement measurement methods, the indirect displacement reconstruction methods based on the strain or acceleration data are also developed in engineering applications. There are still some deficiencies of the displacement reconstruction methods based on strain or acceleration in practice. This paper proposed a novel method based on long short-term memory (LSTM) networks to reconstruct the bridge dynamic displacements with the strain and acceleration data source. The LSTM networks with three hidden layers are utilized to map the relationships between the measured responses and the bridge displacement. To achieve the data fusion, the input strain and acceleration data need to be preprocessed by normalization and then the corresponding dynamic displacement responses can be reconstructed by the LSTM networks. In the numerical simulation, the errors of the displacement reconstruction are below 9% for different load cases, and the proposed method is robust when the input strain and acceleration data contains additive noise. The hyper-parameter effect is analyzed and the displacement reconstruction accuracies of different machine learning methods are compared. For experimental verification, the errors are below 6% for the simply supported beam and continuous beam cases. Both the numerical and experimental results indicate that the proposed data fusion method can accurately reconstruct the displacement.

• 한국지진공학회논문집
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• 제7권5호
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• pp.67-73
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• 2003

현 도로교의 내진해석은 구조물이 하중 이상의 강도를 갖도록 하는 하중기반해석법에 근거하고 있다. 본 연구에서는 이러한 하중기반해석의 대안책으로 구조물의 성능평가 대상을 변위로 하는 변위기반해석의 일종인 역량스펙트럼법을 제시하였다. 하중기반해석에서 내진설계가 수행되어진 기존 철근콘크리트 교각에 대하여 역량스펙트럼법에 의한 내진성능을 평가하였다. 그 결과, 역량스펙트럼법은 간편하고 신속하게 구조물의 비탄성 응답을 현실적으로 평가할 수 있었으며 비탄성 응답을 일으키는 다양한 지반운동 수준에 대해 구조물에 발생하는 변위를 평가할 수 있었고, 기존 구조물의 내진성능에 대한 평가나 신설구조물의 성능목표에 대한 설계검증에 효율적으로 적용 가능하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.301-306
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• 2008

The present seismic analysis of Road-Bridge Design Standard is on a basis of load-vased analysis which lets structures have the strength over load. In this study, the capacity spectrum method, a kind of displacement based method, which is evaluated by displacement of structure, is presented as an alternative to the analysis method based on load. Seismic capacity is performed about the existing reinforced concrete pier which has already secured seismic design by capacity spectrum method. As a result, capacity spectrum method could realistically evaluate the non-elastic behavior of structures easilly and quickly and the displacement of structures for variable ground motion level. And it could efficiently apply to an evaluation of seismic capacity about the existing structures and a verification of design for capacity target of the structure. We propose the seisemic performance method by using the Finite Element Analysis Program.

• 건설안전기술
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• 통권47호
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• pp.56-62
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• 2008

In order to apply the Limit Equilibrium Method generally used for the slope stability analysis to the vertical excavation walls reinforced by soil-nailing, in this study, the Limit Equilibrium Method for the temporary shoring facilities reinforced by soil-nailing was proposed, which is based on the stability for the horizontal displacement. In this study, the relation of the internal friction angles of the ground and the vertical excavation depths was arranged, which is satisfying the stability on the horizontal displacement by using the verification of the Limit Equilibrium Method. And then, the rational reinforcing length of soil-nailing was proposed for the critical areas. In addition, the modified safety ratio satisfying the stability on the horizontal displacement was proposed, when the Limit Equilibrium Method was applied to the vertical excavation walls reinforced by soil-nailing.

• Selected Papers of The Society of Naval Architects of Korea
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• 제1권1호
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• pp.52-64
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• 1993

There exist many frame structural systems having some attachments reducible to damped spring-mass systems, concentracted masses and spring supports. For free and forced vibration analyses of such a system an analytical method based on the receptance method is presented. A framed structure having attachments is considered as a combined system composed of various Timoshenko beam and bar elements and the attachments. So, the vibration characteristics of the system are calculated by synthesizing receptances and Support Displacement Transfer Ratio (SDTR) of beam and bar elements In spectral and/or closed forms, and receptances of the attachments. In forced vibration analysis, arbitrary excitation forces at a point on the structure and displacement excitations at boundaries are considered. Numerical investigations are carried out for verification of the presented method, and the results show good accuracy and very high computational efficiency.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 가을 학술발표회 논문집
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• pp.52-59
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• 2004

In this paper, the efficacy of the MR damper-based control systems for vibration suppression of stay cables has been experimentally investigated. The performance of the several control strategies for the semiactive control system, such as the clipped-optimal control, the Lyapunov stability theory-based control, the maximum energy dissipation and the modulated homogeneous friction, has been compared with that of the passive-type control systems employing MR dampers. To do this, the full-scale stay cable, which is the same as used for the in-service cable-stayed bridge in Korea, is considered. The acceleration and the displacement of the stay cable as well as the damping force of the MR damper are measured. The velocity of the cable at the damper location, which is needed for some control algorithms, is obtained by differentiating the measured displacement. The damping ratios of the cable system employing the MR damper, which can be estimated by the Hilbert transform-based method, shows effectiveness of each control strategy considered.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.448-455
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• 2007

1992년 개정된 도로교표준시방서에 최초의 교량내진설계기준이 제정되었다. 하지만 그 이전에 건설된 대부분의 교량구조물은 지진에 대한 고려 없이 설계되어 있으므로 내진성능평가를 수행하여야하며 성능이 부족할 시 내진보강이 필요하다. 현재 도로교의 내진해석은 단순히 구조물의 하중 이상의 강도만을 갖도록 하는 하중기반해석에 근거하고 있으나, 단순한 강도의 비교만을 통해서는 구조물의 성능이 파악되지 않을 수 있으므로 성능평가 대상을 변위로 하는 변위기반해석법인 ADRS방법(Accleration-Displacement Response Spectrum Method)과 시간이력해석법을 이용하여 ADRS방법의 타당성 여부를 판단하고자 한다. 그 결과, 역량스펙트럼법은 하중기반해석에서의 복잡한 동적해석을 피할 수 있어서, 간편하고 신속하게 내진성능을 평가할 수 있으며, 정량적으로 산출된 성능점을 통하여 기존구조물의 내진성능이나 신설 구조물의 목표성능에 대한 설계 검증에 효율적으로 적용이 가능하나 고차 모드의 효과를 고려할 수 없었으며 또한 반복 주기 하중에 의한 구조물의 성능저하를 고려할 수 없는 문제점이 있었다.

• 한국BIM학회 논문집
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• 제9권3호
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• pp.1-7
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• 2019

Digital twin technology has been actively developed to monitor and assess the current state of actual structures. The digital twin changes the traditional observation method performed in the field to the real-time observation and detection system using virtual online model. Thus, this study designed a digital twin model for a beam and examined the feasibility of the digital twin for bridges. To reflect the current state of the bridge, model updating was performed according to the field test data to construct an analysis model. Based on the constructed bridge analysis model, the relationship between strain and displacement was used to represent a virtual model that behaves in the same way as the actual structure. The strain and displacement relationship was expressed as a matrix derived using an approximate analytical theory. Then, displacements can be obtained using the measured data obtained from strain sensors installed on the bridge. The coordinates of the obtained displacements are used to construct a virtual digital model for the bridge. For verification, a beam was fabricated and tested to evaluate the digital twin model constructed in this study. The displacements obtained from the strain and displacement relationship agrees well with the actual displacements of the beam. In addition, the displacements obtained from the virtual model was visualized at the locations of the strain sensor.