• Steel and Composite Structures
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• 제18권1호
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• pp.149-163
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• 2015

Orthotropic steel highway bridges exist almost everywhere in world, especially in Europe. The design of these bridges started very early in 20th century and ended with a conventional orthotropic steel bridge structure, which is today specified in DIN FB 103. These bridges were mostly built in 1960's and exhibit damages in steel structural parts. The primary reason of these damages is the high pressure that is induced by wheel- loads and therefore damages develop especially in heavy traffic lanes. Constructive rules are supplied by standards to avoid damages in orthotropic steel structural parts. These rules are first given in detail in the standard DIN 18809 (Steel highway- and pedestrian bridges- design, construction, fabrication) and then in DIN- FB 103 (Steel bridges). Bridges built in the past are today subject to heavier wheel loads and the frequency of loading is also increased. Because the vehicles produced today in 21st century are heavier than before and more people have vehicle in comparison with 20th century. Therefore dimensioning or strengthening of orthotropic steel bridges by using stiffer dimensions and shorter spans is an essence. In the scope of this study the complex geometry of conventional steel orthotropic bridge is generated by FE-Program and the effects of cross beam web thickness and cross beam span on steel bridge are assessed by means of a parameter study. Consequently, dimensional and constructional recommendations in association with cross beam thickness and span will be given by this study.

• Smart Structures and Systems
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• 제11권1호
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• pp.87-102
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• 2013

Vibration-based damage detection methods are popular for structural health monitoring. However, they can only detect fairly large damages. Usually impact pulse, ambient vibrations and sine-wave forces are applied as the excitations. In this paper, we propose the method to use the chaotic excitation to vibrate structures. The attractors built from the output responses are used for the minor damage detection. After the damage is detected, it is further quantified using the Kalman Filter. Simulations are conducted. A 5-story building is subjected to chaotic excitation. The structural responses and related attractors are analyzed. The results show that the attractor distances increase monotonously with the increase of the damage degree. Therefore, damages, including minor damages, can be effectively detected using the proposed approach. With the Kalman Filter, damage which has the stiffness decrease of about 5% or lower can be quantified. The proposed approach will be helpful for detecting and evaluating minor damages at the early stage.

• 한국구조물진단유지관리공학회 논문집
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• 제12권3호
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• pp.63-70
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• 2008

본 연구의 목적은 강원도 산악지역에서 교량 설계 지침 개발에 있다. 2002년 태풍 루사, 2003년 매미, 2006년 에위니아에 이은 7월 집중호우로 강원도 산악지역에서는 큰 피해를 당한 바 있다. 이런 피해의 원인은 강원도 산악지역에 위치하는 하천의 지역적, 지형학적 조건을 고려하지 못한 부분적인 이유도 있는 것으로 판단된다. 교량피해의 대부분은 교각과 교대의 기초부분 세굴(침식) 때문에 발생되었다. 다른 이유로는 고사목, 나뭇가지 및 부유잡물 등이 교각과 상판에 걸려서 물의 흐름을 어렵게 만들거나 차단 시켜서 발생되었다. 수해현장의 피해 형태와 원인 등을 분석하여 이로부터 설계 지침을 제시하였다.

• 비파괴검사학회지
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• 제31권3호
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• pp.260-270
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• 2011

The electromechanical impedance(E/M)-based method detects local structural damages based on variations of electrical impedance signatures which are obtained from piezoelectric sensors bonded to the structure and excited in high frequency band. In this method, temperature changes may result in significant impedance variations and lead to erroneous diagnostic results of the structure. To tackle this problem, a new technique providing a 2-dimensional damage feature related to the temperature information is proposed to distinguish the structural damage from the undesirable temperature variation. For experimental tests to validate the proposed method, damages are introduced by bolt loosening to a bolt-jointed steel beam, and impedance signals are measured under varying temperature conditions through a piezoelectric sensor attached on the beam. A freely suspended piezoelectric sensor is additionally utilized to obtain temperature information indirectly from resistance signatures. From a relationship between the damage index (from a constrained sensor) and the temperature (from a freely suspended sensor or a temperature sensor), damages can be detected more clearly under varying temperature compared to other conventional approaches.

• Smart Structures and Systems
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• 제21권5호
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• pp.677-686
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• 2018

The structural responses are often used to identify the structural local damages. However, it is usually difficult to gain the responses of the track, as the sensors cannot be installed on the track directly. The vehicles running on a track excite track vibration and can also serve as response receivers because the vehicle dynamic response contains the vibration information of the track. A damage identification method using the vehicle responses and sensitivity analysis is proposed for the vehicle-track coupling system in this paper. Different from most damage identification methods of vehicle-track coupling system, which require the structural responses, only the vehicle responses are required in the proposed method. The local damages are identified by a sensitivity-based model updating process. In the vehicle-track coupling system, the track is modeled as a discrete point supported Euler-Bernoulli beam, and two vehicle models are proposed to investigate the accuracy and efficiency of damage identification. The measured track irregularity is considered in the calculation of vehicle dynamic responses. The measurement noises are also considered to study their effects to the damage identification results. The identified results demonstrate that the proposed method is capable to identify the local damages of the track accurately in different noise levels with only the vehicle responses.

• Earthquakes and Structures
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• 제9권2호
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• pp.431-453
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• 2015

A destructive earthquake, the magnitude of this earthquake was 7.2, hit Van, Turkey on October 23, 2011. After this devastating earthquake, a moderate earthquake which had 5.7 magnitude on November 9, 2011 occurred in Edremit, Van. These earthquakes caused heavy damages and collapses in many reinforced concrete buildings with loss of lives. In this paper, characteristics of ground motions of these earthquakes were studied and, deficiencies in structural elements and engineering faults such as poor workmanship and quality of construction, soft and weak stories, strong beam-weak column, short column, large overhang, hammering and unconfined gable wall were investigated. According to the observations, it was seen that, low quality of structural materials, lack of engineering services, inappropriate design and construction with insufficient detailing of the structural elements were the main reasons of heavy damages.

• Structural Engineering and Mechanics
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• 제75권4호
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• pp.445-454
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• 2020

Structural damage identification (SDI) is a crucial step in structural health monitoring. However, some of the existing SDI methods cannot provide enough identification accuracy and efficiency in practice. A novel whale optimization algorithm (WOA) based method is proposed for SDI by weighting modal data and flexibility assurance criterion in this study. At first, the SDI problem is mathematically converted into a constrained optimization problem. Unlike traditional objective function defined using frequencies and mode shapes, a new objective function on the SDI problem is formulated by weighting both modal data and flexibility assurance criterion. Then, the WOA method, due to its good performance of fast convergence and global searching ability, is adopted to provide an accurate solution to the SDI problem, different predator mechanisms are formulated and their probability thresholds are selected. Finally, the performance of the proposed method is assessed by numerical simulations on a simply-supported beam and a 31-bar truss structures. For the given multiple structural damage conditions under environmental noises, the WOA-based SDI method can effectively locate structural damages and accurately estimate severities of damages. Compared with other optimization methods, such as particle swarm optimization and dragonfly algorithm, the proposed WOA-based method outperforms in accuracy and efficiency, which can provide a more effective and potential tool for the SDI problem.

• 한국구조물진단유지관리공학회 논문집
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• 제10권6호
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• pp.113-123
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• 2006

사장교가 장경간으로 시공됨에 따라 대형화 되고 지진하중, 풍하중 및 차량하중 등 동적 하중에 의해 유발되는 진동현상에 취약한 단점이 나타난다. 이러한 하중 등에 의해 발생된 구조 손상은 구조물의 진동모드 특성에 영향을 미치게 된다. 기존의 정밀안전진단 기술을 이용하여 사장교의 구조 손상을 검색하고 평가하는 것은 상당한 비용과 시간이 소요될 뿐만 아니라 전체적인 구조거동 특성의 변화를 발견하기 어려울 것이다. 따라서 본 연구는 사장교에 대하여 구조손상 전의 진동모드 특성치와 구조손상 후의 진동모드 특성치를 이용하여 구조거동 특성의 변화를 검토하고 구조손상 검색을 수행하였다.

• Structural Engineering and Mechanics
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• 제34권3호
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• pp.351-366
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• 2010

A novel system identification and structural health assessment procedure of steel framed structures with semi-rigid connections is presented in this paper. It is capable of detecting damages at the local element level under normal operating conditions; i.e., serviceability limit state. The procedure is a linear time-domain system identification technique in which the structure responses are required, whereas the dynamic excitation force is not required to identify the structural parameters. The procedure tracks changes in the stiffness properties of all the elements in a structure. It can identify damage-free and damaged structural elements very accurately when excited by different types of dynamic loadings. The method is elaborated with the help of several numerical examples. The results indicate that the proposed algorithm identified the structures correctly and detected the pre-imposed damages in the frames when excited by earthquake, impact, and harmonic loadings. The algorithm can potentially be used for structural health assessment and monitoring of existing structures with minimum disruption of operations. Since the procedure requires only a few time points of response information, it is expected to be economic and efficient.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.455-458
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• 1999

It has been known that buildings having inappropriate expansion joints in their spacings may be subject to exterior damages due to extensive cracks on the outer walls under service loads, and structural damages due to excessive moment induced by temperature changes at ultimate load conditions. Rather inconsistent code provisions are available regarding spacings of expansion joints from different foreign structural codes and even worse, no quantiative measure on spacings is given in our codes for building structures. In order to establish a rational measure on the spacing of expansion joints, theoretical approaches are taken in this study. The developed theoretical formula is, then, converted to design chart for structural designer's convenience in its use. The chart considers both service and ultimate load stages.