• Smart Structures and Systems
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• 제20권3호
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• pp.385-396
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• 2017

The recent advancements in sensing technologies allow us to record measurements from target structures at multiple locations and with relatively high spatial resolution. Such measurements can be used to develop data-driven methodologies for condition assessment, control, and health monitoring of target structures. One of the state-of-the-art technologies, Fiber Optic Strain Sensors (FOSS), is developed at NASA Armstrong Flight Research Center, and is based on Fiber Bragg Grating (FBG) sensors. These strain sensors are accurate, lightweight, and can provide almost continuous strain-field measurements along the length of the fiber. The strain measurements can then be used for real-time shape-sensing and operational load-estimation of complex structural systems. While several works have demonstrated the successful implementation of FOSS on large-scale real-life aerospace structures (i.e., airplane wings), there is paucity of studies in the literature that have investigated the potential of extending the application of FOSS into civil structures (e.g., tall buildings, bridges, etc.). This work assesses the feasibility of using FOSS to predict operational loads (e.g., wind loads) on chain-like structures. A thorough investigation is performed using analytical, computational, and experimental models of a 4-story steel building test specimen, developed at the University of Southern California. This study provides guidelines on the implementation of the FOSS technology on building-like structures, addresses the associated technical challenges, and suggests potential modifications to a load-estimation algorithm, to achieve a robust methodology for predicting operational loads using strain-field measurements.

• 전기학회논문지P
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• 제59권1호
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• pp.77-82
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• 2010

This study evaluated the characteristics and reliability of an auger crane with a built-in hydraulic extender. The field test of the hydraulic extender was performed with the hydraulic lines filled with hydraulic fluid and free of air. The pressure generated during the test was measured with a digital pressure gauge. The crane was considered to have undergone one cycle of the excavation process after it had performed excavation under three conditions at the same location. This process was performed three times in total. From the results of the excavation using the hydraulic extender, it was found that the maximum pressure and torque measured were 19.9 [MPa] and 895.4 [$kgf{\cdot}m$], respectively. The rotation force of the auger crane generated at this time signifies a horizontal force. If the excavation diameter of the auger crane is increased, the rotation speed is reduced causing the circumferential speed to also be reduced. The torsional shear stress of the extendable auger crane was calculated to be approximately 23.5 [MPa]. However, the rotation shaft material used for this system was carbon steel for machine structural use (SM45C). Since the minimum torsional yield stress is greater than 150 [MPa] according to KS D 3752, it means the equipment has secured a safety factor greater than 6. Therefore, it was found that when performing work using the extendable auger crane, it exhibited no problems with the safety and reliability of its shaft.

• 분석과학
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• 제12권1호
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• pp.40-46
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• 1999

Zn-Ni 도금강판의 도금층 구조 및 형상 변화에 미치는 도금 제조 조건중, 전류 밀도, $Ni^{2+}$ 이온 농도, $Cl^-$ 이온 농도 등의 영향에 대하여 고찰하였다. 먼저 도금 조건의 중요한 변수 중의 하나인 전류 밀도를 변화시켰을 때 전류 밀도가 감소함에 따라 도금층 중의 Ni 함량은 증가하였다. 또한 도금 용액 중의 $Cl^-$ 이온과 $Ni^{2+}$ 이온 농도가 증가하면 도금층의 Ni 함량이 증가하였다. 이러한 도금층 중의 Ni 함량은 도금층의 구조 변화와 밀접한 관계를 나타내었다. 즉, Ni 함량이 10 wt.% 미만인 경우에는 ${\eta}$상과 ${\gamma}$상의 혼합 구조를 가지는데 비해서 10 wt.% 이상이 되면 ${\gamma}$단일상으로 변환되었다. 그리고 ${\eta}$상의 구조에서 Ni 함량이 증가함에 따라 a축 방향의 격자 상수는 증가하고 c축 방향의 격자 상수는 감소하였다. 한편 도금층의 형상 변화는 도금층의 조성과 결정구조가 달라짐에 따라 판상의 결정립 형태에서 부터 작은 구상의 입자상에 이르기까지 다양한 변화를 나타내었다.

• Steel and Composite Structures
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• 제33권6호
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• pp.891-906
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• 2019

This study considers the instability behavior of sandwich plates considering magnetorheological (MR) fluid core and piezoelectric reinforced facesheets. As facesheets at the top and bottom of structure have piezoelectric properties they are subjected to 3D electric field therefore they can be used as actuator and sensor, respectively and in order to control the vibration responses and loss factor of the structure a proportional-derivative (PD) controller is applied. Furthermore, Halpin-Tsai model is used to determine the material properties of facesheets which are reinforced by graphene platelets (GPLs). Moreover, because the core has magnetic property, it is exposed to magnetic field. In addition, Kelvin-Voigt theory is applied to calculate the structural damping of the piezoelectric layers. In order to consider environmental forces applied to structure, the visco-Pasternak model is assumed. In order to consider the mechanical behavior of structure, sinusoidal shear deformation theory (SSDT) is assumed and Hamilton's principle according to piezoelasticity theory is employed to calculate motion equations and these equations are solved based on differential cubature method (DCM) to obtain the vibration and modal loss factor of the structure subsequently. The effect of different factors such as GPLs distribution, dimensions of structure, electro-magnetic field, damping of structure, viscoelastic environment and boundary conditions of the structure on the vibration and loss factor of the system are considered. In order to indicate the accuracy of the obtained results, the results are validated with other published work. It is concluded from results that exposing magnetic field to the MR fluid core has positive effect on the behavior of the system.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2007년도 정기학술발표대회 논문집
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• pp.823-826
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• 2007

건설 사업에서도 공사의 효율적 관리 및 생산성 향상을 위해 빠르게 발달하는 정보기술을 이용하려는 노력이 점차 증가되고 있다. 그 예로 3D CAD와 RFID등을 적용한 현장관리 모델이다. 이 모델은 각 사업단위에서 발생하는 수많은 데이터(설계정보, 자재 정보, 공정관리 정보, 등)를 정의하고 조직화 시키는 것이다. 하지만 지금까지는 사람들이 정보를 옮겨주거나 입력을 해야 하는 수작업으로 인해 데이터의 정확성 부족 및 활용도가 많이 떨어져 실시간으로 모니터링 하는데 문제점이 발생하였다. 본 연구는 자동으로 실시간으로 공정관리를 할 수 있는 RTPM 시스템의 데이터와 현장에서 자동으로 입력되는 데이터를 이용하여 실시간 모니터링 시스템에 필요한 데이터베이스를 구축하고, 비슷한 성격의 데이터로 구성된 테이블간의 관계를 RED Diagram을 통해 연구 하고자 한다.

• 한국산학기술학회논문지
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• 제15권10호
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• pp.6282-6288
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• 2014

본 논문은 용접 산업현장에서 많이 사용 되는 $CO_2$ 용접에서는 차량내부 및 탱크내부 용접에서 제어 패널을 볼 수 없는 곳, 작업장이 먼 곳 등에서 용접사가 용접을 하면서 용접조건에 맞는 전류와 전압을 조절할 수가 없고, 전류와 전압을 조절하기 위해 용접을 중단하고 잦은 이동으로 용접 구조물의 순간적인 냉각에 의해 용접결함이 발생된다. 본 연구에서는 기존의 $CO_2$ 용접기 3종류를 각각 사용하여 원격제어 토치의 용접에 대해 SS400 용접구조용 압연강재를 사용하여 원격제어 토치와 기존 $CO_2$ 용접 토치를 V형 맞대기 수직자세로 용접실험을 실시하고 용접 부의 표면비드 상태의 형상을 육안검사 관찰하고 또한 이를 침투탐상검사 및 굽힘 시험을 통해 용접부의 외관품질에 대하여 중점적으로 수행하여 용접결함 감소 및 기존 상용용접기에 교체사용에 대한 성능 및 호환성여부에 미치는 영향에 대해 평가하였다.

• Steel and Composite Structures
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• 제34권2호
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• pp.261-277
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• 2020

The main objective of this research paper is to consider vibration analysis of vacancy defected graphene sheet as a nonisotropic structure via molecular dynamic and continuum approaches. The influence of structural defects on the vibration of graphene sheets is considered by applying the mechanical properties of defected graphene sheets. Molecular dynamic simulations have been performed to estimate the mechanical properties of graphene as a nonisotropic structure with single- and double- vacancy defects using open source well-known software i.e., large-scale atomic/molecular massively parallel simulator (LAMMPS). The interactions between the carbon atoms are modelled using Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential. An isogeometric analysis (IGA) based upon non-uniform rational B-spline (NURBS) is employed for approximation of single-layered graphene sheets deflection field and the governing equations are derived using nonlocal elasticity theory. The dependence of small-scale effects, chirality and different defect types on vibrational characteristic of graphene sheets is investigated in this comprehensive research work. In addition, numerical results are validated and compared with those achieved using other analysis, where an excellent agreement is found. The interesting results indicate that increasing the number of missing atoms can lead to decrease the natural frequencies of graphene sheets. It is seen that the degree of the detrimental effects differ with defect type. The Young's and shear modulus of the graphene with SV defects are much smaller than graphene with DV defects. It is also observed that Single Vacancy (SV) clusters cause more reduction in the natural frequencies of SLGS than Double Vacancy (DV) clusters. The effectiveness and the accuracy of the present IGA approach have been demonstrated and it is shown that the IGA is efficient, robust and accurate in terms of nanoplate problems.

• Steel and Composite Structures
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• 제29권5호
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• pp.603-622
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• 2018

Precast concrete structures are erected from individual prefabricated components, which are assembled on-site using different types of connections. In the present design of these structures, beam-to-column connections are assumed pin jointed. Bolted billet beam to-column connections have been used in the precast concrete industry for many years. They have many advantages over other jointing methods in component production, quality control, transportation and assembly. However, there is currently limited information concerning their detailed structural behaviour under vertical loadings. The experimental work has involved the determination of moment-relative rotation relationships for semi-rigid precast concrete connections in full-scale connection tests. The study reported in this paper was undertaken to clarify the behaviour of such connections under symmetrical vertical loadings. A series of full-scale tests was performed on sample column for which the column geometry and bolt arrangements conformed to successful commercial practice. Proprietary hollow core floor slabs were tied to the beams by 2T25 tensile reinforcing bars, which also provide the in-plane continuity across the connections. The contribution of the floor strength and stiffness to the flexural capacity of the joint is currently neglected in the design process for precast concrete frames. The flexural strength of the connections in the double-sided tests was at least 0.93 times the predicted moment of resistance of the composite beam and slab. The secant stiffness of the connections ranged from 0.94 to 1.94 times the flexural stiffness of the attached beam. In general, the double-sided connections were found to be more suited to a semi-rigid design approach than the single sided ones. The behaviour of double sided bolted billet connection test results are presented in this paper. The behaviour of single sided bolted billet connection test results is the subject of another paper.

• 한국해양공학회지
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• 제33권5호
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• pp.486-494
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• 2019

Recently, the interest in marine leisure activities has been growing rapidly with the work-life balance trend. In response to this demand, the Korean government is supporting fostering and revitalizing the relevant industries and facilities. In particular, a marina has been making efforts to change itself into a resort with multiple amenities instead of a simple mooring facility. However, the facilities in a marina for the transport of marine leisure equipment mostly consist of cranes and boat-lifts using ropes, which can result in incidents such as damage and accidents during lifting or movement. This paper proposes the equipment and support system for the safe transportation of marine leisure ships. Aluminum transport equipment was designed by performing a structural analysis to achieve a lighter weight than the existing steel products. In addition, a safety support system with alarms for tilting or obstacles and a slope monitoring system was developed to enhance the safety during operation and transportation. The safety support system developed in this study was implemented and installed in the transport system, and verified through commissioning on land.

• Steel and Composite Structures
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• 제41권5호
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• pp.761-773
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• 2021

This study presents a 3D non-linear finite element (FE) assessment of dynamic soil-structure interaction (SSI). The numerical investigation has been performed on the time domain through a Finite Element (FE) system, while considering the nonlinear behavior of soil and the multi-directional nature of genuine seismic events. Later, the FE outcomes are analyzed to the recorded in-situ free-field and structural movements, emphasizing the numerical model's great result in duplicating the observed response. In this work, the soil response is simulated using an isotropic hardening elastic-plastic hysteretic model utilizing HSsmall. It is feasible to define the non-linear cycle response from small to large strain amplitudes through this model as well as for the shift in beginning stiffness with depth that happens during cyclic loading. One of the most difficult and unexpected tasks in resolving soil-structure interaction concerns is picking an appropriate ground motion predicted across an earthquake or assessing the geometrical abnormalities in the soil waves. Furthermore, an artificial neural network (ANN) has been utilized to properly forecast the non-linear behavior of soil and its multi-directional character, which demonstrated the accuracy of the ANN based on the RMSE and R² values. The total result of this research demonstrates that complicated dynamic soil-structure interaction processes may be addressed directly by passing the significant simplifications of well-established substructure techniques.