• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.388-399
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• 2003

Light losses in optical fibers are investigated by a fiber optic OTDR (Optical Time Domain Reflectometry) sensor system to develop fiber optic probes for structural strain measurement. The sensing fibers are manufactured 3 kinds of fibers: one is single mode fiber, and second is multimode fiber, and the third is low-cladding-index fiber. Fiber bending tests are performed to determine the strain sensitivity according to the strain of gage length of optical fibers. In the result of this experiments, the strain sensitivity of the single mode fiber was shown the highest value than others. The fiber optic strain probe was manufactured to verify the feasibility of the structural strain measurement. In this test, the fiber optic strain probe of the OTDR sensor could be easily made by the single mode fiber.

• Structural Engineering and Mechanics
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• v.60 no.4
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• pp.729-747
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• 2016

This study aims to present a novel optimization algorithm known as gravitational search algorithm (GSA) for structural damage detection. An objective function for damage detection is established based on structural vibration data in frequency domain, i.e., natural frequencies and mode shapes. The feasibility and efficiency of the GSA are testified on three different structures, i.e., a beam, a truss and a plate. Results show that the proposed strategy is efficient for determining the locations and the extents of structural damages using the first several modal data of the structure. Multiple damages cases in different types of structures are studied and good identification results can be obtained. The effect of measurement noise on the identification results is investigated.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.109-110
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• 2015

Estimation of rebar quantity may be used as an index to evaluate the economic feasibility of structural designs. However, when using the software to estimate the rebar quantity, there may be some limitations such as data loss caused by human errors and estimation delays caused by increased input time, since the information on arrangement of rebar is inserted manually. To solve the problems of such quantity estimation software, it is necessary to develop a method on automatic input/output of structural design information for quantity estimation and an algorithm for accurate estimation of rebar quantity. The purpose of this study is to improve the existing rebar quantity estimation by connecting with the database on information related to rebar estimation and the algorithm for rebar estimation, in order to develop an algorithm to estimate an accurate, net rebar quantity. The study result can be used as basic data for development of software for efficient structural designs and automatic framework estimation of buildings.

• Structural Engineering and Mechanics
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• v.54 no.5
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• pp.999-1016
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• 2015

In this paper, we introduce a new method for assembly of shipbuilding blocks at sea and present its feasibility focusing on structural safety. The core concept of this method is to assemble ship building blocks by use of bolting, gluing and welding techniques at sea without dock facilities. Due to its independence of dock facilities, shipyard construction capability could be increased considerably by the proposed method. To show the structural safety of this method, a bulk carrier and an oil tanker were employed, and we investigated the structural behavior of those ships to which the new block assembly method was applied. The ship hull models attached with connective parts are analyzed in detail through finite element analyses, and the cargo capacity of the bulk carrier is briefly discussed as well. The results of these studies show the potential for applying this new block assembly method to practical shipbuilding.

• Smart Structures and Systems
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• v.26 no.3
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• pp.311-318
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• 2020

The goal of this study is to analytically and non-stochastically generate structural uncertainty behaviors of isotropic beams and laminated composite plates under plane stress conditions by using an interval finite element method. Uncertainty parameters of structural properties considering resistance and load effect are formulated by interval arithmetic and then linked to the finite element method. Under plane stress state, the isotropic cantilever beam is modeled and the laminated composite plate is cross-ply lay-up [0/90]. Triangular shape with a clamped-free boundary condition is given as geometry. Through uncertainties of both Young's modulus for resistance and applied forces for load effect, the change of structural maximum deflection and maximum von-Mises stress are analyzed. Numerical applications verify the effective generation of structural behavior uncertainties through the non-stochastic approach using interval arithmetic and immediately the feasibility of the present method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.283-290
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• 1999

A practical damage identification scheme for PS concrete bridges via modal testing and system identification (SID) procedures is presented. The potential damage types are classified and the possible approaches which can be implemented into each damage type are designed. Damage identification algorithms are developed on the basis of the SID and modal analysis. The feasibility of the algorithms is verified from experimental tests to detect damage in PS concrete beam structures.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.24-31
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• 2000

An integrated damage identification system (IDIS) using modal information to detect damage in structures is presented. The objective of this study is to develop a system of softwares that facilitates detecting damage locations and estimating damage severities in bridges. Firstly, the theoretical background for IDIS is outlined. Secondly, a GUI-based IDIS software is programmed. Finally, the feasibility and applicability of the IDIS software are experimentally demonstrated using small-scaled plate-girder models.

• The KSFM Journal of Fluid Machinery
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• v.18 no.2
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• pp.5-13
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• 2015

The aim of this study is to investigate the feasibility of a new type of casing for the inline Francis hydro turbine. Comparing with the traditional turbine with spiral casing, this turbine is unique for its flow passage shape at the first stage of flow to the turbine, very similar to a pipe, called inline casing. Before the commercialization of this new type of casing, a global investigation of the inline casing must be conducted. Preserving the structural characteristics of simple, compact-size and convenient for manufacture, different shapes of the belt passage, vertical corner and stay vanes are applied to investigate the influence of flow passage shape on the turbine performance. Stable and relatively high efficiency is achieved regardless of flow passage shape difference proving the feasibility of the inline casing used in a hydro turbine.

• Earthquakes and Structures
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• v.18 no.3
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• pp.337-348
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• 2020

Experimental testing has been considered as one of the most straightforward approaches to realize the structural behavior for earthquake engineering studies. Recently, novel and advanced experimental techniques, which combine numerical simulation with experimental testing, have been developed and applied to structural testing practically. However, researchers have to take the risk of damaging specimens or facilities during the process of developing and validating new experimental methods. In view of this, a small-scale structural laboratory has been designed and constructed in order to verify the effectiveness of newly developed experimental technique before it is applied to large-scale testing for safety concerns in this paper. Two orthogonal steel reaction walls and one steel T-slotted reaction floor are designed and analyzed. Accordingly, a large variety of experimental setups can be completed by installing servo-hydraulic actuators and fixtures depending on different research purposes. Meanwhile, a state-of-the-art digital controller and multiple real-time computation machines are allocated. The integration of hardware and software interfaces provides the feasibility and flexibility of developing novel experimental methods that used to be difficult to complete in conventional structural laboratories. A simple experimental demonstration is presented which utilizes part of the hardware and software in the small-scale structural laboratory. Finally, experimental layouts of future potential development and application are addressed and discussed, providing the practitioners with valuable reference for experimental earthquake engineering.

• Composites Research
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• v.30 no.2
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• pp.126-131
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• 2017

For structural health monitoring of a complex shaped structure a new sensor that can compensate for the drawbacks of the current sensors such as brittleness is needed and the sensor should be highly flexible and durable. In this study a textile sensor made of polyvinylidene fluoride trifluoroethylene (PVDF-TrFE) which is a type of electroactive polymer was fabricated. And the textile sensors were applied to a complex shaped structure (an egg-box panel made of carbon/epoxy composite) for checking their feasibility of structural health monitoring. To correlate the collapse response with failure mechanisms of the structure the multiply-interrupted compressive test was carried out. During the test, the textile sensors succeeded to prove their applicability for damage detection (crack initiation) by generating electric voltages (0.05 V-0.25 V) in the real time.