• Structural Engineering and Mechanics
• /
• 제72권6호
• /
• pp.689-712
• /
• 2019

Time-series models like AR-ARX and ARMAX, provide a robust way to capture the dynamic properties of structures, and their residuals can be effectively used as features for damage detection. Even though several research papers discuss the implementation of AR-ARX and ARMAX models for damage diagnosis, they are basically been exploited so far for detecting the time instant of damage and also the spatial location of the damage. However, the inverse problem associated with damage quantification i.e. extent of damage using time series models is not been reported in the literature. In this paper, an approach to detect the extent of damage by combining the ARMAX model by formulating the inverse problem as a multi-constrained optimization problem and solving using a newly developed hybrid adaptive differential search with dynamic interaction is presented. The proposed variant of the differential search technique employs small multiple populations which perform the search independently and exchange the information with the dynamic neighborhood. The adaptive features and local search ability features are built into the algorithm in order to improve the convergence characteristics and also the overall performance of the technique. The multi-constrained optimization formulations of the inverse problem, associated with damage quantification using time series models, attempted here for the first time, can considerably improve the robustness of the search process. Numerical simulation studies have been carried out by considering three numerical examples to demonstrate the effectiveness of the proposed technique in robustly identifying the extent of the damage. Issues related to modeling errors and also measurement noise are also addressed in this paper.

• Smart Structures and Systems
• /
• 제23권1호
• /
• pp.45-60
• /
• 2019

This paper is devoted to proposing a new approach for damage detection of structures. In this technique, the biconjugate gradient method (BCG) is employed. To remedy the noise effects, a new preconditioning algorithm is applied. The proposed preconditioner matrix significantly reduces the condition number of the system. Moreover, based on the characteristics of the damage vector, a new direct search algorithm is employed to increase the efficiency of the suggested damage detection scheme by reducing the number of unknowns. To corroborate the high efficiency and capability of the presented strategy, it is applied for estimating the severity and location of damage in the well-known 31-member and 52-member trusses. For damage detection of these trusses, the time history responses are measured by a limited number of sensors. The results of numerical examples reveal high accuracy and robustness of the proposed method.

• 한국구조물진단유지관리공학회 논문집
• /
• 제12권1호
• /
• pp.81-90
• /
• 2008

본 연구에서는 유한 요소법과 고도화된 손상 탐지 기법을 결합하여 구조적 손상을 규명하는 방법을 다룬다. 본 연구의 특징은 충격하중을 받는 구조물의 동적 거동 특성을 분석하여 이를 임의의 손상 형태를 갖는 판에 적용한다는 것이다. 이러한 방법은 손상된 부위의 강성 분포를 추정할 뿐만 아니라 손상의 정도도 파악할 수 있는 장점을 갖으며 분할 요소수의 제한을 두지 않는다. 제안된 방법을 검증하기 위하여 본 알고리즘은 임의의 손상을 갖는 박판에 대하여 적용하기 한다. 수치해석 결과로부터 제안된 알고리즘은 수치적 효율성과 함께 임의의 손상 분포를 규명할 수 있음을 보여준다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제16권7호
• /
• pp.2459-2472
• /
• 2022

With the increase in copyright content exports to overseas markets due to the recent globalization of the Korean culture, the added value of the Korean digital content market is increasing at a significant rate. As such, as the size of the copyright market increases, different piracy sites have emerged that generate profits by illegally distributing works without the permission of the copyright holders, resulting in direct and indirect damage to these copyright holders. The existing copyright detection methods used in public institutions for solving this problem are limited, while the piracy sites are ever-changing. Methods are being continuously developed to achieve better detection results. To this end, it is possible to detect the latest infringement site domain by detecting the infringement site domain that is constantly changed through the search engine. This paper proposes an improved piracy site detection method using a search engine to prevent the damage caused by piracy sites.

• Structural Engineering and Mechanics
• /
• 제87권6호
• /
• pp.555-574
• /
• 2023

An efficient optimization algorithm and damage-sensitive objective function are two main components in optimization-based Finite Element Model Updating (FEMU). A suitable combination of these components can considerably affect damage detection accuracy. In this study, a new hybrid damage-sensitive objective function is proposed based on combining two different objection functions to detect the location and extent of damage in structures. The first one is based on Generalized Pseudo Modal Strain Energy (GPMSE), and the second is based on the element's Generalized Flexibility Matrix (GFM). Four well-known population-based metaheuristic algorithms are used to solve the problem and report the optimal solution as damage detection results. These algorithms consist of Cuckoo Search (CS), Teaching-Learning-Based Optimization (TLBO), Moth Flame Optimization (MFO), and Jaya. Three numerical examples and one experimental study are studied to illustrate the capability of the proposed method. The performance of the considered metaheuristics is also compared with each other to choose the most suitable optimizer in structural damage detection. The numerical examinations on truss and frame structures with considering the effects of measurement noise and availability of only the first few vibrating modes reveal the good performance of the proposed technique in identifying damage locations and their severities. Experimental examinations on a six-story shear building structure tested on a shake table also indicate that this method can be considered as a suitable technique for damage assessment of shear building structures.

• Computers and Concrete
• /
• 제11권6호
• /
• pp.541-569
• /
• 2013

There is a wide variety of existing Genetic Algorithms (GA) operators and parameters in the literature. However, there is no unique technique that shows the best performance for different classes of optimization problems. Hence, the evaluation of these operators and parameters, which influence the effectiveness of the search process, must be carried out on a problem basis. This paper presents a comparison for the influence of GA operators and parameters on the performance of the damage identification problem using the finite element model updating method (FEMU). The damage is defined as reduction in bending rigidity of the finite elements of a reinforced concrete beam. A certain damage scenario is adopted and identified using different GA operators by minimizing the differences between experimental and analytical modal parameters. In this study, different selection, crossover and mutation operators are compared with each other based on the reliability, accuracy and efficiency criteria. The exploration and exploitation capabilities of different operators are evaluated. Also a comparison is carried out for the parallel and sequential GAs with different population sizes and the effect of the multiple use of some crossover operators is investigated. The results show that the roulettewheel selection technique together with real valued encoding gives the best results. It is also apparent that the Non-uniform Mutation as well as Parent Centric Normal Crossover can be confidently used in the damage identification problem. Nevertheless the parallel GAs increases both computation speed and the efficiency of the method.

• 한국소음진동공학회논문집
• /
• 제19권9호
• /
• pp.884-891
• /
• 2009

This study investigates some of swarm intelligence algorithms to tackle a traditional damage detection problem having stiffness degradation or damage in mechanical structures. Particle swarm(PSO) and ant colony optimization(ACO) methods have been exploited for localizing and estimating the location and extent damages in a structure. Both PSO and ACO are population-based, stochastic algorithms that have been developed from the underlying concept of swarm intelligence and search heuristic. A finite element (FE) model updating is implemented to minimize the difference in a set of natural frequencies between measured and baseline vibration data. Stiffness loss of certain elements is considered to simulate structural damages in the FE model. It is numerically shown that PSO and ACO algorithms successfully completed the optimization process of model updating in locating unknown damages in a truss structure.

• 한국산업융합학회 논문집
• /
• 제24권6_2호
• /
• pp.891-897
• /
• 2021

In this paper, we propose a destination optimal route algorithm for providing route finding service for the transportation handicapped by using the multi-criteria decision-making technique and the modified A-STAR optimal route search algorithm. This is a method to set the route to the destination centering on safety by replacing the distance cost of the existing A-STAR optimal route search algorithm with the safety cost calculated through AHP/TOPSIS analysis. To this end, 10 factors such as road damage, curb, and road hole were first classified as poor road factors that hinder road driving, and then pairwise comparison of AHP was analyzed and then defined as the weight of TOPSIS. Afterwards, the degree of driving safety was quantified for a certain road section in Busan through TOPSIS analysis, and the development of an optimal route search algorithm for the transportation handicapped that replaces the distance cost with safety in the finally modified A-STAR optimal route algorithm was completed.

• 한국정밀공학회지
• /
• 제23권11호
• /
• pp.78-84
• /
• 2006

The objective of this study is to design the optimal die profile that can prevent material fracture in the tube drawing process for automobile steering input shaft. First, the CDV(Critical Damage Value) of material is obtained by the compression test and FE-analysis. The occurrence of fracture is estimated by the FE-analysis considering the CDV. In order to achieve the objective of this study, optimization technique and FE-analysis are applied. FPS(Flexible Polyhedron Search) method, which is one of the non-gradient optimization techniques often used in engineering, is used to search optimal die profile. The drawing die profile is represented by Bezier-curve to generate all the possible die profile. Using FPS method and FE-analysis the optimal drawing die profile is determined. To verify tile effectiveness of the redesigned optimal die, the tube drawing experiment is performed. In the experimental result, it is possible to produce sound product without material fracture using the redesigned optimal die.

• 한국측량학회지
• /
• 제17권1호
• /
• pp.51-59
• /
• 1999

도시 기반 시설중 하나인 상하수도는 도시 규모의 확대와 인구의 증가, 그리고 시설의 노후화로 인한 기존 관리 방법에 많은 한계가 나타나고 있는 실정이다 또한 최근에는 하수에 의한 지하수의 오염과 수도관 파손 등에 의한 사고시 신속한 대응능력의 부족으로 행정적인 문제가 빈번히 발생하고 있는 현실이 GIS에 의한 시설물관리의 필요성이 절실히 요구되고 있다. 따라서 본 연구에서는 이러한 문제점을 감안하여 시설물관리 방법으로 GIS기법을 이용하여 체계적이고 합리적인 시설물 유지관리가 가능할 수 있는 계기를 마련하고자 한다. 끝으로 상하수도 시설물관리에 GIS기법을 활용하므로써 합리적이고 체계적인 시설물관리가 가능함을 제시하고 시설물관리의 응용방안을 제시하여 실무자의 업무 효율을 극대화하므로써 본 연구의 목적을 달성하고자 한다.