• Structural Monitoring and Maintenance
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• v.2 no.4
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• pp.383-397
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• 2015

This article identifies and addresses current limitations on the use of numerical models for validation and/or calibration of damage detection methodologies that are based on the analysis of the high frequency response of the structure to identify the occurrence of abrupt anomalies. Distributed-plasticity non-linear fiber-based models in combination with experimental data from a full-scale reinforced concrete column test are used to point out current modeling techniques limitations. It was found that the numerical model was capable of reproducing the global and local response of the structure at a wide range of inelastic demands, including the occurrences of rebar ruptures. However, when abrupt sudden damage occurs, like rebar fracture, a high frequency pulse is detected in the accelerations recorded in the structure that the numerical model is incapable of reproducing. Since the occurrence of such pulse is fundamental on the detection of damage, it is proposed to add this effect to the simulated response before it is used for validation purposes.

• Structural Monitoring and Maintenance
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• v.2 no.4
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• pp.339-355
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• 2015

Corrosion of prestressed concrete structures is one of the main challenges that engineers face today. In response to this national need, this paper presents the results of a long-term project that aims at developing a structural health monitoring (SHM) technology for the nondestructive evaluation of prestressed structures. In this paper, the use of permanently installed low profile piezoelectric transducers (PZT) is proposed in order to record the acoustic emissions (AE) along the length of the strand. The results of an accelerated corrosion test are presented and k-means clustering is applied via principal component analysis (PCA) of AE features to provide an accurate diagnosis of the strand health. The proposed approach shows good correlation between acoustic emissions features and strand failure. Moreover, a clustering technique for the identification of false alarms is proposed.

• Structural Monitoring and Maintenance
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• v.2 no.4
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• pp.301-318
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• 2015

This is the story of a bell-tower and its monitoring. The Civic Tower in Portogruaro is a 59 m high masonry bell-tower, originally built in the XIII century, today leaning more than a meter out of plumb. Since 2003, the building inclination has been continuously monitored with an optical inclinometer in an effort to see whether the tilt is still in progress. When the monitoring started, it was thought highly unlikely that the Tower would tilt further. After three years of monitoring and historical investigation, this idea was completely overturned. We show here how the initial view developed to a final awareness via a probabilistic analysis of the information acquired, based on Bayesian logic. We illustrate how the joint use of instrumental monitoring and historical documentation allowed timely recognition of signs of ongoing tilting and accurate calculation not only of the mean inclination trend, but also the credibility of this information.

• Structural Monitoring and Maintenance
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• v.6 no.4
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• pp.269-289
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• 2019

This study investigated experimentally the response of thick reinforced concrete specimens having hollow cores with critical parameters. The investigation includes testing of twelve specimens that are solid and hollow-core slab models. Each specimen consists of two pieces, the piece dimensions are (1.2 m) length, (0.3 m) width and (20 cm) thickness tested under both monotonic and repeated loading. The test program is carried out to study the effects of load type, core diameters, core shape, number of cores, and steel fiber existence. Load versus deflection at mid span, failure modes, and crack patterns were obtained during the test. The test results showed that core shape and core number has remarkable influenced on cracking pattern, ultimate load, and failure mode. Also, when considering repeated loading protocol, the ultimate load capacity, load at yielding, and ductility is reduced.

• Structural Monitoring and Maintenance
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• v.6 no.4
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• pp.347-364
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• 2019

Two seismic response data from the CSMIP strong motion instrumentation of Pacoima dam are selected: San Fernando earthquake (Jan 13, 2001; ML=4.3) and Newhall earthquake (Sept. 1, 2011; ML=4.2), for the identification of the dam system. To consider the spatially nonuniform input ground motion along the dam abutment, the subspace identification technique with multiple-input and multiple-output is used to extract the dynamic behavior of the dam-reservoir interaction system. It is observed that the dam-reservoir interaction is significant from the identification of San Fernando earthquake data. The influence of added mass (from the reservoir) during strong ground motion will create a tuned-mass damper phenomenon on the dam body. The fundamental frequency of the dam will be tuned to two different frequencies but with the same mode shapes. As for the small earthquake event, the dam-reservoir interaction is insignificant.

• The Transactions of the Korea Information Processing Society
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• v.7 no.10
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• pp.3055-3063
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• 2000

In this paper, a task duplication based heuristic scheduling algorithm is proposed to solve the problem of task scheduling on Shared Memory Multiporcessors (SMM). The proposed algorithm pre-allocates network resources so as to avoid potential communication conlhct, and the algorithm uses heuristies to select duplication tasks so as to recuce of a multiprocessors, and generates scheduling accorting to the available number of processors ina system. The proposed algorithm has been applied to some practical task graphs in the simulation, and the results show that the proposed algorithm achieves considerable performance improvement, in respect of schedule length.

• Structural Monitoring and Maintenance
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• v.2 no.3
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• pp.237-252
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• 2015

This paper addresses the issue of reliability and performance in wireless sensor networks (WSN) based structural health monitoring (SHM), particularly with decentralized damage identification techniques. Two decentralized damage identification algorithms, namely, the autoregressive (AR) model based damage index and the Wiener filter method are developed for structural damage detection. The ambient and impact testing have been carried out on the steel beam structure in the laboratory. Seven wireless sensors are installed evenly along the steel beam and seven wired sensor are also installed on the beam to monitor the dynamic responses as comparison. The results showed that wireless measurements performed very much similar to wired measurements in detecting and localizing damages in the steel beam. Therefore, apart from the usual advantages of cost effectiveness, manageability, modularity etc., wireless sensors can be considered a possible substitute for wired sensors in SHM systems.

• Structural Monitoring and Maintenance
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• v.2 no.2
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• pp.133-143
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• 2015

Civil engineering infrastructure is aging and requires cost-effective maintenance strategies to enable infrastructure systems operate reliably and sustainably. This paper presents an approach for determining risk-cost balanced repair strategy of corrosion damaged reinforced concrete structures with consideration of uncertainty in structural resistance deterioration. On the basis of analytical models of cover concrete cracking evolution and bond strength degradation due to reinforcement corrosion, the effect of reinforcement corrosion on residual load carrying capacity of corroded reinforced concrete structures is investigated. A stochastic deterioration model based on gamma process is adopted to evaluate the probability of failure of structural bearing capacity over the lifetime. Optimal repair planning and maintenance strategies during the service life are determined by balancing the cost for maintenance and the risk of structural failure. The method proposed in this study is then demonstrated by numerical investigations for a concrete structure subjected to reinforcement corrosion. The obtained results show that the proposed method can provide a risk cost optimised repair schedule during the service life of corroded concrete structures.

• Structural Monitoring and Maintenance
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• v.5 no.4
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• pp.429-443
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• 2018

Fatigue is a principal failure mode for steel structures, and it is still less understood than any other modes of failure. Fatigue life estimation of metal bridges is a major issue for making cost effective decisions on the rehabilitation or replacement of existing infrastructure. The fatigue design procedures given by the standard codes are either empirical or based on nominal stress approach. Since the fatigue life estimation through field measurements is difficult and costly, more researches are needed to develop promising techniques in the fatigue analysis of bridges through Finite Element Analysis (FEA). This paper aims to develop a methodology for the Fatigue life estimation of railway steel bridge using FEA. The guidelines of IIW-1823-07 were used in the development of the methodology. The Finite Element (FE) package ANSYS and the programming software MATLAB were used to implement this methodology on an Indian Railway Standard (IRS) welded plate girder bridge. The results obtained were compared with results from published literature and found satisfactory.

• Structural Monitoring and Maintenance
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• v.5 no.4
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• pp.445-461
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• 2018

The aim of this research is to evaluate the effects of the number of spans, height of spans, number of floors, height of floors, column to beam moment of inertia ratio, and plastic joints distance of beams from columns on the ductility of moment frames. For the facility in controlling the ductility of the frames, this paper offers a simple relation instead of complex equations of different codes. For this purpose, 500 analyzed and designed frames were randomly selected, and their ductility was calculated by the use of nonlinear static analysis. The results cleared that the column-to-beam moment of inertia ratio had the highest effect on ductility, and if this relation was more than 2.8, there would be no need for using the complex relations of codes for controlling the ductility of frames. Finally, the ductility of the most frames of this research could be estimated by using the combination of genetic algorithm and artificial neural networks properly.