1,721,054 research outputs found
Vibration-based structural damage detection using a decentralized network with limited sensors
No full textOne of the main purposes of modal identification is to estimate the structural mechanical properties, in order to detect a possible damage over time. Several researches have been conducted recently to implement identification techniques based on the assumption of modest number of sensors. Such methods are needed both in the case of decentralized systems of wireless smart sensors, where operating units interact with each other in small groups, and in the case of repeated tests, carried out to identify large structures with a low availability of sensors. In this paper we propose a hybrid adaptive technique for natural vibration-based dynamic identification in the time-frequency domain. The proposed method involves the introduction of a novel procedure for decoupling the modal responses contained in the recorded signals, led by a clustering-based decomposition and reconstruction process; subsequently, decoupled signals, considered as single degree of freedom responses, are subjected to identification procedures in time domain, with the aim of studying the trend of instantaneous modal parameters. Since the procedure involves the real time estimation of dynamic parameters through a wavelet-based technique, it is particularly suitable for non-stationary signals. From the estimated parameters, a structural damage detection procedure is applied by using a flexibility-based technique. In order to test the effectiveness of the proposed method, the identification and damage detection procedures are simulated on a finite element model that represents a reinforced concrete plane frame
Distribution of damper properties along the height and the plan for the seismic retrofit of plan-asymmetric RC frames
No full textThe purpose of this research is to investigate the effectiveness of different vertical and in-plan distributions of the damping coefficients of nonlinear viscous dampers for the seismic retrofit of existing buildings with plan-asymmetry. The different distributions were examined within a procedure proposed in literature for the design of viscous dampers applied to 3D plan-asymmetric buildings. In particular, simple distribution criteria, based on specific structural properties, were considered with the purpose to improve the design of the damping system in terms of cost without significant change of response. All the distributions were applied considering, for comparison, both a simplified and an extended design method, by neglecting or considering, respectively, the plan-asymmetry in the design. The effectiveness of the different distributions was examined by performing time-history analyses of a case study with different configurations of dampers adopting a nonlinear behaviour both for the viscous dampers and the frame members. The dampers were dimensioned considering that the structure can exceed the elastic limit, with the only condition to satisfy the prefixed performance limit. The considered case study is a two bay RC frame with six storeys and an irregular plan configuration. The examined response parameters were maximum interstorey drifts, residual interstorey drifts, peak floor accelerations and maximum damper forces
Instantaneous identification of densely instrumented structures using line topology sensor networks
Full text linkIn this paper, a new strategy for vibration-based structural health monitoring is proposed, specifically designed for smart sensors with edge computing capabilities organized in a line topology. This solution is aimed at maximizing resource optimization and enables the identification of modal parameters even for large or densely instrumented structures, where star-topology monitoring systems are typically unsuitable. In particular, an efficient data management procedure is proposed to reduce data transmission, thus improving efficiency and minimizing maintenance interventions for battery replacement in wireless applications. The maximum volume of transmitted data can be selected by the user, based on the specific requirements of the network. Although the considerable reduction of data size, the proposed approach enables accurate estimation of the structural parameters in challenging scenarios where other techniques generally fail. Modal parameters are identified in an online fashion, enabling near real-time detection and localization of early damage. Applications to a real case study instrumented with a dense sensor network show the effectiveness of the proposed approach and the possibility of localizing structural defects in slightly damaged civil structures
On the Use of Singular Vectors for the Flexibility-Based Damage Detection under the Assumption of Unknown Structural Masses
Full text linkThe main purpose of this work is to investigate the usability of easily obtainable parameters instead of the modal traditional ones, in the context of a flexibility-based damage detection procedure, under the assumption of unknown structural masses. To this aim, a comparison is made between two different approaches: the first involves the calculation of the flexibility matrix by using traditional modal parameters, such as natural frequencies and modal vectors, normalized to unitary values, while the second involves the use of singular vectors, obtained through a simple matrix factorization. The modal parameters and the singular vectors necessary for the implementation of the damage detection procedure are evaluated through two different techniques: the Eigensystem Realization Algorithm and a wavelet-based procedure, for which a variant is proposed by introducing the energy reassignment concept into the original algorithm. Through the latter approach, in particular, it is possible to obtain a high number of singular vectors even in the case of reduced availability of sensors. The study is performed under the assumption of nonstationary excitation, in order to achieve general results, and the effectiveness of the procedures is evaluated through simulated tests regarding different structural schemes
Fusing Modal Parameters and Curvature Influence Lines for Damage Localization Under Vehicle Excitation
No full textTransport infrastructure serves as a vital component for facilitating the movement of people and goods, contributing significantly to sustainable development and territorial cohesion. However, bridges, which are crucial elements of transportation networks, are increasingly susceptible to degradation caused by growing traffic volumes and severe weather events. Recent research efforts have focused on developing damage-sensitive features specifically designed for bridges, with curvature being one of the most used indicators. Traditionally, curvature estimation requires multiple instrumented locations. However, dense networks introduce challenges related to data management, synchronization, and battery replacement. This study presents an algorithm that enables the identification of dense curvature estimates for civil infrastructure using a limited set of accelerometers. The algorithm combines sparse curvature estimates derived from modal parameters with curvature influence lines obtained from the vibration response recorded during vehicle passage. A Kalman filter is employed to fuse these two features, mitigating the error resulting from traffic variations. The effectiveness of the proposed method is demonstrated using data collected from a real steel truss bridge with artificially induced damage
Real time damage detection through single low-cost smart sensor
No full textContinuous vibration-based structural monitoring is increasingly used to assess the state of health of existing structures and infrastructures in environmental conditions through non-inva- sive methods that allow, in most cases, an early identification of damage. To date, the innova- tive wireless smart sensor networks are the subject of numerous researches in the field of structural health monitoring, but their use on real structures is still limited, due to problems related to energy consumption and algorithmic optimization. In fact, most of the traditional identification algorithms work in centralized topology and are not suitable for electronic ele- ments with low computational capacity. Nevertheless, the high energy consumption of wireless communication does not allow continuous data transmission for centralized processing in real time. However, the limited costs of new technologies, compared to traditional wired acquisition systems, shifts the interest towards innovative solutions, both from an algorithmic and hard- ware point of view, in order to provide innovative monitoring systems that can also be used on minor structures, for which traditional systems would be inaccessible. This paper presents a first practical application of a structural identification algorithm specifically designed for low- cost embedded electronic systems on a scaled laboratory model. The proposed solution consists of a single sensing node able to identify natural frequencies in real time, even in conditions of non-stationary excitation and variable structural characteristics. The estimated parameters are periodically uploaded to a cloud platform, where a preliminary real-time damage detection takes place
Damage detection of non-linear reinforced concrete structure by means of single sensing node
No full textThis paper presents an application of an output-only structural identification algorithm specifically designed for low-cost monitoring systems on a structure with strongly non-linear behavior. The identification procedure is conducted simulating the presence of a single smart sensor node on the specimen, in order to identify the natural frequencies and amplitudes of collected accelerations in real time. The estimated parameters are used to develop a non-linear frequency-amplitude model representing the structural response, subsequently employed for damage detection
Dynamic identification of a reinforced concrete structure by means of modal assurance distribution
No full textFor time-varying systems in structural engineering, such as bridges with vehicular traffic and structures during
construction or seismic events, the application of traditional vibration-based identification methods may not be
admissible, since the hypotheses of stationarity of the signal may be far from the real situation. Moreover, in some cases,
real-time approaches to visualize the identified parameters are desirable to allow for a rapid decision-making process,
which assumes the utmost importance for the early warning in structures near to excavation or demolition sites and
strategic infrastructures after seismic events. Time-frequency representations have been largely used for the instantaneous
identification of linear time-varying systems. However, traditional algorithms generally suffer from issues related to the
identification of closely-spaced modes, which make the modal decomposition a non-trivial task. Moreover, by tracking
only natural frequencies, some variations of the dynamic behavior could not be perceived, or the variations induced by
other environmental and operational conditions could prevail over those due to a modification in the structural properties
(e.g., due to ongoing damage). In this paper, a Decomposition Algorithm based on Modal Assurance (DAMA) is applied
to separate modal responses, in order to allow a near real-time identification of modal parameters of structures with time-varying
features. In particular, a Modal Assurance Distribution (MAD) obtained from the analysis of multi-variate signals
is used to track the variations of modal parameters, considering both natural frequencies and modal shapes. The DAMA
is applied to a full-scale structure subjected to a series of dynamic tests performed in different structural conditions. The
analysis of multi-variate signals consisting of acceleration recordings collected at different locations of the structure
allows the online identification of varying dynamic parameters, which can be used to assess the structural state of health
Exploiting traffic-induced vibration for high-resolution damage identification in bridges with sparse instrumentation
No full textGrowing traffic demand on aging civil infrastructure raises the need for reliable structural health monitoring tools for "minor" bridges. Data management can be power-demanding in state-of-the-art dense wireless sensor networks. This study presents an original damage identification algorithm for viaducts to identify a dense curvature distribution of the loaded structure based on sparse acceleration recordings. Moving vehicles are exploited to obtain dense spatial information of the structural features and localize anomalies with high resolution. Modal parameters and curvature influence lines are obtained by pro- cessing the raw acceleration signals with a particular filter bank, efficiently implementable through edge computing technologies
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