BUSCADOR RECOLECTA

Structural identification using dynamical parameters (such as the natural vibration frequencies and mode shapes) is an important issue, especially in bridges or high-rise buildings. However, incorrect decisions could happen on the Structural Health Monitoring (SHM) strategy and the Structural System Identification (SSI) analysis that makes the sometimes expensive and time-consuming process useless due to the large uncertainty of the resulting estimations. This paper discusses the role of the SHM strategy and the SSI analysis based on the constrained observability method (COM) and decision trees (DT) in reducing the estimation error. Here, the COM uses subsets of natural frequencies and/or modal-shapes to deal with the nonlinearity of the SSI derived from the operational aspects of the methods, and combines the unknown items including frequencies and mode shapes into an optimization process. Next, a decision-support tool based on decision trees is applied to help engineers to establish the best SHM + SSI strategy yielding the most accurate estimations. The principle and steps of this new method, the combination of constrained observability m,ethod and decision trees, are presented for the first time. After that, a numerical model of a bridge case is used to show how to choose the optimal strategy, when factors such as the structure layout, span length, measurement set, and parameters of the COM are included as decision variables. The importance ranking of these four factors is the layout, measurement set, parameters of the COM, and length through the sensitivity analysis of the COM estimated. Last, a real bridge is used to validate this methodology under the undamaged and damaged scenarios by comparing an Error Index, which shows the optimal SHM + SSI strategy works well no matter the bridge is damaged or not. The presented analysis leads to significant insights that can help the decision-making of the optimal SHM + SSI strategy, avoiding erroneous decisions if this tool is not used beforehand., This work was mainly funded by the Chinese Scholarship Council through its program (No. 201808390083), which has been provided to Mrs. Peng. It is also to be noted that this work was partially funded by the Spanish Ministry of Economy and Competitiveness for the funding provided through the research projects BIA2013-47290-R and BIA2017-86811-C2-1-R founded with FEDER funds and directed by Professor José Turmo. Authors are also indebted to the Secretaria d’ Universitats i Recerca de la Generalitat de Catalunya for the funding provided through Agaur (2017 SGR 1481)., Peer Reviewed

In structures with reduced monitoring budgets, the high cost of commercial metering devices is always an obstacle for monitoring structural health. This might be an issue when temperatures must be measured for both structural and environmental reasons. To fill this gap, in this paper, a novel monitoring system is proposed for the accurate measurement of indoor temperature in buildings. This protocol is characterized by its generality, as it can be easily adapted to measure any structural or environmental parameters on site. The proposed monitoring system uses from one to eight low-cost sensors to obtain multiple measurements of the ambient temperatures. The accuracy ranges of the developed monitoring systems with different numbers of sensors are statistically analysed. The results indicate that the discrepancy of the measurements decreases with the increase in the number of sensors, as the maximum standard deviation of 10 sensors (0.42) decreases to 0.32 and 0.27 for clusters of 20 and 30 sensors, respectively., This research was funded by the Spanish Ministry of Economy and Competitiveness (grant number BIA2013-47290-R, BIA2017-86811-C2-1-R, and BIA2017-86811-C2-2-R) and by the Universidad de Castilla La Mancha (grant number 2018-COB-9092)., Peer Reviewed

The structural identification using dynamic parameters (such as the natural vibration frequencies and mode shapes of the structure) is an important issue especially in slender structures such as long-span bridges or high-rise buildings. It is the most popular way to assess the structural condition along the service life . This article presents a new approach, under the framework of Structural System Identificaction by Observability Method (OM), to perform the structural system identification. The method is able of determining which actual structural properties (like Young’s modulus, area, inertia, mass) can be uniquely detected when an appropriate subset of mode-shapes and frequencies of the whole structure is provided. Error-Minimizing Observability Method (EMOM), which separates and merges the error items included in frequencies and mode shapes, is used to get an accurate estimate of element properties. A key issue in this method is how to choose the weight factor of frequencies and mode-shapes, when minimizing the objective function. This is still an unsolved problem and will pose a big influence on the results. Hence, a 2-dof example is illustrated in the paper dealing with this issue. . From the analysis of frequencies and mode-shapes with the best weight factor, it is found that through the fine calculation, the weight factor produced by the Bayesian method fits well with the one derived with the regular one-by-one calculation. This provides a criteria to choose the weight factor directly from the experimental samples by the Bayesian approach, thus decreasing the complexity and the computing time., This work is funded by the Spanish Ministry of Economy and Competitiveness projects (BIA2013-47290-R and BIA2017-86811-C2-1-R) and China Scholarship Council (No. 201808390083). The financial support is greatly appreciated.

Due to the inevitable degradation of material properties in structures in daily use, such as stiffness degradation due to cracking in concrete elements, their durability will definitely be influenced, and their serviceability and safety could be in danger. Thus, understanding and identifying the change in the structural parameters provides new approaches to evaluate their durability. Structural system identification by dynamic observability method, which is using subsets of masses, natural frequencies and modal shapes, is a powerful tool to detect the change of structural parameters. Taking into account the presence of noise in the measurement data in real world structures, this method establishes the relative dynamic equation with the error separation items. The equation is solved by error minimization of an objective function combining the measured frequencies and mode shapes through the parameter MAC (Modal Assurance Criterion). Additionally, the algorithms and the steps are introduced based on the dynamic eigenvalue equation, which can fully demonstrate the performance of observability techniques. The present paper provides an example on how to successfully identify structural parameters. Its suitability for practical applications is demonstrated in a large frame structure. The result is a much more accurate identification of the parameters involved in the durability of the structure even in the case of noise-corrupted measurement signals., The authors are indebted to the Spanish Ministry of Economy and Competitiveness for the funding provided through the research projects BIA2013-47290-R and BIA2017-86811-C2-1-R founded with FEDER funds and directed by Professor José Turmo and through the research project BIA2017-86811-C2-2-R. It is also to be noted that the part of this work was done included an exchange of faculty financed by the Chinese government to Mrs.Peng thorough the program (No. 201808390083).

The use of benchmark model aims to establish a model with sufficient accuracy to reflect structure performance. Its purpose is seeking differences through repeated studying on problems using common FE model. In the paper, a novel approach is proposed for the benchmark model updating of a cable stayed bridge. It is based on the interaction of numerical analysis program and FE analysis program with updating model parameters from loop iteration operation. Shell elements and beam elements are both used, and the natural vibration frequencies and mode shapes from plate-shell element model are determined. These are used to modify the parameters used in a spine-beam element model, and to simplify a complicated FE model as a benchmark model. The genetic algorithm (GA) is introduced to complete the calculation process of loop iteration. Finally, an updated benchmark model is proposed for cable stayed bridges., The authors are indebted to research funding provided by the National Key R&D Program of China (2017YFC1500603), and to the Spanish Ministry of Economy and Competitiveness and FEDER funds for the funding provided through the research project BIA2017-86811-C2-1-R.

Structural damage detection using inclinometers is getting wide attention from researchers. However, the high price of inclinometers limits this system to unique structures with a relatively high structural health monitoring (SHM) budget. This paper presents a novel low-cost inclinometer, the low-cost adaptable reliable angle-meter (LARA), which combines five gyroscopes and five accelerometers to measure inclination. LARA incorporates Internet of Things (IoT)-based microcontroller technology enabling wireless data streaming and free commercial software for data acquisition. This paper investigates the accuracy, resolution, Allan variance and standard deviation of LARA produced with a different number of combined circuits, including an accelerometer and a gyroscope. To validate the accuracy and resolution of the developed device, its results are compared with those obtained by numerical slope calculations and a commercial inclinometer (HI-INC) in laboratory conditions. The results of a load test experiment on a simple beam model show the high accuracy of LARA (0.003 degrees). The affordability and high accuracy of LARA make it applicable for structural damage detection on bridges using inclinometers., The authors are indebted to the Spanish Ministry of Economy and Competitiveness for the funding provided through the research project BIA2017-86811-C2-1-R directed by José Turmo and BIA2017-86811-C2-2-R. All these projects are funded with FEDER funds. The authors are also indebted to the Secretaria d’ Universitats i Recerca de la Generalitat de Catalunya, Catalunya, Spain for the funding provided through Agaur (2017 SGR 1482). It is also to be noted that funding for this research has been provided for Seyedmilad Komarizadehasl by Spanish Agencia Estatal de Investigación del Ministerio de Ciencia Innovación y Universidades grant and the Fondo Social Europeo grant (PRE2018-083238)., Peer Reviewed

Nowadays, low-cost accelerometers are getting more attention from civil engineers to make Structural Health Monitoring (SHM) applications affordable and applicable to a broader range of structures. The present accelerometers based on Arduino or Raspberry Pi technologies in the literature share some of the following drawbacks: (1) high Noise Density (ND), (2) low sampling frequency, (3) not having the Internet’s timestamp with microsecond resolution, (4) not being used in experimental eigenfrequency analysis of a flexible and a less-flexible bridge, and (5) synchronization issues. To solve these problems, a new low-cost triaxial accelerometer based on Arduino technology is presented in this work (Low-cost Adaptable Reliable Accelerometer—LARA). Laboratory test results show that LARA has a ND of 51 µg/vHz, and a frequency sampling speed of 333 Hz. In addition, LARA has been applied to the eigenfrequency analysis of a short-span footbridge and its results are compared with those of a high-precision commercial sensor., The authors are indebted to the Spanish Ministry of Economy and Competitiveness for the funding provided through the research project BIA2017-86811-C2-1-R directed by José Turmo and BIA2017-86811-C2-2-R. All these projects are funded with FEDER funds. The authors are also indebted to the Secretaria d’ Universitats i Recerca de la Generalitat de Catalunya, Catalunya, Spain, for the funding provided through Agaur (2017 SGR 1482). It is also to be noted that funding for this research has been provided for the Seyedmilad Komarizadehasl by the Spanish Agencia Estatal de Investigación del Ministerio de Ciencia Innovación y Universidades grant and the Fondo Social Europeo grant (PRE2018-083238)., Peer Reviewed

One of the main features of each society and civilization is the importance of educational system. All countries around the world have used specific educational planning for growing their people as well as developing the country. This paper has comprehensively evaluated civil engineering educational program in universities oflran. In the current system, tendencies of graduates are more toward education of engineers who are ready to have academic jobs but not operative jobs such as increasing and improving national production or meeting technical needs of country. One strategy that can be used in this context is having long term planning for civil engineering students, which includes increasing the budget for establishment of equipped laboratories and at the same time enhancing professional job opportunities., The authors are indebted to the Spanish Ministry of Economy and Competitiveness for the funding provided through the research projects BIA2013-47290-R, BIA2017-86811-C2-l-R, and BIA2017-8681 l-C2-2-R founded with FEDER funds It is also to be noted that funding for this research has been provided to Mr. BEHNAM MOBARAKI by the Spanish Ministry of Economy and Competitiveness through its program for his Ph.D. It is also to be noted that part of this work was done through grant number 2018-COB-9092 from Universidad de Castilla La Mancha (UCLM).

Despite their advantageous performance and reliability, distributed optical fiber sensors (DOFS) still constitute a recent technology and their reliability and accuracy when applied to real world structures is still under probation since there is still room for improvement and for widening their applicability. In general, standardized guidelines need to be developed to ensure success in every DOFSs deployment regarding fiber bonding to the structure, temperature affections on readings, postprocessing of reading anomalies, among other factors. However, real applications, as in the one presented in this paper, show that DOFS are anticipated to have a very important role in Structural Health Management of tunnels in the near future if correctly understood and developed. This paper addresses the implementation of a Distributed Optical Fiber Sensor system (DOFS) to the existing TMB L-9 metro tunnel in Barcelona for Structural Health Monitoring (SHM) purposes as the former could potentially be affected by the construction of a nearby residential building. The results show a good performance of this novel technique in the monitoring of strain along the whole affected sections during the construction of a nearby building. In fact, the DOFS readings reproduce very accurately the tunnel deformation process. The tendencies observed by the sensors were forecasted by a simple theoretical model. The monitoring of the strain at many points in the critical section allowed to conclude that the nearby construction only slightly affected the lining stresses and that safety was guaranteed during the whole monitored period., The authors thank COTCA and TMB respectively for providing access to the necessary data regarding the case study and supporting this research. We would also like to thank Ph D student Mattia F. Bado who provided insight that greatly assisted this research during the data post-processing phase. The authors are indebted to the Spanish Ministry of Economy and Competitiveness for the funding provided through the research project BIA2017-86811-C2-1-R. All these projects are funded with FEDER funds. Authors are also indebted to the Secretaria d’ Universitats i Recerca de la Generalitat de Catalunya for the funding provided through Agaur (2017 SGR 1481).

Bridges can be considered one of the most critical infrastructures of any country. Subsequently, their health state assessment is of great importance. However, durable monitoring of bridges can be highly costly and time-consuming. In addition, the current Structural Health Monitoring applications are only applicable to individual structures with a high budget for their health assessment. For a long-term economic evaluation of bridges, low-cost sensors are currently being developed for SHM applications. However, their resolution and accuracy are not yet suitable for structural system identifications. For that, a novel accelerometer based on Arduino technology is introduced in this work. Experiments show that this accelerometer has a better resolution. Illustrated test results of this paper on a frequency range of 0.5 to 8 Hz validate the performance of the proposed accelerometer., The authors are indebted to the Spanish Ministry of Economy and Competitiveness for the funding provided through the research project BIA2017-86811-C2-1-R directed by José Turmo and BIA2017-86811-C2-2-R. All these projects are funded with FEDER funds. Authors are also indebted to the Secretaria d' Universitats i Recerca de la Generalitat de Catalunya, Catalunya, Spain for the funding provided through Agaur (2017 SGR 1482). It is also to be noted that funding for this research has been provided for Seyedmilad Komarizadehasl by Spanish Agencia Estatal de Investigación del Ministerio de Ciencia Innovación y Universidades grant and the Fondo Social Europeo grant (PRE2018-083238).