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Static-based early-damage detection using symbolic data analysis and unsupervised learning methods
João Pedro SANTOS,Christian CREMONA,André D. ORCESI,Paulo SILVEIRA,Luis CALADO
Front. Struct. Civ. Eng.. 2015, 9 (1): 1-16.
https://doi.org/10.1007/s11709-014-0277-3
A large amount of researches and studies have been recently performed by applying statistical and machine learning techniques for vibration-based damage detection. However, the global character inherent to the limited number of modal properties issued from operational modal analysis may be not appropriate for early-damage, which has generally a local character. The present paper aims at detecting this type of damage by using static SHM data and by assuming that early-damage produces dead load redistribution. To achieve this objective a data driven strategy is proposed, consisting of the combination of advanced statistical and machine learning methods such as principal component analysis, symbolic data analysis and cluster analysis. From this analysis it was observed that, under the noise levels measured on site, the proposed strategy is able to automatically detect stiffness reduction in stay cables reaching at least 1%.
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Continuous dynamic monitoring of a centenary iron bridge for structural modification assessment
Carmelo GENTILE, Antonella SAISI
Front. Struct. Civ. Eng.. 2015, 9 (1): 26-41.
https://doi.org/10.1007/s11709-014-0284-4
A multi-channel continuous dynamic monitoring system has been installed in a centenary iron arch bridge on late November 2011. The historic infrastructure, completed in 1889 and crossing the Adda river about 50 km far from Milan, is the most important monument of XIX century iron architecture in Italy and is still used as roadway and railway bridge. The monitoring project follows a series of preliminary ambient vibration tests carried out on the bridge since June 2009. The paper describes the bridge structure and its dynamic characteristics identified from the experimental studies developed since 2009, the installed monitoring system and the software developed in LabVIEW for automatically processing the collected data. Subsequently, the tracking of automatically identified natural frequencies over a period of about 18 months is presented and discussed, highlighting the effects of environmental and operational conditions on the bridge dynamic characteristics as well as the detection of structural changes, mainly based on natural frequencies shifts.
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Experiment on aluminum alloy members under axial compression
Xiaonong GUO,Shuiping LIANG,Zuyan SHEN
Front. Struct. Civ. Eng.. 2015, 9 (1): 48-64.
https://doi.org/10.1007/s11709-014-0271-9
To improve the design methods of Chinese aluminum alloy members, experiment of 63 profiled aluminum alloy members, made of Chinese aluminum alloy 6061-T6, under axial compression is conducted in this paper. Valuable experimental data are obtained. At the same time, in order to obtain the relevant data, a large number of other experimental data from published papers and technical reports are collected and sorted out. 167 valid experimental data points are obtained finally. Furthermore, for the purpose of creating column curves, the aluminum alloy members under the axial compression, used in experiments, are analyzed by means of FEM. Based on the numerical results, 2 column curves are created by means of the numerical fitting method. The column curves are compared with the calculated data according to the experimental results for verification, and also are verified with the curves in design codes of several relevant countries. The numerical results show that the column curves obtained in this paper are valid and reliable.
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Research on port ecological suitability evaluation index system and evaluation model
Yaofeng XIE, Xia LV, Ru LIU, Liuyan MAO, Xiaoxi LIU
Front. Struct. Civ. Eng.. 2015, 9 (1): 65-70.
https://doi.org/10.1007/s11709-014-0258-6
Along with the rapid development of port building, the negative impacts of port’s construction and operation on the coastline ecosystem are also increasingly strong. Therefore, it’s urgent to establish a scientific and complete system of port ecological suitability evaluation. This paper pointed out the characteristics of port ecological effects and the principles of selecting evaluation index, and used the “pressure-state-response (PSR)” model to analysis the various pressures on the environment caused by port construction and operation, and the system’s response. On this basis, we constructed the port ecological suitability evaluation index. This model used the combination of qualitative and quantitative analytic hierarchy process, to meet the multi-level, multi-objective characteristics of evaluation index system. The evaluation index system and evaluation model can be used to analysis the ecological suitability of port projects comprehensively and have some guiding significance to the port ecological suitability evaluation.
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Investigation of sediment transport pattern and beach morphology in the vicinity of submerged groyne (case study: Dahane Sar Sefidrood)
H. Afsoos Biria, M. A. Lashteh Neshaei, A. Ghabraei, M. A. Mehrdad
Front. Struct. Civ. Eng.. 2015, 9 (1): 82-90.
https://doi.org/10.1007/s11709-014-0275-5
Marine structures, such as Groynes, Sea walls and Detached Breakwaters, are constructed in coast of area to improve coast stability against bed erosions due to changing wave and current pattern. Marine mechanisms and interaction with the hydraulic structures need to be intensively studied. Groynes are one of the most prominent structures that are used in shore protection and littoral sediment. The main hydraulic function of the groyne is to control the long shore current and littoral sediment transport. This structure can be submerged and provide the necessary beach protection without negative aesthetic impact. However, for submerged structures adopted for beach protection, the shoreline response to these structures is not well understood. The objective of this study is to predict sediment transport in the vicinity of submerged groyne and comparison with non-submerged groyne focusing on a part of the coast at Dahane Sar Sefidrood, Guilan Province, Iran, where serious coast erosion has been occurred. The simulations were designed using a one-line model which can be used as a first approximation of shoreline prediction in the vicinity of groyne. The results of the proposed model are compared with experimental data to determine the shape of the coast. The results of predicted beach deformation show that when submerged groyne construct in the beach, sediment accumulation will be slightly less than the non-submerged groyne; because transfer coefficient for the submerged groyne is more than non-submerged groyne. This result will cause more sediment passing on submerged groyne. Finally, the result of the present study show that using submerged groyne is an efficient way to control the sediment and beach erosion without causing severe environmental effect on the coast.
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9 articles
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