After a strong earthquake, it is crucial to evaluate accurately the health of structures in order to decide whether they can continue to be used. Isolation techniques are well known for enhancing the seismic performance of structures; however, a large response displacement anticipated in the design will likely impact the expansion joints. The occurrence of any damage or impact involves a large disturbance in the system or measurement equations. The Kalman filter (KF) is effective and reliable under proper conditions, but a simple simulation may show disrupted stability conditions after a large disturbance, causing a temporary filter divergence. If the filter design cannot be rapidly adjusted, an overall filter divergence may occur, preventing an accurate evaluation of structural health. This study proposes a performance recovery strategy for the unscented KF (UKF). Rather than identifying optimal parameter estimates at the current instant, the filter meets the stability conditions and asymptotically approaches the true estimates. The measurement noise is adaptively adjusted to bound the true noise covariance. Once the filter divergence is identified based on the expected measurement residual error, the state covariance is adjusted by a covariance‐matching technique to bound the true error covariance. After sufficient measurements are obtained, the state covariance is reduced to a low level, indicating filter convergence and a reliable estimation. The effectiveness of the proposed approach is numerically validated for an isolation bridge and building under several scenarios, and two existing UKF variants, which adaptively estimate the system and measurement noise covariances, are compared.
{"title":"Unscented Kalman filter with performance recovery strategy for parameter estimation of isolation structures","authors":"Xinhao He, S. Unjoh, Dan Li","doi":"10.1002/stc.3116","DOIUrl":"https://doi.org/10.1002/stc.3116","url":null,"abstract":"After a strong earthquake, it is crucial to evaluate accurately the health of structures in order to decide whether they can continue to be used. Isolation techniques are well known for enhancing the seismic performance of structures; however, a large response displacement anticipated in the design will likely impact the expansion joints. The occurrence of any damage or impact involves a large disturbance in the system or measurement equations. The Kalman filter (KF) is effective and reliable under proper conditions, but a simple simulation may show disrupted stability conditions after a large disturbance, causing a temporary filter divergence. If the filter design cannot be rapidly adjusted, an overall filter divergence may occur, preventing an accurate evaluation of structural health. This study proposes a performance recovery strategy for the unscented KF (UKF). Rather than identifying optimal parameter estimates at the current instant, the filter meets the stability conditions and asymptotically approaches the true estimates. The measurement noise is adaptively adjusted to bound the true noise covariance. Once the filter divergence is identified based on the expected measurement residual error, the state covariance is adjusted by a covariance‐matching technique to bound the true error covariance. After sufficient measurements are obtained, the state covariance is reduced to a low level, indicating filter convergence and a reliable estimation. The effectiveness of the proposed approach is numerically validated for an isolation bridge and building under several scenarios, and two existing UKF variants, which adaptively estimate the system and measurement noise covariances, are compared.","PeriodicalId":22049,"journal":{"name":"Structural Control and Health Monitoring","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78543084","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study aims to develop a high‐performance active mass damper (AMD) for super high‐rise buildings with a low natural frequency. Conventional AMDs utilize accelerometers to control vibration. However, those AMDs cannot sufficiently damp the vibration because the accelerometer sensitivity is low in a low‐frequency band (e.g., the natural frequency of high‐rise buildings). Under these circumstances, this study proposes the measurement of vibration displacements using cameras and an image processing technique, called template matching, instead of accelerometers. The measurement accuracy in the low‐frequency band was evaluated by comparison to that of the accelerometer. The results indicate that the proposed method achieved a higher measurement accuracy compared to the accelerometers in the low‐frequency band. One problem when applying the displacement measurement using image processing to the vibration control is time delay with calculation. We solved this problem using the Padé approximation. Finally, real‐time hybrid tests attained with a combination of real‐time simulation and experiment were conducted. The results confirmed that the proposed method reduced the first resonance peak value by 24% in the low‐frequency band compared with the accelerometers. In addition, it can prevent the degradation of the vibration damping performance of the higher vibration modes (i.e., spillover phenomena) caused by acceleration control. The proposed method contributes to the development of a novel AMD that suppresses the shaking of super high‐rise buildings.
{"title":"Active vibration control for high‐rise buildings using displacement measurements by image processing","authors":"Tatsuya Ito, Masaharu Tagami, Y. Tagawa","doi":"10.1002/stc.3136","DOIUrl":"https://doi.org/10.1002/stc.3136","url":null,"abstract":"This study aims to develop a high‐performance active mass damper (AMD) for super high‐rise buildings with a low natural frequency. Conventional AMDs utilize accelerometers to control vibration. However, those AMDs cannot sufficiently damp the vibration because the accelerometer sensitivity is low in a low‐frequency band (e.g., the natural frequency of high‐rise buildings). Under these circumstances, this study proposes the measurement of vibration displacements using cameras and an image processing technique, called template matching, instead of accelerometers. The measurement accuracy in the low‐frequency band was evaluated by comparison to that of the accelerometer. The results indicate that the proposed method achieved a higher measurement accuracy compared to the accelerometers in the low‐frequency band. One problem when applying the displacement measurement using image processing to the vibration control is time delay with calculation. We solved this problem using the Padé approximation. Finally, real‐time hybrid tests attained with a combination of real‐time simulation and experiment were conducted. The results confirmed that the proposed method reduced the first resonance peak value by 24% in the low‐frequency band compared with the accelerometers. In addition, it can prevent the degradation of the vibration damping performance of the higher vibration modes (i.e., spillover phenomena) caused by acceleration control. The proposed method contributes to the development of a novel AMD that suppresses the shaking of super high‐rise buildings.","PeriodicalId":22049,"journal":{"name":"Structural Control and Health Monitoring","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80826291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wenzhi Zheng, P. Tan, Yanhui Liu, Hongya Wang, Huating Chen
To improve the resilient capability of bridges, a novel multi‐stage superelastic variable stiffness pendulum isolator (SVSPI) is developed by incorporating superelastic shape memory alloy (SMA) with the multi‐stage variable stiffness pendulum isolator (VSPI), which featured with the favorable adaptability under service conditions and near‐fault excitations. Based on OpenSees platform, the numerical model for novel multi‐stage superelastic variable stiffness pendulum isolator is created. A fractional factor based design method is suggested for parameter optimization of the multi‐stage superelastic variable stiffness pendulum isolator. The example bridges with the novel isolators are designed to conduct the seismic mitigation investigation under near‐fault earthquakes. The effectiveness of the novel superelastic multi‐stage variable stiffness pendulum isolator and suggested design method is further discussed by case study. Results show that the novel multi‐stage superelastic variable stiffness pendulum isolator designed by the proposed fractional factor based design method can perform the dual control of the isolator residual displacement, girder displacement, and base forces in piers for bridges. The effectiveness of the multi‐stage superelastic variable stiffness pendulum isolator with the optimal parameters is demonstrated by case study. The technical achievements can provide reliable basis for structural resilience enhancement and potential structural applications.
{"title":"Multi‐stage superelastic variable stiffness pendulum isolation system for seismic response control of bridges under near‐fault earthquakes","authors":"Wenzhi Zheng, P. Tan, Yanhui Liu, Hongya Wang, Huating Chen","doi":"10.1002/stc.3114","DOIUrl":"https://doi.org/10.1002/stc.3114","url":null,"abstract":"To improve the resilient capability of bridges, a novel multi‐stage superelastic variable stiffness pendulum isolator (SVSPI) is developed by incorporating superelastic shape memory alloy (SMA) with the multi‐stage variable stiffness pendulum isolator (VSPI), which featured with the favorable adaptability under service conditions and near‐fault excitations. Based on OpenSees platform, the numerical model for novel multi‐stage superelastic variable stiffness pendulum isolator is created. A fractional factor based design method is suggested for parameter optimization of the multi‐stage superelastic variable stiffness pendulum isolator. The example bridges with the novel isolators are designed to conduct the seismic mitigation investigation under near‐fault earthquakes. The effectiveness of the novel superelastic multi‐stage variable stiffness pendulum isolator and suggested design method is further discussed by case study. Results show that the novel multi‐stage superelastic variable stiffness pendulum isolator designed by the proposed fractional factor based design method can perform the dual control of the isolator residual displacement, girder displacement, and base forces in piers for bridges. The effectiveness of the multi‐stage superelastic variable stiffness pendulum isolator with the optimal parameters is demonstrated by case study. The technical achievements can provide reliable basis for structural resilience enhancement and potential structural applications.","PeriodicalId":22049,"journal":{"name":"Structural Control and Health Monitoring","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75038837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, the behavior of a passive displacement‐dependent variable friction damper (VFD) was evaluated. The energy response behavior of a VFD specimen was investigated by conducting full‐scale dynamic loading tests. Full‐scale tests demonstrated that the VFD specimen produced a lower sliding force when the device response exceeded a predetermined displacement, resulting in a decreased dissipated energy ratio as the displacement increased. The VFD specimen exhibited stable energy response behavior as well as a stable friction sliding force and friction coefficient under sinusoidal, seismic response, and 100‐cycle loadings. The energy response of the VFD specimen was almost independent of the loading frequency. Moreover, a response simulation was conducted using a two‐dimensional 30‐story nonlinear mainframe model with brace‐type VFDs under various input motions, including observation records and long‐period, long‐duration waves. From the numerical simulations, the peak story drift in the case with brace‐type VFDs was not significantly greater than in the case with conventional friction dampers (FDs). The dissipated energy ratios of the mainframe and dampers in the case with the VFDs were approximately identical to those in the case with the FDs. In comparison with conventional FDs, VFDs can produce a lower peak story shear force and axial compressive force in the lowest‐story columns at the device installation span.
{"title":"Energy response of a passive variable friction damper and numerical simulation on the control effects for high‐rise buildings","authors":"K. Shirai, T. Sano, Y. Suzui","doi":"10.1002/stc.3124","DOIUrl":"https://doi.org/10.1002/stc.3124","url":null,"abstract":"In this study, the behavior of a passive displacement‐dependent variable friction damper (VFD) was evaluated. The energy response behavior of a VFD specimen was investigated by conducting full‐scale dynamic loading tests. Full‐scale tests demonstrated that the VFD specimen produced a lower sliding force when the device response exceeded a predetermined displacement, resulting in a decreased dissipated energy ratio as the displacement increased. The VFD specimen exhibited stable energy response behavior as well as a stable friction sliding force and friction coefficient under sinusoidal, seismic response, and 100‐cycle loadings. The energy response of the VFD specimen was almost independent of the loading frequency. Moreover, a response simulation was conducted using a two‐dimensional 30‐story nonlinear mainframe model with brace‐type VFDs under various input motions, including observation records and long‐period, long‐duration waves. From the numerical simulations, the peak story drift in the case with brace‐type VFDs was not significantly greater than in the case with conventional friction dampers (FDs). The dissipated energy ratios of the mainframe and dampers in the case with the VFDs were approximately identical to those in the case with the FDs. In comparison with conventional FDs, VFDs can produce a lower peak story shear force and axial compressive force in the lowest‐story columns at the device installation span.","PeriodicalId":22049,"journal":{"name":"Structural Control and Health Monitoring","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83290316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Mantakas, K. Kapasakalis, Antonios Alvertos, I. Antoniadis, E. Sapountzakis
In this study, a negative stiffness‐based passive vibration absorber is developed and implemented as a seismic retrofitting measure for typical reinforced concrete (RC) residential buildings. The device, namely, the extended KDamper for retrofitting (EKD‐R), is introduced at the base of the structure, between the foundation level and the first story of the building. The design of the EKD‐R device and the selection of its properties are undertaken by incorporating a harmony search (HS) algorithm that provides optimized parameters for the mechanism, following constraints and limitations imposed by the examined structural system. Nonlinearities due to the plastic behavior of the structural members and soil–structure interaction (SSI) effects are modeled and taken into consideration during the process. Subsequently, a realistic case study of a benchmark three‐story RC building is examined, and the performance of the EKD‐R system is assessed. The building superstructure is designed according to Eurocodes. The structure–foundation system, along with the EKD‐R, is explicitly modeled using finite elements (FE) that may realistically capture structural nonlinearities and SSI effects. The HS algorithm is employed, and optimized EKD‐R components are obtained and implemented in the benchmark structure. Finally, a series of recorded real ground motions are selected, and nonlinear time‐history dynamic analyses are conducted aiming to assess the behavior of the controlled system. Results indicate the beneficial role of the novel dynamic absorber, hence rendering the concept a compelling seismic retrofitting technology.
{"title":"A negative stiffness dynamic base absorber for seismic retrofitting of residential buildings","authors":"A. Mantakas, K. Kapasakalis, Antonios Alvertos, I. Antoniadis, E. Sapountzakis","doi":"10.1002/stc.3127","DOIUrl":"https://doi.org/10.1002/stc.3127","url":null,"abstract":"In this study, a negative stiffness‐based passive vibration absorber is developed and implemented as a seismic retrofitting measure for typical reinforced concrete (RC) residential buildings. The device, namely, the extended KDamper for retrofitting (EKD‐R), is introduced at the base of the structure, between the foundation level and the first story of the building. The design of the EKD‐R device and the selection of its properties are undertaken by incorporating a harmony search (HS) algorithm that provides optimized parameters for the mechanism, following constraints and limitations imposed by the examined structural system. Nonlinearities due to the plastic behavior of the structural members and soil–structure interaction (SSI) effects are modeled and taken into consideration during the process. Subsequently, a realistic case study of a benchmark three‐story RC building is examined, and the performance of the EKD‐R system is assessed. The building superstructure is designed according to Eurocodes. The structure–foundation system, along with the EKD‐R, is explicitly modeled using finite elements (FE) that may realistically capture structural nonlinearities and SSI effects. The HS algorithm is employed, and optimized EKD‐R components are obtained and implemented in the benchmark structure. Finally, a series of recorded real ground motions are selected, and nonlinear time‐history dynamic analyses are conducted aiming to assess the behavior of the controlled system. Results indicate the beneficial role of the novel dynamic absorber, hence rendering the concept a compelling seismic retrofitting technology.","PeriodicalId":22049,"journal":{"name":"Structural Control and Health Monitoring","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81545179","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Brick masonry structures will suffer different degrees of damage in their long‐term service. The common damage modes involve compression and shear damage. The acoustic emission (AE) technology, including improved b‐value (Ib‐value), signal intensity analysis, and the k‐means clustering method, was carried out during uniaxial compression and shear experiments to qualitatively and quantitatively assess the damage state of the brick masonry. Results demonstrate that the shear damage exhibits a more obvious brittle failure characteristic compared with the uniaxial compression damage. The Ib‐value could reflect the damage evolution state of the brick masonry whether it is uniaxial or shear damage (i.e., every decrease in the Ib‐value is a manifestation of damage expansion). The boundary of HI‐Sr in the signal intensity analysis is proposed to differentiate the mild, moderate, and serious damage under uniaxial compressive, and the boundary is proposed to distinguish the mild and serious damage under shear. The appearance of the signal cluster with the highest ring count, energy, and duration implies the failure of the brick masonry under uniaxial compressive and shear.
{"title":"Quantitative damage analysis of brick masonry under uniaxial compression and shear using acoustic emission technology","authors":"Guang‐Ming Wu, Ruiqing Han, Shengli Li, P. Guo","doi":"10.1002/stc.3130","DOIUrl":"https://doi.org/10.1002/stc.3130","url":null,"abstract":"Brick masonry structures will suffer different degrees of damage in their long‐term service. The common damage modes involve compression and shear damage. The acoustic emission (AE) technology, including improved b‐value (Ib‐value), signal intensity analysis, and the k‐means clustering method, was carried out during uniaxial compression and shear experiments to qualitatively and quantitatively assess the damage state of the brick masonry. Results demonstrate that the shear damage exhibits a more obvious brittle failure characteristic compared with the uniaxial compression damage. The Ib‐value could reflect the damage evolution state of the brick masonry whether it is uniaxial or shear damage (i.e., every decrease in the Ib‐value is a manifestation of damage expansion). The boundary of HI‐Sr in the signal intensity analysis is proposed to differentiate the mild, moderate, and serious damage under uniaxial compressive, and the boundary is proposed to distinguish the mild and serious damage under shear. The appearance of the signal cluster with the highest ring count, energy, and duration implies the failure of the brick masonry under uniaxial compressive and shear.","PeriodicalId":22049,"journal":{"name":"Structural Control and Health Monitoring","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78197904","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Although composite box‐girders with corrugated steel webs have been widely applied in practical bridge constructions, the nonuniform temperature field in the composite box‐girders without sufficient study may lead to negative effects on the durability of bridge structures. Thus, this paper focuses on the temperature distribution characteristics of the composite box‐girder with corrugated steel webs. The temperature data of a corrugated steel web box‐girder specimen has been measured. An apparent nonuniform temperature distribution of the experimented specimen under solar radiation can be observed through the measured data. Then, the numerical simulation model of the corrugated steel web composite box‐girder specimen has been established and validated by the measured temperature data. Based on the verified simulation model, the temperature distribution of an actual composite box‐girder has been analyzed numerically. The results show that the difference between the vertical temperature gradients along the north and south sides of the girder can reach up to 11.9°C, and the maximum vertical temperature gradient can be more than 24.0°C in summer days. Moreover, parametric studies have been carried out to reveal the impacts of material parameters on the composite box‐girder's temperature distribution and the thermal loading index. Both the concrete and steel surface absorptivity show significant influences on the temperature distribution and the thermal loading index through the parametric study. It hopes that the current investigation can provide some contributions for further applications of the composite box‐girder with corrugated steel web, and other researches regarding temperature field of the structures.
{"title":"Experimental and numerical investigation on the temperature distribution of composite box‐girders with corrugated steel webs","authors":"Shijin Huang, Chenzhi Cai, Yun-feng Zou, Xuhui He, Tieming Zhou, Xiaojie Zhu","doi":"10.1002/stc.3123","DOIUrl":"https://doi.org/10.1002/stc.3123","url":null,"abstract":"Although composite box‐girders with corrugated steel webs have been widely applied in practical bridge constructions, the nonuniform temperature field in the composite box‐girders without sufficient study may lead to negative effects on the durability of bridge structures. Thus, this paper focuses on the temperature distribution characteristics of the composite box‐girder with corrugated steel webs. The temperature data of a corrugated steel web box‐girder specimen has been measured. An apparent nonuniform temperature distribution of the experimented specimen under solar radiation can be observed through the measured data. Then, the numerical simulation model of the corrugated steel web composite box‐girder specimen has been established and validated by the measured temperature data. Based on the verified simulation model, the temperature distribution of an actual composite box‐girder has been analyzed numerically. The results show that the difference between the vertical temperature gradients along the north and south sides of the girder can reach up to 11.9°C, and the maximum vertical temperature gradient can be more than 24.0°C in summer days. Moreover, parametric studies have been carried out to reveal the impacts of material parameters on the composite box‐girder's temperature distribution and the thermal loading index. Both the concrete and steel surface absorptivity show significant influences on the temperature distribution and the thermal loading index through the parametric study. It hopes that the current investigation can provide some contributions for further applications of the composite box‐girder with corrugated steel web, and other researches regarding temperature field of the structures.","PeriodicalId":22049,"journal":{"name":"Structural Control and Health Monitoring","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74073223","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The interesting to assess the condition of a structure with structural health monitoring data has gained many attentions. Most of the existing methods require the measurement at the force location. This paper presents a novel output‐only condition assessment method that does not require measurement at the force location. The unknown structural damage indices and input force can be identified with the stochastic gradient descent method. The dynamic acceleration response sensitivities with respect to the unknown structural damage indices and input force are derived analytically. Both unknown damage indices and unknown input force can be identified by minimizing the discrepancy between the measured and calculated vibration data. Numerical studies on a two‐dimensional truss and seven‐floor frame and experimental studies on a steel frame structure are presented to verify the accuracy and efficiency of the proposed method. Results demonstrate that the damage severity, location, and unknown input force can be identified. Also, the measurement at the force location is not required. Furthermore, when 20% measurement noise is considered, the identified error is less than 5%.
{"title":"An output‐only structural condition assessment method for civil structures by the stochastic gradient descent method","authors":"P. Ni, X. Ye, Yang Ding","doi":"10.1002/stc.3132","DOIUrl":"https://doi.org/10.1002/stc.3132","url":null,"abstract":"The interesting to assess the condition of a structure with structural health monitoring data has gained many attentions. Most of the existing methods require the measurement at the force location. This paper presents a novel output‐only condition assessment method that does not require measurement at the force location. The unknown structural damage indices and input force can be identified with the stochastic gradient descent method. The dynamic acceleration response sensitivities with respect to the unknown structural damage indices and input force are derived analytically. Both unknown damage indices and unknown input force can be identified by minimizing the discrepancy between the measured and calculated vibration data. Numerical studies on a two‐dimensional truss and seven‐floor frame and experimental studies on a steel frame structure are presented to verify the accuracy and efficiency of the proposed method. Results demonstrate that the damage severity, location, and unknown input force can be identified. Also, the measurement at the force location is not required. Furthermore, when 20% measurement noise is considered, the identified error is less than 5%.","PeriodicalId":22049,"journal":{"name":"Structural Control and Health Monitoring","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77695858","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nguyen Thanh Trung, Nguyen Huu Hung, Thai Thi Kim Chi, Nguyen Duc thi Thu Dinh, Bui Ngoc Dung, Vu Dan Chinh
In online structural health monitoring of the fixed offshore jacket platform, the determination of the time‐dependent degradation of structures due to damages is the most important step in a maintenance strategy. This paper presents the application of the Hilbert Huang transform method based on the iEEMD (improved ensemble empirical mode decomposition) algorithm to identify the instantaneous natural frequency degradation due to damages of the fixed offshore structure under the random wave excitation. The iEEMD algorithm is proposed to restrain the mode mixing and used to adaptively process the big response data of the offshore structure during the wave loading with a wide frequency range. The vibration response measurement experiment for the offshore structure was conducted in a wave tank in this study. The identified fundamental natural frequencies by the iEEMD‐based Hilbert Huang method were evaluated and compared with results of the numerical model of the eigenvalue analysis. The main result demonstrates that the instantaneous frequency degradation and nonlinear time‐varying behavior due to the brace damage of the fixed offshore jacket platform can be successfully identified by the iEEMD‐based Hilbert Huang transform technique under a wave load.
{"title":"Detection of the instantaneous frequency degradation due to damages of a fixed offshore jacket platform using the iEEMD‐based Hilbert Huang transform under a wave excitation","authors":"Nguyen Thanh Trung, Nguyen Huu Hung, Thai Thi Kim Chi, Nguyen Duc thi Thu Dinh, Bui Ngoc Dung, Vu Dan Chinh","doi":"10.1002/stc.3129","DOIUrl":"https://doi.org/10.1002/stc.3129","url":null,"abstract":"In online structural health monitoring of the fixed offshore jacket platform, the determination of the time‐dependent degradation of structures due to damages is the most important step in a maintenance strategy. This paper presents the application of the Hilbert Huang transform method based on the iEEMD (improved ensemble empirical mode decomposition) algorithm to identify the instantaneous natural frequency degradation due to damages of the fixed offshore structure under the random wave excitation. The iEEMD algorithm is proposed to restrain the mode mixing and used to adaptively process the big response data of the offshore structure during the wave loading with a wide frequency range. The vibration response measurement experiment for the offshore structure was conducted in a wave tank in this study. The identified fundamental natural frequencies by the iEEMD‐based Hilbert Huang method were evaluated and compared with results of the numerical model of the eigenvalue analysis. The main result demonstrates that the instantaneous frequency degradation and nonlinear time‐varying behavior due to the brace damage of the fixed offshore jacket platform can be successfully identified by the iEEMD‐based Hilbert Huang transform technique under a wave load.","PeriodicalId":22049,"journal":{"name":"Structural Control and Health Monitoring","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86978743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An inverse input–output method is proposed for long‐term condition monitoring of civil infrastructures through monitoring the prediction error of air temperature recorded at the site of a structure. It is known that structural natural frequencies are affected by temperature. Hence, the proposed method considers the structural natural frequencies as input and temperature as output to train a machine learning algorithm (MLA). To this end, after signal preprocessing using the variational mode decomposition (VMD), different MLAs are employed, and the error associated with this prediction is regarded as damage–sensitive feature. It is hypothesised and further confirmed through solving numerical and benchmark problems that the prediction error deviates significantly from the upper bond control limit of an R‐chart (errors signal) constructed based on the prediction error of temperature as soon as the damage occurs. The frequency–temperature scatter plots indicate a linear dependency between the natural frequencies and temperature. Moreover, the similar slope obtained for the regression line fitted to different frequency–temperature scatter plots indicates high collinearity among pairs of natural frequencies. This observation implies that an interaction term must be considered for such pairs of natural frequencies in the linear regression model. The results of both numerical and experimental studies further confirm that the interaction linear regression model is the most accurate machine learning algorithm for solving the inverse problem of predicting temperature using natural frequencies for condition monitoring of structures. The results of the proposed method are also compared with the direct strategy, whereby its superiority is demonstrated.
{"title":"Monitoring onsite‐temperature prediction error for condition monitoring of civil infrastructures","authors":"M. Mousavi, A. Gandomi, M. Abdel Wahab, B. Glisic","doi":"10.1002/stc.3112","DOIUrl":"https://doi.org/10.1002/stc.3112","url":null,"abstract":"An inverse input–output method is proposed for long‐term condition monitoring of civil infrastructures through monitoring the prediction error of air temperature recorded at the site of a structure. It is known that structural natural frequencies are affected by temperature. Hence, the proposed method considers the structural natural frequencies as input and temperature as output to train a machine learning algorithm (MLA). To this end, after signal preprocessing using the variational mode decomposition (VMD), different MLAs are employed, and the error associated with this prediction is regarded as damage–sensitive feature. It is hypothesised and further confirmed through solving numerical and benchmark problems that the prediction error deviates significantly from the upper bond control limit of an R‐chart (errors signal) constructed based on the prediction error of temperature as soon as the damage occurs. The frequency–temperature scatter plots indicate a linear dependency between the natural frequencies and temperature. Moreover, the similar slope obtained for the regression line fitted to different frequency–temperature scatter plots indicates high collinearity among pairs of natural frequencies. This observation implies that an interaction term must be considered for such pairs of natural frequencies in the linear regression model. The results of both numerical and experimental studies further confirm that the interaction linear regression model is the most accurate machine learning algorithm for solving the inverse problem of predicting temperature using natural frequencies for condition monitoring of structures. The results of the proposed method are also compared with the direct strategy, whereby its superiority is demonstrated.","PeriodicalId":22049,"journal":{"name":"Structural Control and Health Monitoring","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80080845","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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