In the Danish part of the North Sea monopile platforms with a cylindrical shaft have been used at the exploitation of marginal fields. In the paper a new principle for active vibration control of such structures is suggested. The principle is based on a control of the boundary layer flow around the cylinder of the platform, so the drag force in the generalized Morison equation is increased whenever it is acting in the opposite direction of the cylinder motion, whereas an unchanged drag force is applied, whenever it is acting co-directionally to the cylinder motion. The inertial force of the wave load is not subjected to control. The increased drag force is obtained by forcing the boundary layers to separate by blowing air into the boundary layer from the inside through small holes in the cylinder surface placed at a relatively large distance from the water surface. The control is specified by the sign of the fluid velocity relative to the platform, and only this quantity need to be measured, which is easily performed by a flow meter fixed to the platform. The efficiency of the described closed loop control system has been verified by model tests in a wave flume in both regular and irregular wave conditions, where reductions in the vibration level of up to 50% have been registered.
{"title":"Active vibration control of a monopile offshore structure","authors":"S. Nielsen, P. H. Kirkegaard, L. Thesbjerg","doi":"10.1002/STC.4300060203","DOIUrl":"https://doi.org/10.1002/STC.4300060203","url":null,"abstract":"In the Danish part of the North Sea monopile platforms with a cylindrical shaft have been used at the exploitation of marginal fields. In the paper a new principle for active vibration control of such structures is suggested. The principle is based on a control of the boundary layer flow around the cylinder of the platform, so the drag force in the generalized Morison equation is increased whenever it is acting in the opposite direction of the cylinder motion, whereas an unchanged drag force is applied, whenever it is acting co-directionally to the cylinder motion. The inertial force of the wave load is not subjected to control. The increased drag force is obtained by forcing the boundary layers to separate by blowing air into the boundary layer from the inside through small holes in the cylinder surface placed at a relatively large distance from the water surface. The control is specified by the sign of the fluid velocity relative to the platform, and only this quantity need to be measured, which is easily performed by a flow meter fixed to the platform. The efficiency of the described closed loop control system has been verified by model tests in a wave flume in both regular and irregular wave conditions, where reductions in the vibration level of up to 50% have been registered.","PeriodicalId":135735,"journal":{"name":"Journal of Structural Control","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"119317563","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 large worldwide earthquake data-bank is available for numerical and experimental response analyses of base-excited structural systems. Most of these accelerograms are stored in their uncorrected form and this is appropriate and convenient since they must be differently processed for different engineering applications. Record processing is a necessary step toward the use of recorded data in numerical simulations: it deletes spurious low and high frequency content, introduced in detection, acquisition, storage and digitalization of the signal. Moving from numerical to experimental analyses, the testing machine acts as a filter and, hence, the processing could be no longer required. The paper tries to investigate this aspect.
{"title":"Input-signal characterization for shaking-tables","authors":"F. Casciati, L. Faravelli, L. Petrini","doi":"10.1002/STC.4300050203","DOIUrl":"https://doi.org/10.1002/STC.4300050203","url":null,"abstract":"A large worldwide earthquake data-bank is available for numerical and experimental response analyses of base-excited structural systems. Most of these accelerograms are stored in their uncorrected form and this is appropriate and convenient since they must be differently processed for different engineering applications. Record processing is a necessary step toward the use of recorded data in numerical simulations: it deletes spurious low and high frequency content, introduced in detection, acquisition, storage and digitalization of the signal. Moving from numerical to experimental analyses, the testing machine acts as a filter and, hence, the processing could be no longer required. The paper tries to investigate this aspect.","PeriodicalId":135735,"journal":{"name":"Journal of Structural Control","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126241744","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}
We show that the electromechanical coupling factor is the solution of two eigenvalue problems which depends on the piezoelectric, elastic and dielectric properties of the materials. We show that there are at most three eigenvalues and three associated strain eigentensors which render extremum the ratio of mechanical energy converted into electric energy: their value is the same if the three eigenvalues whose associated electric field eigenvectors render extremum the ratio of electrical energy converted into mechanical.
{"title":"The static electromechanical coupling factor in linear piezoelectric material","authors":"F. Daví","doi":"10.1002/STC.4300050204","DOIUrl":"https://doi.org/10.1002/STC.4300050204","url":null,"abstract":"We show that the electromechanical coupling factor is the solution of two eigenvalue problems which depends on the piezoelectric, elastic and dielectric properties of the materials. We show that there are at most three eigenvalues and three associated strain eigentensors which render extremum the ratio of mechanical energy converted into electric energy: their value is the same if the three eigenvalues whose associated electric field eigenvectors render extremum the ratio of electrical energy converted into mechanical.","PeriodicalId":135735,"journal":{"name":"Journal of Structural Control","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125952111","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}
Significant progress has been achieved in the active control of civil engineering structures in recent years. Although many control algorithms has been proposed, only few experiments in active structural control have been performed. In this paper, active structural control experiments were carried out using a scaled model structure simulating a three-story steel frame building. The model was subjected to a base motion on a shake table. A neural network based controller was implemented to control the response of the structure. This trained neural controller was implemented to control the response of the structure. It is experimentally verified that the neural network is able to generalized to new inputs, i.e. a properly trained neural network is capable of providing sensible outputs when presented with input data that has never been used during training. Results from this experimental study indicate great promise for the control of civil engineering structures under dynamic loadings using the artificial neural network controller.
{"title":"Experimental study of active control using neural networks","authors":"H. M. Chen, G. Qi, J. S. Yang, F. Amini","doi":"10.1002/STC.4300050102","DOIUrl":"https://doi.org/10.1002/STC.4300050102","url":null,"abstract":"Significant progress has been achieved in the active control of civil engineering structures in recent years. Although many control algorithms has been proposed, only few experiments in active structural control have been performed. In this paper, active structural control experiments were carried out using a scaled model structure simulating a three-story steel frame building. The model was subjected to a base motion on a shake table. A neural network based controller was implemented to control the response of the structure. This trained neural controller was implemented to control the response of the structure. It is experimentally verified that the neural network is able to generalized to new inputs, i.e. a properly trained neural network is capable of providing sensible outputs when presented with input data that has never been used during training. Results from this experimental study indicate great promise for the control of civil engineering structures under dynamic loadings using the artificial neural network controller.","PeriodicalId":135735,"journal":{"name":"Journal of Structural Control","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116782117","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 reliability assessment is performed for a highly critical existing structure under lack of information on the actual state of its elements. A non-standard probabilistic method is adopted: it makes use of “retrospective information”.
{"title":"Assessing the reliability of the chernobyl shelter","authors":"M. V. Sidorenko","doi":"10.1002/STC.4300050105","DOIUrl":"https://doi.org/10.1002/STC.4300050105","url":null,"abstract":"The reliability assessment is performed for a highly critical existing structure under lack of information on the actual state of its elements. A non-standard probabilistic method is adopted: it makes use of “retrospective information”.","PeriodicalId":135735,"journal":{"name":"Journal of Structural Control","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125047015","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 nonlinear decentralized active tendon controller that substantially reduces the magnitude of the vibrations of a segment of a cable-stayed bridge induced by a seismic excitation is presented in this paper. The model used to represent the dynamic behaviour of the bridge takes into account the inherent nonlinearities due to the stay cables geometry. This is in contrast with traditional models used by previous designers of active controllers of cable-stayed bridges, who assumed completely linear models. The proposed controller is comprised of a linear and a nonlinear part. Its performance is verified via digital computer simulation.
{"title":"Nonlinear decentralized active tendon control of cable-stayed bridges","authors":"M. Magaña, J. Rodellar","doi":"10.1002/STC.4300050103","DOIUrl":"https://doi.org/10.1002/STC.4300050103","url":null,"abstract":"A nonlinear decentralized active tendon controller that substantially reduces the magnitude of the vibrations of a segment of a cable-stayed bridge induced by a seismic excitation is presented in this paper. The model used to represent the dynamic behaviour of the bridge takes into account the inherent nonlinearities due to the stay cables geometry. This is in contrast with traditional models used by previous designers of active controllers of cable-stayed bridges, who assumed completely linear models. The proposed controller is comprised of a linear and a nonlinear part. Its performance is verified via digital computer simulation.","PeriodicalId":135735,"journal":{"name":"Journal of Structural Control","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124353858","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}
Control of structures against environmental loads, such as earthquakes and wind, is generally conceived as the protection of a system with no interaction with the surrounding buildings. When a large facility is considered, subsystems within it are identified and, in case, controlled. Attention is focused throughout this paper on the interaction of these subsytems in extreme conditions. The new concept of controlling the failure mode arises. The paper discusses the motivations leading one to adopt such an approach and the guidelines for its design.
{"title":"Structural control against failure interaction","authors":"M. Anton, F. Casciati","doi":"10.1002/STC.4300050104","DOIUrl":"https://doi.org/10.1002/STC.4300050104","url":null,"abstract":"Control of structures against environmental loads, such as earthquakes and wind, is generally conceived as the protection of a system with no interaction with the surrounding buildings. \u0000 \u0000 \u0000 \u0000When a large facility is considered, subsystems within it are identified and, in case, controlled. Attention is focused throughout this paper on the interaction of these subsytems in extreme conditions. The new concept of controlling the failure mode arises. \u0000 \u0000 \u0000 \u0000The paper discusses the motivations leading one to adopt such an approach and the guidelines for its design.","PeriodicalId":135735,"journal":{"name":"Journal of Structural Control","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124436192","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 present work describes a numerical procedure for the design of a piezoelectric active control system capable of reducing the acoustic emission from forced structural elements. The characterisation of the actively controlled structure is carried out through an integrated electro-elastic Finite Element (FE) approach. Because of the possibility of using piezoelectric layers as self-sensing actuators, a simple and effective collocated control technique is employed; within this framework different control laws are allowed by the use of external electric circuits implementing appropriate measurement conditioning. The acoustic pressure field around the vibrating structure is simulated by using a boundary elements method interfaced to the FE structural model through mobility matrices.
{"title":"Structural vibrations and noise reduction by piezoelectric active control","authors":"G. Ghiringhelli","doi":"10.1002/STC.4300040203","DOIUrl":"https://doi.org/10.1002/STC.4300040203","url":null,"abstract":"The present work describes a numerical procedure for the design of a piezoelectric active control system capable of reducing the acoustic emission from forced structural elements. The characterisation of the actively controlled structure is carried out through an integrated electro-elastic Finite Element (FE) approach. Because of the possibility of using piezoelectric layers as self-sensing actuators, a simple and effective collocated control technique is employed; within this framework different control laws are allowed by the use of external electric circuits implementing appropriate measurement conditioning. The acoustic pressure field around the vibrating structure is simulated by using a boundary elements method interfaced to the FE structural model through mobility matrices.","PeriodicalId":135735,"journal":{"name":"Journal of Structural Control","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126443963","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}
Laminated high damping rubber bearings provide a simple means of isolating structures from horizontal earthquake ground motions. The key properties of the rubber compounds are dynamic shear modulus and damping. The effect of strain amplitude, repeated cycling and temperature on these properties is given. The need to prevent changes in modulus associated with low temperature crystallization of rubber is discussed. Assessment of the long term stability of rubber properties from both accelerated ageing tests and measurements on bearings removed after prolonged service is considered. A model for the behaviour of high damping rubber is presented, and used to show how the response of a structure to ground acceleration depends upon the level of damping.
{"title":"High damping natural rubber seismic isolators","authors":"K. Fuller, J. Gough, T. Pond, H. Ahmadi","doi":"10.1002/STC.4300040202","DOIUrl":"https://doi.org/10.1002/STC.4300040202","url":null,"abstract":"Laminated high damping rubber bearings provide a simple means of isolating structures from horizontal earthquake ground motions. The key properties of the rubber compounds are dynamic shear modulus and damping. The effect of strain amplitude, repeated cycling and temperature on these properties is given. The need to prevent changes in modulus associated with low temperature crystallization of rubber is discussed. Assessment of the long term stability of rubber properties from both accelerated ageing tests and measurements on bearings removed after prolonged service is considered. A model for the behaviour of high damping rubber is presented, and used to show how the response of a structure to ground acceleration depends upon the level of damping.","PeriodicalId":135735,"journal":{"name":"Journal of Structural Control","volume":"99 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124744837","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 new structural system conceived to control Base Isolated System vibrations under random excitations is analyzed. The new system combines the Tuned Mass Damping strategy with the Isolation concept in order to obtain a new system which principally attenuates the effects of the seismic excitation components with frequencies close to the fundamental natural vibration one. The Random response of equivalent linear Base Isolated Systems controlled by Tuned Mass Dampers subject to horizontal random excitations is analyzed. Considering the superstructure motion described by its first modal contribution, a three-degree-of-freedom linear model subject to stationary Gaussian excitations, modelled by the modified Kanai-Tajimi power density spectrum, was used in this analysis. The standard deviation response ratio of the new system respect to the one of the base isolated system was evaluated based on a wide range of parameters. Optimal parameters which minimize structural response were also obtained.
{"title":"Response of base isolated systems equipped with tuned mass dampers to random excitations","authors":"B. Palazzo, L. Petti, M. D. Ligio","doi":"10.1002/STC.4300040105","DOIUrl":"https://doi.org/10.1002/STC.4300040105","url":null,"abstract":"A new structural system conceived to control Base Isolated System vibrations under random excitations is analyzed. The new system combines the Tuned Mass Damping strategy with the Isolation concept in order to obtain a new system which principally attenuates the effects of the seismic excitation components with frequencies close to the fundamental natural vibration one. The Random response of equivalent linear Base Isolated Systems controlled by Tuned Mass Dampers subject to horizontal random excitations is analyzed. Considering the superstructure motion described by its first modal contribution, a three-degree-of-freedom linear model subject to stationary Gaussian excitations, modelled by the modified Kanai-Tajimi power density spectrum, was used in this analysis. The standard deviation response ratio of the new system respect to the one of the base isolated system was evaluated based on a wide range of parameters. Optimal parameters which minimize structural response were also obtained.","PeriodicalId":135735,"journal":{"name":"Journal of Structural Control","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125960637","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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