The present paper focuses on the research activities, namely networking activities and pseudo-dyn... more The present paper focuses on the research activities, namely networking activities and pseudo-dynamic test projects, being carried out at the European Laboratory for Structural Assessment (ELSA) of the Joint Research Centre of the European Commission (EC), as part of the Seismic Engineering Research Infrastructures for European Synergies (SERIES) project financed by the Seventh Framework Programme of the European Commission. The SERIES networking activities aim at providing both off-line access to data by means of a distributed database and on-line access by means of telepresence implementation that allows virtual access to test equipments. The experimental test campaigns are part of SERIES transnational access activities. Ongoing projects at the reaction wall facility of ELSA are: the seismic retrofit of a four-storey reinforced concrete wall with shear walls, the design of a new steel-concrete composite eccentric braced frame with easily replaceable dissipaters, and the seismic as...
The European Laboratory for Structural Assessment (ELSA) is involved in the development of advanc... more The European Laboratory for Structural Assessment (ELSA) is involved in the development of advanced control strategy for improving the performances of the servo-control systems used for pseudo-dynamic testing on large civil structures or on subcomponents using substructuring method. Two research lines are pursued: advancing of control algorithm and exploiting of new actuation system potentialities. Several control strategies are here examined: current PID algorithm is compared to more advanced procedures including full-state feedback and various feed-forward techniques. Coupling of two servovalves acting on the same actuator is also presented with a special attention to velocity feedback. The benefit of these strategies is a reduction of the control error compared to the case where only PID control is used. Hydraulic components, digital servo-controller and tested structures are simulated by using Simulink models. A one degree of freedom PsD test is simulated; particular attention i...
In the last two decades, the increasing complexity of engineering systems boosted the development... more In the last two decades, the increasing complexity of engineering systems boosted the development of very efficient simulation methods based on partitioning. In view of coupling dynamic parts of hybrid systems, the finite element tearing and interconnecting approach emerged as the most promising technique. Nonetheless, there is still a lack of a comprehensive study of algorithmic performances from the experimental perspective. In this view, the present paper sheds light on the application of two well-known parallel partitioning methods for the purpose of the simulation of hybrid models. Thus, an existent reinforced concrete bridge is chosen as a benchmark case study. In order to perform hybrid simulations, a novel coupling software was devised. It allowed for combining two physical piers to the numerical model of the remaining part of the bridge. As a result, successful tests were conducted at the ELSA laboratory of the Joint Research Centre of Ispra (Italy).
Experimental methods such as hybrid or pseudo-dynamic tests are always subjected to experimental ... more Experimental methods such as hybrid or pseudo-dynamic tests are always subjected to experimental errors which effect on the obtained response is important to assess. An analytical linear model formulated on state-space equations has been developed for a multi DoF hybrid testing system including the components of the control and the specimen. For an example of a single DoF steel frame, the parameters of the model have been calibrated through comparison with experimental data of the control system. The model has been used to predict in pseudo-dynamic tests on such specimen the control errors and their consequences in terms of eigenfrequency and damping distortion in the test response. These predictions match with the observed experimental data and allow understanding, for example, the effects on the response of performing the test at different testing speeds or for different parameter configurations of the control algorithm.
Within the frame of the European project IRIS, five reinforced concrete walls have been tested in... more Within the frame of the European project IRIS, five reinforced concrete walls have been tested in shear at the ELSA. The thickness of the wall was exceptionally large (40cm) for this kind of test. The testing setup was able to apply quasistatically a shear force of up to 12 MN by means of four horizontal actuators and the vertical load and rotations were controlled by another four smaller actuators. The applied mixed-variable control at the horizontal actuators, with feedback based on a combination of force and displacement, allowed to have a smooth response of the system also in the situations of collapse of the specimen or at the central gap zone in which the horizontal pistons where not in contact with the loading system. In addition to this control, a low-speed regulator algorithm running in MATLAB closed an external loop that managed the variation of the target to the controllers in order to perform the required loops at the specified force or displacement level. This sophistic...
In the last two decades, the increasing complexity of engineering systems boosted the development... more In the last two decades, the increasing complexity of engineering systems boosted the development of very efficient simulation methods based on partitioning. In view of coupling dynamic parts of hybrid systems, the finite element tearing and interconnecting approach emerged as the most promising technique. Nonetheless, there is still a lack of a comprehensive study of algorithmic performances from the experimental perspective. In this view, the present paper sheds light on the application of two well-known parallel partitioning methods for the purpose of the simulation of hybrid models. Thus, an existent reinforced concrete bridge is chosen as a benchmark case study. In order to perform hybrid simulations, a novel coupling software was devised. It allowed for combining two physical piers to the numerical model of the remaining part of the bridge. As a result, successful tests were conducted at the ELSA laboratory of the Joint Research Centre of Ispra (Italy).
In the IRIS project (European 7 th framework program) we have designed an original experimental s... more In the IRIS project (European 7 th framework program) we have designed an original experimental setting for assessing the structural fragility of thick shear-walls. The main motivation is to improve the understanding of the non-linear behaviour under seismic loads of structures typical for the existing NPPs. In this context it is not only important to assess the ultimate capacity of a structure, but also its dynamic response in the "moderate damage" regime relevant for the verifications of components' fragilities through the FRS (Frequency Response Spectra). The dynamic response of structures of interest (e.g. electrical buildings) is essentially determined by the behaviour of the walls loaded in shear. The main specificity of the shear-wall of a nuclear installation is its much higher thickness than in the conventional civil structures. Many experimental campaigns (pseudo-dynamic or shaking table tests) were already done in this area, also at CEA and JRC, but so far m...
In this paper, two different time-domain methods are proposed. Both have been successful in the i... more In this paper, two different time-domain methods are proposed. Both have been successful in the identification of the natural frequencies, damping ratios and mode shapes of large structures seismically tested by using the pseudodynamic method. The first method is formulated as a spatial model in which the stiffness and damping matrices are directly identified from the experimental displacements, velocities and restoring forces. The obtained matrices are then combined with the theoretical mass in order to obtain the eigenfrequencies and modes. The second method is formulated as a filter model of specified order in which the ground accelerogram acts as input and the experimental displacements act as output. In this case the eigenfrequencies and modes are obtained from the identified coefficients of the filter. This paper also compares the results of such identification methods applied to a 3-storey steel-concrete composite building and a 2-storey seismically retrofitted reinforced con...
The present paper focuses on the research activities, namely networking activities and pseudo-dyn... more The present paper focuses on the research activities, namely networking activities and pseudo-dynamic test projects, being carried out at the European Laboratory for Structural Assessment (ELSA) of the Joint Research Centre of the European Commission (EC), as part of the Seismic Engineering Research Infrastructures for European Synergies (SERIES) project financed by the Seventh Framework Programme of the European Commission. The SERIES networking activities aim at providing both off-line access to data by means of a distributed database and on-line access by means of telepresence implementation that allows virtual access to test equipments. The experimental test campaigns are part of SERIES transnational access activities. Ongoing projects at the reaction wall facility of ELSA are: the seismic retrofit of a four-storey reinforced concrete wall with shear walls, the design of a new steel-concrete composite eccentric braced frame with easily replaceable dissipaters, and the seismic as...
The European Laboratory for Structural Assessment (ELSA) is involved in the development of advanc... more The European Laboratory for Structural Assessment (ELSA) is involved in the development of advanced control strategy for improving the performances of the servo-control systems used for pseudo-dynamic testing on large civil structures or on subcomponents using substructuring method. Two research lines are pursued: advancing of control algorithm and exploiting of new actuation system potentialities. Several control strategies are here examined: current PID algorithm is compared to more advanced procedures including full-state feedback and various feed-forward techniques. Coupling of two servovalves acting on the same actuator is also presented with a special attention to velocity feedback. The benefit of these strategies is a reduction of the control error compared to the case where only PID control is used. Hydraulic components, digital servo-controller and tested structures are simulated by using Simulink models. A one degree of freedom PsD test is simulated; particular attention i...
In the last two decades, the increasing complexity of engineering systems boosted the development... more In the last two decades, the increasing complexity of engineering systems boosted the development of very efficient simulation methods based on partitioning. In view of coupling dynamic parts of hybrid systems, the finite element tearing and interconnecting approach emerged as the most promising technique. Nonetheless, there is still a lack of a comprehensive study of algorithmic performances from the experimental perspective. In this view, the present paper sheds light on the application of two well-known parallel partitioning methods for the purpose of the simulation of hybrid models. Thus, an existent reinforced concrete bridge is chosen as a benchmark case study. In order to perform hybrid simulations, a novel coupling software was devised. It allowed for combining two physical piers to the numerical model of the remaining part of the bridge. As a result, successful tests were conducted at the ELSA laboratory of the Joint Research Centre of Ispra (Italy).
Experimental methods such as hybrid or pseudo-dynamic tests are always subjected to experimental ... more Experimental methods such as hybrid or pseudo-dynamic tests are always subjected to experimental errors which effect on the obtained response is important to assess. An analytical linear model formulated on state-space equations has been developed for a multi DoF hybrid testing system including the components of the control and the specimen. For an example of a single DoF steel frame, the parameters of the model have been calibrated through comparison with experimental data of the control system. The model has been used to predict in pseudo-dynamic tests on such specimen the control errors and their consequences in terms of eigenfrequency and damping distortion in the test response. These predictions match with the observed experimental data and allow understanding, for example, the effects on the response of performing the test at different testing speeds or for different parameter configurations of the control algorithm.
Within the frame of the European project IRIS, five reinforced concrete walls have been tested in... more Within the frame of the European project IRIS, five reinforced concrete walls have been tested in shear at the ELSA. The thickness of the wall was exceptionally large (40cm) for this kind of test. The testing setup was able to apply quasistatically a shear force of up to 12 MN by means of four horizontal actuators and the vertical load and rotations were controlled by another four smaller actuators. The applied mixed-variable control at the horizontal actuators, with feedback based on a combination of force and displacement, allowed to have a smooth response of the system also in the situations of collapse of the specimen or at the central gap zone in which the horizontal pistons where not in contact with the loading system. In addition to this control, a low-speed regulator algorithm running in MATLAB closed an external loop that managed the variation of the target to the controllers in order to perform the required loops at the specified force or displacement level. This sophistic...
In the last two decades, the increasing complexity of engineering systems boosted the development... more In the last two decades, the increasing complexity of engineering systems boosted the development of very efficient simulation methods based on partitioning. In view of coupling dynamic parts of hybrid systems, the finite element tearing and interconnecting approach emerged as the most promising technique. Nonetheless, there is still a lack of a comprehensive study of algorithmic performances from the experimental perspective. In this view, the present paper sheds light on the application of two well-known parallel partitioning methods for the purpose of the simulation of hybrid models. Thus, an existent reinforced concrete bridge is chosen as a benchmark case study. In order to perform hybrid simulations, a novel coupling software was devised. It allowed for combining two physical piers to the numerical model of the remaining part of the bridge. As a result, successful tests were conducted at the ELSA laboratory of the Joint Research Centre of Ispra (Italy).
In the IRIS project (European 7 th framework program) we have designed an original experimental s... more In the IRIS project (European 7 th framework program) we have designed an original experimental setting for assessing the structural fragility of thick shear-walls. The main motivation is to improve the understanding of the non-linear behaviour under seismic loads of structures typical for the existing NPPs. In this context it is not only important to assess the ultimate capacity of a structure, but also its dynamic response in the "moderate damage" regime relevant for the verifications of components' fragilities through the FRS (Frequency Response Spectra). The dynamic response of structures of interest (e.g. electrical buildings) is essentially determined by the behaviour of the walls loaded in shear. The main specificity of the shear-wall of a nuclear installation is its much higher thickness than in the conventional civil structures. Many experimental campaigns (pseudo-dynamic or shaking table tests) were already done in this area, also at CEA and JRC, but so far m...
In this paper, two different time-domain methods are proposed. Both have been successful in the i... more In this paper, two different time-domain methods are proposed. Both have been successful in the identification of the natural frequencies, damping ratios and mode shapes of large structures seismically tested by using the pseudodynamic method. The first method is formulated as a spatial model in which the stiffness and damping matrices are directly identified from the experimental displacements, velocities and restoring forces. The obtained matrices are then combined with the theoretical mass in order to obtain the eigenfrequencies and modes. The second method is formulated as a filter model of specified order in which the ground accelerogram acts as input and the experimental displacements act as output. In this case the eigenfrequencies and modes are obtained from the identified coefficients of the filter. This paper also compares the results of such identification methods applied to a 3-storey steel-concrete composite building and a 2-storey seismically retrofitted reinforced con...
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