Error study of a hybrid testing system of structures through a state-space model

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.JRC.G.5-European laboratory for structural assessmen

Competitive Advantage Through the Customer Involvement in E-commerce Strategies : A Multiple-Case Study in the European Airline Industry

Much research show that strategies of personalization aiming to meet customers' needs and behaviors are an important aspect to influence the competitiveness within an industry. However there is a gap of studies on how airlines use customer involvement for creating personalized strategies in the field of e-commerce while enhancing the competitive advantage. This study is aims to describe how airlines can create personalized e-commerce strategies by considering the customer involvement in order to enhance their competitiveness. In conjunction with this first assumption the study aims to demonstrate how airlines could increase their customer loyalty by implementing the concept of customer relationship management (CRM) within their e-commerce strategies. A theoretical framework has been developed derived from a review of the existing literature in order to describe how airlines can use personalization as a strategy in e-commerce to develop a competitive advantage.  A qualitative multiple-case study has been chosen for this study. Three companies have been studied within the European airline industry and have been led by a deductive approach which will aim to investigate the theoretical framework.The analysis of empirical findings revealed some relevant conclusions, which can bring value to the research area, and also to the practice. The main findings show that airlines are involving customers into their e-commerce strategies in various forms and different levels regarding a specific project. One of the major result of this thesis is that airlines seem to focus on point of contacts with customers external to the e-commerce platform

Reliability of dynamic and hybrid tests in the presence of control errors

The deleterious effect of control errors in the obtained response for shaking-table, pseudo-dynamic and hybrid tests can be quantified in a standard way by assessing the frequency and damping distortion in the obtained response as identified from equivalent linear models. The identified linear models are based only on the measurements done during the experiment, which increases the generality and applicability of the proposed strategy.JRC.DG.G.5-European laboratory for structural assessmen

Reliability Assessment in Pseudo-Dynamic and Dynamic Tests

A general approach to the definition and assessment of response errors in dynamic and pseudo-dynamic tests is presented. By use of complete measurements during the test, either the characteristics of the experimental and the prototype system can be estimated by means of a linear ideal representation. This allows to compare quantitatively in terms of eigenfrequencies and damping ratios the experimental system and the prototype one. In the pseudo-dynamic test, the apparent effect of the control errors is a modification of the linear-equivalent matrices of stiffness and damping which are identified from the experimental data. In the shaking-table test, the control errors may introduce spurious excitation that, if properly measured, can also be shown to modify the response characteristics.JRC.DG.G.5-European laboratory for structural assessmen

Severe loading tests on large-size structures at ELSA laboratory

The ELSA laboratory is provided with a large reaction-wall facility and has acquired its best expertise on the development and implementation of innovative experimental techniques mainly related to testing of large-scale specimens by the pseudo-dynamic method. Important examples are represented by the bidirectional tests performed on multi-storey buildings and the tests with non-linear substructuring applied to bridges. Apart from the relevant achievements within the testing techniques, the role of a reference laboratory in Europe has allowed ELSA to rely on the collaboration of many important research institutions that have collaborated to the projects and added maximum scientific value to the results of the tests. The aspects of advanced testing methods and collaboration through extensive use of networking are very important components for the proposed future European facility for seismic testing within project EFAST in which ELSA is also taking part. Such networking should include shared database, telepresence and geographically distributed testing.JRC.DG.G.5-European laboratory for structural assessmen

Structural Testing Activities at the ELSA Laboratory of the European Commission

The ELSA laboratory is provided with a large reaction-wall facility and has acquired its best expertise on the development and implementation of innovative experimental techniques mainly related to testing of large-scale specimens by the pseudodynamic method. Important examples are represented by the bidirectional tests performed on multi-storey buildings, the tests of structures equipped with isolator or dissipating devices, which are particularly difficult to test with that method due to the strain-rate effect, and the tests with non-linear substructuring. Apart from the relevant achievements within the testing techniques, the role of a reference laboratory in Europe has allowed ELSA to rely on the collaboration of many important research institutions that have collaborated to the projects and added maximum scientific value to the results of the tests.JRC.G.5-European laboratory for structural assessmen

Characterization of a Parallel Interfield Procedure for Pseudo-Dynamic Testing with Heterogeneous Substructuring

This paper presents the convergence analysis of a novel parallel interfield procedure for continuous pseudo-dynamic testing with heterogeneous substructuring. The partitioned method is an extension of a method originally proposed by Gavouil and Combescure which utilizes a domain decomposition enforcing the continuity of the velocity at interfaces. In particular the new method is a parallel interfield procedure instead of a staggered one. The merits of the new method which can couple arbitrary Newmark schemes with diferent time steps in different subdomains and advance all the substructure states sinzultaneously, are analysed in terms of accuracy, stability and error propagation. All theoretical results are derived for single- and two-degrees-of-freedom systems as a multi-degree-of-freedom system is too difficult to analyze mathematically.JRC.G.5-European laboratory for structural assessmen

Convergence Analysis of a Parallel Interfield Method for Heterogeneous Simulations with Dynamic Substructuring

In order to predict the dynamic response of a complex system decomposed by computational or physical considerations, partitioned procedures of coupled dynamical systems are needed. This paper presents the convergence analysis of a novel parallel interfield procedure for time-integrating heterogeneous (numerical/physical) subsystems typical of hardware-in-the-loop and pseudo-dynamic tests. The partitioned method is an extension of a method originally proposed by Gavouil and Combescure which utilizes a domain decomposition enforcing the continuity of the velocity at interfaces. In particular, the merits of the new method which can couple arbitrary Newmark schemes with different time steps in different subdomains and advance all the substructure states simultaneously, are analysed in terms of accuracy and stability. All theoretical results are derived for single- and two-degrees-of-freedom systems as a multi-degree-of-freedom system is too difficult to analyze mathematically. However, the insight gained from the analysis of these coupled problems and the conclusions drawn are confirmed by means of the numerical simulation on three- and four-degrees-of-freedom systems.JRC.G.5-European laboratory for structural assessmen

Ensayos Sismícos en el Laboratorio ELSA de la Comisión Europea

During the last decade, the European Laboratory for Structural Assessment (ELSA) has played a major role in Europe in the execution of seismic tests on large structural models. Most of the tests performed at ELSA have been developed in collaboration with many research centres and have produced results of great value for the validation of several chapters of Eurocode 8. Usually the method applied in those tests is the pseudo-dynamic (PsD) one, which has been continuously improved thanks to the accumulated experience. By means of the PsD method, it is possible to obtain in the laboratory with accuracy the seismic response of large structures in a quasi-static fashion, which avoids many of the problems faced by shaking-table testing. At ELSA, the powerful combination of instruments and software developed within a flexible architecture has allowed to successfully afford the most complicated realistic tests when using substructuring or multi-directional response for example.JRC.G.5-European laboratory for structural assessmen

Monitoring Damping in Pseudo-Dynamic Tests

By comparison of dynamic and pseudo-dynamic tests, it is shown that conventional construction materials exhibit pure hysteretic damping and consequently, when quasistatic restoring forces are measured directly, the addition of viscous damping in the equation of motion must be avoided unless it is intended to reflect missing physical elements. Equally important in pseudo-dynamic testing is the fact that the apparent damping can be easily distorted by the inevitable control errors. The identification of a spatial model from the results of the tests allows obtaining a reliable estimation of the damping distortion for each vibration mode.JRC.G.5-European laboratory for structural assessmen