Recent advances and future needs in experimental earthquake engineering
This Report deals with the recent advances and future needs in experimental Earthquake Engineering and is directed mainly to researchers working in Universities and Research Institutions. The work presented in this report may serve as reference on the state of research supporting reaction wall and shaking table experimental facilities in Europe and might promote the exchange of ideas and solutions among researchers towards the advancement and improvement of these experimental facilities. The report is subdivided in seven chapters and describes the different aspects of research related to the developments, needs and improvements of reaction wall and shaking table facilities. The first Chapter presents a brief assessment of current engineering experimental research in Europe, covering shaking table, pseudo-dynamic and real-time test methodologies, as well as the effects related to time-scale expansion on strain-rate sensitive devices. The second Chapter pinpoints future needs for structural testing, to account for the requirements of performance based earthquake engineering, validation of new structural components and representation of soil-structure interaction by means of experimental testing. The needs identified for the facilities are both in terms of the improvement of the facilities themselves (hardware), including testing rigs, equipment and instrumentation, as well as on control algorithms and strategies to enhance the reliability of the results obtained, to further increase the speed of testing when using the pseudo-dynamic method, and to perform substructuring of complex systems on shaking tables and reaction wall tests. The third Chapter describes developments and improvements of the substructure testing method on reaction walls and shaking table. The chapter focuses mainly on the experience accumulated at the European Laboratory for Structural Assessment (ELSA) in developing continuous pseudo-dynamic testing, facing the problem of load relaxation, improving the quality of results and considerably reducing test duration. The aspects related to substructuring when the continuous PsD test method is employed and the approach to solve communication problems between the analytical and physical processes of complex systems with high nonlinearities at near to real-time testing are presented. The aspects of substructuring related to shaking tables are briefly discussed, and reference is made to the research performed within the framework of the consortium of shaking table laboratories in Europe. The problems of control and increased computing speed were identified as main areas of research that need to be addressed for the successful performance of substructured shaking table tests. The fourth Chapter presents a brief discussion on the improvement of existing facilities based on the needs identified in Chapter three. The aspects related to fast on-line testing, to the introduction of multiple actuator systems and to modelling of interfaces to permit simulation of complex boundary conditions, are presented as areas where improvements of the existing facilities are needed. Chapter five gives an overview of the possible structural dynamic applications outside earthquake engineering, in particular towards mechanical and aerospace engineering. The use of substructuring for vibration control of transport structures considering realistic loads using passive, semi-active and active devices is discussed. In Chapter six, the benchmarking studies carried out to compare the performance of shaking table and reaction wall facilities are discussed. For this, two examples are presented: the benchmark tests of a shaking table and a reaction wall by means of SDOF shear type specimen, and the shaking table and PsD tests performed on a 4-storey base isolated steel frame. The conclusions and recommendations are presented on Chapter seven, summarising the developments, needs and improvements for reaction wall and shaking table facilities in Europe.