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Dynamic identification and testing, modelling and design of shaking table test facilities

Keywords: dynamic identification, dynamic testing, shaking table
Fig. 1. Identification of the natural frequencies (Landi).
Fig. 2. Forced vibration test on pedestrian bridge (Diotallevi).
Fig. 3. Tests on a full-scale 3-storey building realized with RC sandwich panels, at the EUCENTRE Lab in Pavia (Silvestri).

The research group is involved in the experimental study of the dynamic behavior of civil structures. The problem is particularly relevant because from the dynamic characterization of the system (modes, natural frequencies, damping), the most plausible values of the main parameters governing the numerical models able to simulate the behavior of the structure can be defined by identification techniques.

The study can be split in different topics: set-up of experimental tests, determination of the dynamic characteristics of the structure and processing of data to estimate unknown parameters of models such as stiffness and mass of the system (model updating). Within the first topic, different types of structures such as hospitals, schools, bridges, railway bridges and pedestrian bridges were considered. The tests were carried out either using a forced excitation or environmental excitation (wind, traffic). Both conventional instrumentation and low-cost accelerometers (MEMS) were used. Frequencies, modal deformation and damping were then identified by using methods defined in the frequency domain and in the time domain, such as circle fit, ARMA, ARMAV, Lissajous diagrams and coupled timefrequency methods such as wavelet transforms. Moreover, also output-only modal identification techniques were investigated.

With regard to shake table testing, the activity regarded mainly the development of an analytical/ numerical model of the dynamic functioning of the shaking table capable of effectively capturing its actual behaviour. This model revealed to be very useful for: (a) the design project of new shaking tables, (b) for their adjustments, and (c) for the study devoted to the minimisation of the interactions between the table itself and the testes structures. Recently the research group planned, designed and directed two experimental shakingtable test campaigns: (1) tests on a full-scale 3- storey building structure realized with sandwich r.c. panels, at the EUCENTRE Lab in Pavia; (2) tests on scaled models of flat-bottom silos containing grain –like materials, at the EQUALS Lab in Bristol (UK).

Main publications

Silvestri, S., Ivorra, S., Chiacchio, L.D. Trombetti, T., Foti, D., Gasparini, G., Pieraccini, L., Dietz, M., Taylor, C. (2016) Shaking-table tests of flat-bottom circular silos containing grain-like material, Earthquake Engineering & Structural Dynamics, Vol. 45, Issue 1, pp. 69-89.

Bernagozzi, G., Landi, L., Diotallevi, P.P. (2016) On the Output-Only Vibration-Based Damage Detection of Frame Structures. Proceedings of the 34th IMAC, A Conference and Exposition on Structural Dynamics 2016, Orlando, USA.

Bernagozzi, G., Landi, L., Diotallevi, P.P. (2016) Modal Testing Through Forced Sine Vibrations of a Timber Footbridge. Proceedings of the 34th IMAC, A Conference and Exposition on Structural Dynamics 2016, Orlando, USA.

Vincenzi, L., Savoia, M. (2015) Coupling response surface and differential evolution for parameter identification problems, Computer-Aided Civil and Infrastructure Engineering, Vol. 30, Issue 5, pp. 376-393.

Bassoli, E., Vincenzi, L., Bovo, M., Mazzotti, C. (2015) Dynamic identification of an ancient masonry bell tower using a MEMS-based acquisition system, Proceedings of IEEE Workshop on Environmental, Energy, and Structural Monitoring Systems, Article number 7175882, pp. 226-231.

Palermo, M., Ricci, I., Silvestri, S., Gasparini, G., Trombetti, T., Foti, D., Ivorra, S. (2014) Preliminary interpretation of shaking-table response of a full-scale 3-storey building composed of thin reinforced concrete sandwich walls, Engineering Structures, Vol. 76, pp. 75-89.

Guidorzi R., Diversi R., Vincenzi L., Mazzotti C., Simioli V. (2014) Structural monitoring of a tower by means of MEMS-based sensing and enhanced autoregressive models. European Journal of Control, Vol. 20, Issue 1, pp. 4-13.

Vincenzi L., De Roeck G., Savoia M. (2013) Comparison between coupled local minimizers method and differential evolution algorithm in dynamic damage detection problems. Advances in Engineering Software, Vol. 65, pp. 90-100.

C. Belmonte, E. Caetano, A. Cunha, P. P. Diotallevi. (2009). “Extraction of modal parameters through Wavelet Transform”. Proceedings of the IV ECCOMAS Thematic Conference SMART’09. 13-15 July 2009, Porto, Portugal.

Savoia M., Vincenzi L. (2008). Differential Evolution Algorithm for Dynamic Structural Identification. Journal of Earthquake Engineering. Vol. 12, pp. 800-821.

Ozcelik O., Luco E., Conte J.P., Trombetti T. and Restrepo J. (2008). Experimental characterization, modeling and identification of the NEESUCSD shake table mechanical system. Earthquake Engineering & Structural Dynamics, Vol. 37, 2, pp. 243-264.

Vincenzi L., Mazzotti C., Savoia M. (2006). Modal identification of a TAV viaduct using subspace models. 2nd International FIB Congress. 5-8 giugno, Napoli.

Trombetti T. and Conte J.P. (2002). Shaking Table Dynamics: results form a test-analysis comparison study. Journal of Earthquake Engineering, Vol. 6, 4, pp. 513–551.

Conte J.P. and Trombetti T. (2000). Dynamic modeling of a uni-axial shaking table system. Earthquake Engineering & Structural Dynamics, Vol. 29, pp. 1375-1404.

Research projects

2009-2012:Research Project FADLESS (Fatigue damage control and assessment for railway bridges), sponsored by European Commission within program RFCS (Research Fund for Coal and Steel-FP7); partners of the projects are: PISA ricerche, Riva Acciaio, VCE Holding, K. U. Leuven, LMS International NV, Bauhaus Universitat Weimar, Facultade De Engenharia Da Universitade Do Porto, University of Bologna.

2010-2012: SERIES Research Projects:
- "Seismic behavior of structural systems composed of cast in situ concrete walls", EUCENTRE TREES Lab Facility (Pavia, Italy), Lead User: Prof. Salvador Ivorra Chorro, Univ. of Alicante, Resp. Unit of Bologna: Prof. Tomaso Trombetti.
- "Assessment of the seismic behaviour of flatbottom silos containing grain-like materials", EQUALS Laboratories (Bristol, UK), Lead User: Prof. Dora Foti, Politecnico di Bari, Resp. Unit of Bologna: Prof. Tomaso Trombetti.