DYNAMIC IDENTIFICATION AND TESTING

RESEARCH GROUP: Pier Paolo Diotallevi, Claudio Mazzotti, Marco Savoia KEYWORDS: identification, optimization, dynamics test, Wavelet wave, bridge

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

The study can be split in three main topics: set- up of experimental tests, determination of the dynamic characteristics of the structure and pro- cessing of data to estimate unknown parameters of models such as stiffness and mass of the system (model updating). Within the first topic, differ- ent 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 exci- tation (wind, traffic). Both conventional instru- mentation 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 time-frequency methods such as wavelet transforms.

The estimate of the actual values of the param- eters of the mechanical properties (material assumptions, constraints, and structural and nonstructural masses), finally, was obtained by solving an optimization process. The research focuses on the study and application of genetic and evolutionary algorithms and their variants, whereas frequencies and mode shapes were assigned. The shape of the error function for different choices of the number of natural fre- quencies and mode shapes were investigated. In addition, pseudo-experimental or experimental input data were considered. Finally, it was im- plemented a modified version of an evolution- ary algorithm to improve accuracy and speed of convergence.

MAIN PUBLICATIONS

Vincenzi L., De Roeck G., Savoia M. (2013- in press) Comparison between Differential Evolu- tion Algorithm and Coupled local Minimizer Method. Advances in Engineering Software. Guidorzi R., Diversi R., Vincenzi L., Mazzotti C., Simioli V. (2013 – in press) Structural mon- itoring of a tower by means of MEMS–based sensing and enhanced autoregressive models. Eu- ropean Journal of Control.

Vincenzi L., Savoia M., Salvatore W. (2012) Ex- perimental modal analysis and fatigue assessment on the Lagoscuro viaduct. 6th _{International Con-}

ference on Bridge Maintenance, Safety and Man- agement, 8-12/07/2012, Stresa, Lago Maggiore. Pantoli E., Vincenzi L., Savoia M., Testa R. (2011) The effect of local vibrations on fatigue in old steel riveted bridges. A case study: the Manhattan Bridge. 8th _{International Conference on Structural Dynam-}

ics, EURODYN 2011, 4-6/7/2011, Leuven, Belgio Vincenzi L., Mazzotti C., Guidorzi R. (2011) Monitoraggio strutturale della torre della facoltà di Ingegneria di Bologna. XIV convegno ANID- IS, 18-22/09/2011, Bari.

Vincenzi L., Savoia M. (2010) Improving the speed performance of an Evolutionary Algorithm by a second-order cost function approximation. 2nd _{International Conference on Engineering Op-}

timization, 6-9/09/2010, Lisbona, Portogallo Vincenzi L., Mazzotti C., Guidorzi R. (2010). Utilizzo di MEMS per il monitoraggio strutturale. XVIII Convegno CTE, Brescia.

C. Belmonte, P.P. Diotallevi, O. Manfroni. (2010). “Comparison Between Two Methods In Frequen- cy Domain for Dynamic Identification”. Proceed- ings of the 14th _{European Conference on Earth-}

quake Engineering, 30/08-3/09/2010, Ohrid, Republic of Macedonia

C. Belmonte, P. P. Diotallevi, O. Manfroni. (2009). “Metodi nel dominio delle frequenze per l’identifi- cazione dinamica di una passerella pedonale”. XIII Convegno Nazionale L’Ingegneria Sismica in Ita- lia, ANIDIS. 28/06-2/07, Bologna.

C. Belmonte, E. Caetano, A. Cunha, P.P. Dio- tallevi. (2009). “Extraction of modal parame-

ters through Wavelet Transform”. Proceedings of the “IV ECCOMAS Thematic Conference SMART’09”. 13-15 July 2009, Porto, Portugal. Vincenzi L., Mazzotti C. (2009). Identificazione dinamica di una passerella pedonale strallata me- diante algoritmi nel dominio delle frequenze, XIII Convegno Nazionale di Ingegneria Sismica AN- IDIS, 28 giugno-2 luglio, Bologna.

Vincenzi L. Savoia M., (2009). Coupling of differ- ential evolution algorithm and quadratic approx- imation for dynamic identification, ICOSSAR - International conference of structural safety and reliability 2009, Osaka, Japan.

P.P. Diotallevi, O. Manfroni, C. Belmonte. (2008). “Dynamic identification of a timber footbridge subject to vibration tests”. Proceedings of the 14th

World Conference on Earthquake Engineering, Beijing, China, October 12-17, 2008.

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

Vincenzi L., Mazzotti C., Savoia M. (2006). Mod- al identification of a TAV viaduct using subspace models. 2nd _{International FIB Congress. 5-8 gi-}

ugno, Napoli.

Vincenzi L., Savoia M. (2005), Identificazione dei parametri modali autoregressivi di un modello ARMA Vettoriale attraverso algoritmi evolutivi, - AIMeTA di Meccanica Teorica e Applicata, 11-15 settembre, Firenze.

RESEARCH PROJECTS

2009-2012: Research Project FADLESS (Fa- tigue 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. Leu- ven, LMS International NV, Bauhaus Universitat Weimar, Facultade De Engenharia Da Universit- ade Do Porto, University of Bologna.

CONTACTS

[email protected] [email protected] [email protected]

Fig. 1. Diagnosis on Ghirlandina tower, Mode- na: sonic results and velocity classes.

Fig. 2. Evaluation of homogeneity of mansonry by thermography and wireless monitoring.

Fig. 3. Shear test on masonry triplet. Precom- pression apparatus.

EXPERIMENTAL TECHNIQUES FOR THE STUDY OF HISTORICAL MASONRY