Luca Nardini

Structural Health Monitoring (SHM) and Experimental Modal Analysis (EMA) have revealed to be really efficient tools for the damage detection of structures and structural elements in many engineering fields (Shock Vib. Dig. 1998; 30(2):91–105; Philos. Trans. R. Soc. A 2007; 365(1851):303–315; Mech. Syst. Signal Process. 2003; 17(1):133–142; Philos. Trans. R. Soc.: Math. Phys. Eng. Sci. 2001; 359(1778): 131–149; Struct. Control Health Monit. 2006; 14:1083–1100; Mech. Syst. Signal Process. 2004; 17(1): 83–89). Unfortunately the great variety of morphologies, construction materials and structural schemes makes these techniques not easily applicable to buildings, due to inherent problems related to the location and the extent of damage, the sensitivity of the dynamic response to damage, the choice of damage indexes to be used, the sensors' location, etc.On the other hand, the modern seismic capacity design of buildings in earthquake‐prone areas tends to locate dissipative zones in well‐determined portions of structures (CEN, European Committee for Standardization, EN 1998‐1. Eurocode 8: Design of Structures for Earthquake Resistance. Part 1: General Rules, Seismic Actions and Rules for Buildings, European Community, Brussels, Belgium, 2005); thus, the application of vibration‐based damage detection techniques to earthquake‐resistant structures seems to be very promising even if nowadays there are only few studies on these arguments.The present paper reports the experiences of a vibration‐based damage identification study applied to a steel–concrete composite frame structure, suitably designed to be high ductile according to Eurocode 8 and localizing the seismic energy dissipation in the beam‐to‐column joints. The structure was subjected to series of pseudo‐dynamic (PsD) and cyclic tests with increasing peak ground acceleration at the European Laboratory for Structural Assessment of Joint Research Centre at Ispra (VA, Italy). The damaging phenomena, caused by PsD tests, were assessed and quantified by means of a multi‐level vibration‐based approach suitably designed in order to evaluate the changes in the global dynamic structural response and to experimentally estimate the reduction in joint stiffness. Copyright © 2008 John Wiley & Sons, Ltd.

The work described herein was conducted within the framework of an ongoing research program on the dynamic behavior of the Tower of Matilde, the bell tower of the Cathedral of San Miniato, Pisa, Italy, an interesting case study for its current structural arrangement and the modifications it has undergone over the centuries. This is Part 2 of a more extensive publication dealing with the results of such research and presents the experimental measurements and analyses conducted in order to determine the motion of the tower subjected to the actions produced by the motion of the two largest of its six bells. The numerical and analytical models adopted to interpret the experimental results, from the most elaborate and complex to the simplest ones, have all confirmed that the third harmonic frequency of oscillation of the largest bell is very close to the first eigenfrequency of the bell tower structure. Such studies moreover have enabled making a first approximation of the values of the global mechanical param...

The work described herein was conducted within the framework of an ongoing research program on the dynamic behavior of the Tower of Matilde, the bell tower of the Cathedral of San Miniato, Pisa, Italy, an interesting case study for its current structural arrangement and the modifications it has undergone over the centuries. This paper (Part I) details the experimental analyses performed in order to obtain an accurate measure of both the motion of the tower’s bells and, consequently, the time function of the dynamic actions transmitted to the tower during their motion. We then demonstrate how it is possible to arrive at an accurate, even though approximate, analytical description of both the bells’ motion and their actions by means of only a few experimental measurements and a simple mechanical model (also called in the following additional mass model).