The Tracking of Modal Parameters for a Reinforced Concrete Building During Low-Medium Intensity Earthquakes

Abstract

This paper presents the results of the dynamic monitoring carried out on a school building in central Italy during the seismic sequence following the first main shock of the 2016 Central Italy earthquake. The building is located in the historical centre of Camerino and consists of a reinforced concrete frame structure with masonry infill walls. The school, dating back to the 60s, underwent seismic retrofit in 2013 through the construction of 2 dissipative towers, a recent patented system for seismic protection of buildings. In August 2016 a dynamic monitoring system was installed on the building, positioning an array of accelerometers both on the top two floors of the structure and on the foundation level; this made it possible to record the building response to the aftershocks that occurred during the monitoring period, and the corresponding seismic input. The dynamic characteristics of the structure during the monitoring period are identified starting from the response of the structure subjected to the seismic swarm following the main event, and to the environmental vibrations between two subsequent events. Although during the monitoring days the building did not suffer any damage, the response of the structure proved to be nonlinear and strongly dependent on the amplitude of the accelerations to which it was subjected; in this work, a procedure to linearize the structural response and carry out the dynamic identification in terms of modal parameters starting from the nonstationary response of the structure is proposed.

Analytical Assessment of Seismic Damage and Usability of Rc Residential Buildings by Period Elongation

“…Based on the above discussion, it can be simply concluded that, in general, the measure of the period elongation can be assumed as a measure of the damage state of the building: the more the elongation, i.e., the higher the Tin/Tel ratio, the higher the damage state attained by the building. Despite many studies have been carried out on this topic ( [1][2][3][4][5][6][7][8][9][10][11][12] among others), an explicit relation between the Damage State (DS) of 3D RC buildings modelled and analyzed as nonlinear multi-degree-of-freedom system and in presence of infill walls and their period elongation has never been derived. Note that this kind of relations may be also useful to assess, by means of ambient vibration tests, the usability of buildings for which the usability judgment after earthquake may be uncertain only based on visual inspection.…”