Tesi PhD Mastrovito.pdf

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Item Type: Tesi di dottorato
Lingua: English
Date: 31 March 2016
Number of Pages: 106
Institution: Università degli Studi di Napoli Federico II
Department: Ingegneria Civile, Edile e Ambientale
Scuola di dottorato: Scienze fisiche
Dottorato: Rischio sismico
Ciclo di dottorato: 28
Coordinatore del Corso di dottorato:
Magliulo, GennaroUNSPECIFIED
Petrone, CrescenzoUNSPECIFIED
Date: 31 March 2016
Number of Pages: 106
Uncontrolled Keywords: industrial facilities, seismic behavior, nonlinear analyses, shear capacity, displacement control point, flexible diaphragm.
Settori scientifico-disciplinari del MIUR: Area 08 - Ingegneria civile e Architettura > ICAR/09 - Tecnica delle costruzioni
Date Deposited: 14 Apr 2016 19:47
Last Modified: 31 Oct 2016 11:52


The thesis is focused on the seismic behavior of existing RC precast buildings. This structural typology has been characterized by a very quick development since the time of the First World War, due to the reduction of construction time and to the possibility of a better check on each structural element produced in the factories through industrial processes. The main activities carried out in RC precast facilities are certainly associated to the industrial sector, thanks to large spans and high usable height. Therefore, the concept of loss for these buildings is not only related to human lives or to the repair costs, but also to the costs due to the interruption of the activities carried out in them. Emilia earthquake, occurred in May 2012, has sadly demonstrated the inadequacy of industrial facilities in absorbing horizontal seismic forces, causing deaths and injuries, as well as a huge economic loss. The earthquake consequences on industrial buildings are presented in the first part of the thesis, through the description of the reported damage of some facilities inspected after the earthquake. For each industrial building, the main geometrical issues are analyzed, along with the description of the principal structural elements. Among the investigated buildings, two industrial facilities located in Mirandola (MO), a few kilometers away each other, are considered as case-study buildings. The first structure reported the partial collapse due to the breaking of two central columns, with the fall of beams and tiles. The second facility reported only minor damages, such as the fall of a corner cladding element. A tridimensional numerical model has been implemented in order to first verify the seismic performance of the first building, according to the Italian code. Thus, nonlinear static and dynamic analyses have been performed. The N2 method by Fajfar was used, taking into account the flexibility of the roof. Therefore, two different methods for the definition of the displacement control point are followed: one is based on geometrical considerations (proposed method); the other is based on the procedure proposed by Casarotti in its Adaptive Capacity Spectrum Method. At the end of each analysis, both fragile and ductile mechanisms have been checked. The most suitable capacity models have been then selected. In particular, columns shear capacity evaluation have been conducted through the study of the models available in the technical literature. Then, rotations at the columns base have been investigated, as well as the frictional behavior of the tiles-to-beams and beams-to-columns connections. Nonlinear dynamic analysis gave less conservative results than the nonlinear static analysis. In both cases, the obtained results show the frictional connections to be inadequate to adsorb the seismic forces. Comparison between the nonlinear static analysis results obtained following both formulations for the control point definition demonstrated the validity of the proposed method. In order to validate the model, nonlinear dynamic analyses have been carried on using as input signals the acceleration components recorded by one of the Italian RAN stations. The comparison between experimental and theoretical results have been conducted in order to verify the numerical model capability to predict the real damages suffered by the building. For this reason, the model has been completed taking into account the crane, positioned as evidenced by the photos taken shortly after the earthquake. The numerical model has proven to be capable to predict the real damages reported by the building, showing the shear failure of the most stressed columns. In particular, the crane presence has proved to be fundamental in order to justify the columns shear failure. Furthermore, the theoretical-experimental comparison has corroborated the validity of the adopted models. The same modeling issues have been adopted implementing a tridimensional model of the second case-study building. Corresponding columns belonging to both structures have been considered in order to study the different behavior of the facilities. From the comparison it is shown that the first building is subjected to higher shear forces due to larger masses. Furthermore, the vertical component of the earthquake has significantly affected the columns shear capacity, reducing it in correspondence with the minimum axial load values. Finally, a tridimensional model of the second facility taking into account the horizontal cladding panels have been implemented, in order to study their influence on the vibration periods, comparing the seismic response with the bare model one. Results show that the choice, in the numerical model, of the panels constraint typology affects decisively the vibration periods values. In particular, the choice of rigid constraints reduces significantly all the vibration periods; the use of semi rigid constraints results in a reduction of the higher modes vibration periods.

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