Papers by Author: Davide Lavorato

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Authors: Raffaello Bartelletti, Gabriele Fiorentino, Giuseppe Lanzo, Davide Lavorato, Giuseppe Carlo Marano, Giorgio Monti, Camillo Nuti, Giuseppe Quaranta, Nunziante Squeglia
Abstract: Understanding the structural behavior of heritage buildings is usually a very complicated task because they typically present complex deterioration and damage patterns which cannot be fully evaluated by means of visual inspections. Moreover, the reliability of such constructions largely depends on different materials, structural components and details, the health of which is often unknown or affected by great uncertainties. In this regard, the experimental dynamic testing of heritage buildings and monuments subjected to ambient vibrations has become a valuable tool for their assessment because of the minimum interference with the structure. Traffic-induced vibrations are not always a feasible dynamic load for monumental buildings due to their very low intensity or owing to existing restrictions to road and rail traffic. On the other hand, the analysis of the experimental response under earthquakes can lead to more relevant information about the dynamic behavior of historic constructions, provided that the structure is equipped with a permanent sensor network. Within this framework, the present work illustrates preliminary results carried out from time and frequency domain analyses performed on the experimental dynamic response of the leaning tower of Pisa using seismic records. The main dynamic features of the monument have been identified, and then examined taking into account the seismic input and the soil-foundation-structure interaction.
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Authors: Raffaello Bartelletti, Gabriele Fiorentino, Giuseppe Lanzo, Davide Lavorato, Giuseppe Carlo Marano, Giorgio Monti, Camillo Nuti, Giuseppe Quaranta, Fabio Sabetta, Nunziante Squeglia
Abstract: The most recent studies about the seismic behavior of the leaning Tower of Pisa that consider the soil-foundation-structure interaction date back to twenty years ago. From 1999 to 2001, the foundation of the monument was consolidated by means of under-excavation and the "Catino" at the basement was rigidly connected to the foundation. Meanwhile, significant progresses have been made in the field of earthquake engineering. Therefore, the need exists to assess the dynamic behavior of the Tower in light of the novelties occurred in the past decades. In the present study, the mechanical characteristics of the foundation have been calibrated comparing the outcomes of the experimental dynamic monitoring with the results of the finite element analysis performed on a simple but effective model. The scenario earthquakes for return periods equal to 130 years and 500 years are also presented.
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Authors: Zhi Hao Zhou, Camillo Nuti, Davide Lavorato, Alessandro Vittorio Bergami
Abstract: In this paper, a new model named as “brace01” for steel brace is presented on the basis of experimental data on different types of steel struts. This model shows a peasant capability in the structural analysis of Concentrically Braced Frames. A brace is idealized as a pin-ended member with a plastic hinge located at its midspan. This expression of the model is proposed by combining the mechanical properties and the phenomenological characters. The model for steel brace is implemented in an effective way in OpenSees. The calibration of the material model is done by comparing the numerical curves generated by the numerical model with the experimental curves of pin-ended steel braces. The new model is proved applicable to practical Concentrically Braced Frame.
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Authors: Zhi Hao Zhou, Camillo Nuti, Davide Lavorato
Abstract: The material model for reinforcing bar takes a very important role in the seismic analysis of reinforced concrete structures. The seismic performance of the structural elements such as column will be overestimated if the inelastic buckling is not incorporated in the material model. The Monti-Nuti Model could consider the buckling effect properly. The critical slenderness and anisotropy were discussed which has an important effect on the seismic behaviors of the reinforcement. Then this paper proposed a modified Monti-Nuti Model for different types of reinforcing bars, such as carbon steel reinforcement and stainless steel reinforcement including inelastic buckling. Subsequently, the implementation of the modified Mont-Nuti Model in OpenSees was introduced. Through validating with the experimental curves, the numerical curves generated by the modified model verified its capability.
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Authors: Davide Lavorato, Camillo Nuti, Bruno Briseghella, Silvia Santini, Jun Qing Xue
Abstract: A rapid repair and retrofitting technique for reinforced concrete (rc) Chinese existing bridges damaged by a strong earthquake, is proposed and tested. These bridges were designed according to Chinese codes [1] [2] [3] but with insufficient transversal steel reinforcement. The damaged rebar and concrete parts were replaced by new bar systems and concrete cast respectively. Finally, a C-FRP wrapping was applied to increase the insufficient shear strength and to guarantee the necessary ductility in plastic hinge. This repair technique is an upgrade of the one tested with very good results during a previous experimental research [4] on bridge designed according to old Italian code [5] without proper seismic details. A new bar system assures that plastic dissipation is distributed in plastic hinge only. Some pier specimens (in scale 1:6) were built with and without the new bar systems. These specimens were tested by cyclic tests at Fuzhou University lab (China) to evaluate the effectiveness of the intervention.
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