Papers by Giada Gasparini
Proceedings of the 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015)
The SHM has a very important role in the diagnostic process of cultural heritage buildings, for w... more The SHM has a very important role in the diagnostic process of cultural heritage buildings, for which generally, the identification of the structural behaviour is affected by many uncertainties. The use of ambient vibration tests allow to characterize the dynamic behavior of the structures, providing also information to validate numerical modeling. Moreover, continuous monitoring allows to record streams of seismic ambient noise for long time intervals in order to retrieve the temporal evolution of the structural characteristics and to highlight the response of them to seasonal variations of environmental parameters (temperature, humidity) and the stresses due to the human activities or to the rapid (daily or weekly) changes in the ambient conditions (temperature, wind velocity and intensity). Three seismic monitoring experiments were performed in 2012, 2013 and 2014 at the Asinelli and Garisenda Towers, two masonry leaning tower built in the center of Bologna (Italy). The aim of this work is to present the results of the analysis of the data recorded by seismic monitoring that allowed to clearly identify the normal modes of oscillation of the Two Towers. A particular attention was devoted to the identification of transient that, propagating inside the structures, produce beating effects at the top stations. Implication to the structural modeling and to the State of health monitoring are discussed.
The Asinelli tower located in the city center of Bologna (northern Italy), whose construction beg... more The Asinelli tower located in the city center of Bologna (northern Italy), whose construction began at the beginning of the XII century, is one of the tallest masonry towers in Italy, reaching a height of almost 100 m. Due to the large amount of stress induced at the basement, it experienced some soil settlement which leaded to a tilt toward West of 2.23 m. For its structural configuration, the tower appears prone to seismic-induced damages and, therefore, an assessment of its dynamic properties is of primary importance in order to evaluate its own safety against seismic actions. In the present paper, first an assessment of the main dynamic properties of the Tower (i.e. natural frequencies and mode shapes) is carried out by crosscorrelating the response of different structural models (from simple continuum analytical models to more complex finite element models) with the results of a continuous dynamic monitoring performed in 2012 and 2013-2014 by the Italian Institute of Geophysics...
La presente memoria presenta un metodo diretto per il dimensionamento di strutture a telaio dotat... more La presente memoria presenta un metodo diretto per il dimensionamento di strutture a telaio dotate di smorzatori viscosi che permette: (1) di dimensionare la taglia degli smorzatori viscosi da inserire nella struttura in modo da soddisfare un determinato obiettivo prestazionale; (2) di stimare le massime sollecitazioni negli elementi strutturali attraverso l’inviluppo di due analisi statiche equivalenti.
In the present paper the method of equivalent static forces (or lateral force method), widely use... more In the present paper the method of equivalent static forces (or lateral force method), widely used in earthquake engineering especially in the phase of preliminary design of regular framed structures, is extended to the case of structures equipped with added viscous dampers. The method is grounded on basic principles of structural dynamics and, under certain assumptions, allows to estimate the maximum damper forces and maximum internal actions in the structural members due to the design earthquake through analytical formulas only. In order to show its effectiveness, the method is finally applied for the retrofit through external steel “dissipative towers” (namely steel moment-resisting frames equipped with interstorey viscous dampers) of a 16-storey reinforced concrete building.
Within a Displacement-Based Seismic Design approach, the seismic input is described through displ... more Within a Displacement-Based Seismic Design approach, the seismic input is described through displacement design spectra. Until now, these spectra are commonly obtained from the corresponding pseudo-acceleration design spectra, widely used in a Force-Based Seismic Design approach, and are therefore affected by uncertainties regarding the schematization of pseudo-acceleration spectra. In this paper, the relationships between earthquake ground motion parameters and displacement spectra have been faced starting afresh to provide an updated schematization of the spectra which consciously accounts for the most representative ground motion parameters. First, in order to identify the fewest independent parameters which best describes the seismic input, for each record, different earthquake ground motion parameters have been computed and compared to each other through correlation analyses. The results indicate that the parameters Peak Ground Acceleration (PGA), Peak Ground velocity (PGV) and...
As recently also recalled by Priestley in a keynote lecture given at the 1st ECEES, Geneve 2006, ... more As recently also recalled by Priestley in a keynote lecture given at the 1st ECEES, Geneve 2006, the emphasis on Performance-Based Seismic Design has forced a re-examination of the methodology employed in the seismic design of structures. Skipping all details, direct Displacement-Based Design of structures has opened up new possibilities for the structural engineer in terms of conceiving and dimensioning a structural system which offers optimized seismic performances. Focusing directly on the non-linear behavior of the lateral-resisting elements of a given building structure, the secant stiffness approach allows “logical choices regarding the force distribution” between different lateral-resisting elements. This paper aims at investigating how these logical choices concerning strength, stiffness and ductility of lateral-resisting elements can be made. In general, the lateral-resisting system of a given building structure can be seen as composed of a series of single lateral-resistin...
This paper proposes an innovative methodology for the seismic design of flat-bottom silos contain... more This paper proposes an innovative methodology for the seismic design of flat-bottom silos containing granular, grain-like material. In the general issues concerning the actions provoked by earthquake ground motion on the walls of flat-bottom grain silos, the assessment of the horizontal actions seems to be of particular interest. Up to date, the horizontal actions due to the seismic event are usually evaluated under the hypotheses (i) of stiff behavior of the silo and its contents and (ii) that the grain mass corresponding to the whole content of the silo except the base cone with an inclination equal to the internal friction angle of the grain is balanced by the horizontal actions provided by the walls (supposing that the seismic force coming from the base cone is balanced by friction and does not push against the walls). The analyses reported here, which are developed by simulating the earthquake ground motion with constant vertical and horizontal accelerations, lead to the subdiv...
In recent years, the seismic behaviour of reinforced concrete bearing panels structures has been ... more In recent years, the seismic behaviour of reinforced concrete bearing panels structures has been the object of several research works. This paper presents a summary of the results obtained in a wide experimental/analytical correlation campaign carried out as a joint effort between the Universita di Bologna and the EUCENTRE labs in Pavia. This effort was devoted at the assessment of the seismic performances of lightly reinforced concrete bearing panels. The panels are made using leave in place wood-concrete caisson blocks. In order to obtain a correct characterization of seismic behavior (stiffness, strength, ductility) of such panels, a number of tests were performed both upon two dimensional (3.0 m by 3.0 m) panels and upon 6 meter tall H shaped substructure. In the experimental tests a number of horizontal loading cycles were imposed to the structures, while the vertical load was kept constant The results obtained show a good agreement between the experimental data and their analy...
Due to the recent code developments and of the growing attention given to the seismic safety of s... more Due to the recent code developments and of the growing attention given to the seismic safety of structures, especially after the last Italian earthquakes, the analysis and verification of existing building heritage have become a fundamental tool to assess the seismic vulnerability, to safeguard human lives and to plan structural interventions. The Italian building heritage is characterized by high complexity and heterogeneity, both from architectural and structural points of view. It consists in structures built in various ages, placed both in the city center and in the outskirts, erected by different structural techniques and with different uses. For all these reasons, it is important to define a methodology to obtain comparable results to plan the future activities of risk analysis, assessment and management. Before providing a result about the level of safety of an existing building, it is essential to acquire the right knowledge and to choose a method of analysis that can captur...
The non-linear response of in-plan asymmetric systems has been extensively studied since the 1980... more The non-linear response of in-plan asymmetric systems has been extensively studied since the 1980s. Nevertheless, most of the research effort has been devoted to the study of specific asymmetric buildings and, even though relevant progresses have been achieved in the understanding of the complex translational-to-torsional coupled response of such systems, a full knowledge of the seismic behavior of planar asymmetric buildings is still not satisfactory. To provide results of more general validity, the authors developed a wide parametric study to obtain trends of the response parameters such as maximum displacement and rotations developed by linear and non-linear one-storey asymmetric structures under earthquake ground motion. Based on the results of the parametric study, in the present paper correction factors for the displacement response spectrum are presented.
Plan asymmetric (eccentric) structures, characterized by non coincident centre of mass and centre... more Plan asymmetric (eccentric) structures, characterized by non coincident centre of mass and centre of stiffness, when subjected to dynamic excitation, develop a coupled lateral-torsional response that may increase their local peak dynamic response. In order to effectively apply the performance-based design approach to seismic design, there is a growing need for code oriented methodologies aimed at predicting deformation parameter. In this respect, for plan asymmetric structures, estimating maximum displacements at different locations in plan, especially at the perimeter, requires an evaluation of the floor rotations. The ability to predict floor rotations can be also useful to extend simplified procedures of seismic design, such as push-over analyses, to plan irregular structures. In this paper, starting from a closed-form formulation identified in previous re-search works by the authors, an estimation of the maximum rotational response of one-storey asymmetric systems under seismic ...
The Asinelli Tower, built at the end of the 12th century, is one the main symbol of the town of B... more The Asinelli Tower, built at the end of the 12th century, is one the main symbol of the town of Bologna and a valuable historical heritage of the Medieval age of the entire Italy. For its structural configuration, the tower appears prone to seismic damages and, therefore, an assessment of its dynamic properties is of primary importance in order to predict the tower seismic response. In the present paper, based on the results of limited material tests, the mechanical and dynamic properties of the tower are analysed through the development of models of increasing complexity. First, models for the evaluation of the main mechanical properties of the masonry (such as the elastic modulus, the Poisson's coefficient, the compressive and shear strengths) are compared in order to validate the experimental results. Then, different structural models of the tower (from simple continuum analytical models to more complex finite element models) are developed. The analytical and numerical result...
The Cathedral of Modena, built at the end of the XI century, is one of the most important example... more The Cathedral of Modena, built at the end of the XI century, is one of the most important examples of the Romanesque art in Italy. In 1997, the monument was declared as “UNESCO World Heritage” site. The first phase for a meaningful interpretation of the structural behaviour of such a complex monument is the static analysis, which first requires the study of the loads path to the ground. The objective of the present paper is to study the structural behaviour of the Modena Cathedral through a multidisciplinary integrated approach, which makes use of the “survey” as a tool able to provide a comprehensive knowledge of the building. The “survey” is here intended as the integration between: (i) the historical reconstruction of the main interventions and modifications of the structural system over the years; (ii) the materials characterization, (iii) the topographic survey of the geometry of the superstructure and the evolution of the settlements; (iv) materials state of degradation. The i...
Eccentric structures, characterized by non coincident center of mass and center of stiffness, whe... more Eccentric structures, characterized by non coincident center of mass and center of stiffness, when subjected to dynamic excitation, develop a coupled lateral-torsional response that may increase the local peak dynamic response of such a structure: this behaviour becomes particularly important for seismic isolated structures for which large displacements are developed in the isolators. The coupled lateraltorsional response can be estimated only through a three-dimensional analysis which is specifically carried out for a single structure subjected to a determined dynamic input. In this paper the authors present the analytical formulation of a simplified method which allows to understand, predict and govern the global trend of one-storey eccentric structures to develop a torsional response to dynamic inputs through the identification of a system key parameter named “alpha”. This parameter can be easily used to effectively estimate the maximum rotational response of a given eccentric sy...
In countries directly affected by seismic phenomena, the assessment of vulnerability and seismic ... more In countries directly affected by seismic phenomena, the assessment of vulnerability and seismic hazard throughout the territory plays a very important role, in order to minimize seismic effects on the population. Furthermore to effectively apply the performance based design approaches to seismic design it is necessary to accurately identify appropriate Intensity Measures (IM). This paper aims at illustrating a method for determining the probability functions (PDF and/or CDF) of the peak ground acceleration (PGA) and peak ground velocity (PGV) due to the seismic action at a specific site, over a given observation time, which, for Performance Based Seismic Design purposes can be used as vectorial Intensity Measures. The method is based upon the Cornell widely upheld methodology (1968), specifically updated to take into account the latest contributions in geophysics developed for the Italian territory. This methodology assimilates the occurrence of seismic events to Poisson processes ...
IABSE Congress, New York, New York 2019: The Evolving Metropolis
The present work explores the possibilities of 3D printing applied to structural engineering fiel... more The present work explores the possibilities of 3D printing applied to structural engineering field to create innovative design and optimized shapes. By means of Wire-and-Arc Additive Manufacturing, structural members are manufactured by placing layer upon layer of welded steel material in an automated process. Additive Manufacturing, thanks to the theoretical freedom in the geometrical shapes that can be obtained, open completely new possibilities for designers. On the other hand, specific aspects related to material properties and geometrical irregularities characteristics of such innovative manufacturing processes have to be properly considered in the design phase. Along with digital design tools recently developed and applied in architecture and construction for the realization of new shapes and forms through parametric design, the work presents a new structural shape for diagrid columns to obtain structurally optimized forms adapted to be efficiently realized by means of Wire-an...
Masonry towers represent an important portion of the cultural heritage in Italy. Their preservati... more Masonry towers represent an important portion of the cultural heritage in Italy. Their preservation and maintenance through intervention techniques able to guarantee their historical authenticity is essential. Effective structural interventions can be planned only after a deep knowledge of the building and of its structural behaviour. For this purpose, Structural Health Monitoring (SHM) plays a crucial role in providing information both on the dynamic properties of the structures and the damage caused by earthquakes or impacts. SHM can be used either immediately after the event or to monitor the long-term deterioration due to weathering and human use. In the 2011, a static Structural Health Monitoring system (SSHM) was installed in the Two Towers (Asinelli and Garisenda towers), masonry medieval towers located in Bologna, Italy. The data gathered from a SSHM system may be used in conjunction with structural analysis to identify the main vulnerabilities associated with the relevant h...
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Papers by Giada Gasparini