Vaiana, Nicolò (2017) Mathematical models and numerical methods for the simulation of the earthquake response of seismically base-isolated structures. [Tesi di dottorato]

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Tipologia del documento:	Tesi di dottorato
Lingua:	English
Titolo:	Mathematical models and numerical methods for the simulation of the earthquake response of seismically base-isolated structures
Autori:	Autore Email Vaiana, Nicolò nicolovaiana@outlook.it
Data:	5 Aprile 2017
Numero di pagine:	302
Istituzione:	Università degli Studi di Napoli Federico II
Dipartimento:	Strutture per l'Ingegneria e l'Architettura
Dottorato:	Ingegneria strutturale, geotecnica e sismica
Ciclo di dottorato:	29
Coordinatore del Corso di dottorato:	nome email Rosati, Luciano rosati@unina.it
Tutor:	nome email Serino, Giorgio [non definito] Filippou, Filip C. [non definito]
Data:	5 Aprile 2017
Numero di pagine:	302
Parole chiave:	base-isolated structures; mathematical models; numerical methods
Settori scientifico-disciplinari del MIUR:	Area 08 - Ingegneria civile e Architettura > ICAR/08 - Scienza delle costruzioni Area 08 - Ingegneria civile e Architettura > ICAR/09 - Tecnica delle costruzioni
Depositato il:	23 Apr 2017 19:42
Ultima modifica:	13 Mar 2018 09:15
URI:	http://www.fedoa.unina.it/id/eprint/11530
DOI:	10.6093/UNINA/FEDOA/11530

Abstract

Seismic base isolation has become a widely accepted technique for the earthquake protection of buildings and bridges. The concept of base isolation is quite simple: the introduction of a flexible base isolation system between the foundation and the structure allows one to move the period of the latter away from the predominant period of the ground motion with the benefit of reducing floor accelerations, story shears and interstory drifts. The solution of the nonlinear dynamic equilibrium equations of seismically base-isolated structures adopting a conventional non-partitioned solution approach, characterized by the use of an implicit single-step time integration method employed with an iteration procedure, and the use of existing nonlinear mathematical models, such as differential equation models, to simulate the dynamic behavior of seismic isolators, can require a significant computational effort. This thesis deals with the development of five mathematical models and a numerical time integration method for the nonlinear time history analysis of base-isolated structures with the aim of simulating the nonlinear dynamic behavior of seismic isolators at both small and large displacements and reducing numerical computations, making the nonlinear dynamic analysis almost as fast as a linear dynamic analysis. The dissertation is organized into eight chapters. Chapter 1 illustrates the objective and scope of the study. Chapter 2 deals with the modeling of seismically base-isolated structures: starting from the description of the 3d discrete structural model of such structures, the superstructure and the base isolation system modeling are presented and then the dynamic equilibrium equations are formulated. In Chapter 3, two common types of seismic isolators, namely, elastomeric and sliding bearings, are described. Furthermore, the results of an extensive series of experimental tests, conducted at the Department of Industrial Engineering of the University of Naples Federico II on a Recycled Rubber-Fiber Reinforced Bearing (RR-FRB) and four Wire Rope Isolators (WRIs), are presented. Chapter 4 is concerned with the modeling of seismic isolators. After a detailed description of widely used differential equation models, namely, Bouc-Wen Model (BWM), Modified Bouc-Wen Model (MBWM), and 2d Bouc-Wen Model (2d BWM), the proposed mathematical models, that is, Nonlinear Exponential Model (NEM), Advanced Nonlinear Exponential Model (ANEM), Parallel Model (PM), Advanced Parallel Model (APM), and 2d Parallel Model (2d PM), are presented. The chapter concludes with comparisons between the described differential equation models and the proposed ones. In order to demonstrate the validity of the proposed mathematical models, in Chapter 5, the results predicted numerically are compared to those obtained experimentally from horizontal dynamic tests performed on a RR-FRB and four WRIs, as described in Chapter 3. Chapter 6 describes a conventional non-partitioned solution approach developed specifically for seismically base-isolated structures and presents the proposed partitioned solution approach. After the description of the Mixed Explicit-Implicit time integration Method (MEIM), a procedure to evaluate the critical time step is illustrated and then four numerical applications are presented to demonstrate the accuracy and the computational efficiency of the proposed method. Chapter 7 presents a numerical application in order to show the significant reduction of the computational effort due to the use of the MEIM and NEM. Finally, in Chapter 8, conclusions are presented, as well as considerations and suggestions for further research and future developments.

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