Earthquake isolation method with variable natural frequency

By Federico Bartolozzi

Questo studio monografico si occupa di ‘Isolamento Sismico’, che rappresenta – com’è noto – un aspetto tecnico ben specifico ed anche rilevante dell’Ingegneria Sismica. Desidero qui mettere in evidenza che la motivazione, per la quale mi sono deciso di pubblicare questo saggio, non è solo di natura divulgativa, ma anche e soprattutto di concreta applicabilità. Infatti, per quanto il metodo descritto sia stato già numerose volte proposto a Conferenze Internazionali sull‘Ingegneria Sismica – sia come sommario che come memoria, ricevendo il più ampio consenso alla presentazione e alla pubblicazione nei relativi Atti congressuali da parte dei Comitati di Esperti di valutazione – tuttavia esso è rimasto ancorato alle pagine degli Atti senza riuscire ad emergere per le sue prerogative di efficacia, semplicità e concretezza operativa. Mi auguro così che, con l’attuale pubblicazione, destinata per ovvi motivi culturali ad una classe ben selezionata di specialisti nel campo dell’Isolamento Sismico, il metodo descritto possa raggiungere la finalità auspicata, di uscire cioè dall’ambito strettamente di stallo in cui si è trovata per vari anni per aspirare al raggiungimento del suo scopo fondamentale, cioè l’applicazione per pubblica utilità.

Quanto sopra, però, non senza sottoporre il metodo d’isolamento proposto ad ulteriori verifiche analitiche e, soprattutto, ad indispensabili prove sperimentali. Il testo è in lingua inglese ed in lingua italiana.

• Language: English
• Publisher: Youcanprint Self-Publishing
• Release date: Jan 22, 2016
• ISBN: 9788893323208

Book preview

Daffy!

PREFACE

The monographic study, contained in this publication, is interested in ‘Earthquake Isolation’, which represents – as everybody knows - a well specify and also considerable technical aspect of Seismic Engineering.

Without entering the heart of the proposed methodology, of which instead it is diffusely written later on, I wish to point out that the motivation, for which I decided to publish this essay, is not only of popular nature, but also and above all of concrete applicability.

In fact, as far as the described method was already for several times proposed to International Conferences on Earthquake Engineering – both as a summary and as a paper, receiving the widest assent to the presentation and to the publication in the relative congress Acts from the Experts’ Committees for the evaluation - however it remained ‘confined’ to the pages of the Acts without emerging in order to one’s prerogatives of effectiveness, simplicity and operating concreteness.

So I hope that, with the current publication, destined for obvious cultural reason to a well selected class of specialists in the field of the Earthquake Isolation, the described method can reach the desirable aim, that is to come out of the ambit tightly of stalemate in which it has been for several years for aspiring to the reaching of its fundamental purpose, that is the application for public usefulness.

The above, however, not without in advance submitting the method of proposed isolation to further analytical checks and, above all, to indispensable experimental tests.

Heartfelt thanks go to Mrs Marianne Gulstad Pedersen, ‘Project Manager’ at ‘Publizon A/S’, Ǻrhus C, Denmark, who for some years takes care of my publications with diligence and professionalism.

The Author

Italy, 2009

METHOD’S ABSTRACT

The proposed method is based on the following operations:

• interruption of the continuity between the construction and the foundation-soil complex;

• self-centring of the construction after an earthquake.

Through an elastic deformation, every bearing is able to offset automatically one’s variation of rigid deformation, due to the horizontal component of the motion.

The construction remains almost motionless with respect to the foundation-soil complex, which moves.

The vertical motion of the soil, due to the sussultatory shock, only partially changes the construction’s behaviour, in the sense that it, also remaining almost motionless with respect to the horizontal translatory motion, is generally submitted to a vertical translatory motion of small entity generally, but also to the possibility of the resonance.

In order to avoid this danger, the bearings have the capacity to make change the vertical natural frequency of the construction by auxiliary springs, which increase the action of the main springs during the emergency situation, characterized by an interval of vertical seismic frequency, including the between resonance one.

INTRODUCTORY NOTES ON THE SEISMIC ISOLATION

1 PREAMBLE

It is well known that the earthquakes always have harmful - and sometimes devastating – effects on the constructions and, therefore, on the living.

The phenomenon concerns wide areas of the Earth and some countries adopt - already for a long time – special constructional systems in seismic area, based on the application of a suitable regulation.

Instead, other countries apply also the methodology of the seismic isolation, using elastomeric insulators.

Now, without entering the heart of the dynamics of the seismic phenomena, it is useful to make evident that the so-called anti-seismic constructions, planned for bearing - besides the usual stresses – also the ones due to the sussultatory and, especially, undulatory shocks, have a considerable limit concerning the construction’s height.

However, where this limit does not exist - as in the case of constructions with a structure in either normal or pre-stressed reinforced concrete or steel - an increase in the cost of the construction occurs, due to a over-dimensioning of the structural elements.

The constructions, which adopt the isolation system with elastomeric