Highway bridges function as the arteries of our society. Hence, it is essential that they remain operational following an earthquake. Unfortunately, a significant number of bridges worldwide, including in Canada, were constructed prior to the development of modern seismic design provisions. In many cases, such bridges are expected to perform poorly during earthquakes. According to a report published in 2000 by Ministry of Transportation of Ontario (MTO), in eastern Ontario alone, there are over 70 bridges that are structurally deficient. Current methods to retrofit these bridges to bring them into compliance with the existing codes would entail substantial structural modifications. Examples of such modifications include the replacement of existing rocker bearings with elastomeric bearings, structural strengthening of piers, and enlarging the bearing surfaces. These methods involve substantial cost, effort, and materials. An alternative means to retrofit structurally deficient bridges is investigated in this thesis. This method involves using a combination of elastomeric bearings and fluid dampers to retrofit highway bridges. In principle, these devices work in the same way as shock absorbers in automobiles. They absorb shock and dissipate the vibration energy to the environment as heat. In the case of bridges, earthquakes impart the shock to the structure. Before these devices can be implemented in practice, there are many issues that need to be understood with respect to their performance and modelling. Moreover, a comparative assessment between popular retrofit options employing isolation systems needs to be undertaken to verify and provide a benchmark to assess their performance. The Mississippi River Bridge near Ottawa is chosen as a test structure to conduct this study. This bridge already contains an advanced isolation system, and has an extensive documentation available for modelling and verification. Various retrofit options will be studied and compared with the existing isolation design for this bridge. In all cases, the effect of soil-structure interaction is included. A comprehensive set of performance indices are used to evaluate the performance of various retrofit options. All the models are constructed in the open source software, OpenSees. The research demonstrates that the proposed approach is a viable retrofit method for highway bridges. Moreover, compared to advanced isolation systems, retrofit using elastomeric bearings with viscous dampers was successful on transferring lower loads to the substructure, and resulted in lower superstructure displacements. Though this study involved one bridge, it has provided a computational test bed to perform further studies and has provided valuable insight into the modeling and performance of retrofit solutions.

Highway bridges function as the arteries of our society. Hence, it is essential that they remain operational following an earthquake. Unfortunately, a significant number of bridges worldwide, including in Canada, were constructed prior to the development of modern seismic design provisions. In many cases, such bridges are expected to perform poorly during earthquakes. According to a report published in 2000 by Ministry of Transportation of Ontario (MTO), in eastern Ontario alone, there are over 70 bridges that are structurally deficient. Current methods to retrofit these bridges to bring them into compliance with the existing codes would entail substantial structural modifications. Examples of such modifications include the replacement of existing rocker bearings with elastomeric bearings, structural strengthening of piers, and enlarging the bearing surfaces. These methods involve substantial cost, effort, and materials. An alternative means to retrofit structurally deficient bridges is investigated in this thesis. This method involves using a combination of elastomeric bearings and fluid dampers to retrofit highway bridges. In principle, these devices work in the same way as shock absorbers in automobiles. They absorb shock and dissipate the vibration energy to the environment as heat. In the case of bridges, earthquakes impart the shock to the structure. Before these devices can be implemented in practice, there are many issues that need to be understood with respect to their performance and modelling. Moreover, a comparative assessment between popular retrofit options employing isolation systems needs to be undertaken to verify and provide a benchmark to assess their performance. The Mississippi River Bridge near Ottawa is chosen as a test structure to conduct this study. This bridge already contains an advanced isolation system, and has an extensive documentation available for modelling and verification. Various retrofit options will be studied and compared with the existing isolation design for this bridge. In all cases, the effect of soil-structure interaction is included. A comprehensive set of performance indices are used to evaluate the performance of various retrofit options. All the models are constructed in the open source software, OpenSees. The research demonstrates that the proposed approach is a viable retrofit method for highway bridges. Moreover, compared to advanced isolation systems, retrofit using elastomeric bearings with viscous dampers was successful on transferring lower loads to the substructure, and resulted in lower superstructure displacements. Though this study involved one bridge, it has provided a computational test bed to perform further studies and has provided valuable insight into the modeling and performance of retrofit solutions.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / The addition of fluid viscous dampers to structures increases damping and reduce the lateral displacements due large earthquake loads, being an effective technique for seismic control of responses specially by severe earthquakes events and structures at high seismic hazard zone, safeguarding them from possible collapse. The objective of this research is to compare the structural performance of essential structures of confined masonry older than 50 years, asbuilt and retrofitted with viscous dampers. Additionally, the structure is analyzed with a traditional reinforcement technique such as reinforced concrete walls, in order to evaluate the feasibility of the first proposal. It was found that including dampers the drifts are reduced from 0.6% to its half, better performance that implementing concrete walls with 0.45% drift response. Besides stresses levels at masonry walls have been reduced better than retrofit building new concrete walls. It is shown the feasibility of the proposal in structural responses using fluid viscous dampers,

Seismic design with viscous devices is an effective means of dissipating seismic energy and protecting the main structural system from permanent damage. Despite numerous damper placement methods available, there lacks consensus on the best method, thus leaving design engineers without recommended placement strategies. The purpose of this research is to investigate strategic placement of viscous dampers for seismic design and to offer design recommendations for placing dampers, vertically and horizontally. Five damper placement techniques were selected for investigation, including standard methods, Uniform and Stiffness Proportional damping, and advanced methods, the Simplified Sequential Search Algorithm (SSSA method), the Optimal Damper Placement for Minimum Transfer Functions (Takewaki method), and the Fully-stressed Analysis/Redesign method (Lavan A/R method). Effectiveness of the techniques for distributing linear fluid viscous dampers for two building examples was evaluated under a suite of twenty ground motions, two seismic hazard levels, and in terms of peak interstorey drifts, absolute accelerations, and residual drifts using nonlinear time history analysis. The advanced methods showed comparable performance based on performance indicators. Therefore, usability is recommended as the selection criteria. The Lavan A/R method was found to be the most effective and usable method. It is recommended that multiple design ground motions be used for the SSSA Mode and Lavan A/R methods as well as caution against removal of upper storey damping, which prompts susceptibility to larger roof drifts due to higher-mode effects. Various brace-damper arrangements were explored to determine strategic horizontal damper placement. It was found that brace-damper arrangements with diagonals and multiple brace- damper sets per floor pose effective means of distributing the axial damper force and protecting the lower-storey columns from overstressing. Behavioural testing of two nonlinear viscous devices was performed, and results were used to determine analytical models for the nonlinear fluid viscous and fluid spring devices based on fitted parameters. It was found that the stress-relaxation models better captured the nonlinearity of the devices than standard models but yielded only marginally decreased energy dissipation per cycle. Thus, it is recommended that standard models are adequate for analysis of damped structures with these nonlinear viscous devices.

The first purpose of this research is to investigate the effect of added viscous fluid dampers on a nine story special steel moment frame designed for strength in Seattle. At the initial stages of the work, knowing the fact that moment frames are almost always controlled by drift, it was thought that two different moment frames, controlled by strength or controlled by drift (stiffness), could be designed in Seattle and the effect of additional dampers on the structural behavior of the strength controlled design could be studied. However, since ASCE 7 permits determining the elastic drifts by using the seismic design forces based on the computed fundamental period of the structure, without the upper limit (CuTa), the strength controlled design satisfied the drift limit requirements of ASCE 7. Although the strength controlled design meets the drift requirements, the stability checks of both ASCE 7 and the AISC Seismic Design Manual were not satisfied. Thus, the strength controlled frame was redesigned to meet the stability requirements, and the process is called stability controlled design. By adding supplemental dampers to the strength controlled design, it was expected that the seismic drift would be controlled and a better structural behavior would be obtained in terms of dynamic stability. Incremental Dynamic Analysis (IDA) was implemented to investigate the benefits of the dampers on the structural behavior. Using ten different earthquakes scaled up to a maximum target multiplier two, with ten increments, damage measures such as interstory drift, residual displacement, IDA dispersion, base shear, and roof displacement were studied. Using IDA dispersion, the effect of dampers on dynamic instability was also investigated in this study. As a result, it was found that as the damping of the structure increases with the help of added dampers, the structural response gets better. Maximum and residual roof displacements, interstory drifts, and IDA dispersion decreases with increasing damping. In addition, by using supplemental damping, most of the collapses that occur for the inherently damped frames are prevented. The second purpose of this research is to develop an improved "Hybrid" moment frame without added damping but by controlling the inelastic behavior. Hybrid Frames were designed as the combination of three different moment frames: Special, Intermediate and Ordinary Moment Frames (SMF, IMF, OMF). The design procedure of each bay, which corresponds to different moment frame systems, follows the rules of the related moment frame for that bay. By varying the plastic hinge capacities across the same level stories, four different Hybrid Frame designs were obtained. Nonlinear static pushover analysis was applied to these frames, and as expected, the more reduction in the plastic capacity of the Hybrid Frame, the earlier the pushover curve starts yielding and the later the negative post yield stiffness of the pushover curve was reached. It was observed that the effect of early plastic hinge forming in the frame, which caused inelastic hysteretic damping, and the relatively late formation of negative post yield stiffness resulted in a better dynamic behavior. As a result of the IDA studies, as the frames become more "hybrid", the residual displacements decrease significantly and then collapses are even prevented. This is considered as the positive effect of reaching the negative post yield stiffness late. The residual displacement was reduced for low intensity gentle earthquakes. The ductility demand IDA study proves that as the frames become more hybrid, the ductility demand increases for the special detailing frame, where plastic capacity was reduced, and decreases for the ordinary detailing frame, where the plastic capacity was increased. The Hybrid Frame system is expected to perform better than the traditional special moment frame, and to be more economical than the special moment frame because of the limited amount of special detailing. / Master of Science

Several of the bridges along the Bothnia railway line do not fulfill the requirements regarding vertical accelerations that are stated in current design codes. The acceleration of the bridges needs to be reduced, in order to make the Bothnia line suitable for high speed railway traffic. The aim with this thesis is to investigate if it is possible to reduce the vertical acceleration of insufficient bridges to an acceptable level by using post-installed dampers. The expectation was that this method could have major economic advantages compared to other rehabilitation methods. Five different bridges with post-installed dampers were simulated in verified MATLAB codes. The simulations were performed for two cases for each bridge: one where the eccentricities between the attachment of the damper and the centre of gravity of the bridge cross section was taken into consideration, and one where the influence from the eccentricities was excluded. The results showed that it is fully possible to reduce the acceleration to an acceptable level with the use of external damper configurations. It was also shown that the eccentricities of the bridges had a high impact in this kind of simulations. Furthermore, some supplementary investigations regarding the location and position of the damper, were done as well. Finally, a brief analysis and discussion regarding the practical implementation of the post-installed was performed. One challenge is to anchor the damper and take care of the resulting forces in a favourable and safe way. / Flertalet broar längs med Botniabanan uppfyller inte de krav som ställs på de vertikala accelerationsnivåerna i gällande dimensioneringsnormer. Dessa accelerationer måste reduceras för att göra Botniabanan tillgänglig för trafik med höghastighetståg. I denna uppsats undersöks det huruvida det är möjligt att sänka accelerationen i bristfälliga broar med hjälp av eftermonterade externa dämpare. Förväntningen var att denna metod skulle ha stora ekonomiska fördelar gentemot andra upprustningsmetoder. Fem broar med eftermonterade dämpare har simulerats i verifierade MATLAB-koder. Simuleringarna utfördes på två olika sätt för varje bro: i en kod togs eccentriciteten mellan dämparinfästningen och tyngdpunktslinjen för bron i beaktande, och i den andra koden försummades all inverkan av eccentriciteten. Resultatet från simuleringarna visade att det är fullt möjligt att reducera accelerationerna till en acceptabel nivå med hjälp av externa dämpningskonfigurationer. Eccentriciteten visade sig även ha stor inverkan på resultatet i denna typ av simulering. Dessutom utfördes några kompletterande undersökningar gällande längd, position och vinkel på dämparen. Slutligen analyserades och diskuterades den praktiska implementeringen av de eftermonterade dämparna. En utmaning är att förankra dämparna och föra ner de resulterande krafterna på ett fördelaktigt och säkert sätt.

At the moment of writing, an expansion of the Swedish railway network has started, by constructions of new lines for high-speed trains. The aim is to create a high-speed connection between the most populous cities in Sweden - Stockholm, Göteborg and Malmö, and the rest of Europe. Thereby, the likelihood of faster, longer and heavier foreign trains crossing the Swedish lines is increased. However, this could be problematic since the dynamic response in railway bridges and, consequently, the risk of resonance increases with increasing train speeds. Bridges are usually designed based on contemporary conditions and future requirements are rarely considered, due to e.g. cost issues. Prospectively, the dynamic performance of existing bridges may become insufficient. Hence, the current expansion of the high-speed railway network results in an increased demand of innovative design solutions for new bridges and cost-efficient upgrading methods for existing lines. The aim of the present thesis is to propose a vibration mitigation strategy suitable for new and existing high-speed railway bridges. The main focus is a retrofit method with fluid viscous dampers installed between the bridge superstructure and the supports, which is intended to reduce the vertical bridge deck acceleration below the European design code limits. Furthermore, the intention is to investigate the efficiency of such a system, as well as to identify and analyse the parameters and uncertainties which could influence its functionality. In order to examine the applicability of the proposed retrofit, case studies, statistical screenings and sensitivity analyses are performed and analysed. Two different models, a single-degree-of-freedom system and a finite element model, are developed and compared. From the different models, it is possible to study the influence from the damper parameters, the variability of the material properties and different modelling aspects on the bridge response. After the installation of the fluid viscous dampers, it is found that the acceleration level of the bridge deck is significantly reduced, even below the design code requirements. / I skrivande stund har en utbyggnad av det svenska järnvägsnätet initierats. Målet är att skapa en höghastighetsanslutning mellan de folkrikaste städerna i Sverige - Stockholm, Göteborg och Malmö, och vidare ut i Europa. Därmed ökar sannolikheten att snabbare, längre och tyngre utländska tåg korsar de svenska järnvägslinjerna. Dock kan detta bli problematiskt i och med att järnvägsbroars dynamiska respons och, följaktligen, risken för resonans ökar med ökad tåghastighet. Broar dimensioneras ofta utifrån nuvarande förutsättningar och hänsyn tas sällan till framtida hållbarhetskrav, exempelvis p.g.a. kostnadsbesparingar. Ur ett framtidsperspektiv kan därför det dynamiska beteendet hos befintliga broar komma att bli otillräckligt. Utbyggnaden av höghastighetsnätverket ökar därmed behovet av innovativa konstruktionslösningar för nya broar och kostnadseffektiva uppgraderingsmetoder för befintliga sträckor. Syftet med föreliggande avhandling är att föreslå en metod för att minska de vibrationsnivåer som kan uppstå i både nybyggda och befintliga järnvägsbroar för höghastighetståg. Huvudfokus är en eftermonteringsmetod med viskösa dämpare, som har installerats mellan brons överbyggnad och landfästen, för att minska brobanans vertikala acceleration under gällande europeiska dimensioneringskrav. Vidare avses att undersöka effektiveteten av ett sådant system, samt att identifiera och analysera de parametrar och osäkerheter som kan påverka dess funktionalitet. Fall- och parameterstudier, samt statistiska metoder används och utvärderas för att undersöka tillämpbarheten av den föreslagna vibrationsdämpningsmetoden. Två olika modeller, ett enfrihetsgradssystem och en finit elementmodell, har skapats och jämförts. Utifrån dessa modeller kan påverkan av dämparens parametrar, variabiliteten hos materialegenskaperna och behandlingen av olika modelleringsaspekter studeras. Från resultaten är det tydligt att brobanans accelerationsnivå avsevärt reduceras efter monteringen av viskösa dämpare, till och med under dimensioneringskraven. / <p>QC 20170425</p>

Στην εργασία αυτή διερευνάται η δυναμική απόκριση κρυογενικών δεξαμενών υγροποιημένου φυσικού αερίου υποκείμενων σε δράση σεισμού. Επειδή οι εν λόγω δεξαμενές αποτελούν κρίσιμα στοιχεία για τη λειτουργία ενός συστήματος διανομής φυσικού αερίου και επειδή ενδεχόμενη καταστροφική αστοχία τους θα είχε δυσβάστακτες κοινωνικές επιπτώσεις, ιδιαίτερα αυστηρές απαιτήσεις ισχύουν σχετικά με τον αντισεισμικό σχεδιασμό τους. Για το σχεδιασμό έναντι σεισμού προδιαγράφονται συνήθως ένα σεισμικό γεγονός με μέση περίοδο επαναφοράς της τάξης των 500 ετών, κατά το οποίο οι δεξαμενές απαιτείται να παραμένουν πλήρως λειτουργικές, και ένα σεισμικό γεγονός με μέση περίοδο επαναφοράς της τάξης των 5000 έως 10000 ετών, κατά το οποίο απαιτείται η εξασφάλιση της ασφαλούς διακοπής της λειτουργίας των δεξαμενών, ενώ ελάχιστη μόνο βλάβη είναι αποδεκτή στα δομικά στοιχεία τους. Οι εν λόγω δεξαμενές αποτελούνται από δύο κελύφη: Ένα εξωτερικό κυλινδρικό κέλυφος από προεντεταμένο σκυρόδεμα με θολωτή στέγη από οπλισμένο σκυρόδεμα και ένα εσωτερικό κέλυφος από κρυογενικό χάλυβα, εντός του οποίου αποθηκεύεται το προϊόν. Τα δύο κελύφη εδράζονται σε κοινή πλάκα βάσης. Στην εργασία αυτή εξετάζονται δύο εναλλακτικοί τρόποι έδρασης της πλάκας βάσης: α) απλή έδραση επί του διαμορφωμένου εδάφους και β) εφαρμογή κάποιας διάταξης σεισμικής μόνωσης επί της οποίας εδράζεται η πλάκα βάσης. Ειδικότερα, εξετάζονται τα ακόλουθα συστήματα σεισμικής μόνωσης: α) μόνωση με ελαστομεταλλικά εφέδρανα με ελαστομερές υψηλής απόσβεσης, β) μόνωση με ελαστομεταλλικά εφέδρανα με πυρήνα μόλυβδου, και γ) μόνωση με συνδυασμό γραμμικών ελαστομεταλλικών εφεδράνων και μη γραμμικών αποσβεστήρων. Στις ιδιαιτερότητες του δυναμικού προβλήματος περιλαμβάνονται, εκτός από την επίδραση της μόνωσης, η δυναμική αλληλεπίδραση των δύο κελυφών, η δυναμική αλληλεπίδραση υγρού-δεξαμενής, ο κυματισμός της ελεύθερης επιφάνειας του υγρού και η δυναμική αλληλεπίδραση εδάφους-δεξαμενής. Τα φαινόμενα αυτά λαμβάνονται υπόψη στην ανάλυση. Για τη μελέτη του κυματισμού της ελεύθερης επιφάνειας χρησιμοποιείται η γραμμική θεωρία κυμάτων. Για τη μελέτη της αλληλεπίδρασης υγρού-δεξαμενής εφαρμόζεται μια προσέγγιση τύπου Lagrange με χρήση πεπερασμένων στοιχείων υγρού. Για τη μελέτη της αλληλεπίδρασης εδάφους-δεξαμενής χρησιμοποιούνται συγκεντρωμένα στοιχεία δυσπαραμορφωσιμότητας και απόσβεσης. Επίσης, συγκεντρωμένα στοιχεία δυσπαραμορφωσιμότητας και απόσβεσης χρησιμοποιούνται για την προσομοίωση των συστημάτων μόνωσης. Τα χαρακτηριστικά των παραπάνω συγκεντρωμένων στοιχείων για την προσομοίωση της αλληλεπίδρασης εδάφους-δεξαμενής και των συστημάτων μόνωσης επιλέγονται με βάση ρεαλιστικές υποθέσεις για τις δυναμικές ιδιότητες του εδάφους θεμελίωσης και τα χαρακτηριστικά των συστημάτων μόνωσης. Δύο περιπτώσεις υφιστάμενων δεξαμενών υιοθετούνται προς ανάλυση. Οι δύο δεξαμενές διαφέρουν κυρίως ως προς τη χωρητικότητα και το λόγο ύψους προς ακτίνα. Και οι δύο δεξαμενές έχουν μελετηθεί και κατασκευαστεί χωρίς σεισμική μόνωση. Ένα συνθετικό επιταχυνσιογράφημα συμβατό με το φάσμα απόκρισης σχεδιασμού του Ευροκώδικα 8 για λόγο απόσβεσης 5%, για την αντίστοιχη κατηγορία εδάφους και για μέγιστη εδαφική επιτάχυνση λίγο μεγαλύτερη από αυτή για την οποία είναι σχεδιασμένες οι δεξαμενές περιγράφει τη διέγερση της κατασκευής στην οριζόντια διεύθυνση. Για την ανάλυση αναπτύσσεται ένα συνολικό παραμετρικό προσομοίωμα πεπερασμένων στοιχείων το οποίο περιλαμβάνει τα δύο κελύφη και το αποθηκευμένο υγρό. Στο προσομοίωμα συμπεριλαμβάνονται, ανάλογα με την περίπτωση που κάθε φορά αναλύεται, τα κατάλληλα στοιχεία για την προσομοίωση της αλληλεπίδρασης εδάφους-δεξαμενής ή των διαφόρων συστημάτων μόνωσης. Το προσομοίωμα χρησιμοποιείται για τον υπολογισμό των ιδιομορφών και την πραγματοποίηση δυναμικών γραμμικών και μη γραμμικών αναλύσεων με ολοκλήρωση στο πεδίο του χρόνου. Οι μη γραμμικές αναλύσεις είναι αναγκαίες για να ληφθεί υπόψη με ρεαλιστικό τρόπο η έντονα μη γραμμική συμπεριφορά των συστημάτων μόνωσης. Στην περίπτωση αυτή η μη γραμμικότητα είναι συγκεντρωμένη στα στοιχεία που προσομοιώνουν τη μόνωση ενώ για την υπόλοιπη κατασκευή γίνεται σε κάθε περίπτωση η παραδοχή γραμμικής συμπεριφοράς. Η παραδοχή αυτή προκύπτει από το γεγονός ότι για τις δεξαμενές αυτού του τύπου η αποδεκτή βλάβη, και επομένως μη γραμμικότητα στη συμπεριφορά, των δομικών στοιχείων είναι ελάχιστη. Παρουσιάζονται επιλεγμένα αποτελέσματα των αναλύσεων που πραγματοποιήθηκαν με χρήση του προσομοιώματος πεπερασμένων στοιχείων. Τα αποτελέσματα αυτά αναφέρονται κυρίως στην τέμνουσα βάσης, τη ροπή ανατροπής, τις οριζόντιες μετακινήσεις της κατασκευής σε διάφορες στάθμες και το ύψος του κυματισμού. Έμφαση δίνεται στην ποσοτικοποίηση της επίδρασης της αλληλεπίδρασης εδάφους-δεξαμενής και της σεισμική μόνωσης στα ανωτέρω μεγέθη. Η εργασία τελειώνει με γενικά συμπεράσματα. / In the present work the dynamic response of liquefied natural gas cryogenic tanks subjected to earthquake action is investigated. Since these tanks are critical elements for the function of a natural gas distribution system and because a potential failure of them could lead to a major disaster, very severe requirements concerning the seismic design of these tanks are imposed. For the design against earthquake action two seismic events are generally considered: an event with a mean return period of 475 years during which the tanks are expected to remain fully operational and an event with a mean return period of the order of 5000 to 1000 years during which the safe shut down of the tanks is to be ensured, while minimum damage is accepted at the structural parts of the tanks. The type of tanks under consideration is constituted of two shells: an outer one made of prestressed concrete and an inner one made of cryogenic steel in which the product is stored. Both shells rest on a common base slab. In these work two alternative ways for the support of this slab are examined: a) the slab lays directly on the ground and b) the slab lays on a number of devices which provide seismic isolation. The following isolation systems are examined. a) high damping rubber bearings, b) lead core rubber bearings and c) low damping rubber bearing in conjunction with non-linear viscous dampers. The examined structural dynamic problem is characterised by certain particularities, besides the one of the implementation of an isolation system. The most important of them are sloshing of the free surface, dynamic fluid-structure interaction, dynamic soil-structure interaction and interaction between the inner and outer shell. These phenomena are taken into consideration in the preformed analyses. For the modeling of the free surface effect the realistic assumption of small wave height is made and the linear wave theory is employed. For the modeling of the fluid-structure interaction a Lagrangian approach is applied using finite elements for the modeling of the liquid and the solid domain. The soil-structure interaction is simulated by using concentrated stiffness and damping elements. Concentrated stiffness and damping elements are used for the modeling of the isolation systems as well. Two cases of existing tanks are adopted for analysis. The two tanks differ mainly in capacity and in the height to radius ratio. Both tanks are designed and constructed without seismic isolation. A global parametric finite element model is developed for the analyses. In this model the appropriate elements are incorporated for the modeling of the soil-structure interaction and the seismic isolation system, depending on the analysed case. The model is used for the calculation of eigenmodes and eigenfrequencies and for performing linear and non-linear transient analyses in time domain. Non-linear analyses are necessary in order for the highly non-linear behavior of the isolation devices to be properly simulated. In these cases the non-linearity is concentrated at the elements which simulate the seismic isolation system while the rest of the structure is considered elastic in all cases. This consideration is justified by the fact that for these tanks the acceptable damage, and consequently non-linearity in the behavior of the structural part, is minimum. Selective results of the performed analyses are presented. These results refer mainly to base shear forces, overturning moments, horizontal displacements at different levels of the tank and sloshing heights. Emphasis is on the quantification of the impact of the soil-structure interaction and the implementation of the examined seismic isolation systems.