This thesis focuses on the experimental studies conducted on the development of low-cost seismic base isolation pads using scrap automobile tires. Seismic base isolation is a well-defined building protection system against earthquakes, on which numerous studies have been conducted. The majority of the previous studies focus on the performance improvement of the base isolation systems. However, this study aims at cost and weight reduction of seismic base isolation pads by recycling otherwise useless material: scrap tires. Elastomer-based isolators have been heavily studied and used for the last 25 years. Steel or fiber reinforcement inside the elastomer isolators provides high vertical stiffness, whereas rubber segments between reinforcement layers provide low horizontal stiffness for the seismic base isolation. Since 1960&rsquo / s, automobile tires have been produced by means of vulcanizing rubber with steel mesh in different forms which have a similar effect as the steel plates or fibers inside the conventional elastomer-based isolators. Therefore, rectangular shaped layers cut from tread sections of used tires and then piled on top of each other can function as an elastomeric bearing. Since the tires are being designed for friction, load transfer between scrap tire layers would be large enough to keep all layers intact. A minimal slip generated between the piled layers at high strain rates may even help to dissipate some extra energy. Axial compression, dynamic free vibration, static shear and shaking table tests have been conducted on Scrap Tire Pads (STP) prepared by using different tire brands for different number of layers and orientations. The results have shown that the average shear modulus of STPs change between 0.9MPa and 1.85MPa. At the end of the dynamic tests it has been noticed that the lateral stiffness of STPs can be simply adjusted by changing the number of tread layers placed on top of each other. The amount of wire mesh inside the tire tread layers is relatively low compared to the steel plates in regular elastomeric pads / consequently, axial load capacity of STPs has been found to be around 8.0MPa. Static large deformation shear experiments have been performed to obtain the horizontal stiffness and shear modulus values at high strains and the results are tabulated in the manuscript. Steel and rubber layers are produced separately and just put on top of each other without any adhesive to form the &frac14 / scaled versions of STPs which were used to isolate a &frac14 / scaled masonry house on the shaking table available in METU Structural Laboratory. The experiment showed that non-vulcanized rubber-steel layers put on top of each other can also be used to isolate structures. In conclusion, STPs may be used as a low-cost alternative to conventional elastomer-based pads for seismic isolation of massive structures (e.g. stone wall rural masonry) or for temperature induced deformation compensation of rural bridges. STP usage is demonstrated using three hypothetical design examples in the manuscript.

No description available.

Στην παρούσα διατριβή παρουσιάζονται τα αποτελέσματα ψευδοδυναμικών δοκιμών σε γέφυρα από οπλισμένο σκυρόδεμα, πολλών ανοιγμάτων, σεισμικά μονωμένης με απλά ελαστομεταλλικά εφέδρανα χαμηλής απόσβεσης. Το μέγεθος της γέφυρας καθιστά αδύνατη την προσομοίωση ολόκληρου του φορέα στο εργαστήριο σε πλήρη κλίμακα ή έστω σε μικρότερη αλλά ρεαλιστική κλίμακα. Παράλληλα, η απόκριση του καταστρώματος και των βάθρων αναμένεται να είναι ελαστική κατά την διάρκεια της σεισμικής διέγερσης ενώ η ανελαστική παραμόρφωση θα εντοπίζεται στην στάθμη της σεισμικής μόνωσης. Για αυτό το λόγο, ο οικονομικότερος και πιο κατάλληλος τρόπος δοκιμής είναι η χρήση της μεθόδου των υπο-κατασκευών. Με τον τρόπο αυτό τα εφέδρανα χρησιμοποιούνται ως δοκίμιο και η απόκριση τους μετράται εργαστηριακά, ενώ η υπόλοιπη κατασκευή (κατάστρωμα και βάθρα) προσομοιώνονται αναλυτικά. Οι ψευδοδυναμικές δοκιμές έγιναν με την μέθοδο αυτή εφαρμόζοντας ως διέγερση το πραγματικό επιταχυνσιογράφημα του σεισμού της 15ης Απριλίου του Montenegro, τροποποιώντας το κατάλληλα, ώστε το φάσμα του να είναι συμβατό με το φάσμα του Ευρωκώδικα 8 για έδαφος τύπου C. Το τυπικό όμως πρόβλημα το οποίο εμφανίζεται κατά την εκτέλεση ψευδοδυναμικών δοκιμών μη πραγματικού χρόνου σε συσκευές, των οποίων η απόκριση επηρεάζεται από την ταχύτητα παραμόρφωσης, όπως είναι τα εφέδρανα, είναι η διαφοροποίηση των μετρούμενων δυνάμεων με την πραγματοποίηση της δοκιμής σε διεσταλμένη κλίμακα του χρόνου. Συνεπώς είναι απαραίτητο να χρησιμοποιηθεί μια διαδικασία, ώστε σε κάθε βήμα η μετρούμενη δύναμη αντίδρασης των εφεδράνων, η οποία εκφράζει την δυσκαμψία τους, να διορθώνεται ώστε να αντιστοιχεί στην δύναμη που θα μετριόταν εάν η δοκιμή ήταν πραγματικού χρόνου. Για τα λόγο αυτό πραγματοποιήθηκαν προκαταρκτικές δοκιμές χαρακτηρισμού, με στόχο αφενός τον προσδιορισμό των μηχανικών χαρακτηριστικών των εφεδράνων σε διάφορα επίπεδα παραμόρφωσης και αφετέρου τον υπολογισμό απαραίτητων συντελεστών διόρθωσης, οι οποίοι θα χρησιμοποιηθούν στην ψευδοδυναμική δοκιμή για να ληφθεί υπόψη η επιρροή του ρυθμού παραμόρφωσης. Οι δοκιμές αυτές πραγματοποιήθηκαν σε επίπεδα διατμητικής παραμόρφωσης των εφεδράνων που έφταναν το 100% της αντοχής τους και σε συχνότητες που ήταν κοντά στις ιδιοσυχνότητες που αναμένονται για την κατασκευή κατά την διάρκεια της σεισμικής διέγερσης. Κατά τη διεξαγωγή των δοκιμών τα εφέδρανα υποβάλλονται σε καθορισμένη ιστορία φόρτισης που αποτελείται από συνεχείς ημιτονοειδείς κύκλους μειούμενου εύρους και ένα τμήμα τυχαίας χρονοϊστορίας. Μετά τον προσδιορισμό των διορθωτικών συντελεστών πραγματοποιήθηκαν οι ψευδοδυναμικές δοκιμές σε διάφορα επίπεδα έντασης της εδαφικής σεισμικής επιτάχυνσης. Για τις δοκιμές χρησιμοποιήθηκαν δύο ζευγάρια εφεδράνων, για καθένα από τα οποία έγινε ξεχωριστή δοκιμή χαρακτηρισμού. Η ταχύτητα εκτέλεσης των δοκιμών επιλέχθηκε να είναι μια τάξη μεγέθους πιο γρήγορη από αντίστοιχες προηγούμενες δοκιμές. Τα αποτελέσματα των δοκιμών έδειξαν καταρχάς ότι η διαδικασία που επιλέχθηκε για να ληφθεί υπόψη η επιρροή του ρυθμού παραμόρφωσης ήταν επιτυχής. Επιπλέον, κατέδειξαν ότι η μόνωση γεφυρών με χρήση του συγκεκριμένου τύπου εφεδράνων δεν αποτελεί αποτελεσματική μέθοδο αντισεισμικής προστασίας καθώς τα εφέδρανα αστόχησαν σε επίπεδα παραμόρφωσης χαμηλότερα από αυτά που απαιτούν οι κανονισμοί. / The results of hybrid tests performed on a multi-span RC bridge are presented. The bridge, typical example of bridges employing only plain, elastomeric, low damping isolation devices, is sub-structured for testing purposes: the isolators are physically tested while the response of the remaining structure is simulated numerically. Hybrid testing is performed quasi-statically and - to account for the actual influence of real-time loading on the properties of the isolation devices - a pre-testing phase is carried out in which isolators are strained dynamically at different velocity levels to determine the relation of the real-time response to that during static conditions. Following this phase of characterization, pairs of isolators in a back-to-back (parallel) configuration are tested with the hybrid method, with on-line modification of the measured restoring forces based on the results of the pre-test campaign. The experimental program revealed that the specific type of elastomeric bearings used in the study do not comply to current code provisions as they rupture at deformation levels considerably lower than the code-prescribed ones.

The diploma thesis deals with a design of a steel loadbearing structure of a footbridge over a river. The footbridge is located in Svitavy and is designed for span length of 60 meters. The construction is preliminarily designed in two variants. A part of the thesis is also a comparison of both variants. The chosen variant has been elaborated in detail. It is an arched construction with a semi-through bridge deck. The main loadbearing structure consists of a pair of arches that support the steel-concrete bridge deck by means of rods in tension. The main loadbearing arches are inclined from the vertical plane towards the bridge axis and are fixed at the ends. All steel parts are designed from S355 steel, except for the rods that are designed from S460 steel. The bridge deck is designed from C 35/45 concrete. The spatial rigidity of the structure in the transverse direction is achieved by means of arc sway bracings.

No description available.

The thesis deal with structural design of steel footbridge for pedestrians and cyclist over the Bečva river in Černotín village. Span of the footbridge is 50 m. The basic material is steel S355 and S460. At the beginning were created two variants. First one is an arched footbridge and the second one is cable stayed footbridge. After evaluation variants was selected the cable stayed footbridge. The selected variant was assessed in detail including joints and bearings. Structure is designed in compliance with valid standards of ČSN EN and corresponds with ultimate and serviceability limit state. For structural design was used software RFEM 5.17.01 of Dlubal company.

This diploma thesis contains a study of current composite structure of footbridge and in part II design and assessment of steel structure of footbridge for pedestrians and cyclists placed on current footbridge location. Current footbridge is located on "nábřeží Dukelských hrdinů" in Rožnov pod Radhoštěm. In part I, assessment of the current composite structure of footbridge is done, using ČSN and ČSN EN standards for adjusted static behavior of the structure. Comparison of both assessments is made and also with an original assessment from 1988. In part II, design and assessment of steel structure of footbridge placed on currents footbridge location described in part I is done.The structure was designed as two vierendeels trusses connected with cross beams, supporting concrete bridge deck. 9 variants were examined, differing with truss height and the number of verticals. Detailed design and assessment for parts of the structure is done for the chosen variant.

The Diploma thesis deals with design and static assessment of timber footbridge structural system for pedestrians and cyclist across the Trebuvka river in Lostice on the site of the existing footbridge. Structural system is designed in two alternatives and assessed according to the current standards. Spans of the bridge are 2x18 m and 1x6 m. The main beams are made of glued laminated timber, other parts of the structure are made of timber and steel elements. First alternative is designed as a simple half-through truss beam, second alternative as continuous beam with variable height where the deck is sitting on top of the girders.

This master's thesis deals with the designing of the appropriate supporting steel structure footbridge for pedestrians. The footbridge is used to connect two separate buildings (buildings D and Z at the Faculty of Civil Engineering Brno University of Technology). Four variants have been designed about solutions supporting steel structure. The final variant was prepared in detail and was carried out static assessment of the individual elements and selected details. The main supporting structure of this variant are two trusses. Diagonals of these trusses are designed linkage system of Macalloy 460. Bridge deck is designed of composite steel a concrete board with crossbars. The footbridge is designed as simple beam with an overhanging end. Length span is 34.8 m, length overhanging ends is 5.8 meters. The total length of the footbridge is 40.6 meters. Width of footbridge is 2.8 meters. Free width is 2 meters. In the cross point with the axis of local road is height of footbridge above ground 4.43 meters. Next to the building Z, there is a footbridge stored on a concrete support, near the building D, the footbridge is stored on a steel frame of support. The footbridge is deposited on elastomeric bearings. The footbridge is being protected from the weather. The sheating of the building is designed by Wictec 60 system. The master's thesis also contains drawing documentation of the proposed solution.