The response of lightweight equipment in structures supported on resilient-friction-base isolators (R-FBI) subjected to harmonic ground motion and various earthquake ground motions is examined. The equipment-structure base system is modeled as a three degree-of-freedom discrete system (SDOF subsystems). An efficient semi-analytical numerical solution procedure for the determination of equipment response is presented. Parametric studies to examine the effects of subsystem frequency (isolator, structure, equipment), subsystem damping, mass ratio, friction coefficient and frequency content of the ground motion on the response of the equipment are performed. The equipment response on a fixed-base structure subjected to ground motion is also calculated. Friction type isolation devices can induce high frequency effects in the isolated structure due to the stick-slip action. These effects on equipment response are examined. The results show that the high frequency effect in the structure generated from a friction-type base isolator doesn't, in general, cause amplifications in the response. The R-FBI system appears to be an effective aseismic base isolator for protecting both the structure and sensitive internal equipment. / Graduation date: 1992

As a capstone to several Mid-America Earthquake Center (MAE Center) projects, a full-scale two story unreinforced masonry (URM) building was tested following the application of several retrofit techniques, which included the use of fiber reinforced polymer (FRP) overlays, near surface mounted (NSM) rods, vertical unbonded post-tensioning, and joist anchors. The test structure was composed of four URM walls, flexible timber diaphragms and interior stud walls, and was designed and built following construction practices consistent with those used in Mid-America prior to 1950. Initial testing subjected both the roof diaphragm and in-plane walls to slowly applied lateral load reversals in an unreinforced sate. Following this series of tests, each in-plane wall was retrofit and retested. Experimental results indicated that global issues such as flange participation and the effects of overturning moment substantially impacted the response of primary components both before and after retrofit. FRP retrofit techniques resulted in strength increases up to 32% and displayed a pseudo-ductile response caused by progressive debonding. For cases where such retrofits forced sliding failures, large increases in energy dissipation resulted. The use of vertical unbonded post-tensioning resulted in strength increases between 40%-60%; however, piers displayed a tendency to switch from a ductile rocking/sliding mode to a more brittle diagonal tension mode. In addition, results highlighted the need for retrofit schemes to employ both horizontal and vertical reinforcement to prevent progressive crack opening that can decrease wall displacement capacity. Based on the experimental results, the model implied by the and quot Prestandard for the Rehabilitation of Existing Structures and quot, FEMA 356, for the analysis of in-plane URM walls was modified and extended to (1) include the effect of FRP pier retrofits and (2) consider the global effects of URM structures. The resulting model displayed reasonable estimates of measured response both before and after retrofit, with an average error of 14%. In addition, the proposed model displayed improvements over the current model from 14% to 66%. Based on the results of sensitivity analyses this improved accuracy was primarily attributed to the consideration of global effects.

The large number of bridge collapses that have occurred in recent earthquakes has exposed the vulnerabilities in existing bridges. One of the emerging tools for protecting bridges from the damaging effects of earthquakes is the use of isolation systems. Seismic isolation is achieved via inserting flexible isolator elements into the bridge that shift the vibration period and increase energy dissipation. To date, the structural performance of bridges incorporating sliding seismic isolation is not well-understood, in part due to the lack of adequate models that can account for the complex behavior of the isolators. This study investigates and makes recommendations on the structural performance of bridges utilizing sliding type seismic isolators, based on the development of state-of-the-art analytical models. Unlike previous models, these models can account simultaneously for the variation in the normal force and friction coefficient, large deformation effects, and the coupling of the vertical and horizontal response during motion. The intention is to provide support for seismic risk mitigation and insight for the analysis and design of seismically isolated bridges by quantifying response characteristics. The level of accuracy required for isolator analytical models used in typical highway bridges are assessed. The comparative viability of the two main isolator types (i.e. sliding and elastomeric) for bridges is investigated. The influence of bridge and sliding isolator design parameters on the system s seismic response is illustrated.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 256-262). Available also in a digital version from Dissertation Abstracts.

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (p. 129-142). Also available in print.

Thesis (M.S.)--California Polytechnic State University, 2009. / Mode of access: Internet. Title from PDF title page; viewed on Jan. 11, 2010. Major professor: Daniel C. Jansen. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Civil and Environmental Engineering." "December 2009." Includes bibliographical references (p. 176-180).

Thesis (Ph. D.)--Lehigh University, 2003. / In three parts. Includes vita. Includes bibliographical references (leaves 770-775).

A confined masonry (CM) wall consists of a masonry wall panel surrounded by reinforced concrete (RC) members on its perimeters. Low-rise CM structures are widely used in earthquake-risked (EQ-risked) rural or suburban areas all over the world. Most of these structures fail in shear pattern under lateral EQ loads, and some of them collapse under a severe or even a moderate EQ due to inappropriate design. On the other hand, buildings constructed of RC frames have much better performance in resisting EQs, since their RC members have larger dimensions and heavier reinforcing ratios than those in CM structures. Nonetheless, RC-frame buildings are normally too expensive for most inhabitants in less developed regions. In this study, as an improvement to the conventional CM buildings for EQ resistance and for the sake of post-EQ restoration, a hybrid masonry – RC (HMR) structure, whose working mechanism is different from that of a conventional CM structure, is proposed. The RC members (i.e. “tie beams” and “tie columns”), which function only as confinement in a CM building, will resist most of gravity load and part of lateral EQ load in an HMR structure, while the wall panels will take most of lateral EQ load and part of gravity load. This is achievable by slightly increasing the sizes and reinforcing ratios of RC members in HMR structures. Such buildings will not collapse in the absence of masonry wall panels because the gravity load bearing system is still intact. On the other hand, as the wall panels in the proposed HMR structure will absorb most of the energy induced by lateral EQ load, severe damages will be controlled within the wall panel region, so that only the wall panels need to be replaced instead of rebuilding the whole structure after the EQ event. To investigate the mechanical behaviours of masonry assemblages to be used in HMR structures, a series of experimental tests were conducted. Having established the relevant material properties for HMR structures, finite element (FE) simulation was performed to verify its work mechanism. Prior to applying the FE simulation to HMR structures, the FE technique was first applied to simulate the behaviours of two concrete-brick masonry panels under diagonal compression loading and a CM wall under cyclic lateral loading. The results show a good correlation between the experimental results and the simulated ones. This has validated the feasibility of using the FE software to study the proposed HMR structure. The theoretical simulation results show that in a properly designed HMR wall, depending on the masonry reinforcing details and the boundary conditions of simulated load cases, about 70% of the gravity load imposed on the RC beam will be transferred to the RC columns and more than 80% of the seismic energy (in terms of strain energy) will be absorbed by the masonry panel. Therefore, it is obvious that the proposed HMR structure is very feasible to replace the conventional CM structure in resisting EQ attacks with no risk of collapse. / published_or_final_version / Civil Engineering / Master / Master of Philosophy

Η παρούσα διπλωματική εργασία πραγματεύεται την στατική και αντισεισμική μελέτη και σχεδιασμό του Β’ Κτηρίου Διοίκησης Ε.Α.Π. Ο φέροντας οργανισμός του συγκεκριμένου κτηρίου συνίσταται από μεταλλική ανωδομή με σύμμικτες πλάκες και υπόγειο οπλισμένου σκυροδέματος. Η ανάλυση έγινε βάση των αρχών που επιβάλλουν οι Ευρωκώδικες 1, 3, 4 και ο Ελληνικός Κανονισμός Ωπλισμένου Σκυροδέματος (Ε.Κ.Ω.Σ.) καθώς και ο Ελληνικός Αντισεισμικός Κανονισμός (Ε.Α.Κ.). Η ανάλυση έγινε από τα προγράμματα FESPA, που έχει αναπτυχθεί από την εταιρία LH ΛΟΓΙΣΜΙΚΗ, και STRAD, STEEL, που έχουν αναπτυχθεί από την εταιρία 4Μ. Η εργασία αποτελείται από έξι(6) κεφάλαια. Στο πρώτο κεφάλαιο γίνεται μια σύντομη εισαγωγή στο οπλισμένο σκυρόδεμα και τον δομικό χάλυβα. Παρουσιάζονται οι δυνατότητες καθώς και οι αδυναμίες του κάθε υλικού κατασκευής. Επίσης, γίνεται μια συνοπτική περιγραφή της κατασκευής που πρόκειται να αναλυθεί και να διαστασιολογηθεί. Στο δεύτερο κεφάλαιο γίνεται η παρουσίαση των βασικών αρχών των Ευρωκώδικων 1,3,4, του ΕΚΩΣ και του ΕΑΚ σύμφωνα με τις οποίες γίνεται η ανάλυση και διαστασιολόγηση της κατασκευής. Στο τρίτο κεφάλαιο παρουσιάζονται τα προγράμματα FESPA, STRAD και STEEL με τα οποία πραγματοποιείται η ανάλυση και η διαστασιολόγηση της κατασκευής. Παρουσιάζονται κατά σειρά η μέθοδος με την οποία εκτελούν την στατική, αλλά και τη δυναμική-φασματική ανάλυση, οι συμβάσεις αξόνων και μελών, οι έλεγχοι που πραγματοποιούνται κ.α. Στο τέταρτο κεφάλαιο, γίνεται η εύρεση των απαραίτητων για την ανάλυση δεδομένων σύμφωνα με τις αρχές που δίνονται στο κεφάλαιο 2. Κατ’αρχήν παρουσιάζεται το μοντέλο της κατασκευής. Έπειτα, προσδιορίζονται κατασκευαστικά στοιχεία όπως το πάχος πλακών, προσδιορίζονται τα φορτία λόγω ίδιου βάρους, φορτία επικαλύψεων και τοιχοποιίας, ωφέλιμα φορτία, φορτία χιονιού και ανέμου. Καθορίζονται τα φασματικά δεδομένα που απαιτούνται για την δυναμική-φασματική ανάλυση της κατασκευής. Τέλος, γίνεται αναφορά στο τρόπο που έγινε η προσομοίωση και εξιδανίκευση του φορέα και στις παραδοχές που χρειάστηκαν για να γίνει. Στο πέμπτο κεφάλαιο-που ίσως είναι και το ουσιαστικότερο όλων-γίνεται ο έλεγχος και η διαστασιολόγηση της κατασκευής με κάθε πρόγραμμα ξεχωριστά. Συγκεκριμένα γίνεται ο έλεγχος των μελών, από δομικό χάλυβα και από οπλισμένο σκυρόδεμα, σε επίπεδο διατομής και μέλους καθώς και ο αναλυτικός έλεγχος των δυσμενέστερων μελών, γίνονται οι έλεγχοι λειτουργικότητας και παραμορφώσεων (όπως έλεγχος επιρροής φαινομένων δεύτερης τάξης και έλεγχος βλαβών) και τέλος παρουσιάζεται η ανάλυση και η διαστασιολόγηση του υπογείου και της θεμελίωσης. Στο έκτο και τελευταίο κεφάλαιο γίνεται η επίλυση των σύμμικτων πλακών της οροφής ισογείου και της οροφής α’ ορόφου. Συγκεκριμένα γίνεται η επιλογή της γεωμετρίας των σύμμικτων πλακών και ο έλεγχος τους σε κάμψη, εγκάρσια και διαμήκη διάτμηση, λειτουργικότητας και ρηγμάτωσης. Επειδή τα συγκεκριμένα προγράμματα δεν επιλύουν σύμμικτες πλάκες, η επίλυσή τους έγινε στο χέρι και στη συνέχεια τα αποτελέσματα δόθηκαν στα προγράμματα ώστε να γίνει η επίλυση όλου του φορέα. / This project concerns a static-earthquake resistant construction of a building in the University of Patras.

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