<p>The masonry construction industry represents a historically significant and substantial portion of both existing and new residential, commercial and institutional low- to medium-rise structures across Canada. Although commonly chosen for its aesthetic qualities by architects, structural masonry walls constructed with concrete block units are also an effective lateral force (wind or seismic) resisting system. The purpose of this dissertation is to address what are perceived to be overly conservative and outdated practices within masonry construction and design by adopting analysis and design practices which have had success with similar reinforced concrete wall systems. The results from a test program reporting on the behavior of nine fully-grouted reinforced masonry (RM) structural walls containing confined boundary elements are analyzed and presented according to force-, displacement- and performance-based seismic design considerations. The boundary element containing four vertical bars with lateral confinement stirrups selected represents a readily codified and practically achievable means of achieving seismic performance enhancement. The design and detailing of the specimens represented a range of parameters that would be anticipated to vary within low- to medium-rise RM buildings. In addition, an analytical study is carried out to derive, from first principles of stress equilibrium and strain compatibility, the necessary constitutive material and mechanics-based equations needed to solve for the state of shear stress and strain in an idealized cracked masonry macro-element. The algorithm proposed is validated by comparing the proposed model to existing test data and is further developed towards predicting the design shear strength of RM structural walls. The results from these experimental and analytical research programs are subsequently used to provide a set of proposed code clauses at the end of the thesis. Prescriptive design requirements are proposed for a new category of <em>Special Ductile Masonry Shear Wall</em> containing boundary elements including integration of a new shear strength expression. These clauses have been written with the intention of adoption within the CSA S304.1 and the MSJC North American masonry designs standards.</p> / Doctor of Philosophy (PhD)

Steel flexural yielding arms can be an effective energy dissipation device for several seismic force resisting systems, including controlled rocking masonry walls. In controlled rocking masonry walls, uplift of the wall from the foundation is allowed in a way that can localize damage and minimize post-earthquake residual drifts. However, along with other modes of failure, sliding of the rocking walls can increase drifts and damage if not adequately addressed. Controlled rocking systems have different alternatives to prevent sliding, which include the use of additional mechanical components (e.g. metal stoppers) at the corners to resist lateral forces while allowing the wall rocking motion. However, these mechanical components hinder the constructability of the wall in some cases. The use of an energy dissipation device (i.e. steel flexural yielding arm) to also prevent the wall sliding mechanism has not been fully explored to date. The development of an easily replaceable energy dissipation device with the ability to simultaneously resist sliding demands is expected to maintain the overall performance of controlled rocking masonry walls, while also enhancing post-earthquake repairability. The objective of the current study is to experimentally investigate the effect of axial forces on the behaviour of steel flexural yielding arms under cyclic loading. In this respect, the study first presents a description of the experimental program, test setup, and instrumentation. Next, the experimental results of the tested specimens are discussed in terms of the effect of axial forces on the load, displacement, and energy dissipation capacities of the tested devices. Finally, new design equations that account for axial forces are proposed and verified against the experimental data along with a finite element model. Based on the results, recommendations are given for the further development of externally attached and replaceable flexural yielding arms for controlled rocking masonry walls. / Thesis / Master of Applied Science (MASc) / Controlled rocking masonry walls can be a cost-efficient alternative to traditional masonry shear walls because of their enhanced performance, specifically to reduce and localize structural damage induced by seismic loads. However, a controlled rocking wall requires additional energy dissipation devices or post-tensioning techniques to compliment the rocking wall to achieve the desired performance. This thesis explores and improves a type of energy dissipation device for controlled rocking masonry walls and aims to provide detailed design specifications for professional engineers. A design and considerations from previous studies are discussed, followed by the experimental validation, and finally new design equations are proposed for this type of reliable, flexural energy dissipation device.

Metal buildings account for over 40% of low-rise construction in the US. Despite this, predictive fundamental period equations that were obtained empirically for mid-rise construction are used in seismic design. Analytical modeling of metal building frames implied that these equations significantly underpredict the period, which led to the development of a new predictive equation. However, experimental tests showed that these models may overestimate the measured period. In this work, further tests were carried out in order to single out possible causes. Buildings were tested during different stages of construction to evaluate how non-structural elements could affect the behavior. Both planar and three-dimensional models were developed to determine if design assumptions are accurate for the purpose of estimating the period. The results from tests showed that, unlike other single-story buildings, non-structural components seem to have negligible effect on the structural behavior. However, several buildings seemed to exhibit signs of fixed conditions at the column base. This assertion was corroborated by updating the analytical models. The two modeling approaches showed good agreement with each other as well, validating the use of planar models to predict the period. Finally, new predictive equations are proposed that take into account the type of cladding, as it was found to be an important variable not previously considered. However, low mass participation ratios coupled with the stiffness provided by the secondary framing put the use of the equivalent lateral force procedure into question. / Master of Science / When designing buildings for earthquake loads it is necessary to know their dynamic properties in order to define the equivalent forces that must be applied. Building codes provide predictive equations that were obtained empirically for typical mid-rise construction. Metal buildings do not fall within the range of buildings tested for their development, and so a new equation was proposed for them based on a database of planar models. However, previous tests implied that this equation was predicting larger periods than those obtained experimentally. In this work, further tests were carried out during different stages of construction to evaluate how non-structural elements could affect the behavior. Models were also created for each building in order to determine if the approach used to develop the metal building database was adequate for estimating the period. The results from tests showed that, unlike other single-story buildings, non-structural components seem to have negligible effect on the structural behavior, and the modeling assumptions within the database were validated. Further analysis showed that the type of cladding (concrete or metal sheeting) had a large influence on the properties of metal buildings. In consequence, a new set of predictive equations is proposed that takes this into account.

In the past two decades, there have been significant advances in the development of self-centering (SC) seismic force resisting systems. However, examples of SC systems used in practice are limited due to unusual field construction practices, high initial cost premiums and deformation incompatibility with the gravity framing. A self-centering beam moment frame (SCB-MF) has been developed that virtually eliminates residual drifts and concentrates the majority of structural damage in replaceable fuse elements. The SCB consists of a I-shaped steel beam augmented with a restoring force mechanism attached to the bottom flange and can be shop fabricated. Additionally, the SCB has been designed to eliminate the deformation incompatibility associated with the self-centering mechanism. The SCB-MF system is investigated and developed through analytical, computational, and experimental means. The first phase of the work involves the development of the SCB concepts and the experimental program on five two-thirds scale SCB specimens. Key parameters were varied to investigate their effect on global system hysteretic response and their effect on system components. These large-scale experiments validated the performance of the system, allowed the investigation of detailing and construction methods, provided information on the behavior of the individual components of the system. The experimental results also provided data to confirm and calibrate computational models that can capable of capturing the salient features of the SCB-MF response on global and component level. As a part of the second phase, a set of archetype buildings was designed using the self-centering beam moment frame (SCB-MF) to conduct a non-linear response history study. The study was conducted on a set of 9 archetype buildings. Four, twelve and twenty story frames, each with three levels of self-centering ratios representing partial and fully self-centering systems, were subjected to 44 ground motions scaled to two hazard levels. This study evaluated the performance of SCB-MFs in multi-story structures and investigated the probabilities of reaching limit states for earthquake events with varying recurrence period. The experimental and computational studies described in this dissertation demonstrate that the SCB-MF for steel-framed buildings can satisfy the performance goals of virtually eliminating residual drift and concentrating structural damage in replaceable fuses even during large earthquakes. / Ph. D.

A new type of steel plate shear wall has been devised which resists out-of-plane buckling without requiring stiffeners. The ring-shaped steel plate shear wall (RS-SPSW) includes a web plate that is cut with a pattern of holes leaving ring-shaped portions of steel connected by diagonal links. The ring shape resists out-of-plane buckling through the mechanics of how a circular ring deforms into an ellipse. It has been shown that the ring's compression diagonal will shorten a similar amount as the tension diagonal elongates, essentially eliminating the slack in the direction perpendicular to the tension field. Because of the unique features of the ring's mode of distortion, the load-deformation response of the resulting RS-SPSW system can exhibit full hysteretic behavior and possess greatly improved stiffness relative to thin unstiffened SPSW. The concept has been validated through testing on seven 34 in x 34 in panels. General conclusions about influence of different geometric parameters on plate behavior have been made. / Master of Science

With the advancement in knowledge of inelastic response of structures, the design and construction practices of reinforced concrete buildings have been changing worldwide. Most of the codes are incorporating the near-fault factors and performance based designs in the seismic codes. However, further investigation is needed to identify the physical behaviour of multi-storey buildings to near-fault ground motions. At present, quantitative evaluation of response and its mitigation to near field ground motions is a popular topic in earthquake engineering field. The present study discusses the inelastic response of symmetric and asymmetric multi-storey buildings to near-fault ground motions. The possibility of design approach is based on ‘expendable top storey’ for the multi-storey RC- buildings to near field records. If such behaviour is feasible one can conceive of a structure whose top storey is permitted and designed to undergo large inelastic deformations while reducing damage in the lower storey. The concept was first proposed in an earlier research (RaghuPrasad, 1977). Such a concept juxtaposes the often-mentioned ‘soft first storey’ concept. Further in this report, the performance evaluation of multi-storey buildings near Chiplun fault in Mumbai, India is also discussed. The thesis is organized in the following chapters: Introduction in Chapter-1 contains detailed literature review on inelastic response of symmetric and asymmetric buildings, response of buildings to near-fault records, elastic and inelastic vibration absorber concepts and performance based designs. The literature reveals that considerable amount of research has been carried out on the elastic, inelastic response of structures and vibration absorber concepts to ordinary ground motions. Recently, the effect of near field ground motions on the response of multi-storey buildings is gaining much importance. Most of the research publications are available on response of symmetric buildings subjected to near field ground motions. But many problems are yet to be investigated. They are, identification of important ground motion parameters in near fault records, vibration absorber concepts and torsional response of structures subjected to pulse type ground motions. These problems are clearly mentioned in the recently published state-of-the-art review by Shuang and Li-Li (2007). In this report an attempt has been made to solve these problems. Effect of near-fault ground motions on symmetric multi-storey buildings in Chapter-2, describes simplified non-dimensionalized equations of motion to study the response behaviour of multi-storey buildings to near fault records. The non-dimensionalized equations of motion are expressed in terms of near fault ground motion parameters. The objective is to find a relation between ductility demand and near field ground motion parameters through neural network approach. For this a neural network modeling was done to predict the ductility demand in terms of peak ground acceleration, peak ground velocity, epicentral distance and pulse period of the near field ground motion. A thorough sensitive analysis is carried out, to ascertain which parameters are having maximum influence on ductility demand. In this chapter further, a comparative study is made on the inelastic seismic response of multi-storey buildings to pulse type and non pulse type ground motions. The study shows that, it is necessary to consider the effect of near fault ground motions separately and make provisions for the design in the codes of practice accordingly. Vibration absorber effect in multi-storey buildings in chapter-3, discusses the behaviour of top storey as a vibration absorber during near field ground motions. For this purpose, a five storey symmetric building model is considered as an example problem to demonstrate the effectiveness of the proposed concept. Response of the structure is obtained for the various combinations of absorber storey parameters such as mass ratio, frequency ratio and yield displacement ratio. Here mass ratio means mass of the absorber storey to that of the bottom storey and similarly for the frequency and yield displacement ratios. Observing the storey-wise variation of these responses, we can say that for a range of mass ratios, frequency ratios and yield displacement ratios, the inelastic response of top storey is large compared to the lower storeys. This range is termed as ‘effective range’. Further, in this range the top storey absorbs the vibration energy of the structure by keeping the lower storeys in elastic state i.e. acts as a vibration absorber. The top storey can also be termed as ‘expendable top storey’. Effect of near-fault ground motions on asymmetric multi-storey buildings in Chapter-4, discusses the inelastic response of asymmetric buildings to single horizontal component and two horizontal components of near fault ground motions viz., fault normal and fault parallel components. For numerical investigations eight building models are considered. Eccentricity has been created by keeping the stiffness and mass centre separately. The building models are subjected to strong motion records of Imperial Valley Array-5 (1979) and Northridge-Sylmar (1994). A detailed study on the effect of base shear strength, eccentricity and pulse period of near fault ground motions on the response is investigated. Performance of multi-Storey buildings in Chapter-5, reported a detailed procedure for the performance evaluation of structures. The procedure is applied to find the performance evaluation of multi-storeyed buildings located in near fault region. Chiplun fault in Mumbai, India has been chosen for the study because several features of that fault are clearly published (RaghuKanth and Iyengar, 2006). Results of performance evaluation of five and ten storeyed symmetric buildings with and without infill panels are studied. Ground motion records consistent with the hazard spectrum for the design are considered. The performance of the building near the Chiplun fault in Mumbai, India shows operational under UHS-500 (uniform hazard spectrum) event and it collapses when the building is exposed to UHS-2500 record. The thesis is concluded in Chapter-6 with an overall summary of the report and suggestions for further scope of the work.

Master of Science / Department of Architectural Engineering and Construction Science / Kimberly W. Kramer / The basic tenets of performance based seismic design (PBSD) are introduced. This includes a description of the underlying philosophy of PBSD, the concept of performance objectives, and a description of hazard levels and performance indicators. After establishing the basis of PBSD, analysis procedures that fit well within the PBSD framework are introduced. These procedures are divided into four basic categories: linear static, linear dynamic, nonlinear static, and nonlinear static. Baseline FEMA requirements are introduced for each category. Each analysis category is then expanded to include a detailed description of and variations on the basic procedure. Finally, optimization procedures that mesh well with a PBSD framework are introduced and described. The optimization discussion focuses first on the solution tools needed to effectively execute a PBSD multi-objective optimization procedure, namely genetic and evolutionary strategies algorithms. Next, multiple options for defining objective functions and constraints are presented to illustrate the versatility of structural optimization. Taken together, this report illustrates the unique aspects of PBSD. As PBSD moves to the forefront of design methodology, the subjects discussed serve to familiarize engineers with the advantages, possibilities, and finer workings of this powerful new design methodology.

Στην παρούσα εργασία παρουσιάζεται μία νέα βασισμένη στην επιτελεστικότητα μέθοδος αντισεισμικού σχεδιασμού χωρικών μεταλλικών κατασκευών, οι οποίες υπόκεινται σε σεισμικές διεγέρσεις μακρινού πεδίου. Η μέθοδος αυτή συνδυάζει τα πλεονεκτήματα της μεθόδου σχεδιασμού με βάση τις δυνάμεις και με βάση της μετατοπίσεις και γι’ αυτό ονομάζεται υβριδική δυνάμεων-μετατοπίσεων (ΥΔΜ) μέθοδος. Για τη δημιουργία της προτεινόμενης μεθόδου γίνεται παραμετρική σεισμική μελέτη κανονικών καμπτικών μεταλλικών κτιρίων με και χωρίς τυχηματικές εκκεντρότητες, καθώς και μεταλλικών κτιρίων τα οποία εμφανίζουν γεωμετρικές μη κανονικότητες λόγω ανομοιόμορφης καθ’ ύψος κατανομής μάζας και λόγω παρουσίας εσοχών. Αρχικά γίνεται μια βιβλιογραφική ανασκόπηση για τις ήδη υπάρχουσες μεθόδους, όσον αφορά στο σχεδιασμό και στην εκτίμηση της ανελαστικής σεισμικής απόκρισης επίπεδων και χωρικών κατασκευών. Στη συνέχεια περιγράφεται η επιλογή των παραμέτρων και η όλη διαδικασία που ακολουθήθηκε για τη δημιουργία μίας βάσης δεδομένων σεισμικής απόκρισης η οποία απαίτησε 43176 μη γραμμικές δυναμικές αναλύσεις. Με βάση την στατιστική επεξεργασία που έγινε προέκυψαν εμπειρικές σχέσεις αντισεισμικού σχεδιασμού, οι οποίες καθιστούν δυνατό τον έλεγχο της βλάβης κατά το σχεδιασμό νέων κατασκευών και οι οποίες λαμβάνουν υπόψη την επιρροή διαφόρων παραμέτρων, όπως ο αριθμός ανοιγμάτων, ο αριθμός ορόφων, η μορφή της κάτοψης, καθώς και η μη κανονικότητα της κατασκευής. Επιπλέον εξετάστηκε η επιρροή της φυσικής μονοαξονικής εκκεντρότητας, μεταξύ κέντρου μάζας και κέντρου δυσκαμψίας στην ανελαστική σεισμική απόκριση χωρικών κατασκευών με μεικτό σύστημα ανάληψης σεισμικών δυνάμεων. Ωστόσο, επειδή ο αριθμός των κτιρίων που χρησιμοποιήθηκαν ήταν μικρός, δεν έγινε προσπάθεια κατασκευής κάποιων εμπειρικών σχέσεων από τα αποτελέσματα που προέκυψαν για αυτήν την περίπτωση. Τα πλεονεκτήματα της νέας ΥΔΜ μεθόδου αντισεισμικού σχεδιασμού, παρουσιάζονται μέσω τριών παραδειγμάτων, όπου η προτεινόμενη μέθοδος συγκρίνεται με τη μέθοδο σχεδιασμού με βάση τις δυνάμεις στην οποία βασίζονται όλοι σχεδόν οι υπάρχοντες αντισεισμικοί κανονισμοί. Από τη σύγκριση που γίνεται προκύπτει ότι, σε αντίθεση με τη μέθοδο των δυνάμεων, η ΥΔΜ μέθοδος μπορεί να κάνει κατά το σχεδιασμό άμεσο έλεγχο της βλάβης. / This dissertation proposes a preliminary performance-based seismic design method for three-dimensional steel building frames under ordinary (i.e., without near fault effects) ground motions. This method combines the advantages of the well-known force-based and displacement-based seismic design methods in a hybrid force/displacement design scheme. The proposed method was developed based on the results of an extensive parametric study involving the inelastic seismic response of regular and irregular moment resisting frames (MRFs). The regular MRFs are structures with and without the presence of accidental eccentricities, whereas the irregular MRFs, are structures with vertical mass irregularities and structures with setbacks. In total 146 buildings have been studied. The results of 43176 nonlinear dynamic analyses were post-processed in order to create a databank with the response quantities of interest. The main parameters that affect the inelastic response of the examined structures were recognised after the statistical analysis of the created response. Based on regression analysis, a procedure in terms of simple formulae for estimating the maximum roof displacement, the maximum interstorey drift ratio and the maximum rotation ductility along the height of the frame was developed. In addition, the inelastic seismic response of 20 buildings with natural eccentricities has been studied, which combines MRFs with buckling restrained braces. However, the conclusions of this case cannot be generalized, because only few cases were investigated. Comparison of the proposed method with the procedures adopted in current seismic design codes demonstrated the efficiency of the former. The results revealed that the proposed procedure seems to be more rational and efficient than the procedures used in the current seismic design codes. Nonlinear time history analyses proved the consistency of the proposed method to accurately estimate inelastic deformation demands and the tendency of the current seismic design codes to overestimate the maximum roof displacement and underestimate the maximum interstorey drift ratio along the height of the frames.

This study was initiated to quantify the effect of different degrees of irregularity on structures designed for earthquake using simplified analysis. The types of irregularity considered were: (a) Vertical Irregularity • Mass • Stiffness -Strength (b) Horizontal (Plan) Irregularity • Diaphragm Flexibility Simple models were used to allow many analyses to be conducted in a relatively short time. For vertical irregularity studies, simple shear-type structures were designed according to the New Zealand design Standard, NZS1170.5, firstly as regular structures, and then they were redesigned as irregular structures to the same target drift. Both regular and irregular structures were then subjected to a suite of records, and vertical irregularity effects evaluated from the difference in response. For the flexible diaphragm effect study, simple models of structures were developed with: (a) a rigid diaphragm assumption; and (b) a flexible diaphragm assumption. Flexible diaphragm effects were evaluated by conducting time-history analyses and comparing the responses of structures with rigid and flexible diaphragms. A mechanics based approach was developed to quantify flexible diaphragm effects, which was shown to produce consistent results with those from time-history analyses. Relationships between the degree of irregularity and the change in behaviour were developed. This information facilitates designers and plan checkers to rapidly evaluate the likely effect of irregularity on structures. It provides guidance as to: (a) when the effect of structural irregularity can be ignored, and (b) the change in demands for different degrees of structural irregularity. The relations developed also provide a rigorous technical basis for future regularity provisions in the NZS1170.5 and other world-wide seismic design codes.

This thesis investigates the performance of concentrically braced zipper frames through complementary experimental and numerical simulation approaches and proposes a design methodology for an innovative bracing scheme labeled as the suspended zipper frame. The suspended zipper frame intends to ensure that the top-story hat truss remains elastic, resulting in very ductile behavior of the structure. In the first part of the work, a three-story prototype frame was designed based on a preliminary design method. Three tests were conducted on one-third scale models of this prototype to verify the design procedure and assess the system performance under very different load histories. Comparisons of the results between analyses and experiments validated the partial-height zipper mechanism envisioned, and led to refinements of the design procedure and establishment of appropriate design details for these frames. The design and performance of this structural system are illustrated with three-, nine-, and twenty-story buildings designed for the same masses as those used in the SAC studies for the Los Angeles area. The proposed design strategy results in suspended zipper frames having more ductile behavior and higher strength than typical zipper frames. In addition, the suspended zipper frames also appear to reduce the tendency of chevron-braced frames to form soft stories and to improve seismic performance without having to use overly stiff beams. Finally, an explanation of the design philosophy as well as code language format of the design procedure is given.