Unbonded post-tensioned concrete block (UPCB) shear walls are an effective seismic force resisting system due to their ability to contain expected damage attributed to their self-centering capabilities. A few design procedures were proposed to predict the in-plane flexural response of UPCB walls, albeit following only basic mechanics and/or extensive iterative methods. Such procedures, however, may not be capable of capturing the complex nonlinear relationships between different parameters that affect UPCB walls’ behavior or are tedious to be adopted for design practice. In addition, the limited datasets used to validate these procedures may render their accuracy and generalizability questionable, further hindering their adoption by practitioners and design standards. To address these issues, an experimentally-validated nonlinear numerical model was adopted in this study and subsequently employed to simulate 95 UPCB walls with different design parameters to compensate for the lack of relevant experimental data in the current literature. Guided by mechanics and using this database, an evolutionary algorithm, multigene genetic programming (MGGP), was adopted to uncover the relationships controlling the response of UPCB walls, and subsequently develop simplified closed-form wall behavior prediction expressions. Specifically, through integrating MGGP and basic mechanics, a penta-linear backbone model was developed to predict the load-displacement backbone for UPCB walls up to 20% strength degradation. Compared to existing predictive procedures, the prediction accuracy of the developed model and its closed-form nature are expected to enable UPCB wall adoption by seismic design standards and code committees. / Thesis / Master of Applied Science (MASc)

Reinforced concrete block shear walls (RCBSWs) are used as seismic force resisting systems in low- and medium-rise buildings. However, attributed to their nonlinear behavior and composite material nature, accurate prediction of their seismic performance relying only on mechanics is challenging. This study introduces multi-gene genetic programming (MGGP)— a class of bio-inspired artificial intelligence, to uncover the complexity of RCBSW behaviors and develop simplified procedures for predicting the full backbone curve of flexure-dominated fully grouted RCBSWs under cyclic loading. A piecewise linear backbone curve was developed using five secant stiffness expressions associated with cracking, yielding, 80% ultimate, ultimate, and 20% strength degradation (i.e., post-peak stage) derived through controlled MGGP. Based on the experimental results of large-scale cyclically loaded RCBSWs, compiled from previously reported studies, a variable selection procedure was performed to identify the most influential variable subset governing wall behaviors. Utilizing individual wall results, the MGGP stiffness expressions were first trained and tested, and their accuracy was subsequently compared to that of existing models employing various statistical measures. In addition, the predictability of the developed backbone model was assessed at the system-level against experimental results of two two-story buildings available in the literature. The outcomes obtained from this study demonstrate the power of MGGP approach in addressing the complexity of the cyclic behavior of RCBSWs at both component- and system-level—offering an efficient prediction tool that can be adopted by relevant seismic design standards pertaining to RCBSW buildings. / Thesis / Master of Applied Science (MASc)

The traditional construction practice used in masonry buildings throughout the world is limited to walls with rectangular cross sections that, when reinforced with steel bars, typically accommodate only single-leg horizontal ties and a single layer of vertical reinforcement. This arrangement provides no confinement at the wall toes, and it may lead to instability in critical wall zones and significant structural damage during seismic events. Conversely, the development of a new building system, constructed with reinforced masonry (RM) walls with boundary elements, allows closed ties to be used as confinement reinforcement, thus minimizing such instability and its negative consequences. Relative to traditional walls, walls with boundary elements have enhanced performance because they enable the compression reinforcement to remain effective up to much larger displacement demands, resulting in a damage tolerant system and eventually, more resilient buildings under extreme events. Research on the system-level (complete building) performance of RM walls with boundary elements is, at the time of publication of this dissertation, nonexistent in open literature. What little research has been published on this innovative building system has focused only on investigating the component-level performance of RM walls with boundary elements under lateral loads. To address this knowledge gap, the dissertation presents a comprehensive research program that covered: component-level performance simulation; system-level (complete building) experimental testing; seismic risk assessment tools; and simplified analytical models to facilitate adoption of the developed new building system. In addition, and in order to effectively mobilize the knowledge generated through the research program to stakeholders, the work has been directly related to building codes in Canada and the USA (NBCC and ASCE-7) as well as other standards including FEMA P695 (FEMA 2009) (Chapter 2), TMS 402 and CSA S304 (Chapter 3), FEMA P58 (FEMA 2012) (Chapter 4), and ASCE-41 (Chapter 5). Chapter 1 of the dissertation highlights its objectives, focus, scope and general organization. The simulation in Chapter 2 is focused on evaluating the component-level overstrength, period-based ductility, and seismic collapse margin ratios under the maximum considered earthquakes. Whereas previous studies have shown that traditional RM walls might not meet the collapse risk criteria established by FEMA P695, the analysis presented in this chapter clearly shows that RM shear walls with boundary elements not only meet the collapse risk criteria, but also exceed it with a significant margin. Following the component-level simulation presented in Chapter 2, Chapter 3 focused on presenting the results of a complete two-story asymmetrical RM shear wall building with boundary elements, experimentally tested under simulated seismic loading. This effort was aimed at demonstrating the discrepancies between the way engineers design buildings (as individual components) and the way these buildings actually behave as an integrated system, comprised of these components. In addition, to evaluate the enhanced resilience of the new building system, the tested building was designed to have the same lateral resistance as previously tested building with traditional RM shear walls, thus facilitating direct comparison. The experimental results yielded two valuable findings: 1) it clearly demonstrated the overall performance enhancements of the new building system in addition to its reduced reinforcement cost; and 2) it highlighted the drawbacks of the building acting as a system compared to a simple summation of its individual components. In this respect, although the slab diaphragm-wall coupling enhanced the building lateral capacity, this enhancement also meant that other unpredictable and undesirable failure modes could become the weaker links, and therefore dominate the performance of the building system. Presentation of these findings has attracted much attention of codes and standards committees (CSA S304 and TMS 402/ACI 530/ASCE 5) in Canada and the USA, as it resulted in a paradigm shift on how the next-generation of building codes (NBCC and ASCE-7) should be developed to address system-levels performance aspects. Chapter 4 introduced an innovative system-level risk assessment methodology by integrating the simulation and experimental test results of Chapters 2 and 3. In this respect, the experimentally validated simulations were used to generate new system-level fragility curves that provide a realistic assessment of the overall building risk under different levels of seismic hazard. Although, within the scope of this dissertation, the methodology has been applied only on buildings constructed with RM walls with boundary elements, the developed new methodology is expected to be adopted by stakeholders of other new and existing building systems and to be further implemented in standards based on the current FEMA P58 risk quantification approaches. Finally, and in order to translate the dissertation findings into tools that can be readily used by stakeholders to design more resilient buildings in the face of extreme events, simplified backbone and hysteretic models were developed in Chapter 5 to simulate the nonlinear response of RM shear wall buildings with different configurations. These models can be adapted to perform the nonlinear static and dynamic procedures that are specified in the ASCE-41 standards for both existing and new building systems. The research in this chapter is expected to have a major positive impact, not only in terms of providing more realistic model parameters for exiting building systems, but also through the introduction of analytical models for new more resilient building systems to be directly implemented in future editions of the ASCE-41. This dissertation presents a cohesive body of work that is expected to influence a real change in terms of how we think about, design, and construct buildings as complex systems comprised of individual components. The dissertation’s overarching hypothesis is that previous disasters have not only exposed the vulnerability of traditional building systems, but have also demonstrated the failure of the current component-by-component design approaches to produce resilient building systems and safer communities under extreme events. / Dissertation / Doctor of Philosophy (PhD)

Recent research interests in studying the performance of different seismic force resisting systems (SFRS) have been shifting from component- (individual walls) to system-level (complete building) studies. Although there is wealth of knowledge on component-level performance of reinforced masonry shear walls (RMSW) under seismic loading, a gap still exists in understanding the response of these components within a complete system. Consequently, this study’s main objective is to investigate the influence of the diaphragm’s out-of-plane stiffness on the seismic response of RMSW buildings. In addition, the study aims to synthesize how this influence can be implemented in different seismic design approaches and assessment frameworks. To meet these objectives a two-story scaled asymmetrical RMSW building was tested under quasi-static cyclic loading. The analysis of the test results showed that the floor diaphragms’ out-of-plane stiffness played an important role in flexurally coupling the RMSW aligned along the loading direction with those walls orthogonal to it. This system-level aspect affected not only the different wall strength and displacement demands but also the failure mechanism sequence and the building twist response. The results of the study also showed that neglecting diaphragm flexural coupling influence on the RMSW at the system-level may result in unconservative designs and possibly undesirable failure modes. To address these findings, an analytical model was developed that can account for the aforementioned influences, in which, simplified load-displacement relationships were developed to predict RMSW component- and system-level responses under lateral seismic loads. This model is expected to give better predictions of the system response which can be implemented, within the model limitations, in forced- and displacement-based seismic design approaches. In addition, and in order to adapt to the increasing interest in more resilient buildings, this study presents an approach to calculate the system robustness based on the experimental data. Finally, literature shows that the vast majority of the loss models available for RMSW systems were based on individual component testing and/or engineering judgment. Consequently, this study proposes system damage states in lieu of component damage states in order to enhance the prediction capabilities of such models. The current dissertation highlights the significant influence of the diaphragm out-of-plane stiffness on the system-level response that may alter the RMSW response to seismic events; an issue that need to be addressed in design codes and standards. / Dissertation / Doctor of Philosophy (PhD)

Regular starches contain two principal types of glucan polymers: amylopectin and amylose. The structure of amylopectin is characterized according to the unit chain length profile and the nature of the branching pattern, which determine the alignment of glucan chains during biosynthesis. The organization of glucan chains in amylopectin and their impact on the structure of starch are still open to debate. The location of amylose and its exact contribution to the assembly of crystalline lamellae in regular and high-amylose starch granules also remain unknown. The primary focus of this thesis is the organization and flexibility of glucan chains in crystalline lamellae. The organization and flexibility of glucan chains in native, annealed (ANN), and heat-moisture treated (HMT) normal, waxy, hylon V, hylon VII, and hylon VIII corn starches were examined. This study has shown for the first time that increased amounts of apparent amylose in B-type starches hinder the polymorphic transition (from B to A+B) during HMT. The research has also demonstrated that an iodine-glucan complex transformed the B-type polymorphic pattern of hylon starches into a V-type pattern. The differential scanning calorimetry (DSC) results showed that ANN- and HMT-induced changes were most pronounced in hylon starches. These findings suggest that the glucan tie chains influences the assembly of crystalline lamellae in high-amylose starches. The relationship between the internal unit chain composition of amylopectin, and the thermal properties and annealing of starches from four different structural types of amylopectin was investigated by DSC. The onset gelatinization temperature (To) correlated negatively with the number of building blocks in clusters (NBbl) and positively with the inter-block chain length (IB-CL). The enthalpy of gelatinization (∆H) correlated positively with the external chain length of amylopectin. Annealing results showed that starches with a short IB-CL were most susceptible to ANN, as evidenced by a greater increase in the To and Tm. The increase in enthalpy was greater in starches with long external chains and IB-CLs. These data suggest that the internal organization of glucan chains in amylopectin determines the alignment of chains within the crystalline lamellae and thereby the thermal properties and annealing of the starch granules.