Structural systems have been evolving in terms of material properties and construction techniques, and their levels of protection against hazardous events have been the focus of different studies. For instance, the performance of the lateral force resisting systems has been investigated extensively to ensure that such systems would provide an adequate level of strength ductility capacity when subjected to seismic loading. However, with the increased occurrence of accidental and deliberate explosion incidents globally by more than three fold from 2004 to 2012, more studies have been focusing on the performance of such systems to blast loads and the different methods to quantify the inflicted damage. Although both blast and seismic design requires structures to sustain a level of ductility to withstand the displacement demands, the distributions of such demands from seismic ground excitation and blast loading throughout the structural system are completely different. Therefore, a ductile seismic force resisting system may not necessarily be sufficient to resist a blast wave. To address this concern, North American standards ASCE 59-11, CSA S850-12 provide response limits that define the different damage states that components may exhibit prior to collapse. Over the past ten years, a new configuration of reinforced masonry (RM) shear walls utilizing boundary elements (BEs) at the vertical edges of the wall has been investigated as an innovative configuration that enhances the wall’s in-plane performance. As such, they are included in the North American Masonry design standards, CSA S304-14 and TMS 402-16 as an alternative means to enhance the ductility of seismic force resisting systems. However, investigations regarding the out-of-plane performance of such walls are generally scarce in literature which hindered the blast design standards from providing unique response limits that can quantify the different damage states for RM walls with BEs. This dissertation has highlighted that some relevant knowledge gaps may lead to unconservative designs. Such gaps include (a) the RM wall with BEs out-of-plane behavior and damage sequence; and more specifically, (b) the BEs influence on the wall load-displacement response; as well as, (c) the applicability of using of the current response limits originally assigned for conventional RM walls to assess RM walls with BEs. Addressing these knowledge gaps is the main motivation behind this dissertation. In this respect, this dissertation reports an experimental program, that focuses on bridging the knowledge gap pertaining to the out-of-plane performance of seismically-detailed RM shear walls with BEs, which were not designed to withstand blast loads. Meanwhile, from the analytical perspective, plastic analyses were carried out taking into account the different mechanisms that the wall may undergo until peak resistance is achieved. This approach was adopted in order to quantify the resistance function of such walls and determine the contribution of the BEs and web to the overall wall resistance. In addition, the experimental results of the tested walls were used to validate a numerical finite element model developed to compare the resistance function of RM walls with and without BEs. Afterwards, the model was further refined to capture the walls’ performance under blast loads. The pressure impulse diagrams were generated to assess the capability of the current response limits in quantifying the different damage states for walls with different design parameters. Furthermore, new response limits were proposed to account for the out-of-plane ductility capacities of different wall components. Finally, a comparison between conventional rectangular walls and their counterparts with BEs using the proposed limits was conducted in the form of pressure-impulse diagram to highlight the major differences between both wall configurations. / Thesis / Doctor of Philosophy (PhD)

Low-aspect-ratio reinforced concrete (RC) shear walls, characterized by height-to-length ratios of less than two, have been widely used as a seismic force-resisting system (SFRS) in a wide array of structures, ranging from conventional buildings to critical infrastructure systems such as nuclear facilities. Despite their extensive applications, recent research has brought to light the inadequate understanding of their seismic performance, primarily attributed to the intricate nonlinear flexure-shear interaction behaviour unique to these walls. In this respect, the current research dissertation aims to bridge this knowledge gap by conducting a comprehensive evaluation to quantify the seismic performance of low-aspect-ratio RC shear walls when used in different applications. Chapter 2 focuses on low-aspect-ratio RC shear walls that are employed in residential and industrial structures. Considering their significance, the seismic response modification factors of such walls, as defined in various standards, are thoroughly examined and evaluated utilizing the FEMA P695 methodology. The analysis revealed potential deficiencies in the current code-based recommendations for response modification factors. Consequently, a novel set of response modification factors, capable of mitigating the seismic risk of collapse under the maximum considered earthquake, is proposed. Such proposed values can be integrated into the forthcoming revisions of relevant building codes and design standards. While the FEMA P695 methodology offers a comprehensive approach to assessing building seismic performance factors, its practical implementation is associated with many challenges for practicing engineers. Specifically, the methodology heavily relies on resource-intensive and time-consuming incremental dynamic analyses, making it less feasible for routine engineering practices. To enhance its practicality, a data-driven framework is developed in Chapter 3, circumventing the need for such demanding analyses. This framework provides genetic programming-based expressions capable of producing accurate predictions of the median collapse intensities—a key metric in the acceptance criteria of the FEMA P695 methodology, for different structural systems. To demonstrate its use, the developed framework is operationalized to low-aspect-ratio RC shear walls and the predictive expression is evaluated considering several statistical and structural parameters, which showed its adequacy in predicting the median collapse intensities of such walls. Furthermore, the adaptability of this framework is showcased, highlighting its applicability across various SFRSs. Chapters 4 and 5 tackle the scarcity of experimental assessments pertaining to the seismic performance of low-aspect-ratio RC walls in nuclear facilities. The seismic hybrid simulation testing technique is employed herein to merge the simplicity of numerical simulations with the efficiency of experimental tests. Hybrid simulation can overcome obstacles related to physical specimen sizes, limited actuator capacities, and space constraints in most laboratories. In these two chapters, the experimental program delves into evaluating the seismic performance of three two-storey low-aspect-ratio nuclear RC walls under different earthquake levels, including operational, design, and beyond-design-level scenarios. Diverse design configurations, including the use of increased thickness boundary elements and different materials (i.e., normal- and high-strength reinforcement), are considered in such walls to provide a comprehensive understanding of several structural parameters and economic metrics. Key structural parameters, such as the force-displacement responses, multi-storey effects, lateral and rotational stiffnesses, ductility capacities, displacement components, rebar strains, crack patterns and damage sequences, are all investigated to provide direct comparisons between the walls in terms of their seismic performances. Additionally, economic metrics, including the total rebar weights, overall construction costs and the expected seismic repair costs, are considered in order to evaluate the seismic performance of the walls considering an economic perspective. The findings of this experimental investigation are expected to inform future nuclear design standards by enhancing the resilience and safety of their structures incorporating low-aspect-ratio RC shear walls. / Thesis / Doctor of Philosophy (PhD)