This dissertation describes the analytical research as part of a comprehensive research program to develop a new floor anchorage system for seismic resistant design, termed the Inertial Force-limiting Floor Anchorage System (IFAS). The IFAS intends to reduce damage in seismic resistant building structures by limiting the inertial force that develops in the building during earthquakes. The development of the IFAS is being conducted through a large research project involving both experimental and analytical research. This dissertation work focuses on analytical component of this research, which involves stand-alone computational simulation as well as analytical simulation in support of the experimental research (structural and shake table testing). The analytical research covered in this dissertation includes four major parts: (1) Examination of the fundamental dynamic behavior of structures possessing the IFAS (termed herein IFAS structures) by evaluation of simple two-degree of freedom systems (2DOF). The 2DOF system is based on a prototype structure, and simplified to represent only its fundamental mode response. Equations of motions are derived for the 2DOF system and used to find the optimum design space of the 2DOF system. The optimum design space is validated by transient analysis using earthquakes. (2) Evaluation of the effectiveness of IFAS designs for different design parameters through earthquake simulations of two-dimensional (2D) nonlinear numerical models of an evaluation structure. The models are based on a IFAS prototype developed by a fellow researcher on the project at Lehigh University. (3) Development and calibration of three-dimensional nonlinear numerical models of the shake table test specimen used in the experimental research. This model was used for predicting and designing the shake table testing program. (4) Analytical parameter studies of the calibrated shake table test model. These studies include: relating the shake table test performance to the previous evaluation structure analytical response, performing extended parametric analyses, and investigating and explaining certain unexpected shake table test responses. This dissertation describes the concept and scope of the analytical research, the analytical results, the conclusions, and suggests future work. The conclusions include analytical results that verify the IFAS effectiveness, show the potential of the IFAS in reducing building seismic demands, and provide an optimum design space of the IFAS.

Several studies were undertaken by various investigators during the last five decades to better understand the engineering behaviour of unsaturated soils. These studies are justified as more than 33% of soils worldwide are found in either arid or semi-arid regions with evaporation losses exceeding water infiltration. Due to this reason, the natural ground water table in these regions is typically at a greater depth and the soil above it is in a state of unsaturated conditions. Foundations of structures such as the housing subdivisions, multi-storey buildings, bridges, retaining walls, silos, and other infrastructure constructed in these regions in sandy soils are usually built within the unsaturated zone (i.e., vadose zone). Limited studies are reported in the literature to understand the influence of capillary stresses (i.e., matric suction) on the bearing capacity, settlement and liquefaction potential of unsaturated sands. The influence of matric suction in the unsaturated zone of the sandy soils is ignored while estimating or evaluating bearing capacity, settlement and liquefaction resistance in conventional engineering practice. The focus of the research presented in the thesis has been directed towards better understanding of these aspects and providing rational and yet simple tools for the design of shallow foundations (i.e., footings) in sands under both static and dynamic loading conditions. Terzaghi (1943) or Meyerhof (1951) equations for bearing capacity and Schmertmann et al. (1978) equation for settlement are routinely used by practicing engineers for sandy soils based on saturated soil properties. The assumption of saturated conditions leads to conservative estimates for bearing capacity; however, neglecting the influence of capillary stresses contributes to unreliable estimates of settlement or differential settlement of footings in unsaturated sands. There are no studies reported in the literature on how capillary stresses influence liquefaction, bearing capacity and settlement behavior in earthquake prone regions under dynamic loading conditions. An extensive experimental program has been undertaken to study these parameters using several specially designed and constructed equipment at the University of Ottawa. The influence of matric suction, confinement and dilation on the bearing capacity of model footings in unsaturated sand was determined using the University of Ottawa Bearing Capacity Equipment (UOBCE-2011). Several series of plate load tests (PLTs) were carried out on a sandy soil both under saturated and unsaturated conditions. Based on these studies, a semi-empirical equation has been proposed for estimating the variation of bearing capacity with respect to matric suction. The saturated shear strength parameters and the soil water characteristic curve (SWCC) are required for using the proposed equation. This equation is consistent with the bearing capacity equation originally proposed by Terzaghi (1943) and later extended by Meyerhof (1951) for saturated soils. Chapter 2 provides the details of these studies. The cone penetration test (CPT) is conventionally used for estimating the bearing capacity of foundations because it is simple and quick, while providing continuous records with depth. In this research program, a cone penetrometer was specially designed to investigate the influence of matric suction on the cone resistance in a controlled laboratory environment. Several series of CPTs were conducted in sand under both saturated and unsaturated conditions. Simple correlations were proposed from CPTs data to relate the bearing capacity of shallow foundations to cone resistance in saturated and unsaturated sands. The details of these studies are presented and summarized in Chapter 3. Standard penetration tests (SPTs) and PLTs were conducted in-situ sand deposit at Carp region in Ottawa under both saturated and unsaturated conditions. The test results from the SPTs and PLTs at Carp were used along with other data from the literature for developing correlations for estimating the bearing capacity of both saturated and unsaturated sands. The proposed SPT-CPT-based technique is simple and reliable for estimation of the bearing capacity of footings in sands. Chapter 4 summarizes the details of these investigations. Empirical relationships were proposed using the CPTs data to estimate the modulus of elasticity of sands for settlement estimation of footings in both saturated and unsaturated sands. This was achieved by modifying the Schmertmann et al. (1978) equation, which is conventionally used for settlement estimations in practice. Comparisons are provided between the three CPT-based methods that are commonly used for settlement estimations in practice and the proposed method for seven large scale footings in sandy soils. The results of the comparisons show that the proposed method provides better estimations for both saturated and unsaturated sands. Chapter 5 summarizes the details of these studies. A Flexible Laminar Shear Box (FLSB of 800-mm3 in size) was specially designed and constructed to simulate and better understand the behaviour of model surface footing under seismic loads taking account of the influence of matric suction in an unsaturated sandy soil. The main purpose of using the FLSB is to simulate realistic in-situ soils behaviour during earthquake ground shaking. The FLSB test setup with model footing was placed on unidirectional 1-g shake table (aluminum platform of 1000-mm2 in size) during testing. The resistance of unsaturated sand to deformations and liquefaction under seismic loads was investigated. The results of the study show that matric suction offers significant resistance to liquefaction and settlement of footings in sand. Details of the equipment setup, test procedure and results of this study are presented in Chapter 6. Simple techniques are provided in this thesis for estimating the bearing capacity and settlement behaviour of sandy soils taking account of the influence of capillary stresses (i.e., matric suction). These techniques are consistent with the methods used in conventional geotechnical engineering practice. The studies show that even low values of capillary stresses (i.e., 0 to 5 kPa) increases the bearing capacity by two to four folds, and the settlement of footings not only decreases significantly but also offers resistance to liquefaction in sands. These studies are promising and encouraging to use ground improvement techniques; such as capillary barrier techniques to maintain capillary stresses within the zone of influence below shallow foundations. Such techniques, not only contribute to the increase of bearing capacity, they reduce settlement and alleviate problems associated with earthquake effects in sandy soils.

This research consists of full-scale shake table tests to investigate liquefaction of sandy soils. Consideration of the potential and consequences of liquefaction is critical to the performance of any structure built in locations of high seismicity underlain by saturated granular materials as it is the leading cause of damage associated with ground failure. In certain cases the financial losses associated with liquefaction can significantly impact the financial future of an entire region. Most liquefaction triggering studies are performed in the field where liquefaction has been previously observed, or in tabletop laboratory testing. The study detailed herein is a controlled laboratory test performed at full scale to allow for the measurement of field-scale index testing before and after cyclic loading. Testing was performed at the Parson’s geotechnical and Earthquake Laboratory at Cal Poly San Luis Obispo on the 1-dimensional shake table with a mounted flexible walled testing apparatus. The testing apparatus, originally constructed for soil-structure interaction experiments utilizing soft clay was retrofitted for the purpose of studying liquefaction. This research works towards comparing large-scale simple-shear liquefaction testing to small-scale simple-shear liquefaction testing of a #2/16 Monterey sand specimen. The bucket top was modified in order to apply a vertical load to the soil skeleton to replicate overburden soil conditions. Access ports were fitted into the bucket top for instrument cable access and to allow cone penetration testing before and after cyclic loading. A shear-wave generator was created to propagate shear waves into the sample for embedded accelerometers to measure small strain stiffness of the sample. Pore-pressure transducers were embedded in the soil sample to capture excess pore water pressure produced during liquefaction. Displacement transducers were attached to the bucket in order to measure shear strains during cyclic testing and to measure post-liquefaction volumetric deformations. The results of this investigation provide an empirical basis to the behavior of excess pore water production, void re-distribution, shear wave velocity, shear strain and cone penetrometer tip resistance of #2/16 Monterey sand before, during, and after liquefaction in a controlled laboratory environment at full-scale.

Nowadays, earthquakes are one of the most catastrophic natural events that have a significant human, socio-economic and environmental impact. Besides, based on both observations of damage following recent major/moderate seismic events and numerical/experimental studies, it clearly emerges that critical non-structural components (NSCs) that are ubiquitous to most industrial facilities are particularly and even disproportionately vulnerable to those events. Nonetheless and despite their great importance, seismic provisions for industrial facilities and their process equipment are still based on the classical load-and-resistance factor design (LRFD) approach; a performance-based earthquake engineering (PBEE) approach should, instead, be preferred. Along this vein, in recent years, much research has been devoted to setting computational fragility frameworks for special-risk industrial components and structures. However, within a PBEE perspective, studies have clearly remarked: i) a lack of definition of performance objectives for NSCs; ii) the need for fully comprehensive testing campaigns data on coupling effects between main structures and NSCs. In this respect, this doctorate thesis introduces a computational framework for an efficient and accurate seismic state-dependent fragility analysis; it is based on a combination of data acquired from an extensive experimental shake table test campaign on a full-scale prototype industrial steel frame structure and the most recent surrogate-based UQ forward analysis advancements. Specifically, the framework is applied to a real-world application consisting of seismic shake table tests of a representative industrial multi-storey frame structure equipped with complex process components, carried out at the EUCENTRE facility in Italy, within the European SPIF project: Seismic Performance of Multi-Component Systems in Special Risk Industrial Facilities. The results of this experimental research campaign also aspire to improve the understanding of these complex systems and improve the knowledge of FE modelling techniques. The main goals aim to reduce the huge computational burden and to assess, as well, when the importance of coupling effects between NSCs and the main structure comes into play. Insights provided by innovative monitoring systems were then deployed to develop and validate numerical and analytical models. At the same time, the adoption of Der Kiureghian's stochastic site-based ground motion model (GMM) was deemed necessary to severely excite the process equipment and supplement the scarcity of real records with a specific frequency content capable of enhancing coupling effects. Finally, to assess the seismic risk of NSCs of those special facilities, this thesis introduces state-dependent fragility curves that consider the accumulation of damage effects due to sequential seismic events. To this end, the computational burden was alleviated by adopting polynomial chaos expansion (PCE) surrogate models. More precisely, the dimensionality of a seismic input random vector has been reduced by performing the principal component analysis (PCA) on the experimental realizations. Successively, by bootstrapping on the experimental design, separate PCE coefficients have been determined, yielding a full response sample at each point. Eventually, empirical state-dependent fragility curves were derived.

<p>This thesis reports on shake table tests on fully-grouted reinforced masonry (RM) shear walls. The test walls covers a range of design parameters to facilitate benchmarking, a thorough performance investigation, and calibration of numerical models as well as development of fragility curves within the context of Performance Based Seismic Design (PBSD). The details of the experimental program undertaken, including general observations in terms of cracking patterns and failure modes of the tested walls and the results on the lateral strength, hysteretic response, dynamic properties, and the contribution of different displacement components to the response of the walls, are presented. More detailed analyses include seismic performance quantification of the walls in terms of inelastic behaviour characteristics, various energy components, and the effective dynamic properties of the tested walls. The analysis is concluded with development of simplified nonlinear response history analytical models and seismic fragility assessment tools for the tested walls. In general, the study results indicated that the displacement ductility capacity of the RM walls and their capability to dissipate energy through plastic hinging are higher than what is currently recognized by the National Building Code of Canada (NBCC). The fragility assessment study further indicated that similar walls are expected to conform to the current drift limits of the NBCC even at high seismic regions in Canada. The results of this study are expected to contribute to the growing Seismic Performance Database (SPD) of RM Seismic Force Resisting System (SFRS), and to the understanding of the lightly reinforced masonry wall system behaviour.</p> / Master of Applied Science (MASc)

Sliding isolation bearings are used widely around the world to minimize damage to structures and their contents during earthquakes. Past studies have typically focused on the behavior of sliding isolation bearing under design conditions; however, as the performance-based earthquake engineering advances, it is necessary and critical to understand the ultimate or even failure behavior, of structural systems under extreme conditions. Using a double friction pendulum bearing with non-articulated slider as an example, this thesis comprehensively investigates the extreme behavior of the sliding bearing components as well as steel frame buildings isolated using these bearings. This thesis is comprised of two major parts. The first includes numerical and experimental studies of double friction pendulum bearings at the component-level. Finite element investigation shows that depending on the superstructure mass there are two major failure modes for the double friction pendulum bearings. When the superstructure mass is sufficiently large, the failure mode is dominated by the restraining rim yielding; however, when the mass is relatively small, its failure mode shifts to bearing uplift. A simplified analytical model which can directly simulate the impact and uplift behavior of double friction pendulum bearing is also implemented, comparing well to the finite element analysis. Then, to validate the ability of the models to predict extreme behavior as well as to investigate the effect of the restraining rim design, which varies around the world, an experimental study was carried out. Uplift behavior and significant rim yielding were observed during the shake table tests. Moreover, other response parameters, including uplift and shear forces, are evaluated and compared among different rim designs. It is found the restraining rim design has a substantial influence on the bearing’s extreme behavior. The second part of the thesis investigates the system-level behavior of steel frame buildings isolated with double friction pendulum bearings. It is found that the stiffness of the superstructure largely dictates the system-level failure modes and collapse probability. Initially, bearings with rigid restraining rims are investigated. For flexible moment-resisting frames, the system-level failure modes are mixed: both the bearing uplift and superstructure yielding contribute; also, using current code-minimum design results in acceptably low probability of collapse. However, for stiff concentrically-braced frames, the impact force can impose large ductility demands on the superstructure regardless of its strength. As a result, the system-level failure comes exclusively from superstructure yielding, and only by increasing bearing’s displacement capacity beyond the minimum code allowed can the design meet as acceptably low collapse probability. When flat rims are used instead for the bearing design, the failure modes for both building types are exclusively bearing failure. Furthermore, while it is more apparent for concentrically-braced frames, using flat rims for the bearings can reduce the collapse probability compared to using rigid rims. / Thesis / Doctor of Philosophy (PhD)

Current seismic design practice promotes inelastic response in order to reduce the design forces. By allowing the structure to yield while increasing the ductility of the structure, the global forces can be kept within the limited bounds dictated by the yield strength. However, during severe earthquakes, the structures undergo significant inelastic deformations leading to stiffness and strength degradation, increased interstory drifts, and damage with residual drift. The research presented in this thesis has three components that seek to address these challenges. To prevent the inelastic effects observed in yielding systems, a new concept “apparent weakening” is proposed and verified through shake table studies in this thesis. “Apparent weakening” is introduced in the structural system using a complementary “adaptive negative stiffness device” (NSD) that mimics "yielding” of the global system thus attracting it away from the main structural system. Unlike the concept of weakening and damping, where the main structural system strength is reduced, the new system does not alter the original structural system, but produces effects compatible with an early yielding. Response reduction using NSD is achieved in a two step sequence. First the NSD, which is capable of exhibiting nonlinear elastic stiffness, is developed based on the properties of the structure. This NSD is added to the structure resulting in reduction of the stiffness of the structure and NSD assembly or “apparent weakening”-thereby resulting in the reduction of the base shear of the assembly. Then a passive damper, designed for the assembly to reduce the displacements that are caused due to the “apparent weakening”, is added to the structure-thereby reducing the base shear, acceleration and displacement in a two step process. The primary focus of this thesis is to analyze and experimentally verify the response reduction attributes of NSD in (a) elastic structural systems (b) yielding systems and (3) multistory structures. Experimental studies on 1:3 scale three-story frame structure have confirmed that consistent reductions in displacements, accelerations and base shear can be achieved in an elastic structure and bilinear inelastic structure by adding the NSD and viscous fluid damper. It has also been demonstrated that the stiffening in NSD will prevent the structure from collapsing. Analogous to the inelastic design, the acceleration and base shear and deformation of the structure and NSD assembly can be reduced by more than 20% for moderate ground motions and the collapse of structure can be prevented for severe ground motions. Simulation studies have been carried on an inelastic multistoried shear building to demonstrate the effectiveness of placing NSDs and dampers at multiple locations along the height of the building; referred to as “distributed isolation”. The results reported in this study have demonstrated that by placing a NSD in a particular story the superstructure above that story can be isolated from the effects of ground motion. Since the NSDs in the bottom floors will undergo large deformations, a generalized scheme to incorporate NSDs with different force deformation behavior in each storey is proposed. The properties of NSD are varied to minimize the localized inter-story deformation and distribute it evenly along the height of the building. Additionally, two semi-active approaches have also been proposed to improve the performance of NSD in yielding structures and also adapt to varying structure properties in real time. The second component of this thesis deals with development of a novel device to control the response of structural system using adaptive length pendulum smart tuned mass damper (ALP-STMD). A mechanism to achieve the variable pendulum length is developed using shape memory alloy wire actuator. ALP-STMD acts as a vibration absorber and since the length is tuned to match the instantaneous frequency, using a STFT algorithm, all the vibrations pertaining to the dominant frequency are absorbed. ALP-STMD is capable of absorbing all the energy pertaining to the tuned-frequency of the system; the performance is experimentally verified for forced vibration (stationary and non-stationary) and free vibration. The third component of this thesis covers the development of an adaptive control algorithm to compensate hysteresis in hysteretic systems. Hysteretic system with variable stiffness hysteresis is represented as a quasi-linear parameter varying (LPV) system and a gain scheduled controller is designed for the quasi-LPV system using linear matrix inequalities approach. Designed controller is scheduled based on two parameters: linear time-varying stiffness (slow varying parameter) and the stiffness of friction hysteresis (fast varying parameter). The effectiveness of the proposed controller is demonstrated through numerical studies by comparing the proposed controller with fixed robust H∞ controller. Superior tracking performance of the LPV-GS over the robust H∞ controller in different displacement ranges and various stiffness switching cases is clearly evident from the results presented in this thesis. The LPV-GS controller is capable of adapting to the parameter changes and is effective over the entire range of parameter variations.

Immediate occupancy and functionality of critical facilities including hospitals, emergency operations centers, communications centers, and police and fire stations is of utmost importance immediately after a damaging earthquake, as they must continue to provide fundamental health, emergency, and security services in the aftermath of an extreme event. Although recent earthquakes have proven the acceptable performance of the structural system in such buildings, when designed according to recent seismic design codes, in many cases damage to the nonstructural components and systems was the main cause of disruption in their functionality. Seismic isolation is proven to be an effective technique to protect building structures from damaging earthquakes. It has been the method of choice for critical facilities, including hospitals in Japan and the United States in recent years. Seismic isolation appears to be an ideal solution for protecting the nonstructural components as well. While this claim was made three decades ago, the supporting research for freestanding (unanchored) equipment and contents (EC) is fairly new. With the focus on freestanding EC, this study investigates the seismic performance of sliding and wheel/caster-supported EC in fixed-base and base-isolated buildings. The study adopts a comparative approach to provide a better understanding of the advantages and disadvantages of using each structural system. The seismic response of sliding EC is investigated analytically in the first part of the thesis, while the response of EC supported on wheels/casters is examined through shake table experiments on two pieces of hospital equipment. The study finds base isolation to be generally effective in reducing seismic demands on freestanding EC, but it also exposes certain situations where isolation in fact increases demands on EC. Increasing the frictional resistance for sliding EC or locking the wheel/casters in the case of wheel/caster-supported EC is highly recommended for EC in base-isolated buildings to prevent excessive displacement demands. Furthermore, the study suggests several design probability functions that can be used by practicing engineers to estimate the peak seismic demands on sliding and wheel/caster-supported EC in fixed-base and base-isolated buildings. / Dissertation / Doctor of Philosophy (PhD)

The performance of nonstructural components in critical infrastructure, such as nuclear power plants (NPPs), has been primarily based on experience and historical data. This topic has been attracting increased interest from researchers following the Fukushima Daiichi nuclear disaster in 2011. This disaster demonstrated the importance of using batteries in NPPs as an auxiliary power system, where such systems can provide the necessary power to mitigate the risk of serious accidents. However, little research has been conducted on such nonstructural components to evaluate their performance following the post- Fukushima safety requirements, recommended by several nuclear regulators worldwide [e.g., Nuclear Regulatory Commission (NRC), and Nuclear Safety Commission (NSC)]. To address this research gap, this dissertation investigates the lateral performance of an auxiliary battery power system (ABPS) similar to those currently existing/operational in NPPs in Canada. The ABPS was experimentally tested under displacement-controlled quasi-static cyclic fully-reversed loading that simulates lateral seismic demands. Due to the presence of sliding batteries, the ABPS was then tested dynamically under increased ground motion levels on a shake table. The experimental results demonstrated that the design guidelines and fragility curves currently assigned to battery rack systems in the FEMA P58 prestandards do not encompass all possible failure mechanisms. A 3D numerical model was also developed using OpenSees software. The model was validated using the experimental results. The model results showed that the lateral performance of ABPS with different configurations (i.e. different lengths, tiers, and seismic categories) is influenced by the capacity of the L-shaped connection between the side rails and the end rail. However, the model was not able to predict all the damage states from the dynamic experimental tests, since the rocking/sliding/impact behavior of the batteries is a highly complex nonlinear problem by nature and beyond the scope of this study. The model presented is limited to the assessment of the lateral performance of different ABPS statically. This dissertation demonstrated the difference between the observed behavior of laboratory-controlled lateral performance tests of ABPSs operational/existing in NPPs and the behavior of ABPSs found in the literature that relied on limited historical and experience data. Finally, this dissertation laid the foundations for the need to further investigate the behavior of other safety-related components in NPPs and assess their compliance with new post-Fukushima design requirements. / Thesis / Doctor of Philosophy (PhD)