Steel plate shear walls (SPSWs) are a lateral force resisting system consisting of thin infill steel plates surrounded by boundary frame members. The infill steel plates are allowed to buckle in shear and subsequently form diagonal tension field actions during earthquake events. Hysteretic energy dissipation of this system is primarily achieved through yielding of the infill plates. Conceptually, in a SPSW system with ideally rigid columns pinned to ground, the infill plates at different stories will yield simultaneously as a result of the lateral loads. However, when the columns become flexible, infill plate yielding may initially occur at one story and progressively spread into the other stories with increasing roof displacement. This research investigates the effect of column stiffness on infill plate yielding sequence and distribution along the height of steel plate shear walls subjected to earthquake forces. Analytical models are derived and validated for two-story SPSWs. Based on the derived model, probabilistic simulations are conducted to calculate the probability of achieving infill plate yielding in both stories before occurrence of a premature failure caused by excessive inter story drift at the initially yielded story. A total of three simulation methods including the Monte-Carlo method, the Latin Hypercube sampling method, and the Rosenblueth’s 2K+1 point estimate method were considered to account for the uncertain infill plate thickness and lateral force distributions in the system.The investigation is also extended to multi-story SPSWs. Three example six-story SPSWs are evaluated using the Rosenblueth's 2K+1 point estimation method which is identified to be most efficient from the simulation on two-story SPSWs. Moreover, the effectiveness of the column minimum moment of inertia required in the current code for achieving infill plate yielding at every story of SPSWs is evaluated.

This paper presents the axial compressive behaviour of stub concrete-filled columns with elliptical stainless steel and carbon steel hollow sections. The finite element method developed via ABAQUS/Standard solver was used to carry out the simulations. The accuracy of the FE modelling and the proposed confined concrete stress-strain model were verified against experimental results. A parametric study on stub concrete-filled columns with various elliptical hollow sections made with stainless steel and carbon steel was conducted. The comparisons and analyses presented in this paper outline the effect of hollow sectional configurations to the axial compressive behaviour of elliptical concrete-filled steel tubular columns, especially the merits of using stainless steel hollow sections is highlighted.

<p>Computer-based surgical simulation and non-rigid medical image registration in image-guided interventions are examples of applications that would benefit from real-time deformation simulation of soft tissues. The physics of deformation for biological soft-tissue is best described by nonlinear continuum mechanics-based models which then can be discretized by the Finite Element Method (FEM) for a numerical solution. Computational complexity of nonlinear FEM-based models has limited their use in real-time applications. The data-parallel nature and intense arithmetic operations in nonlinear FEM models are suitable for massive parallelization of the computations, in order to meet the response time requirements in such applications.</p> <p>This thesis is concerned with computational aspects of complex nonlinear deformation analysis problems with an emphasis on the speed of response using a parallel computing philosophy. It proposes a fast, accurate and scalable Graphic Processing Unit (GPU)-based implementation of the total Lagrangian FEM using implicit time integration for dynamic nonlinear deformation analysis. This is a general formulation valid for large deformations and strains and can account for material nonlinearities. A penalty method is used to satisfy the physical boundary constraints due to contact between deformable objects. The proposed set of optimized GPU kernels for computing the FEM matrices achieves more than 100 GFLOPS on a GTX 470 GPU device. The use of a novel vector assembly kernel and memory optimization strategies result in a performance gain of up to 25 GFLOPS in the PCG computations.</p> / Doctor of Philosophy (PhD)

Tensegrity-membrane systems are a class of new bar-tendon-membrane systems. Such novel systems can be treated as extensions of tensegrity structures and are generally lightweight and deployable. These two major advantages enable tensegrity-membrane systems to become one of the most promising candidates for lightweight space structures and gossamer spacecraft. In this dissertation, modeling and control of tensegrity-membrane systems is studied. A systematic method is developed to determine the equilibrium conditions of general tensegrity-membrane systems. Equilibrium conditions can be simplified when the systems are in symmetric configurations. For one-stage symmetric systems, analytical equilibrium conditions can be determined. Three mathematical models are developed to study the dynamics of tensegrity-membrane systems. Two mathematical models are developed based on the nonlinear finite element method. The other model is a control-oriented model, which is suitable for control design. Numerical analysis is conducted using these three models to study the mechanical properties of tensegrity-membrane systems. Two control strategies are developed to regulate the deployment process of tensegrity-membrane systems. The first control strategy is to deploy the system by a nonlinear adaptive controller and use a linear H∞ controller for rapid system stabilization. The second control strategy is to regulate the dynamics of tensegrity-membrane systems using a linear parameter-varying (LPV) controller during system deployment. A gridding method is employed to discretize the system operational region in order to carry out the LPV control synthesis. / Ph. D.

Deep soil mixing to construct stiff columns is one of the methods used today to improve performance of loose ground and remediate liquefaction problems. This research adopts a numerical approach to study seismic performance of soil-cement columnar reinforcements in loose sandy profiles. Different constitutive models were investigated in order to find a model that can properly predict soil behavior during seismic excitations. These models included NorSand, Dafalias-Manzari, Plasticity Model for Sands (PM4Sand) and Pressure-Dependent-Multi-Yield-02 (PDMY02) model. They were employed to predict behavior of soils with different relative densities and under different confining pressures during monotonic and cyclic loading. PDMY02 was identified as the most suitable model to represent soil seismic behavior for the system studied herein. The numerical aspects of the finite element approach were investigated to minimize the unintended numerical miscalculations. The focus was put on convergence tolerance, solver time-step, constraint definition, and, integration, material and Rayleigh damping. This resulted in forming a robust numerical configuration for 3-D nonlinear models that were later used for studying behavior of the reinforced grounds. Nonlinear finite element models were developed to capture the seismic response of columnar reinforced ground during dynamic centrifuge testing. The models were calibrated with results from tests with unreinforced profiles. Thereafter, they were implemented to predict the response of two reinforced profiles during seismic excitations with different intensities and liquefaction triggering. Model predictions were compared with recordings and the possible effects from the reinforcements were discussed. Finally, parametric studies were performed to further evaluate the efficiency of the reinforcements with different extension depths and area replacement ratios. The results collectively showed that the stiff elements, if constructed appropriately, can withstand seismic excitations with different intensities, and provide a firm base for overlying structures. However, the presence of the stiff elements within the loose ground resulted in stronger seismic intensities on the soil surface. The columns were not able to considerably reduce pore water pressure generation, nor prevent liquefaction triggering. The reinforced profiles, comparing to the free-field profiles, had larger settlements on the soil surface but smaller settlements on the columns. The results concluded that utilization of the columnar reinforcements requires great attention as these reinforcements may result in larger seismic intensities at the ground surface, while not considerably reducing the ground deformations. / Ph. D.

Reinforced concrete (RC) moment frame structures make up a notable proportion of buildings in earthquake-prone regions in the United States and throughout the world. The beam-column (BC) joints are the most crucial regions in a RC moment frame structure as any deterioration of strength and/or stiffness in these areas can lead to global collapse of the structure. Thus, accurate simulations of the joint behavior are important for assessment of the local and global performance of both one-way and two-way interior BC joints. Such simulations can be used to study the flexural-shear-bond interaction, the failure modes, and sensitivity of various parameters of structural elements. Most of the existing analytical approaches for interior BC joints have either failed to account for the cyclic bond-slip behavior and the triaxial compressive state of confined concrete in the joint correctly or require so many calibrations on parameters as to render them impractical. The core motivation for this study is the need to develop robust models to test current design recommendations for 3D beam-column-slab subassemblies subjected to large drifts. The present study aims to first evaluate the flexural-shear-bond interactive behavior of two-way beam-column-slab interior connections by both finite element and nonlinear truss methodologies. The local performance such as bond-slip and strain history of reinforcing steel are compared with the experimental results for the first time. The reliability of applied finite element approach is evaluated against a series of one-way interior BC joints and a two-way interior beam-column-slab joint. The accuracy and efficiency of the nonlinear truss methodology is also evaluated by the same series of joints. Results show good agreement for finite element method against both global and local response, including hysteretic curve, local bond-slip development and beam longitudinal bar stress/strain distributions. The nonlinear truss model is also capable in obtaining satisfactory global response, especially in capturing large shear cracks. A parametric study is exhibited for a prototype two-way interior beam-column-slab joint described in an example to ACI 352R-02, to quantify several non-consensus topics in the design of interior BC connections, such as the joint shear force subjected to bidirectional cyclic loading, the development of bond-slip behavior, and the failure modes of two-way interior joints with slab. Results from connections with different levels of joint shear force subjected to unidirectional loading show that meeting the requirements from ACI 352 is essential to maintain the force transfer mechanism and the integrity of the joint. The connections achieved satisfactory performance under unidirectional loading, while the bidirectional monotonic loading decreases the joint shear force calculated by ACI 352 by 10%~26% based on current results. Poorer performance is obtained for wider beams and connections fail by shear in the joint rather than bond-slip behavior when subjected to bidirectional cyclic loading. In general, the study indicates that the ACI352-02 design methodology generally results in satisfactory performance when applied to 2D joints (planar) under monotonic and cyclic loads. Less satisfactory performance was found for cases of 3D joints with slabs. / Doctor of Philosophy / Reinforced concrete (RC) moment frames are one of the most popular structure types because of their economical construction and adaptable spaces. Moment frames consist of grid-like assemblages of vertical columns and horizontal beams joined by cruciform connections commonly labelled as beam-column joints. Because of the regularity of the grid and the ability to have long column spacing, moment frames are easy to form and cast and result in wide open bays that can be adapted and readapted to many uses. In RC structures, steel bars embedded in the concrete are used to take tensile forces, as concrete is relatively weak when loaded in tension. Forces are transferred between the steel and concrete components by so-called “bond” forces at the perimeter of the bars. The proper modeling of the behavior of bond forces inside the beam-column joints of reinforced concrete moment frames is the primary objective of this dissertation. Reinforced concrete moment frames constitute a notable proportion of the existing buildings in earthquake-prone regions in the United States and throughout the world. The beam-column joints are the most crucial elements in a RC moment frame structure as any deterioration of strength and/or stiffness in these areas can lead to global collapse of the structure. Physical experimentation is the most reliable means of studying the performance of beam-column joints. However, experimental tests are expensive and time-consuming. This is why computational simulation must always be used as a supplemental tool. Accurate simulations of the behavior of beam-column joints is important for assessment of the local and global behavior of beam-column joints. However, most of the existing analytical approaches for interior beam-column joints have either failed to account for the bond-slip behavior and the triaxial compressive state of confined concrete in the joint correctly or require so many calibration parameters as to render them impractical. The present study aims to provide reliable numerical methods for evaluating the behavior of two-way beam-column-slab interior joints. Two methods are developed. The v first method is a complex finite element model in which the beam-column joint is subdivided into many small 3D parts with the geometrical and material characteristics of each part carefully defined. Since the number of parts may be in the hundreds of thousands and the geometry and material behavior highly non-linear, setting up the problem and its solution of this problem requires large effort on the part of the structural engineer and long computation times in supercomputers. Finite element models of this type are generally accurate and are used to calibrate simpler models. The second method developed herein is a nonlinear truss analogy model. In this case the structure is modelled as nonlinear truss elements, or elements carrying only axial forces. When properly calibrated, this method can produce excellent results especially in capturing large shear cracks. To evaluate the accuracy and to quantify the current seismic design procedure for beam-column joints, a prototype two-way interior beam-column-slab joint described in an example to ACI 352R-02, the current design guide used for these elements in the USA, is analytically studied by the finite element methodology. The study indicates that the ACI352-02 design methodology generally results in satisfactory performance when applied to one-way (planar) joints under monotonic and cyclic loads. Less satisfactory performance was found for cases of three-dimensional (3D) joints with slabs.

Este estudo foca uma análise comparativa de diferentes painéis internos de capôs de veículos, com o objetivo de minimizar as lesões ao pedestre em caso de um atropelamento. As lesões na cabeça do pedestre são medidas através de um modelo em elementos finitos de uma cabeça padrão de acordo com o comitê europeu de melhorias da segurança de veículos. Os valores de desaceleração obtidos nas análises são comparados com valores toleráveis de acordo com o critério HIC (Head Injury Criteria), criado pela NHTSA (National Highway Traffic Safety Administration). Baseando-se nos resultados obtidos demonstra-se a influência dos tipos de estruturas internas de capô e recomenda-se a melhor estrutura para aplicações na indústria automobilística. / This study focus on comparative analysis of different vehicle hood inner panels, with the objective to minimize the injuries to the pedestrian in case of a running over accident. The method to measure the injuries in the head of the pedestrian will be made through a finite element model of a standard head in accordance with the European committee of improvements of the security of vehicles. The values of decelerations obtained in the analysis are compared with human tolerance levels according to HIC criteria (Head Injury Criteria), created by NHTSA (National Highway Traffic Safety Administration). Based on the finite element analysis results, this study demonstrate the influence of different hood inner panels and recommends the best structure to be applied by automobile industry.

Two types of connection are generally considered in the design of steel structures in practice. These are classified as completely rigid (moment) and simple (shear) connections. In theory, completely rigid connections can not undergo rotation and simple connections can not transfer moment. However, in reality rigid connections have a relative flexibility which makes them to rotate and simple connections have some reserve capacity to transfer moments. In many modern design specifications, this fact is realized and another type which is called partially restrained or semi-rigid connection is introduced. These types of connections have got the transfer of some beam moment to column together with shear. However, there is a lack of information on the amount of moment transferred and rotation of connection during the action of the moment transfer. The only way to quantify the moment and rotation of the partially restrained connections is to draw momentrotation curves. Nevertheless, drawing such curves requires great amount of expenses for experiments. Taking these into account, the use of finite elements with the help of increased computational power is one way to obtain moment-rotation curves of connections. Available test results guides the finite element analysis for justifications. So these analyses can be further implemented into design functions. This thesis is intended to conduct 3-D non-linear finite element analyses to compliment with tests results for different types of semi-rigid connections with angles and compare them with mathematical models developed by different researchers.

The incorporation of inflatable structures into aerospace systems can produce significant advantages in stowed volume to mechanical effectiveness and overall weight. Many applications of these ultra-lightweight systems are designed to precisely control internal or external surfaces, or both, to achieve desired performance. The modeling of these structures becomes complex due to the material nonlinearities inherent to the majority of construction materials used in inflatable structures. Furthermore, accurately modeling the response and behavior of the interfacing boundaries that are common to many inflatable systems will lead to better understanding of the entire class of structures. The research presented involved using nonlinear finite element simulations correlated with photogrammetry testing to develop a procedure for defining material properties for commercially available polyurethane-coated woven nylon fabric, which is representative of coated materials that have been proven materials for use in many inflatable systems. Further, the new material model was used to design and develop an inflatable pathfinder system which employs only internal pressure to control an assembly of internal membranes. This canonical inflatable system will be used for exploration and development of general understanding of efficient design methodology and analysis of future systems. Canonical structures are incorporated into the design of the phased pathfinder system to allow for more universal insight. Nonlinear finite element simulations were performed to evaluate the effect of various boundary conditions, loading configurations, and material orientations on the geometric precision of geometries representing typical internal/external surfaces commonly incorporated into inflatable pathfinder system. The response of the inflatable system to possible damage was also studied using nonlinear finite element simulations. Development of a correlated material model for analysis of the inflatable pathfinder system has improved the efficiency of design and analysis techniques of future inflatable structures.

Este estudo foca uma análise comparativa de diferentes painéis internos de capôs de veículos, com o objetivo de minimizar as lesões ao pedestre em caso de um atropelamento. As lesões na cabeça do pedestre são medidas através de um modelo em elementos finitos de uma cabeça padrão de acordo com o comitê europeu de melhorias da segurança de veículos. Os valores de desaceleração obtidos nas análises são comparados com valores toleráveis de acordo com o critério HIC (Head Injury Criteria), criado pela NHTSA (National Highway Traffic Safety Administration). Baseando-se nos resultados obtidos demonstra-se a influência dos tipos de estruturas internas de capô e recomenda-se a melhor estrutura para aplicações na indústria automobilística. / This study focus on comparative analysis of different vehicle hood inner panels, with the objective to minimize the injuries to the pedestrian in case of a running over accident. The method to measure the injuries in the head of the pedestrian will be made through a finite element model of a standard head in accordance with the European committee of improvements of the security of vehicles. The values of decelerations obtained in the analysis are compared with human tolerance levels according to HIC criteria (Head Injury Criteria), created by NHTSA (National Highway Traffic Safety Administration). Based on the finite element analysis results, this study demonstrate the influence of different hood inner panels and recommends the best structure to be applied by automobile industry.