Standards and regulations for dimensioning of load-bearing structures are based on the response of load-bearing structures subjected to loads without variation in time. In the event of an accidental load, e.g. a collision or explosion, causes the load to have a rapid variation in the time resulting in a dynamic response. Previous studies have shown that structures that respond in a certain way under static load have shown a completely different behavior under dynamic influence and therefore it is of interest to study the dynamic response of structures.By testing concrete beams with varying amounts of shear reinforcement subjected to impact loading, the purpose of this report is to analyze how the beams responds in terms of crack width and vibrations when they are exposed to a dynamic load. For comparison, reference tests have also been performed on beams subjected to a quasi-static load.The result of the project shows that the shear reinforcement comes into play as the beams with a larger amount of reinforcement have more capacity to hold the flexural shear cracks together. There is also an indication that the dynamic flexural shear capacity could be lower than static shear capacity as the shear cracks had an increased inclination during dynamic loading for some of the beams. This results in a decreased flexural shear capacity as only one stirrup carried the load across the shear crack.Measured signal shows that beams failing respond when impacted by the similar to a plastic collision, while beams responding with a flexure dominated mode without going to failure instead answer similar to an elastic collision. Furthermore, there is indication that the natural frequencies change significantly due to both flexural cracks and flexural shear cracks.

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The deterioration of the nation's civil infrastructure has prompted the investigation of numerous solutions to offset the problem. Some of these solutions have come in the form of innovative materials for new construction, whereas others have considered rehabilitation techniques for repairing existing infrastructure. A relatively new system that appears capable of encompassing both of these solution methodologies is the Sandwich Plate System (SPS), a composite bridge deck system that can be used in both new construction or for rehabilitation applications. SPS consists of steel face plates bonded to a rigid polyurethane core; a typical bridge application utilizes SPS primarily as a bridge deck acting compositely with conventional support girders. As a result of this technology being relatively new to the bridge market, design methods have yet to be established. This research aims to close this gap by investigating some of the key design issues considered to be limiting factors in implementation of SPS. The key issues that will be studied include lateral load distribution, dynamic load allowance and deck design methodologies. With SPS being new to the market, there has only been a single bridge application, limiting the investigations of in-service behavior. The Shenley Bridge was tested under live load conditions to determine in-service behavior with an emphasis on lateral load distribution and dynamic load allowance. Both static and dynamic testing were conducted. Results from the testing allowed for the determination of lateral load distribution factors and dynamic load allowance of an in-service SPS bridge. These results also provided a means to validate a finite element modeling approach which would could as the foundation for the remaining investigations on lateral load distribution and dynamic load allowance. The limited population of SPS bridges required the use of analytical methods of analysis for this study. These analytical models included finite element models and a stiffened plate model. The models were intended to be simple, but capable of predicting global response such as lateral load distribution and dynamic load allowance. The finite element models are shown to provide accurate predictions of the global response, but the stiffened plate approach was not as accurate. A parametric investigation, using the finite element models, was initiated to determine if the lateral load distribution characteristics and vibration response of SPS varied significantly from conventional systems. Results from this study suggest that the behavior of SPS does differ somewhat from conventional systems, but the response can be accommodated with current AASHTO LRFD bridge design provisions as a result of their conservativeness. In addition to characterizing global response, a deck design approach was developed. In this approach the SPS deck was represented as a plate structure, which allowed for the consideration of the key design limit states within the AASHTO LRFD specification. Based on the plate analyses, it was concluded that the design of SPS decks is stiffness-controlled as limited by the AASHTO LRFD specification deflection limits for lightweight metal decks. These limits allowed for the development of a method for sizing SPS decks to satisfy stiffness requirements. / Ph. D.

Industrial forklifts consist of one of the most common handling methods for pallets in warehouses and distribution centers. Pallets deflect while they are being transported by forklifts due to the weight of the unit load. Thus, most of the deflection is observed to occur on the outside edges and corners of the pallet. Several international standards are used in order to define the maximum deflection for pallet bending, including ISO 8611 and ASTM D1185. However, there is still a lack of understanding on the accuracy of these deflection limits and the exact performance of a pallet during a forklift support condition. Understanding pallet bending during forklift support condition and how it affects the stability of a unit load helps create an industry accepted deflection limit that will help to design safer and more cost-effective pallets. For this study, two chapters were proposed in order to assess pallet deflection and unit load stability. The first chapter consisted of measuring and analyzing the vibration levels for three different industrial forklifts affect by factors such as the speed, the payload of the unit load carried, sensor location, forklift type, and road conditions. The results obtained showed that the highest vibration intensity occurred at 3-4 Hz, while the highest overall Grms value observed was 0.145 G2/Hz (between 1-200 Hz). An increase in the forklift speed caused an increase in vibration intensity. In contrast, an increase in the unit load weight carried by the forklift caused a decrease in vibration intensity. Among the three forklifts studied, the gas-powered forklift had the highest vibration intensity, and all forklifts, when driven on asphalt, experienced more vibration. The second chapter of the research project consisted of evaluating pallet deflection under forklift handling conditions. These conditions included fork tines configuration (leveled and 4° angle), unit load condition (bound and unbound), pallet orientation (across width and across length), and type of handling condition (static and dynamic). The results showed that when unit loads were handled in a static condition, they survived the throughout the entire testing. However, when they were tested under a dynamic condition, and specifically, with the unbound unit loads, they did not survive the entire testing. Moreover, unit loads that were tested with the 4° angle forktines configuration tended to survive longer during the dynamic testing. For this particular case, the unit load capacity obtained based on the ISO 8611 standard was too conservative. / M.S. / Forklifts play an important role in the transportation of materials goods in the supply chain. Pallets experience vibration when they are handled by industrial forklifts. This vibration plus the combined effects mainly due to the unit load weight affects the amount that pallets bend. Thus, depending on the amount of pallet bending, they can produce unit load instability. Currently, there is a lack of understanding of how much pallet bending is acceptable. Therefore, the goal of this research was to understand the behavior of pallet bending when they are handled under forklift conditions. Two experiments were conducted in order to study pallet deflection under forklift handling conditions. The first experiment, which consisted in analyzing forklift vibration, showed that an increase in the forklift speed caused an increase in vibration intensity. In contrast, an increase in the payload of the unit load resulted in a decrease in vibration intensity. Among the three forklifts studied, the gas-powered forklift showed the highest vibration intensity. Forklifts driven on asphalt experienced more vibration in comparison to the ones driven on concrete. The second experiment, which consisted in assessing pallet deflection under a simulated forklift handling condition, showed that unit loads under a dynamic environment (vibration) increased the probability of unit load instability. Furthermore, it was observed that applying stretch wrap to a unit load decreased its instability and at the same time increases its survivability. Also, the results showed that the proposed ISO 8611 deflection limit is too conservative for this particular handling condition.

Multidisciplinary design optimization (MDO) for large-scale engineering problems poses many challenges (e.g., the design of an efficient concurrent paradigm for global optimization based on disciplinary analyses, expensive computations over vast data sets, etc.) This work focuses on the application of distributed schemes for massively parallel architectures to MDO problems, as a tool for reducing computation time and solving larger problems. The specific problem considered here is configuration optimization of a high speed civil transport (HSCT), and the efficient parallelization of the embedded paradigm for reasonable design space identification. Two distributed dynamic load balancing techniques (random polling and global round robin with message combining) and two necessary termination detection schemes (global task count and token passing) were implemented and evaluated in terms of effectiveness and scalability to large problem sizes and a thousand processors. The effect of certain parameters on execution time was also inspected. Empirical results demonstrated stable performance and effectiveness for all schemes, and the parametric study showed that the selected algorithmic parameters have a negligible effect on performance. / Master of Science

Load models have evolved from simple ZIP model to composite model that incorporates the transient dynamics of motor loads. This research utilizes the latest trend on Machine Learning and builds reliable and accurate composite load model. A composite load model is a combination of static (ZIP) model paralleled with a dynamic model. The dynamic model, recommended by Western Electricity Coordinating Council (WECC), is an induction motor representation. In this research, a dual cage induction motor with 20 parameters pertaining to its dynamic behavior, starting behavior, and per unit calculations is used as a dynamic model. For machine learning algorithms, a large amount of data is required. The required PMU field data and the corresponding system models are considered Critical Energy Infrastructure Information (CEII) and its access is limited. The next best option for the required amount of data is from a simulating environment like PSSE. The IEEE 118 bus system is used as a test setup in PSSE and dynamic simulations generate the required data samples. Each of the samples contains data on Bus Voltage, Bus Current, and Bus Frequency with corresponding induction motor parameters as target variables. It was determined that the Artificial Neural Network (ANN) with multivariate input to single parameter output approach worked best. Recurrent Neural Network (RNN) is also experimented side by side to see if an additional set of information of timestamps would help the model prediction. Moreover, a different definition of a dynamic model with a transfer function-based load is also studied. Here, the dynamic model is defined as a mathematical representation of the relation between bus voltage, bus frequency, and active/reactive power flowing in the bus. With this form of load representation, Long-Short Term Memory (LSTM), a variation of RNN, performed better than the concurrent algorithms like Support Vector Regression (SVR). The result of this study is a load model consisting of parameters defining the load at load bus whose predictions are compared against simulated parameters to examine their validity for use in contingency analysis. / Master of Science / Independent system Operators (ISO) and Distribution system operators (DSO) have a responsibility to provide uninterrupted power supply to consumers. That along with the longing to keep operating cost minimum, engineers and planners study the system beforehand and seek to find the optimum capacity for each of the power system elements like generators, transformers, transmission lines, etc. Then they test the overall system using power system models, which are mathematical representation of the real components, to verify the stability and strength of the system. However, the verification is only as good as the system models that are used. As most of the power systems components are controlled by the operators themselves, it is easy to develop a model from their perspective. The load is the only component controlled by consumers. Hence, the necessity of better load models. Several studies have been made on static load modeling and the performance is on par with real behavior. But dynamic loading, which is a load behavior dependent on time, is rather difficult to model. Some attempts on dynamic load modeling can be found already. Physical component-based and mathematical transfer function based dynamic models are quite widely used for the study. These load structures are largely accepted as a good representation of the systems dynamic behavior. With a load structure in hand, the next task is estimating their parameters. In this research, we tested out some new machine learning methods to accurately estimate the parameters. Thousands of simulated data are used to train machine learning models. After training, we validated the models on some other unseen data. This study finally goes on to recommend better methods to load modeling.

A group of researchers, engineers, and government transportation officials have teamed up to design two bridges with simply-supported FRP composite structural beams. The Toms Creek Bridge, located in Blacksburg, Virginia, has been in service for six years. Meanwhile, the Route 601 Bridge, located in Sugar Grove, Virginia, has been in service for two years. Researchers have conducted load tests at both bridges to determine if their performance has changed during their respective service lives. The key design parameters under consideration are: deflection, wheel load distribution, and dynamic load allowance. The results from the latest tests in 2003 yield little, yet statistically significant, changes in these key factors for both bridges. Most differences appear to be largely temperature related, although the reason behind this effect is unclear. For the Toms Creek Bridge, the largest average values from the 2003 tests are 440 me for service strain, 0.43 in. (L/484) for service deflection, 0.08 (S/11.1) for wheel load distribution, and 0.64 for dynamic load allowance. The values for the Route 601 Bridge are 220 me, 0.38 in. (L/1230), 0.34 (S/10.2), and 0.14 for the same corresponding paramters. The recommended design values for the dynamic load allowance in both bridges have been revised upwards to 1.35 and 0.50 for the Toms Creek Bridge and Route 601 Bridge, respectively, to account for variability in the data. With these increased factors, the largest strain in the toms Creek Bridge and Route 601 Bridge would be less than 13% and 12%, respectively, of ultimate strain. Therefore, the two bridges continue to provide a large factor of safety against failure. / Master of Science

Cette thèse traite du problème de la redistribution dynamique parallèle efficace de la charge pour les problèmes numériques de très grande taille. Nous présentons tout d'abord un état de l'art des algorithmes permettant de résoudre les problèmes du partitionnement, du repartitionnement, du placement statique et du re-placement. Notre première contribution vise à étudier, dans un cadre séquentiel, les caractéristiques algorithmiques souhaitables pour les méthodes parallèles de repartitionnement. Nous y présentons notre contribution à la conception d'un schéma multi-niveaux k-aire pour le calcul sequentiel de repartitionnements. La partie la plus exigeante de cette adaptation concerne la phase d'expansion. L'une de nos contributions majeures a été de nous inspirer des méthodes d'influence afin d'adapter un algorithme de raffinement par diffusion au problème du repartitionnement.Notre deuxième contribution porte sur la mise en oeuvre de ces méthodes sur machines parallèles. L'adaptation du schéma multi-niveaux parallèle a nécessité une évolution des algorithmes et des structures de données mises en oeuvre pour le partitionnement. Ce travail est accompagné d'une analyse expérimentale, qui est rendue possible grâce à la mise en oeuvre des algorithmes considérés au sein de la bibliothèque Scotch. / This thesis concerns efficient parallel dynamic load balancing for large scale numerical problems. First, we present a state of the art of the algorithms used to solve the partitioning, repartitioning, mapping and remapping problems. Our first contribution, in the context of sequential processing, is to define the desirable features that parallel repartitioning tools need to possess. We present our contribution to the conception of a k-way multilevel framework for sequential repartitioning. The most challenging part of this work regards the uncoarsening phase. One of our main contributions is the adaptation of influence methods to a global diffusion-based heuristic for the repartitioning problem. Our second contribution is the parallelization of these methods. The adaptation of the aforementioned algorithms required some modification of the algorithms and data structure used by existing parallel partitioning routines. This work is backed by a thorough experimental analysis, which is made possible thanks to the implementation of our algorithms into the Scotch library.

L'équilibrage de charge est une étape importante conditionnant les performances des applications parallèles. Dans le cas où la charge varie au cours de la simulation, il est important de redistribuer régulièrement la charge entre les différents processeurs. Dans ce contexte, il peut s'avérer pertinent d'adapter le nombre de processeurs au cours d'une simulation afin d'obtenir une meilleure efficacité, ou de continuer l'exécution quand toute la mémoire des ressources courantes est utilisée. Contrairement au cas où le nombre de processeurs ne varie pas, le rééquilibrage dynamique avec un nombre variable de processeurs est un problème peu étudié que nous abordons ici.Cette thèse propose différentes méthodes basées sur le repartitionnement de graphe pour rééquilibrer la charge tout en changeant le nombre de processeurs. Nous appelons ce problème « repartitionnement M x N ». Ces méthodes se décomposent en deux grandes étapes. Dans un premier temps, nous étudions la phase de migration et nous construisons une « bonne » matrice de migration minimisant plusieurs critères objectifs comme le volume total de migration et le nombre total de messages échangés. Puis, dans un second temps, nous utilisons des heuristiques de partitionnement de graphe pour calculer une nouvelle distribution optimisant la migration en s'appuyant sur les résultats de l'étape précédente. En outre, nous proposons un algorithme de partitionnement k-aire direct permettant d'améliorer le partitionnement biaisé. Finalement, nous validons cette thèse par une étude expérimentale en comparant nos méthodes aux partitionneursactuels. / Load balancing is an important step conditioning the performance of parallel programs. If the workload varies drastically during the simulation, the load must be redistributed regularly among the processors. Dynamic load balancing is a well studied subject but most studies are limited to an initially fixed number of processors. Adjusting the number of processors at runtime allows to preserve the parallel code efficiency or to keep running the simulation when the memory of the current resources is exceeded.In this thesis, we propose some methods based on graph repartitioning in order to rebalance the load while changing the number of processors. We call this problem \M x N repartitioning". These methods are split in two main steps. Firstly, we study the migration phase and we build a \good" migration matrix minimizing several metrics like the migration volume or the number of exchanged messages. Secondly, we use graph partitioning heuristics to compute a new distribution optimizing the migration according to the previous step results. Besides, we propose a direct k-way partitioning algorithm that allows us to improve our biased partitioning. Finally, an experimental study validates our algorithms against state-of-the-art partitioning tools.

L’émergence des applications de bases de données dans les domaines tels que le data warehousing,le data mining et l’aide à la décision qui font généralement appel à de très grands volumes de donnéesrend la parallélisation des algorithmes des jointures nécessaire pour avoir un temps de réponse acceptable.Une accélération linéaire est l’objectif principal des algorithmes parallèles, cependant dans les applicationsréelles, elle est difficilement atteignable : ceci est dû généralement d’une part aux coûts de communicationsinhérents aux systèmes multi-processeurs et d’autre part au déséquilibre des charges des différents processeurs.En plus, dans un environnement hétérogène multi-utilisateur, la charge des différents processeurspeut varier de manière dynamique et imprévisible.Dans le cadre de cette thèse, nous nous intéressons au traitement de la jointure et de la multi-jointure surles architectures distribuées hétérogènes, les grilles de calcul et les systèmes de fichiers distribués. Nousavons proposé une variété d’algorithmes, basés sur l’utilisation des histogrammes distribués, pour traiterde manière efficace le déséquilibre des données, tout en garantissant un équilibrage presque parfait dela charge des différents processeurs même dans un environnement hétérogène et multi-utilisateur. Cesalgorithmes sont basés sur une approche dynamique de redistribution des données permettant de réduire lescoûts de communication à un minimum tout en traitant de manière très efficace le problème de déséquilibredes valeurs de l’attribut de jointure.L’analyse de complexité de nos algorithmes et les résultats expérimentaux obtenus montrent que cesalgorithmes possèdent une accélération presque linéaire. / The appeal of parallel processing becomes very strong in applications which require ever higher performanceand particularly in applications such as : data-warehousing, decision support, On-Line Analytical Processing(OLAP) and more generally DBMS. A linear speed-up is the main objective of parallel algorithms. However,in real applications, it’s not obvious to reach this objective due to the high communication cost in parallel anddistributed systems and to the possible skew in the charge of different processors. In addition, on heterogeneousmulti-user architectures, the load of each processor may highly vary in a dynamic and unpredictableway.In this thesis, we are interested in treating the join and multi-join queries on distributed multi-user heteregeneoussystems, grid systems and distributed file systems. We have proposed several algorithms based onusing distributed histograms. These algorithms are based on a dynamic data distribution and task allocationwhich makes them insensitive to data skew and ensure perfect balancing properties during all stages of joincomputation even on heteregeneous multi-user environment. The complexity analysis of our algorithms andthe experimental results show that they have a near-linear speedup.