Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 143-149). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 143-149). Also available on the Internet.

Thesis (Ph.D.)--Aerospace Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Dr. Vitali Volovoi; Committee Co-Chair: Dr. Massimo Ruzzene; Committee Member: Dr. Andrew Makeev; Committee Member: Dr. Dewey Hodges; Committee Member: Dr. Peter Cento

L'objectif de ce travail est de comprendre l'influence de nano-plaquettes d'argile sur le comportement mécanique de polymères nano-renforcés. Cette compréhension nécessite une caractérisation fine de la micro-structure mais aussi l'étude du comportement mécanique de ces matériaux (en élasticité et en visco-élasticité). A l’échelle microscopique, la taille des agrégats de plaquettes d'argile et la distribution spatiale de ces agrégats ont été observées au TEM. A l’échelle nanoscopique, le d-spacing entre plaquettes d'un agrégat a été mesuré en utilisant la XRD. Ces techniques expérimentales ont permis de mettre en évidence une micro-structure intercalée. A l’échelle macroscopique, des essais de traction monotones ainsi que des essais dynamiques (DMA) ont été réalisé afin d'étudier le comportement mécanique des matériaux. Pour prédire les propriétés élastiques macroscopiques, la combinaison de deux approches a été envisagée; modèles hybrides et modèles matrice-inclusion. Cet outil permet d'anticiper les propriétés de ces matériaux sans avoir à les fabriquer ainsi que de tester simplement l'influence de la micro-structure sur le comportement macroscopique. Le schéma d'homogénéisation mis en place permet de prendre en compte la micro-structure intercalée d'une matrice polymère renforcée par des empilements de sandwiches bi-couches (plaquettes d'argile et polymère). On observe, en élasticité, un bon encadrement des données expérimentales. Une extension de cette approche en visco-élasticité a été développée. Les prédictions en visco-élasticité comparées aux données expérimentales ont fourni une bonne estimation du module complexe et des modules de conservation et de perte. / This work aims to understand the influence of nano-clay platelets on the mechanical behavior of nano–reinforced polymers. This understanding requires a good description of the micro-structure and a characterization of the mechanical behavior of these materials (elastic and visco-elastic). At the micro-scale, the size of the aggregates of nano-platelets and their spatial distribution were observed using TEM. At the nano-scale, the d-spacing between platelets within an aggregate was measured using XRD. These experimental techniques highlighted intercalated micro-structures. At the macroscale, monotonic tensile tests and Dynamic Mechanical Analysis (DMA) have been performed to study the mechanical behavior of the materials. To predict the macroscopic elastic behavior, the combination of two approaches has been considered; hybrid and matrix-inclusion models. This needed tool allows to anticipate the behavior of these materials without process them. By the consideration of the morphology into the modeling scheme, the influence of the micro-structure on the macroscopic behavior can be studied. The considered multiscale approach is able to estimate the macroscopic behavior of an intercalated nano-composite, in which a polymeric matrix is reinforced by stacks of bi-layers sandwiches (nano-clay platelets and polymer). It was observed from their comparison that the modeling predictions well bounded the experimental data in elasticity. This multi-scale approach was extended in the context of viscoelasticity and the predictions in this context were in good agreement with the experimental data for the complex modulus and for the storage and loss moduli.

No description available.

No description available.

A roof is a critical envelope of a building. It provides protection for the building interior against various weather elements, such as snow, rain and wind. Roofs are normally composed of several components such as insulation, barriers and water proofing membrane. A roof edge is the perimetric part of a roof that serves as termination for roof components. In generic terms, a roof edge system is composed of a parapet with metal components, such as coping and cleat/clip. The edge system is typically subjected to negative pressure (suction) due to wind flow over the roof. Therefore, a roof edge is the front-line of defence against wind action. To develop testing standards and design guidelines for roof edges, a project referred as REST (Roof Edge Systems and Technologies) has been initiated in cooperation with the NSERC (Natural Sciences and Engineering Research Council). For the REST project, this thesis contributes in two folds: wind design procedure and the development of an experimental method for testing roof edge components. The present thesis analyzes the wind load calculation procedures as per the National Building Code of Canada (NBCC) and American Society of Civil Engineers (ASCE). This has been achieved by taking side-by-side cities along Canada-USA border; wind load calculations were performed to demonstrate the differences and similarities between the NBCC and ASCE. As a part of the current contribution, the existing version of the online Wind-RCI Calculator was updated from NBCC2005 to NBCC2010 provisions. Towards the experimental contribution, the current study presents a new experimental method for testing and evaluating wind uplift resistance of roof edge systems by simulating wind loads in a lab environment on full-scale mock-ups. The test apparatus had a gust simulator device to mimic wind gusting (dynamic loading). This research investigates three widely used edge systems in North America: Continuous Cleat Configuration (CCC), Discontinuous Cleat Configuration (DCC) and Anchor Clip Configuration (ACC). Preliminary data show that CCC edge system has higher resistance in comparison to DCC and ACC edge systems. The experiments also revealed the need for experimental setup enhancement. Additional investigations by using the enhanced experimental setup were performed on both CCC and DCC edge systems.

Under the direction of the Federal Highway Administration the Long Term Bridge Performance Program (LTBP) selected Minnesota Bridge number 5718 as a pilot bridge for evaluation. This program focuses on the monitoring of bridges for a 20-year period to understand the structural behavior over time due to the various loads and weathering. In monitoring this bridge a better understanding can be acquired for the maintenance issues related to the nation's deteriorating bridge infrastructure. Bridge Number 5718, which is located just outside of Sandstone Minnesota, is a steel truss bridge that spans the Kettle River. Constant monitoring of the bridge along with periodic testing of the bridge will allow for the collection of data over a 20-year period. The focus of this work is to establish a baseline for the bridges characteristics through nondestructive dynamic testing. Later tests will be compared to these results and changes can then be tracked. In order to perform the required testing, two electromagnetic shakers were used to produce the excitation. The bridge was also outfitted with an array of velocity transducers to allow for the response to be recorded. The data was then used to extract the resonant frequencies, mode shapes, and damping ratios. A modal assurance criterion was also performed to solidify the findings. These parameters define the structural identity of the bridge. Through performing these tests the database that is being collected under the Long Term Bridge Performance Program will be used to better the overall health and safety of the nation's bridges.

As part of the Long-Term Bridge Performance (LTBP) program, a flagship research program funded by the Federal Highway Administration in response to the aging bridge network, the Lambert Road Bridge near Elk Grove California was selected as the California Pilot bridge set to undergo non-destructive testing and monitoring. The purpose of the program is to obtain a database of scientific quality data concerning the health and maintenance procedures currently in use across the nation. FHWA program managers along with members of the Utah State University LTBP research team selected the bridge with the assistance of the National Bridge index and site visits. Dynamic modal analysis and long-term health monitoring are two of the test procedures that the test bridge will undergo. Dynamic modal analysis is performed by introducing a known vibration into the system and recording the response. The dynamic properties are extracted in this manner, which allows any changes in the structure to be tracked over time as the dynamic properties change. The long-term health monitoring of the bridge will include an array of sensors designed to capture the real-time structural response of the bridge under normal operating conditions at key locations. An array of 1-Hz Velocity Transducers was used to record the bridge response to the introduced vibrations. The data collected over 4 days of testing was analyzed using the "peak picking method" to locate the resonant frequencies, mode shapes, and damping ratios of the structure. In this thesis the dynamic testing results and the finite element model were compared and correlated both visually and with a modal assurance criterion. The long-term health monitoring is also discussed in this thesis. The types and reason for each sensor are presented and the installation procedure is explained and documented.

No description available.