Development of a structural health monitoring system for bridges and components

This dissertation summarizes the development of an autonomous, continuous structural health monitoring (SHM) system that can be used to monitor typical girder bridges. The developed system features two key uses. First, the system can be integrated into an active bridge management system that tracks usage and structural changes. Second, the system helps bridge owners to identify overload occurrence, vehicle collision to the structure, damage and deterioration.;The primary objective of this research was to develop a SHM system that could be used to monitor typical girder bridges for detecting and identifying overload occurrence, vehicle collision to the structure, changes in structural behavior, identification of damage and deterioration, and for tracking usage. These specific needs were established to give owners the tools to better manage bridge assets and were accomplished by completing three distinct work tasks.;The first task involved developing bridge-specific live load structural analysis software, BEC Analysis. Like many analysis software packages, the fundamental algorithm was based upon classic beam theory and the direct stiffness method structural analysis. BEC Analysis can be used for (1) analyzing beams or girders under moving loads, (2) computing absolute maximums in each span or at a specific location, and (3) generating envelopes of maximum moments and strains.;The second task involved developing the field data collection and analysis software that integrates with select data acquisition hardware. The software was designed to automatically collect, process, and evaluate the measured response of a bridge. Its use may allow bridge owners to quantitatively monitor a bridge for potential damage as well as gradual change in behavior. Significant effort was given to developing algorithms that include temperature compensation and fundamental sound data reduction and data mining techniques.;After the development of the SHM system was completed, the system was tested and implemented on a highway bridge to demonstrate and verify its general usage. The system was validated and several observations were given concerning the overall bridge performance during the brief monitoring period

Sustainability of Concrete as A Civil Engineering Material

With increasing concern about the environment, energy consumption, climate change, and depletion of natural resources, the importance of sustainability has become mainstream among engineering and scientific communities. Concrete infrastructure is superbly durable and comes with a myriad of benefits. Yet, the production of concrete is energy intensive and represents a substantial portion of air pollution. Largely due to cement manufacturing, concrete represents 7% of greenhouse gas emissions globally and 1% in the United States. Focusing on sector-specific emissions in the United States., this paper outlines the environmental concerns of concrete production and discusses the forefront of research in reducing these effects including innovations in cement manufacturing, alternative clinker technologies, and carbon capture use and storage. Also discussed are various approaches and efforts in concrete recycling and incorporation of industrial wastes and supplementary cementitious materials into concrete. Finally, this study reviews the role of civil engineering design at various scales in the sustainability of concrete infrastructure

Evaluation of bridges strengthened or newly constructed with innovative materials

Bridge engineers and owners have spent considerable time and effort researching viable, cost effective solutions to improve the condition, durability, and capacity of bridges and, thus, reduce overall life-cycle costs. Among the many projects funded through the Innovative Bridge Research and Construction Program, this thesis summarizes three projects that utilize innovative materials to strengthen existing deficient bridges and in the construction of a new bridge. The projects presented in this thesis focus on the demonstration of the use of new, cost-effective, innovative materials and associated performance monitoring. In the first two parts (Part I and Part II), the use of carbon fiber reinforced polymer (CFRP) materials to strengthen existing, structurally deficient steel girder bridge is summarized. Among various strengthening materials, CFRP composite materials were selected due to their outstanding mechanical characteristics and non-corrosive nature. Two bridges were strengthened using these materials in an effort to improve the live load carrying capacity of the bridges. In one case (Part I), a bridge was strengthened using CFRP bars that were post-tensioned in the positive moment region. In the other case (Part II), a bridge was strengthened by installing CFRP plates to the bottom flange of girders in the positive moment region. In Part III, a portion of a project that investigates corrosion of reinforcement steel in the deck slab of two, newly constructed, prestressed concrete girder bridges is presented. The decks of the two bridges were constructed with two different types of steel; one with Micro-composite Multi-structural Formable Steel (MMFX) reinforcing steel, a relatively new form of corrosion resistant steel, and the other with epoxy coated steel. During the construction of the bridges, embeddable sensors were installed on selected reinforcing bars in the deck slab to identify signs of corrosion initiation and severity. Data were recorded periodically to assess and compare the performance of two different types of reinforcing steel

Investigation of High-Strength Bolt-Tightening Verification Techniques

The current means and methods of verifying that high-strength bolts have been properly tightened are very laborious and time consuming. In some cases, the techniques require special equipment and, in other cases, the verification itself may be somewhat subjective. While some commercially available verification techniques do exist, these options still have some limitations and might be considered costly options. The main objectives of this project were to explore high-strength bolt-tightening and verification techniques and to investigate the feasibility of developing and implementing new alternatives. A literature search and a survey of state departments of transportation (DOTs) were conducted to collect information on various bolt-tightening techniques such that an understanding of available and under-development techniques could be obtained. During the literature review, the requirements for materials, inspection, and installation methods outlined in the Research Council on Structural Connections specification were also reviewed and summarized. To guide the search for finding new alternatives and technology development, a working group meeting was held at the Iowa State University Institute for Transportation October 12, 2015. During the meeting, topics central to the research were discussed with Iowa DOT engineers and other professionals who have relevant experiences

Investigation of Field Corrosion Performance and Bond/Development Length of Galvanized Reinforcing Steel

In reinforced concrete systems, ensuring that a good bond between the concrete and the embedded reinforcing steel is critical to long-term structural performance. Without good bond between the two, the system simply cannot behave as intended. The bond strength of reinforcing bars is a complex interaction between localized deformations, chemical adhesion, and other factors. Coating of reinforcing bars, although sometimes debated, has been commonly found to be an effective way to delay the initiation of corrosion in reinforced concrete systems. For many years, the standard practice has been to coat reinforcing steel with an epoxy coating, which provides a barrier between the steel and the corrosive elements of water, air, and chloride ions. Recently, there has been an industry-led effort to use galvanizing to provide the protective barrier commonly provided by traditional epoxy coatings. However, as with any new structural product, questions exist regarding both the structural performance and corrosion resistance of the system. In the fall of 2013, Buchanan County, Iowa constructed a demonstration bridge in which the steel girders and all internal reinforcing steel were galvanized. The work completed in this project sought to understand the structural performance of galvanized reinforcing steel as compared to epoxy-coated steel and to initiate a long-term corrosion monitoring program. This work consisted of a series of controlled laboratory tests and the installation of a corrosion monitoring system that can be observed for years in the future. The results of this work indicate there is no appreciable difference between the bond strength of epoxy-coated reinforcing steel and galvanized reinforcing steel. Although some differences were observed, no notable difference in either peak load, slip, or failure mode could be identified. Additionally, a long-term monitoring system was installed in this Buchanan County bridge and, to date, no corrosion activity has been identified

High‐Color‐Purity Subtractive Color Filters with a Wide Viewing Angle Based on Plasmonic Perfect Absorbers

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110824/1/adom201400533.pd

Evaluation of Steel Bridges, Volumes I & II

This report is divided into two volumes. Volume I summarizes a structural health monitoring (SHM) system that was developed for the Iowa DOT to remotely and continuously monitor fatigue critical bridges (FCB) to aid in the detection of crack formation. The developed FCB SHM system enables bridge owners to remotely monitor FCB for gradual or sudden damage formation. The SHM system utilizes fiber bragg grating (FBG) fiber optic sensors (FOSs) to measure strains at critical locations. The strain-based SHM system is trained with measured performance data to identify typical bridge response when subjected to ambient traffic loads, and that knowledge is used to evaluate newly collected data. At specified intervals, the SHM system autonomously generates evaluation reports that summarize the current behavior of the bridge. The evaluation reports are collected and distributed to the bridge owner for interpretation and decision making. This volume (Volume II) summarizes the development and demonstration of an autonomous, continuous SHM system that can be used to monitor typical girder bridges. The developed SHM system can be grouped into two main categories: an office component and a field component. The office component is a structural analysis software program that can be used to generate thresholds which are used for identifying isolated events. The field component includes hardware and field monitoring software which performs data processing and evaluation. The hardware system consists of sensors, data acquisition equipment, and a communication system backbone. The field monitoring software has been developed such that, once started, it will operate autonomously with minimal user interaction. In general, the SHM system features two key uses. First, the system can be integrated into an active bridge management system that tracks usage and structural changes. Second, the system helps owners to identify damage and deterioration

Synthesis and characterization of Na03RhO206H2O - a semiconductor with a weak ferromagnetic component

We have prepared the oxyhydrate Na03RhO206H2O by extracting Na+ cations from NaRhO2 and intercalating water molecules using an aqueous solution of Na2S2O8. Synchrotron X-ray powder diffraction, thermogravimetric analysis (TGA), and energy-dispersive x-ray analysis (EDX) reveal that a non-stoichiometric Na03(H2O)06 network separates layers of edge-sharing RhO6 octahedra containing Rh3+(4d6, S=0) and Rh4+ (4d5, S=1/2). The resistivities of NaRhO2 and Na03RhO206H2O (T < 300) reveal insulating and semi-conducting behavior with activation gaps of 134 meV and 7.8 meV, respectively. Both Na03RhO206H2O and NaRhO2 show paramagnetism at room temperature, however, the sodium-deficient sample exhibits simultaneously a weak but experimentally reproducible ferromagnetic component. Both samples exhibit a temperature-independent Pauli paramagnetism, for NaRhO2 at T > 50 K and for Na03RhO206H2O at T > 25 K. The relative magnitudes of the temperature-independent magnetic susceptibilities, that of the oxide sample being half that of the oxyhydrate, is consistent with a higher density of thermally accessible electron states at the Fermi level in the hydrated sample. At low temperatures the magnetic moments rise sharply, providing evidence of localized and weakl -ordered electronic spins.Comment: 15 fages 5 figures Solid State Communications in prin

Molecular Design Approach Managing Molecular Orbital Superposition for High Efficiency without Color Shift in Thermally Activated Delayed Fluorescent Organic Lightâ Emitting Diodes

Molecular design principles of thermally activated delayed fluorescent (TADF) emitters having a high quantum efficiency and a color tuning capability was investigated by synthesizing three TADF emitters with donors at different positions of a benzonitrile acceptor. The position rendering a large overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) enhances the quantum efficiency of the TADF emitter. Regarding the orbital overlap, donor attachments at 2â and 6â positions of the benzonitrile were more beneficial than 3â and 5â substitutions. Moreover, an additional attachment of a weak donor at the 4â position further increased the quantum efficiency without decreasing the emission energy. Therefore, the molecular design strategy of substituting strong donors at the positions allowing a large molecular orbital overlap and an extra weak donor is a good approach to achieve both high quantum efficiency and a slightly increased emission energy.Overlap to emit: The substitution of strong donors at the positions rendering a large HOMOâ LUMO overlap and the addition of a weak donor constitute an effective design approach to realize TADF emitters having high efficiency.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147817/1/chem201805616-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147817/2/chem201805616.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147817/3/chem201805616_am.pd