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

Lexical differentiation in language production and comprehension

This paper presents the results of three experiments that explore the breadth of the relevant discourse context in language production and comprehension. Previous evidence from language production suggests the relevant context is quite broad, based on findings that speakers differentiate new discourse referents from similar referents discussed in past contexts (Van Der Wege, 2009). Experiment 1 replicated and extended this “lexical differentiation” effect by demonstrating that speakers used two different mechanisms, modification, and the use of subordinate level nouns, to differentiate current from past referents. In Experiments 2 and 3, we examine whether addressees expect speakers to differentiate. The results of these experiments showed no evidence of an expectation for differentiation, for either lexically differentiated modified expressions (Experiment 2), nor for subordinate level nouns (Experiment 3). Taken together, the present findings suggest that the breadth of relevant discourse context differs across language production and comprehension. Speakers show more sensitivity to things they have said before, possibly due to better knowledge of the relevant context. In contrast, listeners have the task of inferring what the speaker believes is the relevant context; this inferential process may be more error-prone

Mechanisms of conversation: audience design and memory

It is well established that conversational partners jointly establish brief labels for repeatedly mentioned entities. When speaking to a new partner who is unfamiliar with the labels, speakers use longer expressions to facilitate understanding. How this process of audience design scales up to conversations among three or more individuals is unknown. Further, while memory is thought to play an essential role in audience design, the link between memory for language and language use is not well explored. This dissertation consists of two parts that examine these two issues. In Chapter 2, I propose, and test, potential hypotheses regarding how speakers design referring expressions in multiparty conversation. The results of four experiments help to elucidate the mechanisms that support audience design in multiparty conversation. In Chapter 3, I explore the memory contributions to the referential phenomenon of lexical differentiation, aiming to understand the relationship between memory for discourse referents in dialogue and referential form. The results of three experiments provide insights into how memory for the discourse history guides language use during conversation. Taken together, these findings allow us to better understand the mechanisms of audience design and the interplay between language use and memory in conversation

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

Room temperature near-ultraviolet emission from In-rich InGaN/GaN multiple quantum wells

We grew In-rich InGaNGaN multiple quantum wells (MQWs) using growth interruption (GI) by metalorganic chemical vapor deposition. The quality of overgrown InGaNGaN QW layers in MQWs was largely affected by the crystalline quality and interfacial abruptness of the underlying QW layer. Introduction of 10 s GI was very effective in improving the crystalline quality and interfacial abruptness of InGaN QW layers, and we grew a ten periods of 1-nm -thick In-rich InGaNGaN MQW with 10 s GI and obtained a strong near-ultraviolet (UV) emission (~390 nm) at room temperature. We believe that use of less than 1-nm -thick In-rich InGaN MQW can be a candidate for near-UV source, which might replace the conventional low-indium content (<10%), thicker InGaN QW layer.open313

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

CORRELATIONS BETWEEN EXPERTS’ SCORING AND BIOMECHANICAL ASSESSMENT IN BALLET MOVEMENT

The purpose of this study was to investigate the relationship between assessment of ballet movement by experts and biomechanical variables. Releve point movement was recorded by a video camcorder (Sony, Japan) for the expert assessment. Eight infrared cameras (Qualisys, Sweden) and two force plates (Kistler, Switzerland) were used for biomechanical analysis. A High reliability in score for flexibility and assistance among three judges was found. Based on the analysis of correlations, flexibility and ROM were positively correlated as the subject who performed wider motion at the ankle achieved higher sores in flexibility from the judges. Negative correlations were found between the judges’ scores in assistance and ankle joint power as well as their scores in balance and COP on the left side. Development of objective and reliable scoring standards in ballet based on the understanding of body movements supported by the verification of scientific method is needed