Browsing by Author "Atadero, Rebecca A., advisor"
Now showing 1 - 5 of 5
Results Per Page
Sort Options
Item Open Access A study on bridge inspections: identifying barriers to new practices and providing strategies for change(Colorado State University. Libraries, 2021) Abdallah, Abdelrahman M., author; Atadero, Rebecca A., advisor; Ozbek, Mehmet E., advisor; Jia, Gaofeng, committee member; Chai, Dae Seok, committee memberBridge inspections are one of the key elements required for a successful bridge management process to ensure adequate bridge performance. Inspections significantly inform maintenance decisions and can help in managing maintenance activities to achieve a reliable bridge network. In the United States (U.S.) routine visual inspections are required for most bridges at a maximum interval of 24-months regardless of the bridge condition. However, limitations of current bridge inspection practices impact the quality of information provided about bridge condition and the subsequent decisions made based on that information. Accordingly, the overarching goal of this research project is to support bridge inspection practices by providing a systematic and rational framework for bridge inspection planning and identifying the factors that can facilitate innovation and research transfer in the bridge inspection field. To do so, this dissertation includes three separate yet related studies; each focusing on essential aspects of bridge inspection planning. Much research in bridge inspection has been conducted to improve the inspection planning process. The first study provides an overview of current bridge inspection practices in the U.S. and conducts a systematic literature review on innovations in the field of bridge inspection planning to identify research gaps and future needs. This study provides a background on the history of bridge inspection in the U.S., including current bridge inspection practices and their limitations, and analyzes the connections between nondestructive evaluation techniques, deterioration models and bridge inspection management. The primary emphasis of the first study is a thorough analysis of research proposing and investigating different methodologies for inspection planning. Studies were analyzed and categorized into three main types of inspection planning approaches; methods that are based on: reliability, risk analysis, and optimization approaches. This study found that one of the main barriers that may be preventing the implementation of new inspection planning frameworks in practice is that the approaches presented focus on a single bridge element or deterioration mechanism in the decision-making process. Additionally, it was concluded that approaches in the literature are either complex to apply or depend solely on expert judgement. Limitations of the uniform calendar-based approach used to schedule routine inspections have been reported in the literature. Accordingly, the objective of the second study is to provide a new systematic approach for inspection planning that integrates information from bridge condition prediction models, inspection data, and expert opinion using Bayesian analysis to enhance inspection efficiency and maintenance activities. The proposed uncertainty-based inspection framework can help bridge owners avoid unnecessary or delayed inspections and repair actions, determine the inspection method, and consider more than one deterioration process or bridge component during the inspection planning process. The inspection time and method are determined based on the uncertainty and risks associated with the bridge condition. As uncertainty in the bridge condition reaches a defined threshold, an inspection is scheduled utilizing nondestructive techniques to reduce the uncertainty level. The framework was demonstrated on a new and on an existing reinforced concrete bridge deck impacted by corrosion deterioration. The results showed that the framework can reduce the number of inspections compared to conventional scheduling methods, while also reducing the uncertainty regarding the transition in the bridge deck condition and repair time. As identified through the first study, over the last two decades many researchers have focused on providing new ideas to improve conventional bridge inspection practices, however, little guidance is provided for implementing these new research products in practice. This, along with resistance to change and complexity of the proposed ideas, resulted in a lack of consistency and success in applying new technologies in bridge inspection programs across state departments of transportation (DOTs). Accordingly, the third paper presents a qualitative study set out to identify the factors that can help improve research products and accelerate change and research transfer in bridge inspection departments. This study used semi-structured interviews, written interviews, and questionnaires for data collection and engaged with twenty-six bridge staff members from different DOTs. The findings of this study are expected to be both specific to changes in bridge inspection practice and have some generalizability to other significant changes to engineering practice at DOTs. To improve research products, this study suggested that researchers need to collaborate more with DOT staff members and provide relevant research products that are not specific to certain bridge cases and can be applied on different bridges. Also, to facilitate change in transportation organizations, change leaders should focus on showing the need for change, gaining support from the FHWA, allocating the required resources, and enhancing the capacity of DOT staff members through training and effective communication. The investigation also presented participants' opinions on some of the aspects related to conventional inspection practices such as their support of a uniform inspection interval over a variable interval, and the main barriers limiting the use of NDE methods. This study contributes to the body of knowledge in the bridge inspection field by providing a new inspection planning approach that depends on the uncertainty and the risks associated with the bridge condition and uses both computational methods and expert judgment allowing bridge owners select inspection time and method while considering more than one deterioration process or bridge element. In addition, this study presents some of the factors that can help reduce the gap between research and practice and facilitate innovation and change in transportation organizations.Item Open Access High-volume use of self-cementing spray dry absorber material for structural applications(Colorado State University. Libraries, 2009) Riley, Charles E., author; Heyliger, Paul R., advisor; Atadero, Rebecca A., advisorSpray dry absorber (SDA) material, or spray dryer ash, is a byproduct of energy generation by coal combustion and sulfur emissions controls. Like any resource, it ought to be used to its fullest potential offsetting as many of the negative environmental impacts of coal combustion as possible throughout its lifecycle. Its cementitious and pozzolanic properties suggest it be used to augment or replace another energy and emissions intensive product: Portland cement. There is excellent potential for spray dryer ash to be used beneficially in structural applications, which will offset CO2 emissions due to Portland cement production, divert landfill waste by further utilizing a plentiful coal combustion by-product, and create more durable and sustainable structures. The research into beneficial use applications for SDA material is relatively undeveloped and the material is highly underutilized. This dissertation explored a specific self-cementing spray dryer ash for use as a binder in structural materials. Strength and stiffness properties of hydrated spray dryer ash mortars were improved by chemical activation with Portland cement and reinforcement with polymer fibers from automobile tire recycling. Portland cement at additions of five percent of the cementitious material was found to function effectively as an activating agent for spray dryer ash and had a significant impact on the hardened properties. The recycled polymer fibers improved the ductility and toughness of the material in all cases and increased the compressive strength of weak matrix materials like the pure hydrated ash. The resulting hardened materials exhibited useful properties that were sufficient to suggest that they be used in structural applications such as concrete, masonry block, or as a hydraulic cement binder. While the long-term performance characteristics remain to be investigated, from an embodied-energy and carbon emissions standpoint the material investigated here is far superior to Portland cement.Item Open Access Multi-criteria decision-making approach for building maintenance in facility management(Colorado State University. Libraries, 2021) Besiktepe, Deniz, author; Ozbek, Mehmet E., advisor; Atadero, Rebecca A., advisor; Grigg, Neil S., committee member; Bradley, Thomas H., committee member; Valdes-Vasquez, Rodolfo, committee memberFacility Management (FM) encompasses multi-disciplinary processes to ensure the built environment functions properly for its intended use and service. Maintenance practices are critical to sustaining the longevity of the built environment. As buildings continue to age, there is an increasing need for effective maintenance practices and strategies. In addition, cost and financial constraints require enhanced processes in building maintenance decision-making to assure the resources are allocated efficiently to get the best possible outcome. Building maintenance decisions present challenges to FM professionals. These challenges arise from the complexity of building systems as well as the participation of multiple stakeholders in the process, such as the property owner, facility manager, engineer, project supervisors, technicians, and occupants. The overarching goal of this dissertation is to develop a systematic and structured multi-criteria decision-making (MCDM) approach for building maintenance practices in a resource-constrained environment. To do so, this dissertation includes three separate but related studies; each focusing on the essential pieces of the MCDM approach. The first study identified the set of fundamental criteria needed for constructing an MCDM model for FM decision-making utilizing the results of a nationwide survey conducted with the members of the International Facility Management Association (IFMA) and the Leadership in Educational Facilities (APPA) in the United States, two globally recognized FM organizations. The first study also has an exploratory aspect and tries to establish the decision-making and condition assessment practices currently used in FM practices. The second study focused on developing a resource-efficient and quantitative condition assessment (CA) framework to establish a condition rating value. Condition information is essential in the decision-making process of building maintenance; however, financial challenges limit the practice of CA, which currently is mostly based on visual inspections and likely to generate a subjective outcome. Fuzzy sets theory is utilized to obtain a quantitative condition rating value that would be less subjective than that obtained through visual inspections, as fuzzy sets theory deals with imprecise, uncertain, and ambiguous judgments with the membership relations. In the third study, an MCDM method, Choosing by Advantages (CBA), is used to develop a structured and systematic decision-making approach in building maintenance and FM. CBA allows the identification of the most-value generating alternative in the absence of cost and financial constraints, which helps to eliminate the dominancy of financial considerations in the decision-making process. In addition, CBA provides a practical framework to decision-makers in FM with various backgrounds, allowing the participation of multiple stakeholders in the process. This study contributes to the body of knowledge in the FM domain by identifying criteria in the building-maintenance decision-making process, developing a less subjective and quantitative CA framework, and demonstrating an MCDM method for a systematic approach in building-maintenance decision-making. Additionally, this study will benefit FM professionals and decision-makers at all levels by helping to prioritize maintenance activities, justify maintenance budget requests, and support strategic planning.Item Open Access Understanding and mitigating tsunami risk for coastal structures and communities(Colorado State University. Libraries, 2011) Park, Sangki, author; Atadero, Rebecca A., advisor; van de Lindt, John W., advisor; Heyliger, Paul R., committee member; Senior, Bolivar A., committee memberTsunamis have attracted the world's attention over the last decade due to their destructive power and the vast areas they can affect. The 2004 Indian Ocean Tsunami, killed more than 200,000 people, and the 2011 Great Tohoku Japan Earthquake and Tsunami, resulted in 15,000 deaths and an estimated US $300B in damage, are recent examples. An improved understanding of tsunamis and their interactive effects on the built environment will significantly reduce loss of life in tsunamis. In addition, it is important to consider both the effect of the earthquake ground motion and the tsunami it creates for certain coastal regions. A numerical model to predict structural behavior of buildings subjected to successive earthquakes and the tsunamis was developed. Collapse fragilities for structures were obtained by subjecting a structure to a suite of earthquake ground motions. After each motion the numerically damaged structural model was subjected to tsunami wave loading as defined by FEMA P646. This approach was then extended to the community level; a methodology to determine the probability of fatalities for a community as a function of the number of vertical evacuation shelters was computed. Such an approach also considered the location and number of vertical evacuation sites as an optimization problem. Both the single structure cases and the community analyses were presented in terms of fragilities as a function of the earthquake intensity level and evacuation time available. It is envisioned that the approach may be extended to any type of structure as they are typically modeled nonlinearly with strength and stiffness degradation. A logical fragility-based, or performance-based, procedure for vertical evacuation for coastal buildings and for whole communities was developed. A mechanism to obtain a reduction in the collapse risk of structure and more critically maximize the survival rate for a community was a major outcome of this dissertation. The proposed tsunami vertical evacuation methodology was intended to provide key information to better understand and mitigate risk caused by earthquakes and tsunamis, thus it is possible to mitigate hazard for a community with only several large vertical evacuation shelters. It is able to provide a framework for a vertical evacuation plan and for the mitigation of collapse risk and fatalities of structures and a community based on a limited amount of information.Item Open Access Valuable utilization of spray dryer ash and its performance in structural concrete(Colorado State University. Libraries, 2010) Namagga, Carolyne Alex, author; Atadero, Rebecca A., advisor; Ozbek, Mehmet E., committee member; Van de Lindt, John W., committee memberThis research focuses on the valuable utilization of Spray Dryer Ash (SDA) and investigates its performance in concrete for structural and transportation applications. Based on the challenges associated with coal ash (including SDA) and the economic costs linked to cement production, this research seeks to provide an environmentally friendly and more cost effective concrete product by utilizing SDA in partial replacement of cement in concrete. Cement production is a rather expensive venture and yet there is an abundance of coal ash that is disposed of in landfills that could be utilized positively. The fineness and low carbon content properties of SDA/ Class C fly ash provide potential benefits of increased strength (compressive and bond) and durability (freeze-thaw and corrosion) when used in concrete. With the exception of high sulfur content, SDA exhibits very excellent properties that are closely related to Class C fly ash and Portland cement. The addition of Spray Dryer Ash in non-air entrained concrete provided a general increase in its strength. The compressive strength test results indicate that replacing proportions of cement with SDA would provide improved strength and a most cost effective solution. When utilized within optimal limits of 25-35% replacement, SDA presents reasonable benefits to compressive and bond strength. The utilization of SDA provided modest benefits when used in certain proportions and at the very least it did not seem to degrade the properties much. It produced a negligible effect on the freeze-thaw durability of the concrete while an increase in the SDA provided an increased corrosion resistance and a reduced corrosion rate in concrete. Based on the results of this research, SDA has great potential for its utilization as a structural material in transportation infrastructures.