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NUMERICAL ANALYSIS AND EXPERIMENTAL INVESTIGATION OF ULTRA-HIGH-PERFORMANCE CONCRETE HYBRID BRIDGE DECK CONNECTIONS
No full textIn recent years, the use of modular bridge deck components has gained popularity for facilitating more durable components in bridge decks, but these components require field-applied connections for constructing the entire bridge. Ultra-High-Performance Concrete (UHPC) is being extensively used for highway bridges in the field connections between girders and deck panels for its superior quality than conventional concrete. Thus far, very limited data is available on the modeling of hybrid-bridge deck connections. In this study, finite element models have been developed to identify the primary properties affecting the response of hybrid deck panel system under monotonic and reverse cyclic loads. The commercial software ABAQUS was used to validate the models and to generate the data presented herein. The concrete damage plasticity (CDP) model was used to simulate both the conventional concrete and UHPC. In addition, numerical results were validated against experimental data available in the literature. The key parameters studied were the mesh size, the dilation angle, reinforcement type, concrete constitutive models, steel properties, and the contact type between the UHPC and the conventional concrete. The models were found to capture the load – deformation response, failure modes, crack patterns and ductility indices satisfactorily. The damage in concrete under monotonic loading is found higher in normal concrete than UHPC with no signs of de-bonding between the two materials. It is observed that increasing the dilation angle leads to an increase in the initial stiffness of the model. Changing the dilation angle from 20° to 40° results in an increase of 7.81% in ultimate load for the panel with straight reinforcing bars, whereas for the panel with headed bars, the increase in ultimate load was found 8.56 %. Furthermore, four different types of bridge deck panels were simulated under reversed cyclic loading to observe overall behavior and the damage pattern associated with the reversed cyclic load. The key parameters investigated were the configurations of steel connections between the precast concrete deck elements, the loading position, ductility index, and the failure phenomena. The headed bar connections were found to experience higher ductility than the ones with straight bars in the range of 10.12% to 30.70% in all loading conditions, which is crucial for ensuring safe structural performance. This numerical investigation provides recommendations for predicting the location of the local damage in UHPC concrete bridge deck precast panel connections under reversed cyclic loading. Despite of having excellent mechanical and material properties, the use of Ultra-High-Performance Fiber Reinforced Concrete (UHP-FRC) is not widespread due to its high cost and lack of widely accepted design guidelines. This research also aims to develop a UHPC mixture using locally and domestically available materials without heat curing in hopes of reducing the production cost. Several trial mixtures of UHPC have been developed using locally available basalt and domestically available steel fibers. Among them, one trial mixture of 20.35 ksi compressive strength was selected for further study. To investigate the applicability of this locally produced UHPC in bridge closure, two full scale-8 ft. span hybrid bridge deck slabs with UHPC closure were constructed and tested under monotonic loading to identify the structural and material responses. The load- deflection response of the hybrid connection confirms that the deflection increased linearly until the initiation of first crack, after that it increased non-linearly up to the failure of the connection. The strain response also confirms that UHPC experiences less strain than normal strength concrete under compression loading. In addition, a moment curvature analytical graphical user interface model of hybrid bridge deck connection has been developed using MATLAB to predict ductility, curvature, and the stress distributions in those connections. The predicted value of moment and curvature from the code was found in good agreement with experimental data as well. The code provides a tool to professional engineers to predict ductility, curvature, and the stress distributions in those connections. The code is built in such a way to allow various input parameters such as concrete strength, dimensions of hybrid connection and deck panels, reinforcement configuration and the shape of the connection. Though, ultra-high-performance fiber reinforced concrete (UHP-FRC) has very high compressive strength compared to conventional concrete, the failure strain of UHP-FRC is not enough to withstand large plastic deformations under high stain rate loading such as impact and blast loading. Hence, a numerical study has been conducted to simulate low-velocity impact phenomenon of UHP-FRC. The responses obtained from the numerical study are in good agreement with the experimental results under impact loads. Five different types of UHP-FRC beams were simulated under impact loading to observe the global and local material responses. The key parameters investigated were the reinforcement ratio (ρ), impact load under various drop heights (h), and the failure phenomena. It was observed that higher reinforcement ratio showed better deflection recovery under the proposed impact. Also, for a specific reinforcement ratio, the maximum deflection increases approximately 15% when drop height decreases from 100 mm to 25 mm. Moreover, the applicability of concrete damage plasticity model for impact loading is investigated. The results also provided recommendations for predicting the location of the local damage in UHP-FRC beams under impact loading. Moreover, this research work includes a nonlinear finite element analysis of high-strength concrete confined with opposing circular spiral reinforcements. The spiral reinforcement is a very common technique used for reinforcing columns in active seismic regions due to its high ductility and high energy absorption. The results are compared with previously tested small-scale concrete columns made with the same technique under monotonic axial loads. The proposed technique is developed to improve the strength and ductility of concrete columns confined with conventional spiral systems. The finite element (FE) analysis results have shown that the proposed model can predict the failure load and crack pattern of columns with reasonable accuracy. Beside this, the concrete plasticity damage showed very good results in simulating columns with opposing spirals. The FE model is used to conduct a study on the effect of spiral spacing, γ (ratio of the core diameter to the whole cross section diameter) and compressive strength on the behavior of circular spiral reinforced concrete columns confined with opposing circular spiral reinforcements. The results of the parametric study demonstrated that for the same spacing between spirals and same strength of concrete, increasing γ increases the failure load of the column. It is also observed from the study that the ductility of the studied columns is not affected by changing the value of γ. In addition, a correlation between the γ factor, three different compressive concrete strengths, and the spacing of opposing spirals was developed in this study.doctoral, Ph.D., Civil Engineering -- University of Idaho - College of Graduate Studies, 2019-0
Silenced Female Voices: How Institutionalized Avoidance Condones a Culture of Workplace Aggression and Shame in Higher Education
No full textNumerous studies describe the harsh realities of workplace aggression. Many of these studies originated in Scandinavia and Australia, but in recent years research in workplace aggression has increased in the U.S. Researchers attribute workplace aggression to negative emotional, physical, and psychological outcomes. More recently, researchers studied workplace aggression in higher education populations such students, faculty, and administrators, however, research on professional staff is insufficient. In this three-manuscript dissertation study, I explored the lived adverse interpersonal experiences of female professional staff in higher education and discovered how they moved through the experiences. I offer an alternative to the male “normal experience” through a feminist post-intentional phenomenological lens of female professional staffs’ experiences with workplace aggression in higher education. Tentative manifestations, or themes, and discussion provide insight to the female lived experiences of workplace aggression and shame in higher education. I found the participants’ experiences included different types of workplace aggression: incivility, bullying, harassment, and emotional abuse. As a result, female professional staff felt elements of shame such as being trapped, powerless, and isolated. I explored how the participants moved through their experiences utilizing components of shame resilience. The majority of participants’ voices were silenced as they reached out for help. Their institutional representatives avoided reports of bullying and abuse, consequently silencing and shaming their voices. The results of this study contribute to the literature on higher education organizational culture, workplace aggression, feminist phenomenology, and shame resilience theory.doctoral, Ph.D., Leadership and Counseling -- University of Idaho - College of Graduate Studies, 2019-0
A River Runs Through It: The Wild and Scenic Rivers Act as an Archetype for Complex Natural Resource Management Issues
No full textN/Amasters, M.S., Natural Resources -- University of Idaho - College of Graduate Studies, 2019-0
Evaluation of Impurities and Oxidation on the Propensity for Spontaneous Combustion of Oil and Biodiesel
No full textClimate change and the increasing demand for renewable energy has created a new world that is frantically looking for innovative answers to solve both. Biofuels, energy sources built from solar energy and atmospheric carbon, is regaining popularity as a potential solution. An advanced biofuel called biodiesel shows promise through its energy density, cleaner emissions, and ability to run in diesel engines without any engine modification. Biodiesel is unique because it can be made from any plant or animal oil. Since a large variety of these oils can be used to produce high-quality fuels, each biofuel has its own set of distinct properties. While all these oils can be used to create biodiesel, unsaturated oils undergo autoxidation faster than saturated oils. Autoxidation causes the plant oils to become rancid, giving the oil a foul taste and undesirable properties to the fuel. In addition, the fuel loses energy density and becomes susceptible to forming polymers which can plug fuel filters. When highly unsaturated oils are thermally insulated while drying, spontaneous combustion may occur. Spontaneous combustion is considered the result of autoxidation, an exothermic curing reaction. Several biodiesel production facilities have recently burnt down, costing millions in damages without a known cause, with some events being attributed to spontaneous combustion. Considering the production of biofuels is increasing and many locations are hitting record high temperatures, it is significant to understand how both biofuels and plant oils spontaneously combust to safeguard future investments and establish safer operations. Using off-the-shelf components and minimal custom fabrication, a safe testing device was developed. The device provides a safe and repeatable testing method for investigating spontaneous combustion phenomena. Using this device, a Spontaneous Combustion Severity Index (SCSI) was developed based on heat generation pattern inside the reactor in a short-term experiment. The SCSI number provided a way to quantify the likelihood of spontaneous combustion. An experiment for spontaneous combustion was designed from a combination of oils, biodiesels, and chemicals commonly encountered in biodiesel industries. The test showed that both types of feedstock and impurities in biodiesel and oil played a significant role in the likelihood of spontaneous combustion.masters, M.S., Biological & Agricultural Engineering -- University of Idaho - College of Graduate Studies, 2019-0
Protection Scheme of an Integrated Photovoltaic and Type 3 Wind Turbines System
No full textThe increasing penetration of renewable energy sources into power grids has been driven by the rapid growth of both renewable technologies and economic benefits. Among various renewable generation sources, photovoltaic (PV) and wind energy have grown faster than others. Normally most installations use the same type of renewables integrated into a collector bus. In this thesis a system with different renewables, PVs and Type 3 WTGs integrated into the same collector bus is proposed for the greater usage of the renewable energy sources, especially in a resource rich area. A PV model using an averaged voltage source converter representation is designed and implemented, and the real power characteristic of the PV site with daily insolation and temperature variation in steady-state is investigated with the simulation in RTDS/RSCAD and data post-processed in MATLAB. A Type 3 WTG using averaged voltage source converters is also modelled for the integrated system. An overcurrent protection scheme using symmetrical components is applied on the collector feeder of the integrated PVs and Type 3 WTGs system, and the good performance is shown with the simulation results of the system response to unbalanced and balanced faults. The protection scheme is also verified with the fault responses when different wind speeds are among WTGs, and the same protection performance is achieved.masters, M.S., Electrical and Computer Engineering -- University of Idaho - College of Graduate Studies, 2019-1
Wildfire and Rehabilitation History Effects on Artemisia tridentata subsp. wyomingensis Communities Invaded by Bromus tectorum
No full textCurrently, ~50% of the sagebrush steppe in the Great Basin, USA, has been lost to land-use change, plant invasions, and fire. These threats warrant potential rehabilitation treatments in order to maintain native plant communities; however, little research exists on the effects of rehabilitation treatment and fire history on native communities or sites with a history of rehabilitation across landscapes. To fill this gap we used a combination of fieldwork and spatial analysis to examine the effect of fire history, rehabilitation history, and environmental variables on plant community assembly, Bromus tectorum invasion, and changes in fire regime characteristics. Environmental variables explained 41% of the variation in plant communities while fire and rehabilitation history explained 44% of the variation in plant cover. Native species richness increased with elevation, but nonnative species richness did not. Bromus tectorum cover and density were inhibited by diverse native bunchgrass communities. Bromus tectorum decreased as the number rehabilitation treatments or time since treatment increased which was attributed to native bunchgrass establishment success and population growth, respectively. Fire regimes were in part determined by site moisture with more xeric sites burning more overall and more frequently at shorter intervals in the last twenty years. The type of vegetation treatment prior to the most recent fire played a role in fire regimes with sites that were aerially seeded prior to a fire having shorter fire turn intervals and more frequent fires in the last twenty years. The number of fires increased as sites became drier for aerially seeded sites, but not those with drill seeding. When the most recent treatment was drill seeding, it could increase the fire return interval and decrease frequency even when sites had a history of aerial seeding. This suggests increasing the number of drill seeding treatments can be used to establish diverse native plant communities that are resistant to Bromus tectorum and resilient to fire. Drill seeding can also reduce the numbers and frequency of fires and increase fire return intervals which may assist in Artemisia tridentata recruitment.doctoral, Ph.D., Natural Resources -- University of Idaho - College of Graduate Studies, 2019-1
Providing a basis for optimum investment in the community to create a favorable business climate
No full textUsing Area Sector Analysis Process (ASAP) data collected from the Community and Business Survey, we generate a utility that captures trade-offs between community and business needs. We use the General Algebraic Modeling System (GAMS) to calculate the marginal impact of different business climate factors on the utility of 19 regions in Utah, Nevada, Arizona, and New Mexico. We find that quality education and health care, favorable tax compensation, quality of workforce, access to supplies and customers, and low crime rates have relatively larger marginal impacts on social planners’ development goals. High quality natural ecosystems, outdoor recreation, social and cultural opportunities, and affordable housing have relatively small impacts on development objectives. This paper provides a benchmark for policy makers and planners, suggesting that they focus on policies that encourage investment in assets with relatively larger marginal impacts.masters, M.S., Agricultural Economics and Rural Sociology (Applied Economics) -- University of Idaho - College of Graduate Studies, 2019-0
Synthesis of Biofuel: Strategies for Upgrading Bio-oil
No full textThe biomass to biofuel process requires both initial conversion or densification of raw biomass followed by an upgrading step which can address high oxygen content, low hydrogen content, and stability prior to being considered petroleum compatible in a traditional refinery for processing into gasoline or diesel. Processing strategies exist with the goal of developing biofuels independently of petroleum product, though co-processing or refining is considered as the most viable path to commercialization. Upgrading processes are intensive, thus addressing issues to commercialization of biomass based biofuel can be accomplished through optimization of existing conversion i.e., CFP, and altering are development of new methods to treat bio-oil for aforementioned issues. The paper herein presents methods for addressing CFP optimization in various ways:via cyber physical modeling and application of AI methodology to solve complex issues and chemical reactions, in additional to outlining existing bio-oil treatments and experimenting with catalytic transfer hydrogenation and blending as a means for upgrading, or in the case of blending, skipping the upgrading process altogether. Both biomass to bio-oil conversion, and post conversion upgrading processes represent a major stumbling block to commercialization and success of 2nd generation biofuels as a whole, thus addressing both steps in the supply chain represents a significant gain in advancing the state of technology of the biofuel production process. The research presented herein aims to outline the existing state of technology, and provides several mechanisms for addressing the deficiencies both qualitatively and analytically. In addition to innovative advancements in biofuel production, Appendix B and C outline potential ways to optimize biomass to bio-oil conversion using AI and integrated system design.masters, M.S., Mechanical Engineering -- University of Idaho - College of Graduate Studies, 2019-0
A Predictive Metabolic Model for Polyhydroxyalkanoate Production by a Mixed Microbial Consortium cultured under Aerobic Dynamic Feeding Conditions and fed Dairy Manure Fermenter Liquor
No full textGlobal plastic use and disposal has become increasingly detrimental to the marine environment. The plastic problem is broad in scope with a complex solution; however, replacement of petro-plastics with bioplastics addresses the root of the issue, plastic accumulation. Polyhydroxyalkanoates (PHA) are biodegradable thermoplastics that are naturally produced by a variety of microorganisms and possess mechanical properties favorable for replacing fossil fuel derived plastics in single-use applications. Current PHA production processes utilize synthetic feed and pure cultures, a costly method that leaves economic viability to be desired. By employing an engineered PHA production process known as aerobic dynamic feeding (ADF), PHA can be synthesized by mixed microbial consortia (MMC) fed otherwise unused organic-rich waste streams. The inherent sustainability, coupled with reduced cost of substrate procurement and sterilization practices, place ADF configurations at the forefront of potentially feasible bioplastic solutions. Nevertheless, operational parameters that maximize volumetric productivity for a limited waste stream have yet to be defined. Research presented herein focused on the optimization of a three-stage ADF PHA production process by assessing the impacts of operational parameters, solids retention time (SRT) and organic loading rate (OLR). Additionally, a metabolic model was developed in order to describe ADF metabolism using complex substrate mixtures, ultimately providing insight for continued optimization efforts. Factorial-based evaluation of PHA production assessments led to the determination of a 2-day SRT and 20 Cmmol/L-d OLR as near-optimal culture enrichment operational criteria. Under said operation, the MMC converted nearly 100% of carbon to PHA resulting in an average maximum intracellular PHA accumulation of 38% (w/w). Furthermore, the metabolic model developed quantified the dynamic ADF microbial processes and led to accurate prediction of PHA composition for variable substrate mixtures.masters, M.Engr., Civil Engineering -- University of Idaho - College of Graduate Studies, 2019-1
THE PUBLIC’S ROLE AS ENVIRONMENTAL STEWARDS: A STUDY OF THE IDAHO MASTER NATURALIST PROGRAM
No full textABSTRACT The role the public plays in protecting nature is crucial. To be effective stewards the public must be environmentally literate. Environmental literacy is understanding the biophysical environment to the degree that it leads to the ability to act as environmental stewards. Myriad studies revealed the public has limited knowledge of nature. The Idaho Master Naturalist Program (IMNP) was created to educate the public about nature and advance environmental volunteerism. This qualitative research studied if IMNP was fulfilling its mission to develop a corps of environmentally literate volunteers. The participants were 18 years or older who attended IMNP between 2008 and 2013. The findings were collected using an Internet-based survey, netting a 52.5% response rate. The findings indicated that 79.2% of the participants believed they had received a satisfactory education to be environmental stewards. Nonetheless, the responses showed the need for modifications to IMNP to enhance the participants’ experience.masters, M.Ed., Agricultural Education & 4H Youth Development -- University of Idaho - College of Graduate Studies, 2019-0