Browsing by Author "Strong, Kelly, committee member"
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Item Open Access A framework for life-cycle cost optimization of buildings under seismic and wind hazards(Colorado State University. Libraries, 2014) Cheng, Guo, author; Mahmoud, Hussam, advisor; Atadero, Rebecca, committee member; Strong, Kelly, committee memberThe consequential life and economic impact resulting from the exposure of building structures to single hazards have been well quantified for seismic and wind loading. While it has been recognized that structures are likely to be subjected to multiple hazards during their service life, designing for such scenario has been achieved by as considering the predominant hazard. Although from a structural reliability perspective, this might be a reasonable approach, it does not necessarily result in the most optimal life-cycle cost for the designed structure. Although such observation has been highlighted in recent studies, research is still needed for developing an approach for multi-hazard life-cycle optimization of structures. This study presents a framework, utilizing structural reliability, for cost optimization of structures under wind and seismic hazards. Two example structures, on which the framework is applied, are investigated and their life-cycle cost analyzed. The structures represent typical medium and high rise residential buildings located in downtown San Francisco area. The framework comprises of using the first order reliability method (FORM), programed in MATLAB and interfaced with ABAQUS finite element software to obtain the corresponding reliability factors for the buildings under various loading intensities characterized by the probability of exceedance. The finite element analyses are carried out based on real seismic and wind pressure records using nonlinear finite element time-history dynamic analysis. The random variables selected include hazard intensity (wind load and seismic intensity) and elastic modulus of steel. Once the failure probabilities are determined for the given limit state functions, the expected failure cost for the building service duration considering earthquake or wind hazard, or both, is calculated considering discount rate. The expected life-cycle cost is evaluated using life-cycle cost function, which includes the initial construction cost and the expected failure cost. The results show that the optimal building design considering the wind hazard alone, the seismic hazard alone or a combination of both is different. The framework can be utilized for an optimal design of both wind and seismic load for a given level of hazard intensity.Item Open Access Development of the Construction Training Attitudes and Intentions Scale(Colorado State University. Libraries, 2013) Elliott, Jonathan W., author; Gloeckner, Gene, advisor; Lopez Del Puerto, Carla, advisor; Makela, Carole, committee member; Strong, Kelly, committee memberThe events of the Great Recession (2007-2009) have resulted in high unemployment and underemployment rates in the United States and abroad. The plight of domestic young adults, particularly young men with few work-related skills, is evident. Failing to receive a first job has long-term negative consequences for these individuals and their families. In the United States, job opportunities exist for properly trained individuals in the construction industry, which is currently experiencing a shortage of skilled labor. Recognition of the unemployment situation and job opportunity in new construction, renovation, and maintenance of existing infrastructure has led to the creation of publicly funded construction skills training programs that target young adults (16-24 years). However, despite the great deal of effort and funding, participant retention is a significant problem and dropout rates ranging between 45-65% have been reported. Training practitioners posit that no model exists for predicting performance and attrition of individuals in training and express the desire for a metric that measures individual characteristics to better inform individual training successes. A review of literature revealed no instrument for predicting performance, completion, or attrition of the unemployed in training. Therefore, the purpose of this dissertation was to develop an internally consistent and valid instrument that measures the appropriate constructs to inform and predict human behavior within the domain of construction training for the unemployed. The resulting instrument, the Construction Training Attitudes and Intentions Scale (CTAIS), was developed through two phases. The CTAIS was complete by construction management undergraduate students (N = 247) during phase one. The purpose of phase one was to reduce the number of CTAIS items (N = 98) using inter-item correlations and exploratory factor analysis (EFA). An evaluation of the internal consistency and validity was conducted on the reduced pool of CTAIS items. Phase one resulted in a 44-items CTAIS, which contain four emergent factors: planned training behavior (PTB), construction training self-efficacy (CTSE), training motivation attitudes (TMA), and training locus of control (TLOC). The CTAIS and its factors PTB, CTSE, TMA, and TLOC were found to be internally consistent (α = 0.926, 0.943, 0.942, 0.941, and 0.829, respectively). Face and convergent construct validity were shown through significant (p < 0.01) correlations between the emergent factors that mirrored those found in previous construct validation research. The 44-item CTAIS was administered during phase two to a separate group of undergraduate construction management students (N = 174). The internal consistency of the 44-item CTAIS (α = 0.902) and PTB, CTSE, TMA, and TLOC factors (α = 0.909, 0.950, 0.925, and 0.832, respectively) were confirmed in phase two. Significant (p < 0.01) correlations between the emergent factors mirrored those found in phase one and previous construct validation research, providing further support for the face and convergent construct validity of the CTAIS. Supplemental analysis was performed using the phase-two data to investigate difference in mean PTB, CTSE, TMA and TLOC by the demographic characteristics of the sample. The results revealed significant differences in mean PTB, CTSE, and TMA (p < 0.001, p = 0.008, and 0.032, respectively) by gender and in mean PTB and CTSE (p = 0.027 and 0.019, respectively) by hands-on construction experience (dichotomous, experiences/no experience). ANOVA yielded significant differences in mean PTB and CTSE by age (p < 0.001 and p = 0.01, respectively) and mean PTB by level of hands-on experience (p = 0.03). However, it was noted in the post-hoc analysis that these differences were considered statistical artifacts due to the small and unbalanced sample sizes and overlapping confidence intervals around the means. No significant differences (p ≥ 0.05) were found between young adults (24 years and younger) and adults (25 years and older) or by respondent year in school, amount of construction management experience, participation in construction management competitions or internships. No significant differences (p ≥ 0.05) in TLOC were found in the supplemental analysis. The CTAIS developed and validated through this study allows training organizations to quantitatively measure and evaluate construction domain level characteristics that have been shown in research to predict performance in work setting and attendance in educational settings. Identification of participant characteristics, which contribute to attrition and performance in construction training, can assist training organizations in programmatic decision-making. Pre-training assessment of trainees allows practitioners to make informed decisions, at the individual level, about appropriate interventions to increase the likelihood of training success. The CTAIS, when administered at pre- and post-training intervals, provides trainers with a measure of individual characteristics that indicate training successes. High self-efficacy and motivation are predictive of persistence in job search activities and on-the-job performance. Therefore, higher post-training CTSE and TMA are indicators of training program effectiveness. The utility of the CTAIS can be enhanced with refinements based on its application in a variety of construction training programs.Item Open Access Evaluation of rapid scanning techniques for inspecting concrete bridge decks with asphalt overlay(Colorado State University. Libraries, 2016) Vemuri, Sri Harsha, author; Atadero, Rebecca, advisor; Chen, Suren, committee member; Strong, Kelly, committee memberThe average age of bridges in the USA is 42 years. The life expectancy of a majority of these bridges is 50 years. At the current rates of aging and replacement, almost half of the nation’s bridges will require major structural investment in the next 15 years as stated by the Federal Highway Administration. There is a severe deficiency in both time and resources available to address this problem, and methods to increase efficiency are needed. Bridge decks are the most critical elements of a bridge structure as they are directly and continuously exposed to harsh weather conditions and cyclic loading from traffic throughout their lifespan. This thesis attempts to improve management practices for bridge decks by addressing current challenges faced by the Colorado Department of Transportation (CDOT) in estimating the extent of damage on bridge decks. The current bridge deck inspection method being employed by CDOT is sounding and chipping. This procedure involves sounding the deck with chains, hammers and rotary percussion to detect the deteriorated areas followed by chipping. The issues with this procedure include its time-consuming nature, the requirement for traffic to be diverted for extended periods and the costs associated with the inspection and traffic diversion. Additionally, sounding is not adequate to provide a rough estimation of the class of damaged area and the resulting expenses. CDOT wants to take the advantage of newer alternative techniques to evaluate bridge decks. The alternative evaluation considered by CDOT involves using Ground Penetrating Radar (GPR) and Infrared Thermography (IR) thermography together for evaluating bridge decks. The major advantage of using GPR is that it is the only available method that can estimate the deterioration in concrete decks with asphalt overlay. Additionally, GPR can estimate the deterioration in early stages, unlike sounding which detects damage in advanced stages and GPR is also capable of detecting corrosion in rebars. Thus, GPR not only has the potential to address the disadvantages of sounding it also has additional advantages which can benefit the life of the bridge deck. This study attempts to understand the limitations that this newer evaluation method comes with and possibly solve some of these limitations to take complete advantage of this technology. This study took advantage of the available as-built data of four bridge decks rebuilt after sounding and chipping and the data available from GPR and IR scanning of the respective decks to study the limitations from using GPR and IR technologies. The scanned results from GPR and IR thermography are compared to the deck condition data from sounding and chipping. In two cases the damage detected by GPR and IR thermography did not correlate well with the damage detected from sounding and chipping. The two decks with reasonable correlation are compared to the decks with poor correlation in an effort to understand the possible causes for deviation in results. It was observed that for the decks with poor correlation the GPR showed areas with higher cover as deteriorated in the estimation. An improved data processing procedure to solve such miss-interpretation issue is suggested, and a coring strategy to assist future research in the direction of eliminating the depth-amplitude effects in GPR scans.Item Open Access Experimental assessment of cracked steel beams under mechanical loading and elevated temperatures(Colorado State University. Libraries, 2016) Ahmadi, Bashir, author; Mahmoud, Hussam, advisor; van de Lindt, John, committee member; Strong, Kelly, committee memberBridge fire is a major engineering problem that has been gaining attention by researchers and engineers. As reported in the New York Department of Transportation database, there has been approximately 50 cases of bridge collapse due to fire nationwide with many more cases where fires resulted in repairable damage. The fires are typically due to vehicle crash, arson, and in some cases wildfires. The affected bridges are mostly fabricated from steel, concrete, and temper. The problem of bridge fire is further aggravated by the presence of fatigue cracks in steel bridges. Various experimental and numerical studies have been conducted to evaluate the response of steel beams under elevated temperature. However, to date, there is lack of information on the response of steel beams with pre-existing cracks under elevated temperature. The importance of evaluating cracked steel beams under elevated temperature stems from the fact that many steel bridges that are currently in service suffer from major deteriorations manifested in the presence of fatigue cracks that are the result of cyclic loading from daily traffic. With no available data on failure behavior of cracked steel beams under fire, this thesis introduces a new testing protocol for evaluating the response of cracked steel beams under elevated temperature. Specifically, the results of experimental tests, conducted at the structural engineering laboratory at Colorado State University, of four initially cracked W8x24 steel beams under point loading and non-uniform elevated temperature are presented. The cracks are introduced across the bottom flange and the beams are loaded to failure while being subjected to various non-uniform elevated temperature distributions varying from 200 °C to 600 °C. The competition between two different failure modes: excessive deflection and fracture along the crack plane, is evaluated with respect to temperature distributions in the beams. In cases where fracture prevailed, different types of fractures were observed including brittle fracture, ductile fracture, and brittle/ductile transition failure, which depended on the temperature distribution. The results presented include load versus displacement and time versus temperature curves. In addition, digital image correlation method was utilized to develop strain and displacement fields around the cracked regions. This experimental study provides an alternative method for evaluating cracked beams under elevated temperature and will provide engineers with insight into various behavioral aspects of steel beams under the investigated loading demands. Furthermore, the results of this study can be used to calibrate advanced numerical finite element models, capable of capturing large deformations and fracture, which can in turn be used to conduct a parametric study for various sizes of bridge girders under an ensemble of thermal loading scenarios.Item Open Access Fatigue reliability and post-fracture residual capacity of a two-girder steel bridge(Colorado State University. Libraries, 2016) Hartung, Lena F., author; Mahmoud, Hussam, advisor; Atadero, Rebecca, committee member; Strong, Kelly, committee memberDue to the immense and always increasing traffic volume, bridges are permanently subjected to repetitive loadings. These high numbers of cyclic loads can cause the initiation of fatigue cracks. If these flaws remain undetected they may become through-thickness cracks and further propagate, if left unrepaired, until they eventually lead to fracture of the entire member. The criticality of a full member fracture is not well defined nor agreed upon. Previous failure cases have demonstrated the ability of two-girder steel bridges to withstand full girder fracture of one of the two girders without structural collapse. Other cases, however, have shown the criticality of a complete girder failure on complete system collapse. Due to uncertainties in bridge redundancy and the ability to develop alternative load path, the American Association of State Highway and Transportation Officials (AASHTO) attempts to prevent fracture or collapse by classifying bridges with respect to their redundancy into fracture critical bridges (FCB) and decreasing their inspection periods. However, this leads to higher construction and maintenance costs for the owners of FCBs. Clearly, the level of uncertainty in bridge performance when one of its two girders suffer complete fracture should be represented in a probabilistic manner to evaluate the probability of fatigue crack growth and system collapse. To that end, thesis uses probabilistic analysis to assess the crack propagation behavior in a girder of a two-girder steel bridge by conducting finite element Monte Carlo simulations. The simulations account for the scatter in the load and the resistance by treating those uncertainties as random variables with predefined statistical distributions. Additionally, the post fracture redundancy is evaluated by comparing the resulting equivalent plastic strain to the failure strain of steel. The results show that the bridge provides sufficient redundancy to redistribute the load after full depth fracture a FC member. Furthermore, the results of the probabilistic analyses provide a basis for choosing the inspection intervals for FCBs.Item Open Access Improving construction machine engine system durability in Latin American conditions(Colorado State University. Libraries, 2018) Azevedo, Kurt Milward, author; Olsen, Daniel, advisor; Bradley, Thomas, committee member; Grigg, Neil, committee member; Strong, Kelly, committee memberBetween 2016 and 2030, the Latin America region needs to spend $7 trillion dollars (Bridging global infrastructure gaps, 2016). Thus, for the foreseeable future, the Latin American market will experience high demand for construction equipment such as backhoes, excavators, crawler-dozers, and loaders to construct roads, housing, airports, and sea ports. Construction equipment employed in Latin America operates in conditions which are often more severe compared to developed countries such as the United States. Consequently, the durability of construction equipment diesel engines is reduced within the context of the system engineering life cycle. This results in a greater number of warranty claims, increased customer product dissatisfaction, and delays in completing contracted projects. Peer-reviewed literature lacks information regarding the wear and failure of construction equipment diesel engines operating in Latin America. Thus, the purpose of this research is to contribute to the system and maintainability engineering fields of knowledge by analyzing oil samples taken from diesel engines operating in Latin America. Oil samples are leading indicators and predictors for wear in specific components of diesel engines, as they directly connect to the use conditions of actual work environments. The methodology approach considers data points from different sources and countries. The engine oil sample analysis results are evaluated in the context of local diesel fuel quality, machine diagnostic trouble codes, and the work environments for the following countries: Bolivia, Colombia, Costa Rica, Dominican Republic, Ecuador, Guatemala, Honduras, Mexico, Paraguay, Peru, and Uruguay. The following data sources are used to answer the research questions: (1) database of oil sample laboratories of eleven countries, (2) construction equipment diagnostic trouble codes, (3) construction equipment surveys, (3) John Deere service manager's surveys, (4) two John Deere 200D excavators, (5) engine operating data, and (6) Engine Control Unit sensor data. It is determined that cross-system contamination was key contributors of oil contamination. Contamination related to environmental conditions in which the equipment was operated is also a key factor, as there is a high statistical correlation of sodium, silicone, and aluminum oil contamination present in the oil of equipment operating at higher altitudes. It is determined that sulfur, diesel fuel quality, humidity, bio-diesel, temperature, and altitude are factors that must be considered in relation to diesel engine reliability and maintenance. The research found that by correlating the engine oil sample contamination with the environment risk drivers (a) altitude and diesel fuel quality have the greatest impact on iron readings, (b) bio-diesel impacts copper, and (c) precipitation and poor diesel quality are associated with silicon levels. Wear metals present in the oil samples indicate that scheduled maintenance frequency must not exceed 250 hours for diesel engines operating in many areas of Latin America. The leading and earliest indicator of engine wear is a high level of iron particles in the engine oil, reaching abnormal levels at 218 hours. The research found that engine idling for extended periods contributes to soot accumulation.Item Open Access Joint elimination retrofits and thermal loading analysis in plate girder bridge using health monitoring and finite element simulations(Colorado State University. Libraries, 2016) Rager, Karly, author; Mahmoud, Hussam, advisor; Atadero, Rebecca, advisor; Strong, Kelly, committee memberDegradation of United States' public infrastructure has attracted attention from the public and governing agencies alike. A challenge facing transportation departments is management of leaking and clogged expansion joints in bridge structures, which result in significant deterioration to bridge substructures and superstructures. Some agencies have started eliminating these joints. However, technical understanding of which retrofit methodology to employ based on thermal loading and specific characteristics of the structure is lacking. In this study, this problem is investigated with both numerical modeling and analysis of field measurements. Various sensors were installed on the bridge including thermocouples, strain gauges, and linear differential displacement transducers. Following sensor installation, controlled load testing was conducted and the collected data evaluated against numerical and analytical predictions. The installed sensors will allow for long-term monitoring of the bridge to evaluate the effect of seasonal temperature profiles that are characteristic of Colorado on bridge behavior. In addition to gaining technical understanding of site-specific bridge characteristics that influence joint movement using field-testing, numerical finite element analysis was conducted. Specifically, a 3D finite element model was developed and used in a parametric study to assess the effect of various parameters on the stresses occurring in the bridge. The stresses occur due to 1) variation in thermal loading and thermal gradient, 2) clogging of the joint with different materials including gravel and sand, and 3) employment of various repair techniques in eliminating the expansion joints. The results of the numerical models show that clogged joints induce some localized stress but do not significantly affect the global performance of the superstructure. The results also show that a reduction in moment demand on the superstructure is not apparent until a Full-Moment Splice connection is utilized. This study will help engineers to choose the most appropriate method of designing a retrofit for expansion joint removal.Item Open Access Life cycle cost analysis for joint elimination retrofits and thermal loading on Colorado bridges(Colorado State University. Libraries, 2017) Harper-Smith Kelly, Aura Lee, author; Mahmoud, Hussam, advisor; Atadero, Rebecca, advisor; Strong, Kelly, committee memberBridge expansion joints are a particularly troublesome component of bridges and many Departments of Transportation (DOTs) are looking for a solution to deteriorating expansion joints on highway bridges. Bridge expansion joints create a break in the structural continuity of a bridge allowing clogging gravels and corroding chlorides to enter. They are designed to absorb thermal movements of the bridge between two bridge elements. There are three main issues regarding expansion joint: maintenance, knowledge about thermal movements, and costs. In order to prevent deterioration due to expansion joints the joints must be cleaned regularly and replaced promptly after failure. However, most DOTs do not have the personnel, time or resources to maintain expansion joints in their districts which leads to bridge deterioration. Other similar maintenance and component issues have been addressed using a Life Cycle Cost Analysis. For this to be used on expansion joints the three main issues of thermal knowledge, maintenance, and costs must first be addressed. The main goal of this project is to help transportation agencies make better decisions about bridge expansion joints. The specific objectives of this study are to 1) expand understanding of thermal loading effects on bridge expansion joints and 2) conduct a LCCA for joint elimination and retrofits for bridges in Colorado. These objectives were accomplished utilizing data from in field instrumentation and finite element models. The study has been developed jointly between the Colorado Department of Transportation (CDOT) and researchers at Colorado State University Three main tasks were conducted to achieve the objectives: 1) collect and analyze long-term thermal loading data from existing bridges to assess thermal loading impacts on joints; 2) perform a parametric study using a calibrated finite element model to further understanding of joint behavior and retrofit options under thermal loads; 3) perform a LCCA for bridge expansion joint retrofitting including impacts on bridge superstructure. The significance of this work includes the results of the data collection and analysis, the parametric study, and the LCCA findings. The preliminary data on the concrete bridge C-17-AT presented in this thesis only accounts for mid-winter temperatures. However, these limited observations do imply that if CDOT is interested in removing an expansion joint, the bridge superstructure and retrofit option would need to support the movement of the bridge. The parametric study and data analysis of thermal gradients indicate a stark need for further research into thermal gradients experienced by bridges. Finally, the LCCA concluded that a retrofit continuous bridge design would provide the most cost effective design by decreasing joint replacement costs and pier cap corrosion.Item Open Access Numerical simulation of out-of-plane distortion fatigue crack growth in bridge girders(Colorado State University. Libraries, 2014) Miller, Paula A., author; Mahmoud, Hussam, advisor; Heyliger, Paul, committee member; Strong, Kelly, committee memberAging of the United States infrastructure systems has resulted in the degradation of many operational bridge structures throughout the country. Structural deficiencies can result from material fatigue caused by cyclical loadings leading to localized structural damage. While fatigue crack growth is viewed as a serviceability problem, unstable crack growth can compromise the integrity of the structure. Multi-girder bridges designed with transverse cross bracing systems can be prone to distortion fatigue at unstiffened web gaps. Cracking is exhibited within this fatigue prone region from the application of cyclical multi-mode loadings. Focus of fatigue analysis has largely been directed at pure Mode I loading through the development of AASHTO fatigue classifications for crack initiation and the Paris Law for crack propagation. Numerical modeling approaches through the ABAQUS Extended Finite Element Method offers a unique avenue in which this detail can be assessed. Finite element simulations were developed to first evaluate the applicability of the Paris Law crack propagation under multi-mode loading against experimental data. Following the validation, fatigue crack growth in plate girders with various web gap sizes was assessed due to mixed-mode loadings. Modeling results showed enlargement of horizontal initial crack lengths within stiffer web gap regions arrested crack development. Crack directionality was also seen to change as initial crack lengths were increased. From this research it is hypothesized that deterioration of the transverse stiffener connection can be minimized by increasing the horizontal length of initial fatigue cracks. Enlargement of the crack plane away from regions of localized stress concentrations within the web gap may result in arrestment of the out-of-plane distortion induced cracking.Item Open Access Quantifying sustainability metrics for trunkline bridges in the Mountain Plains region(Colorado State University. Libraries, 2016) Gopi, Vaishak, author; Van de Lindt, John W., advisor; Senior, Bolivar, advisor; Strong, Kelly, committee memberThe use of millions of cubic yards of concrete and steel to support the U.S infrastructure may result in a significant negative impact on the environment. CO2 released by the construction processes as well as the material production, is taking a toll on the environment. This study is aimed at developing a ranking system to determine the emission of CO2 for bridges and rank them based on their CO2 emission. Firstly, in order to accomplish this objective, rating systems for buildings from around the world were analyzed for common attributes applicable to bridges. Secondly, a sample of bridges from the state of Colorado was selected and analyzed for their sustainability by only considering their main materials and a ranking system based on the emission of CO2 was developed. This served as the first step in developing a rating system for bridges in Colorado where only the CO2 emission from the production and transport of concrete and steel were considered. This rating system can be further developed to include CO2 emissions from construction processes, demolition and disposal and other factors that contribute to sustainability, but its current version is intended only to provide an example of an approach for development of a ranking system.Item Open Access Seismic fragility analysis of reinforced masonry buildings(Colorado State University. Libraries, 2013) Zamora, José EfraÃn Mazariegos, author; van de Lindt, John W., advisor; Atadero, Rebecca, committee member; Strong, Kelly, committee memberReinforced masonry walls are a widely used lateral force resisting system for buildings around the world. These structures, if not correctly detailed to resist earthquake loads, are a main cause of casualties and economic losses, particularly in developing countries. This thesis presents the result of a study whose objective was to apply the seismic fragility methodology to both in-plane (shear) and out-of-plane (transverse) reinforced masonry shear walls to quantify probabilities of exceedance for ASCE 41-06 drifts associated with continued occupancy, life safety, and collapse prevention, performance states. The load-displacement curves (hysteresis) were obtained from quasi-static out-of-plane and in-plane experimental testing by Klingner et al. (2010). In this thesis, that data was applied to obtain the parameters for a widely used ten-parameter hysteretic model. The software SAPWood Version 2.0 was selected for use in this thesis to enable nonlinear modeling of the shear wall and out-of-plane components. An analytical model of the reinforced masonry walls was developed in SAPWood and subjected to each earthquake within a well-known suite of 22 earthquakes. The peak of drifts for each ground motion record was recorded and each earthquake intensity increased over the range interest, i.e. an incremental dynamic analysis (IDA) was performed. Finally, as mentioned the information obtained from the IDA was used to develop fragility curves for the in-plane and out-of-plane walls based on peak story drift limits defined in ASCE 41 for continued occupancy, life safety, and collapse prevention.Item Open Access Seismic performance of skewed and curved RC bridges(Colorado State University. Libraries, 2013) Wilson, Thomas, author; Chen, Suren, advisor; Mahmoud, Hussam, advisor; Strong, Kelly, committee member; Johnson, Joshua, committee memberExplicit knowledge of the behavioral response of complex reinforced concrete (RC) highway bridges to seismic events is essential to designing safe transportation systems. In the past, a number of skewed and curved highway bridges have experienced damage or suffered collapse due to earthquakes; and have most recently been observed during the Chile earthquake in 2010. Yet, there is very limited information on the combined effects of skew and curvature on the seismic response of RC bridges, and in particular identifying critical vulnerabilities to localized failures or system collapse. Recent research has also shown that the vertical component of earthquake ground motion, previously not considered, may have significant bearing on the response of highway bridges, particularly in near-fault regions. This study is comprised of two parts, including an examination of skewed and curved RC bridges of various configurations representative of a low seismic region, and an evaluation of the effect of vertical ground motion on complex geometry bridges in a moderate, near-fault, seismic region. Detailed numerical models are developed for various configurations of skew and curvature, and subjected to earthquake ground motion using nonlinear time-history analysis. In part one, detailed finite element models are developed and analyzed for eight bridge configurations of various degrees of skew and curvature, with consistent structural and geometric components. The bridge designs and earthquake hazard level are characteristic of the Mountain West region where the seismic risk is typically classified as low to moderate. Nonlinear time-history analysis is conducted on each bridge configuration for seven sets of earthquake records scaled to a site location in Denver, Colorado. The effects of earthquake input loading direction and abutment support condition, including integral and bearing supports, are also considered. The results show significant impacts on the seismic performance due to the effects of skew and curvature with stacking effects observed in the combined geometries. Insights on the complexities of curvature, skew, loading direction and support condition are made, which may lend themselves to more informed design decisions in the future. Part two of this study presents an assessment of the effect of vertical ground motion on horizontally skewed and curved highway bridges in moderate-to-high seismic regions. A numerical model of a skewed and curved, three-span bridge located in Tacoma, Washington is subjected to a suite of ground motions using non-linear time-history analysis. The ground motions selected represent a range of near-fault records with varying characteristics such as site condition, fault distance, and vertical-to-horizontal acceleration component ratios. The scenario developed characterizes the behavior of a bridge with a short fundamental period of vibration in a moderate seismic zone, where vertical ground motion effects may be applicable yet not considered by structural code. The results of the numerical simulations depict a significant impact from vertical ground motion in the substructure and superstructure, including responses typically not documented in existing studies. The implications of the results for structural designers may be to reconsider the current design approach involving vertical ground motion, particularly with shorter period bridges involving configurations of skew and curvature.Item Open Access Use of BIM-based energy simulations to analyze the impact of occupant behavior on energy performance of commercial buildings(Colorado State University. Libraries, 2017) Yogi, Sanjeev, author; Olbina, Svetlana, advisor; Strong, Kelly, committee member; Malinin, Laura, committee memberThe impact of occupant behavior on the energy performance of a building has been studied for a very long time. However, despite many studies, occupant behavior is difficult to understand due to its complex and unpredictable nature. Usually, occupant behavior is oversimplified and poorly represented; hence, one fails to make the correct assessment of the impact of occupant behavior on building energy performance. To make a precise prediction of the impact of occupant behavior on building energy consumption, it is imperative to develop better techniques in terms of analyzing occupant behavior and methods of research. Occupant behavior is stochastic in nature and varies widely depending on the characteristics of the building. Some occupants are proactive in saving energy while others are wasteful. Based on the workstyles of the occupants, occupant workstyles can be divided into three categories: austerity, standard and wasteful. As building characteristics influence both occupant behavior and energy performance of buildings, it is important to incorporate building characteristics into any building energy analysis to make the correct assessment of the impact of occupant behavior on the energy performance of the building. This can be achieved by using the building information modeling (BIM) based energy simulation for different categories of occupant behavior. This research used BIM to study and analyze the effect of different categories of occupant behavior on the energy performance of the building. To achieve this goal, most influential building characteristics and parameters of occupant behavior were identified; case study of occupant behavior on commercial building at Colorado. State University (CSU) was performed and guidelines to minimize the impact of wasteful workstyle on energy performance of the commercial buildings were developed. The identified most influential building characteristics of commercial buildings in this research were used to create the building information models in Revit which were then exported to DesignBuilder for simulations of annual building energy consumption. The identified parameters of occupant behavior for different types of workstyles were inputted in DesignBuilder before performing energy simulations. The simulation procedure was also illustrated in one of the commercial building at Colorado State University. The analysis of the simulation results showed that energy performance of the building is affected by the occupant behavior. The change of occupant workstyle from wasteful to austerity decreased the annual energy consumption between 41% and 58% while change of occupant workstyle from wasteful to standard decreased the annual energy consumption between 9% and 19%. Similarly, the decrease of annual energy consumption was between 33% and 45% due to change of workstyle from standard to austerity.