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- Title
- An Analytical Investigation of Prestressed Beam Bridge Performance Before and After Widening.
- Creator
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ORiordan Adjah, Chris, Zhou, Lei, Chopra, Manoj, Catbas, Necati, University of Central Florida
- Abstract / Description
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As traffic and congestion increase, so does the likelihood of collisions. The solution to this problem is usually through a rehabilitation process with two primary options: (1) widening/expansion of existing roadway and bridges and (2) complete replacement (new construction) of roadway and bridges. The first option is the most feasible and cost-effective. While roadway widening/expansion pose minimal issues, the same cannot be said of bridge widening. An existing bridge presents a multitude...
Show moreAs traffic and congestion increase, so does the likelihood of collisions. The solution to this problem is usually through a rehabilitation process with two primary options: (1) widening/expansion of existing roadway and bridges and (2) complete replacement (new construction) of roadway and bridges. The first option is the most feasible and cost-effective. While roadway widening/expansion pose minimal issues, the same cannot be said of bridge widening. An existing bridge presents a multitude of challenges during the planning and design phases, during construction, and throughout the structure's service life. Special attention is required in both the design and detailing of the widening in order to minimize construction and maintenance problems. The primary objective of this dissertation is to present a better understanding of structural behavior and capacity by studying an existing widened structure: a bridge that has been in service for over 40 years (constructed in 1972 and widened in 2002). The load demand on this bridge has doubled over the years. Consequently, the widened structural system is composed of four-span continuous prestressed concrete bridge segments.To better understand the widened 2002 bridge used in this study, an initial comparative analysis was performed, comparing the original 1972 bridge and the 2002 widened bridge. This comparative analysis included a determination of bridge capacity, distribution factors, and load-rating factors using current American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Specifications design codes. However, the original codes used for the two bridges should also be noted, as follows: (1) the AASHTO Load Factor Design (LFD) Code was used for the original bridge; and (2) a combination of the AASHTO LFD and AASHTO LRFD Specifications were used for the existing widened bridge. Linear three-dimensional finite element models were developed for both bridges to obtain the maximum moment and shear values with varying HL-93 load cases for these analyses.To develop models that describe the possible existing condition of the 2002 widened bridge, a nonlinear model of one of the critical members in the structure was developed by changing the most critical parameters. The critical parameters are categorized as material properties and prestress losses. Sensitivity studies were conducted using parametric models for simulations with moving loads for the different load cases using the HL-93 truck. The load-rating and reliability indexes were computed for all the cases under different loading conditions. The parameters that have the most influence on load rating and reliability are also presented in the analyses. The information generated from these analyses can be used for better(-)focused visual inspection and widened bridge load rating criteria, and can also be used for developing a long(-)term widening structural monitoring plan. Additionally, this study will be used as a benchmark for future studies, and to establish a procedure and methodology for future bridge widening projects.
Show less - Date Issued
- 2017
- Identifier
- CFE0006773, ucf:51866
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006773
- Title
- STRUCTURAL CONDITION ASSESSMENT OF PRESTRESSED CONCRETE TRANSIT GUIDEWAYS.
- Creator
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Shmerling, Robert, Catbas, F. Necati, University of Central Florida
- Abstract / Description
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Objective condition assessment is essential to make better decisions for safety and serviceability of existing civil infrastructure systems. This study explores the condition of an existing transit guideway system that has been in service for thirty-five years. The structural system is composed of six-span continuous prestressed concrete bridge segments. The overall transit system incorporates a number of continuous bridges which share common design details, geometries, and loading conditions...
Show moreObjective condition assessment is essential to make better decisions for safety and serviceability of existing civil infrastructure systems. This study explores the condition of an existing transit guideway system that has been in service for thirty-five years. The structural system is composed of six-span continuous prestressed concrete bridge segments. The overall transit system incorporates a number of continuous bridges which share common design details, geometries, and loading conditions. The original analysis is based on certain simplifying assumptions such as rigid behavior over supports and simplified tendon/concrete/steel plate interaction. The current objective is to conduct a representative study for a more accurate understanding of the structural system and its behavior. The scope of the study is to generate finite element models (FEMs) to be used in static and dynamic parameter sensitivity studies, as well load rating and reliability analysis of the structure. The FEMs are used for eigenvalue analysis and simulations. Parameter sensitivity studies consider the effect of changing critical parameters, including material properties, prestress loss, and boundary and continuity conditions, on the static and dynamic structural response. Load ratings are developed using an American Association for State Highway Transportation Officials Load and Resistance Factor Rating (AASHTO LRFR) approach. The reliability of the structural system is evaluated based on the data obtained from various finite element models. Recommendations for experimental validation of the FEM are presented. This study is expected to provide information to make better decisions for operations, maintenance and safety requirements; to be a benchmark for future studies, to establish a procedure and methodology for structural condition assessment, and to contribute to the general research body of knowledge in condition assessment and structural health monitoring.
Show less - Date Issued
- 2005
- Identifier
- CFE0000658, ucf:46520
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000658
- Title
- Structural Identification through Monitoring, Modeling and Predictive Analysis under Uncertainty.
- Creator
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Gokce, Hasan, Catbas, Fikret, Chopra, Manoj, Mackie, Kevin, Yun, Hae-Bum, DeMara, Ronald, University of Central Florida
- Abstract / Description
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Bridges are critical components of highway networks, which provide mobility and economical vitality to a nation. Ensuring the safety and regular operation as well as accurate structural assessment of bridges is essential. Structural Identification (St-Id) can be utilized for better assessment of structures by integrating experimental and analytical technologies in support of decision-making. St-Id is defined as creating parametric or nonparametric models to characterize structural behavior...
Show moreBridges are critical components of highway networks, which provide mobility and economical vitality to a nation. Ensuring the safety and regular operation as well as accurate structural assessment of bridges is essential. Structural Identification (St-Id) can be utilized for better assessment of structures by integrating experimental and analytical technologies in support of decision-making. St-Id is defined as creating parametric or nonparametric models to characterize structural behavior based on structural health monitoring (SHM) data. In a recent study by the ASCE St-Id Committee, St-Id framework is given in six steps, including modeling, experimentation and ultimately decision making for estimating the performance and vulnerability of structural systems reliably through the improved simulations using monitoring data. In some St-Id applications, there can be challenges and considerations related to this six-step framework. For instance not all of the steps can be employed; thereby a subset of the six steps can be adapted for some cases based on the various limitations. In addition, each step has its own characteristics, challenges, and uncertainties due to the considerations such as time varying nature of civil structures, modeling and measurements. It is often discussed that even a calibrated model has limitations in fully representing an existing structure; therefore, a family of models may be well suited to represent the structure's response and performance in a probabilistic manner.The principle objective of this dissertation is to investigate nonparametric and parametric St-Id approaches by considering uncertainties coming from different sources to better assess the structural condition for decision making. In the first part of the dissertation, a nonparametric St-Id approach is employed without the use of an analytical model. The new methodology, which is successfully demonstrated on both lab and real-life structures, can identify and locate the damage by tracking correlation coefficients between strain time histories and can locate the damage from the generated correlation matrices of different strain time histories. This methodology is found to be load independent, computationally efficient, easy to use, especially for handling large amounts of monitoring data, and capable of identifying the effectiveness of the maintenance. In the second part, a parametric St-Id approach is introduced by developing a family of models using Monte Carlo simulations and finite element analyses to explore the uncertainty effects on performance predictions in terms of load rating and structural reliability. The family of models is developed from a parent model, which is calibrated using monitoring data. In this dissertation, the calibration is carried out using artificial neural networks (ANNs) and the approach and results are demonstrated on a laboratory structure and a real-life movable bridge, where predictive analyses are carried out for performance decrease due to deterioration, damage, and traffic increase over time. In addition, a long-span bridge is investigated using the same approach when the bridge is retrofitted. The family of models for these structures is employed to determine the component and system reliability, as well as the load rating, with a distribution that incorporates various uncertainties that were defined and characterized. It is observed that the uncertainties play a considerable role even when compared to calibrated model-based predictions for reliability and load rating, especially when the structure is complex, deteriorated and aged, and subjected to variable environmental and operational conditions. It is recommended that a family-of-models approach is suitable for structures that have less redundancy, high operational importance, are deteriorated, and are performing under close capacity and demand levels.
Show less - Date Issued
- 2012
- Identifier
- CFE0004232, ucf:48997
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004232
- Title
- An Assessment of Biosorption Activated Media for the Removal of Pollutants in Up-Flow Stormwater Treatment Systems.
- Creator
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Hood, Andrew, Randall, Andrew, Wanielista, Martin, Chopra, Manoj, O'Reilly, Andrew, Moore, Sean, University of Central Florida
- Abstract / Description
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Nitrogen and phosphorus are often the limiting nutrients for marine and freshwater systems respectively. Additionally, stormwater often contains elevated levels of pathogens which can pollute the receiving water body and impact reuse applications [1-4]. The reduction of limiting nutrients and pathogens is a common primary target for stormwater best management practices (BMPs) [5]. Traditional BMPs, such as retention/detention treatment ponds require large footprints and may not be practical...
Show moreNitrogen and phosphorus are often the limiting nutrients for marine and freshwater systems respectively. Additionally, stormwater often contains elevated levels of pathogens which can pollute the receiving water body and impact reuse applications [1-4]. The reduction of limiting nutrients and pathogens is a common primary target for stormwater best management practices (BMPs) [5]. Traditional BMPs, such as retention/detention treatment ponds require large footprints and may not be practical in ultra-urban environments where above ground space is limited. Upflow filters utilizing biosorption activated media (BAM) that can be placed underground offer a small footprint alternative. Additionally, BAM upflow filters can be installed at the discharge point of traditional stormwater ponds to provide further treatment. This research simulated stormwater that had already been treated for solids removal; thus, most of the nutrients and solids in the influent were assumed to be as non-settable suspended solids or dissolved solids. Three different BAM mixtures in an upflow filter configuration were compared for the parameters of nitrogen, phosphorus, total coliform, E. coli, and heterotrophic plate count (HPC). Additionally, genetic testing was conducted using Polymerase Chain Reaction (PCR), in conjunction with a nitrogen mass balance, to determine if Anammox was a significant player in the nitrogen removal. The columns were run at both 22-minute and 220-minute Empty Bed Contact Times (EBCTs). All the BAM mixtures analyzed were shown to be capable at the removal of nitrogen, phosphorus, and total coliform during both the 22-minute and 220-minute EBCTs, with BAM #1 having the highest removal performance for all three parameters during both EBCTs. All BAM mixtures experienced an increase in HPC. Additionally, PCR analysis confirmed the presence of Anammox in the biofilm and via mass balance it was determined that the biological nitrogen removal was due to Anammox and endogenous denitrification with Anammox being a significant mechanism.
Show less - Date Issued
- 2019
- Identifier
- CFE0007817, ucf:52875
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007817