Theses and Dissertations - Department of Civil, Construction & Environmental Engineering

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Determination of rational tornado design wind speed for residential woodframe structures
(University of Alabama Libraries, 2012) Amini, Mohammad Omar; Van de Lindt, John W.; University of Alabama Tuscaloosa
Tornadoes are an extremely devastating natural hazard with significant consequences but are not considered in current structural design codes. This is due to their low probability of occurrence making them what has been termed a low-occurrence high-consequence event. This thesis aims to determine a rational design wind speed for tornadoes considering the current state-of-practice construction methods and is achieved through application of the fragility methodology. Five arche-type buildings are developed to be representative of the typical residential structures in tornado-prone regions in the United States. Wind analysis is performed using the ASCE 7-10 standard loading in combination with the existing literature which provides loading for a tornado on structures. Fragilities are developed for the main components along the vertical load path that included roof sheathing, roof-to-wall connection, and wall-to-foundation anchorage. The results obtained from the fragility analysis are validated with the EF scale ratings for residential construction and are then used to identify critical components that affect system performance. Based on the developed fragilities, (2)16d roof-to-wall connection and wall racking present the most critical components. Developing fragilities for all components along the vertical load path is essential in identifying critical components and deciding on improving a particular component. The effect of component improvement on system performance can range from minimal to significant depending on its fragility in comparison to the other components. Based on the analysis conducted in this thesis, it was found that using hurricane clips and improving the nail pattern will yield better system performance in an EF1 (86-110 mph) tornado. However, typical construction methods and products would not prove to be as effective in the case of an EF2 (111-135 mph) tornado with a high probability of failure of one or more components of the load path. The methodology presented in this thesis can be used in developing new design provisions that will essentially help in saving lives and preventing economic losses, assessment of the current building stock, post-disaster damage assessment, and provide a quantitative approach to more accurate evaluation of tornado ratings.
Development and testing of a bridge weigh-in-motion method considering vehicles traveling at variable speed
(University of Alabama Libraries, 2015) Lansdell, Andrew; Song, Wei; University of Alabama Tuscaloosa
Government stakeholders rely upon traffic information such as the weight of trucks on the roadways to provide and maintain safe and reliable highway/bridge infrastructure. Bridge weigh-in-motion (BWIM) provides an alternative to conventional static weigh stations for obtaining vehicle axle weights. Traditional BWIM algorithms are capable of predicting the axle weights of vehicles traveling at constant speed across a bridge with known influence line, but they often lose accuracy when measuring vehicles are traveling at nonconstant speed. This thesis presents a methodology to improve BWIM accuracy when measuring a vehicle traveling at nonconstant speed by transforming variable speed response data to constant speed data. A BWIM package capable of determining vehicle speed and axle spacing, calculating the influence lines of a bridge, and predicting the axle weights of a vehicle crossing the bridge is developed in MATLAB. A numerical study is performed using finite element analysis in MATLAB to evaluate the performance of the BWIM package when measuring loads traveling at constant speed and variable speed. The results of the numerical study show the speed correction is able to improve BWIM accuracy for a variable speed vehicle to nearly the accuracy level of a constant speed vehicle. A field study is also performed. A vehicle with known weight was used as a calibration vehicle to measure the influence line of a bridge on the University of Alabama campus. A different vehicle was then driven across at constant speed, then again at variable speed to generate data for various study cases. Results of the field study showed that correcting variable speed response data can significantly improve the accuracy of axle weight predictions, but more research is required to reach the accuracy level BWIM is able to achieve when measuring constant speed vehicles.
Development of crash modification factors for bridge rail improvements
(University of Alabama Libraries, 2015) Fields, Robert Tyler; Jones, Steven L.; University of Alabama Tuscaloosa
Bridge components such as bridge railings are safety features designed to protect drivers. The guidelines for those safety features have recently been updated to accommodate for the increase in vehicle size. One method to bring non-conforming bridges up to current standards is retrofitting. The objective of this research is to determine the safety effectiveness of retrofitted bridges that have been updated to current standards. Bridge data and bridge related crash data from historical data for Alabama were collected. The data was cleaned and processed in a geographic information system. The remaining data was used in the development of Safety Performance Functions (SPFs) and Crash Modification Factors (CMFs). The SPFs used in this study were developed to predict crash frequency and severity in future years based on roadway and geometric characteristics. The SPFs for general crashes were developed using Negative Binomial. The SPFs for severity of single vehicle crashes were developed using both Negative Binomial and Conway-Maxwell-Poisson. The SPFs used in this study were developed in a connected study and used in this study as part of the CMF development. After obtaining the various prediction models for general crashes and for single vehicle severity crashes, the research utilized the information obtained from them in the development of the CMFs. This research employed the empirical Bayes (EB) before-after approach to develop the CMFs. The CMFs were a measure of effectiveness for retrofitting bridge railings to meet current standards. CMFs were determined for both the general crash and for severity of single vehicle crashes. The findings of this research were that retrofitting bridges to conform to the current standards results in a reduction in crashes and a reduction in the severity of crashes. The findings of this research can aid in the decision making process involving bridge railing improvements
The impact of building information modeling (BIM) on change orders for university construction projects
(University of Alabama Libraries, 2014) Bruhn, John Richard; Johnson, Philip W.; University of Alabama Tuscaloosa
Recent growth in construction volume is leading The University of Alabama to identify areas for improvement in the construction process. Change orders have a significant impact on project cost and schedule; therefore they are in need of improvement. Researchers have worked on improving the change order management and prevention plan and implementing it into their construction management. With the implementation of Building Information Modeling (BIM) for the design and construction of new facilities new research is necessary in order to determine the impact of BIM on the change order management and prevention strategy. The University of Alabama recently completed the construction of two similar engineering facilities, The South and North Engineering Research Centers (SERC and NERC), designed for labs and classrooms. The first building is designed and built using 2-Dimension modeling while the second building is designed and built using BIM for 3-Dimension modeling and coordination. Change orders due to design errors/omissions are noted as preventable, and the main focus of the research. Pertinent information was extracted and analyzed when reviewing change orders from both SERC and NERC. Change orders due to design errors/omissions diminish from 45 on SERC to 9 on NERC. The change in the project cost due to change orders from design errors/omissions decreased from 0.54% on SERC to 0.18% on NERC. Researchers found that BIM is not the only contributing factor in change order reduction. A thorough design review process coupled with the implementation of BIM, allows a level of reduction not yet achieved on other projects.
Mechanics and subcritical cracking of FRP-concrete interface
(University of Alabama Libraries, 2011) Zhang, Chao; Wang, Jialai; University of Alabama Tuscaloosa
The need for safe, effective, and efficient methods to strengthen and upgrade our nation's infrastructures is clear. Strengthening Reinforced Concrete (RC) members using Fiber Reinforced Polymer (FRP) composites through external bonding has emerged as a viable technique to retrofit/repair deteriorated infrastructures. The interface between the FRP and concrete plays a critical role in this technique. This study proposes a life-cycle analytical framework on the integrity and long-term durability of the FRP-concrete interface through a combined analytical, numerical, and experimental approach. A novel three-parameter elastic foundation model (3PEF) is first established to provide a general tool to analyze and evaluate the design of the FRP strengthening system. This model correctly predicts the location where debonding can occur. To simulate the interface stress redistribution and creep deformations accumulated during service life due to the strong time dependent features of the adhesive layer, linear viscoelastic analytical solutions are then developed for the FRP-strengthened RC beams. Small cracks usually exist within the FRP-concrete interface, making fracture mechanics a more appropriate tool to evaluate the integrity of the FRP-concrete interface. Analytical solutions of energy release rate (ERR) and its phase angle at the tip of a crack along the FRP-concrete interface are obtained. Under the synergistic effects of the service loads and environments species, these small cracks can grow slowly even if the ERR at the crack tip is lower than the critical value. This slow-crack growth process is known as environment-assisted subcritical cracking. A series of subcritical cracking testing are conducted using a wedge-driven testing to gain the ability to accurately predict the long-term durability of the FRP-concrete interface. It has been found that water, deicing salt and alkaline solutions can substantially reduce the ERR at the crack tip needed to drive the subcritical crack growth along the epoxy-concrete interface. Once the small cracks grow to the critical length, critical debonding will occur, leading to the premature failure of the structure. A nonlinear fracture mechanics model using a Cohesive Zone Model (CZM) is finally developed to simulate this final failure phase of the FRP-concrete interface.
Performance of concrete bridge deck sealers
(University of Alabama Libraries, 2015) Dunn, Jonathan Riley; Giannini, Eric R.; University of Alabama Tuscaloosa
The main objective of this research was to determine an improved method for evaluating bridge deck sealer products for the Alabama Department of Transportation (ALDOT) through a synthesis of two testing methods: NCHRP Report 244 Series II tests and standards developed by the Alberta Ministry of Transportation (BT Series). Five sealer products were evaluated for their resistance to moisture and chloride ingress, performance after simulated traffic wear, and depth of sealer penetration into the concrete. The products tested included four epoxy-based sealer products and one sodium silicate sealer product. The sealers were evaluated on three different concrete mix designs representing the range of bridge deck concrete in service with ALDOT. Concrete cube specimens were fabricated, sealed, conditioned, and subjected to different tests. One test evaluated the waterproofing performance of sealers before and after abrasive conditioning (representing traffic wear). Another test determined the products’ ability to resist chloride penetration and their waterproofing performance in a saltwater solution. The chloride content was measured by potentiometric titration with silver nitrate and X-ray fluorescence spectroscopy (XRF). Sealer penetration depth as determined by a dye method and scanning electron microscopy (SEM). Initial (pre-abrasion) waterproofing performance results generally showed a good correlation to chloride resistance. XRF and titration analyses provided nearly identical results for measuring chlorides in concrete; however, XRF is a preferred method for determination of chloride content because it is much faster than titration. Two epoxy sealers outperformed all products for all evaluation criteria. A third epoxy sealer had good overall performance, but many specimens sealed with this product developed cracks that warranted further investigation. The sodium silicate sealer performed poorly compared to all four epoxy-based sealers. The epoxy-based sealers did not exhibit any measurable sealer penetration into the concrete and the sodium silicate sealer penetrated less than 100 m into the concrete.
Urban stormwater runoff contamination associated with gutter and pipe material degradation
(University of Alabama Libraries, 2013) Ogburn, Olga Nikolaevna Loukianova; Pitt, Robert; University of Alabama Tuscaloosa
In addition to typical stormwater pollutant sources (erosion materials, automotive activity, landscaping chemicals, pet wastes, etc.), urban stormwater runoff can also be contaminated with substances that leach from materials with which the water contacts as the rain water travels through an urban area to the discharge point. Prior studies have shown that the composition of roofing materials and the drainage system pipes can significantly affect the amounts of pollutants, particularly heavy metals, released into the runoff, especially for roof runoff. This dissertation research indicated that water chemistry (pH, salinity, major ions, etc.) and time of contact may also affect the release of contaminants from materials. The primary objective of this research was to examine how different drainage system and tank materials, water chemical characteristics, and exposure times affect contaminant losses during controlled tests examining the expected range of these characteristics. Static leaching tests for eight pipe and gutter materials were conducted over two separate three month periods during which pipe and gutter test materials were exposed to roof runoff and stormwater buffered to pH 5 and 8 and for exposure to different salinity conditions. A suite of heavy metal and nutrient constituents were periodically analyzed during the exposure periods. Also, pH, Eh, toxicity, alkalinity, total and calcium hardness, chloride and sulfate analysis were evaluated. This research found that the metallic gutter and pipe materials released significant heavy metals. Some of these materials were found to release large amounts of zinc, copper, and lead during the tests, with galvanized steel materials being the most significant sources of lead and zinc, while copper materials were the most important source of copper (as expected). Zinc, copper, and lead releases were detected during both short and long exposure times under low and high pH conditions and low and high salinity conditions. Statistical analyses were conducted to determine the effects of time, pH, salinity and each type of material on the release of the metals. Model fitting was performed on the time series plots to predict the release rate of metals as a function of exposure time and surface area. Chemical speciation modeling was also conducted to predict the forms of the measured metals, to compare the maximum concentrations observed with the expected solubility conditions, and to predict the relative toxicities and treatabilites of the different metallic compounds and ionic species likely present. A simple model was developed that quantified the expected pollutant releases for various materials for different uses (drainage systems vs. storage tanks) and water types (low and high pH conditions, saline and non-saline waters).

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