Methane is one of two primary gases produced from the decomposition of landfill waste. Studies have been directed to collection and mitigation of methane gas. In small landfills, collection is not an economically feasible solution. Bio-cover placement is an inexpensive approach to mitigating methane emissions. The enhancing of oxidation processes by placement of bio-covers will reduce emissions even while gas extraction is employed and improve aesthetic quality of solid waste facilities. The overall objective of the research is to mitigate methane emissions from landfills. To reach this objective, a test site was selected to evaluate the effects of compost placement over a closed landfill. The static chamber technique was used to estimate methane emissions and the stable isotope tracing method was used to determine oxidation rates. Hot spots were identified in the grid area and emissions at these spots were analyzed more in detail. Results obtained during the first year of the study are presented in this thesis. In these investigative efforts, it was noted that moisture content plays a significant role in controlling emissions and oxidation. At high water contents, low flux emissions were measured observed and at low water contents, emissions were higher. Oxidation rates varied in much the same way. High water contents corresponded with low oxidation rates and vise versa. Further study on the effects of moisture content and other variables on flux emission and oxidation is warranted. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Degree Awarded: Spring Semester, 2005. / Date of Defense: February 21, 2005. / Bio-Reactive Covers, Landfill, Methane Emissions, Mitigation, Oxidation / Includes bibliographical references. / Tarek Abichou, Professor Directing Thesis; Jeff Chanton, Committee Member; Amy Chan-Hilton, Committee Member; Dave Powelson, Committee Member.

Recent innovation in the engineered wood industry has produced Structural Composite Lumber (SCL) that tends to achieve maximum strength, stiffness and efficient use of wood. Product variations of SCL such as Laminated Veneer Lumber (LVL) and Parallel Strand Lumber (PSL), are currently being used in the transportation sector to produce bridge girders, decks etc. for rural and other low traffic volume roads. Although, the elastic and shear properties of SCL materials are clearly understood, no attempt has been made to estimate fatigue performance of these bridge girders. With their increasing use, they are repeatedly being subjected to numerous cycles of wheel load that raises concern about their behavior under fatigue. The current research tested 12 newly procured and 2 old and weathered pre-built SCL T-beam bridge girders for flexural fatigue under a stress controlled test setup. The girders were of 20 ft span and having variation in their constituent material types and applied preservatives. Loading was applied according to the AASHTO LRFD specifications for bridge design. The number of load application cycles was consistent with expected traffic volume for a sixty year time span. In a regular bridge structure comprised of pre-built SCL T-beam girders, transverse post-tension is applied to adjacent girders to form a stress laminated deck. This effect had been simulated on the girders and the effect of fatigue loading on the loss of post-tension force was observed. Results from the study indicated that the SCL Tbeam bridge girders were capable of withstanding the repetitive loads coming from the heavy truck traffic. Most of the beams did not suffer any physical damage. A few of them had severe de-lamination at the SCL-epoxy interface. The girders without any damage due to fatigue were loaded statically up to failure. This result was compared to the ultimate flexural strength of fresh beams of similar material type, to investigate their residual strengths after fatigue loading. Some weathered girders were also fatigued under the same experimental setup for comparison purposes. This provided a comparison of the fatigue performance of fresh and weathered SCL T-beam bridge girders. Comparably high strength fatigue loading was applied to two additional girders. The fatigue lives for these girders were less and compared well with those of clear wood at the same stress level. A rudimentary fatigue curve was proposed based on the data. A finite element model was developed, using layered shell elements, to simulate the structural behavior of these girders. Subsequent analyses of this model produced results that were highly representative of the data obtained in experimental testing of SCL T-beam girders. / A Dissertation submitted to Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Spring, 2008. / Date of Defense: December 19, 2007. / SCL, Structural Composite, Lumber, LVL, PSL, Fatigue Re / Includes bibliographical references. / Primus V. Mtenga, Professor Directing Dissertation; Kamal S. Tawfiq, Professor Directing Dissertation; Lisa Spainhour, Committee Member; Peter N. Kalu, Outside Committee Member.

Transportation projects will have impact on the environment. The general environmental pollution and damage caused by roads is closely associated with the level of economic activity. Although Environmental Impact Assessments (EIAs) are dependent on geo-spatial information in order to make an assessment, there are no rules per se how to conduct an environmental assessment. Also, the particular objective of each assessment is dictated case-by-case, based on what information and analyses are required. The conventional way of Environmental Impact Assessment (EIA) study is a time consuming process because it has large number of dependent and independent variables which have to be taken into account, which also have different consequences. With the emergence of satellite remote sensing technology and Geographic Information Systems (GIS), this research presents a new framework for the analysis phase of the Environmental Impact Assessment (EIA) for transportation projects based on the integration between remote sensing technology, geographic information systems, and spatial modeling. By integrating the merits of the map overlay method and the matrix method, the framework analyzes comprehensively the environmental vulnerability around the road and its impact on the environment. This framework is expected to:1) improve the quality of the decision making process, 2) be applied both to urban and inter-urban projects, regardless of transport mode, and 3) present the data and make the appropriate analysis to support the decision of the decision-makers and allow them to present these data to the public hearings in a simple manner. Case studies, transportation projects in the State of Florida, were analyzed to illustrate the use of the decision support framework and demonstrate its capabilities. This cohesive and integrated system will facilitate rational decisions through costeffective coordination of environmental information and data management that can be tailored to specific projects. The framework would facilitate collecting, organizing, analyzing, archiving, and coordinating the information and data necessary to support technical and policy transportation decisions. / A Dissertation submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Spring Semester, 2005. / Date of Defense: March 25, 2005. / Environment, Transportation, GIS, Remote Sensing / Includes bibliographical references. / Yassir A. AbdelRazig, Professor Directing Dissertation; Douglas A. Zahn, Outside Committee Member; John O. Sobanjo, Committee Member; Renatus N. Mussa, Committee Member.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005. / Includes bibliographical references (leaves 211-235). / (cont.) characterization, and kink criterion implementation, form a synergistic analysis of the mechanistic debonding behavior affected by moisture. Results have shown that moisture affected debonding is a highly complex phenomenon that involves physical changes in the bond as well as in its constituent materials. In particular, moisture can initially enhance or reduce the interface fracture toughness, depending on the epoxy formulation being used. The toughness can, however, decrease by as much as 60% and become asymptotic upon reaching a certain moisture concentration threshold, which can be attained in as short as 2 weeks in case of peel fracture. While various debonding modes have been observed for dry specimens, epoxy/concrete interface separation, which has generally been considered an unlikely debonding mode, is observed consistently in all wet fracture specimens. Interface fracture analysis indicates that this newly discovered interfacial debonding mode is attributed to various interfacial material toughening or weakening mechanisms, and has also hinted on the possible interphase formation as a consequence of moisture diffusion. The new knowledge and results obtained from this research provide a basis for further analysis directions and for design of FRP bonded concrete systems against moisture affected debonding. / The objective of this research is to develop new mechanistic understanding of moisture affected debonding failures in carbon fiber-reinforced plastic (FRP) bonded concrete systems by means of an interface fracture approach. Central to the investigation is the use of interface fracture toughness as the quantification parameter, which is considered a bond property, to analyze, compare, and correlate physical observations of FRP bonded concrete joints. Owing to the non-negligible epoxy bond line thickness found in real-world retrofitted systems, a new tri-layer fracture energy model is derived to facilitate the computation of interface fracture toughness values. Also, with this model, the five possible debonding scenarios in FRP bonded concrete that include interface separation and material decohesion, are quantitatively distinguished and precisely described for the first time. Debonding characterization is conducted using mesoscale peel and shear fracture models manufactured with full-scale bond lines. These models are subjected to accelerated moisture conditioning to achieve various levels of moisture content in the bond region. They are then mechanically tested at selected time intervals for capturing the change in bond property and debonding mode with respect to increasing moisture concentration, which is evaluated by means of 3-dimensional moisture diffusion simulations. Diffusion and mechanical properties of the constituent materials with respect to moisture uptake are physically determined to act as inputs in the diffusion simulation and in the computation of toughness values. The knowledge of computed toughness values, simulated diffusion behavior, and observed debonding modes, combined with finite element fracture computation, mode-mix / by Ching Au. / Sc.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 1999. / Includes bibliographical references (leaves 73-75). / by Coach K. Wei. / S.M.

Massachusetts Institute of Technology. Dept. of Civil Engineering. Thesis. 1966. M.S. / MICROFICHE COPY ALSO AVAILABLE IN BARKER ENGINEERING LIBRARY. / Bibliography: leaves 36-38. / M.S.

There has been much research done on the reduction, or attenuation, of hydrogen sulfide (H2S), particularly within landfill cover soils, as H2S can cause many issues when exposed to the atmosphere. The objective of this research study was to understand hydrogen sulfide (H2S) attenuation within landfill cover soils, and to use mass balancing to determine how much sulfur was retained within each layer of test pad. Both of these were completed through 403 days of monitoring three 65 feet by 35 feet lysimeter test pads constructed at the Riverbend Landfill. Test Pad 1 was constructed with 18 inches of local soil and an underlying 6 inch gravel layer. Test Pad 2 was constructed with 12 inches of compost, 6 inches of local soil and an underlying 6 inch gravel layer. Test Pad 3 was constructed with 6 inches of local soil and an underlying 6 inch gravel layer. Monitoring on Test Pad 3 was stopped on April 27th, 2015 due to erosion of the 6 inch soil layer, while Test Pads 1 and 2 were monitored until July 20th, 2015. Readings of landfill gas and H2S inflow, and bottom landfill gas and H2S concentrations were taken in each testing pad on a weekly basis. Bottom H2S loading into the soil layer and top H2S emissions from the soil layer were also measured to determine the removal efficiency of H2S. The average H2S removal efficiency of the test pads is 95%, with Test Pad 1 having a removal efficiency of 99%, Test Pad 2 having a removal efficiency of 99%, and Test Pad 3 having a removal efficiency of 82%. Six soil samples and five water samples were taken to measure sulfur concentration within the testing pads. Soil samples were also taken within each of the layers of each testing location within each test pad to determine the soil type and the water content of each soil layer. Mass balance was calculated by taking the amount of sulfur loaded into the bottom of each testing pad, and subtracting the sum of sulfur loaded into the soil cover, sulfur emitted from the soil cover into the atmosphere, and sulfur removed from the system with water as sulfate. Test Pads 1 and 2 yielded similar results, both retaining about 6000 grams of sulfur within their cover layers, while the results from Test Pad 3 suggest that more sulfur was removed from the system than was originally pushed into the system, which is not possible and suggests errors with either testing methods or the testing pad itself. While the concentrations of sulfur within each test pad layer were measured, there were concerns with their dependability that caused them to not be used to determine the amount of sulfur in each layer. / A Thesis submitted to the Department of Civil Engineering in partial fulfillment of the Master of Science. / Fall Semester 2015. / October 30, 2015. / attenuation, geotechnical, hydrogen sulfide, landfills / Includes bibliographical references. / Tarek Abichou, Professor Directing Thesis; Clayton Clark, II, Committee Member; Gang Chen, Committee Member.

This paper examines the application of Evolver, a genetic algorithm (GA) solving program, in a three-parameter optimization of a steel truss floor system with a concrete slab floor deck. The floor system is comprised of truss girders supporting beams running in a direction perpendicular to the truss girders with a composite floor deck along the top. Using Evolver, three parameters are optimized for two truss girder topologies in order to find the least cost floor system. The weight of the structural members is correlated to the expenses of material, labor, equipment, and overhead and profit required for the construction of the floor through information given by Means Building Construction Cost Data and interviews with steel fabricators. This procedure may be modified to optimize the cost of any floor area size that may use different truss girder topologies, beam sections, and connections. Parametric optimization is defined in this paper as the combination of configuration, size, and topology optimization of a truss girder, the size optimization of beams, and the optimization of the spacings of both beams and truss girders in the system. A discrete set of values has been selected for each variable that makes up the search space from which all solutions to the problem exist. A GA is a search algorithm, incorporated to quickly explore a wide range of answers and focus on better areas of the search space to find improved solutions. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Degree Awarded: Summer Semester, 2006. / Date of Defense: June 21, 2006. / Genetric Algorithms, Truss, Structures, Engineering / Includes bibliographical references. / Primus V. Mtenga, Professor Directing Thesis; John O. Sobanjo, Committee Member; Kamal S. Tawfiq, Committee Member.

Since civil structures have little damping capability, extensive damage and even failure often occur when they are subjected to seismic excitations. Control devices have therefore been developed and implemented to dissipate energy from earthquakes and reduce structural vibrations. Magnetorheological (MR) dampers are examples of such devices and consist of a hydraulic cylinder containing a solution that, in the presence of a magnetic field, can reversibly change from viscous fluid to semi-solid. The objective of this research is to develop fuzzy controllers to regulate the damping properties of MR dampers and reduce structural responses of single degree-of-freedom seismically excited structures. Three fuzzy controllers were therefore designed and their effectiveness evaluated through series of numerical simulations. Since fuzzy control uses expert knowledge instead of differential equations, it allows for the development of simple and robust algorithms that do not require information on plant's structural and vibration characteristics. They are therefore an attractive alternative for controlling systems that are complex, nonlinear, or that contain ambiguity or vagueness. The first algorithm proposed is a fuzzy control system with two inputs: structural displacement and velocity. The second is referred to as gain-scheduled fuzzy control and varies the velocity input scaling factor according to incoming ground acceleration. The last one, self-tuning fuzzy control, uses a fuzzy inference mechanism based on ground acceleration intensity and building displacement to adjust the velocity input scaling factor. Robustness of these controllers to changes in seismic motions and structural characteristics were evaluated by subjecting two different buildings controlled by each of these strategies to a wide range of earthquake records. Results show that the algorithms proposed effectively reduced responses of both structures to a wide range of seismic motions. They were also found to be robust to changes in ground excitations and structural characteristics. In addition, adjusting the velocity input scaling factor according to ground acceleration intensity considerably improved the controller's ability to reduce structural vibrations, since both the gain-scheduled and the self-tuning fuzzy algorithms reduced structural responses more effectively than the fuzzy controller with constant scaling factors. Finally, the self-tuning controller outperformed all other strategies for most earthquakes considered. / A Dissertation submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Summer Semester, 2005. / Date of Defense: June 27, 2005. / Semi-Active Control, MR Damper, Fuzzy Control, Vibration Control / Includes bibliographical references. / Makola M. Abdullah, Professor Directing Dissertation; Emmanuel G. Collins, Outside Committee Member; Lisa K. Spainhour, Committee Member; Nur Yazdani, Committee Member.

The ever changing world of today's construction industry has brought about an increase in the number state transportation departments across the country choosing the design-build project delivery system to build its highways and bridges. Design-build offers a dramatic decrease in the overall time from initial design to project completion by incorporating the two together. However, along with this fast track approach comes an increased amount of risk associated with the project schedules. There are some options available to asses this schedule risk, although there is a lack of research and well documented studies to support this. A broad review of previous research is put forward in this thesis along with new Monte Carlo simulation techniques. A methodology is developed for assessing project schedule risk on DB projects using the Crystal Ball software. Schedules and data from the Hathaway Bridge project that was recently completed in Panama City Beach, Florida is used to apply the methodology developed. The results of this study indicate that a much more realistic estimation of a projects duration can made using the application. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Degree Awarded: Fall Semester 2008. / Date of Defense: August 8, 2008. / Simulation, Design Build, Risk Anlysis / Includes bibliographical references. / John O. Sobanjo, Professor Directing Thesis; Yassir Abdel Razig, Committee Member; Lisa K. Spainhour, Committee Member.