Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004. / Includes bibliographical references. / Reliable prediction and control of ground movements represent an essential component of underground construction projects in congested urban environments, to mitigate against possible damage to adjacent structures and utilities. This research was motivated by the construction of a large underground cavern for the Rio Piedras station in San Juan, Puerto Rico. This project involved the construction of a large, horseshoe-shaped cavern (17m wide and 16m high) in weathered alluvial soils. The crown of the cavern is located less than 5.5m below existing buildings in a busy commercial district. Structural support for the cavern was provided by a series of 15 stacked drifts. These 3m square-section galleries were excavated mainly by hand and in-filled with concrete, while a compensation grouting system was designed to mitigate effects of excavation-induced ground movements on the overlying structures. Unexpectedly large settlements occurred during drift construction and overwhelmed the grouting system that was intended to compensate for tunnel-induced movements. Although two dimensional, non-linear finite element analyses of the stacked- drift construction suggest that movements exceeding 100mm can be expected, the 2-D representation of excavation and ground support is overly simplistic and represents a major source of uncertainty in these analyses. Massive computational efforts make more comprehensive 3-D models of the construction sequence completely impractical using existing finite element software with direct or iterative solver methods. / (cont.) This thesis develops, implements, and applies an efficient parallel computation scheme for solving such large-scale, non-linear finite element analyses. The analyses couple a non- overlapping Domain Decomposition technique known as the FETI algorithm (Farhat & Roux, 1991) with a Newton-Raphson iteration scheme for non-linear material behavior. This method uses direct factorization of the equilibrium equations for sub-domains, while solving a separate interface problem iteratively with a mechanically consistent, Dirichlet pre- conditioner. The implementation allows independence of the number of sub-domains from the number of processors. This provides flexibility on mesh decomposition, control between iterative interface solutions and direct sub-domain solutions, and load balance in shared heterogeneous clusters. The analyses are performed with the developed code, FETI- FEM (programmed in C++ and MPI) using syntax consistent with pre-existing ABAQUS software. Benchmark testing on a Beowulf cluster of 16 interconnected commodity PC computers found excellent parallel efficiency, while the computation time scales with the number of finite elements, NE, according to a power law with exponent, p = 1.217. Parallel 3-D FE analyses have been applied in modeling the drift excavation, primary lining and infilling for the stacked-drift construction assuming a simplified soil profile. The resulting FE model comprised approximately 30,000 20-noded quadratic displacement-based elements, representing almost 400,000 degrees of freedom (at least one order of magnitude larger than any prior model reported in the geotechnical literature) and was sub-divided into 168 sub-domains ... / by Yo-Ming Hsieh. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1994. / Includes bibliographical references (leaves 126-129). / by Ichiro Soma. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2006. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references. / In recent years, the airline industry has seen diminished performance of traditional Revenue Management (RM) systems largely due to the growth of Low Cost Carriers and the increased use of their "simplified" fare structures. With the removal of many of the fare restrictions essential to RM systems, standard demand forecasters can no longer segment demand and passengers are able to book air travel in fare classes lower than their actual willingness to pay. These "semi-restricted" fare structures typically contain several homogenous fare classes undifferentiated except by price, as well as several distinct fare classes with unique combinations of booking restrictions and advance purchase requirements. This thesis describes" Hybrid Forecasting" (HF) -- a new technique which separately forecasts "product-oriented" demand using traditional forecasting methods, and "price-oriented" demand for passengers who purchase only in the lowest priced fare class available when booking. The goal of this thesis is two-fold: to first measure the potential benefit of Hybrid Forecasting in terms of network revenue in semi-restricted fare structures, and then to measure potential improvements to Hybrid Forecasting. / (cont.) "Path Categorization" attempts to improve revenues by exploiting the expected higher level of passenger willingness-to-pay for non-stop service versus connecting service. And "Fare Adjustment" accounts for passenger sell-up behavior from lower to higher fare classes, and is applied within an RM system's seat inventory optimizer. Experiments with the Passenger Origin-Destination Simulator demonstrate that HF in these semi-restricted fare structures can improve an airline's network revenue by approximately 3% compared to traditional forecasting methods. This improvement grows by 0.25% with Path Categorization, by 1% with Fare Adjustment, and by up to 2.5% over Hybrid Forecasting alone with Path Categorization and Fare Adjustment together -- all significant impacts on an airline's network revenue. Though these results are encouraging, the revenue gains of these new RM forecasting methods are still not enough to offset the revenue loss associated with the easing of traditional fare class restrictions. / by Michael H. Reyes. / S.M.

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003. / Includes bibliographical references (leaves 67-69). / The objective of this thesis is to determine what, if any, significant effects effluent from the carpet dyeing industry has on the water quality of the Bagmati River in Kathmandu, Nepal. The water quality parameters studied were absorbance, as a color indicator, total chromium, dissolved oxygen (DO) and chemical oxygen demand (COD). Total chromium was measured both in samples from the Bagmati River and in dye samples. All four dyes tested contained chromium. Three of them contained high levels of chromium (1,200 - 2,400ppm). The highest level of chromium measured in any of the river samples was 0.03mg/L (found in two samples). This is below the World Health Organization's (WHO) guideline for chromium in drinking water, 0.05mg/L. This fact does not, however, necessarily indicate that there is not a chromium problem in the Bagmati River. Samples were collected and tested in January 2003, at which time carpet manufacturing was at a low. An increase in carpet production and subsequent increase of dye waste to the Bagmati River could increase chromium in the river to dangerous levels. There is a noticeable decrease in water quality as the Bagmati River flows through Kathmandu City. This water quality deterioration can be seen by looking at DO and COD levels along the river. Other researchers have theorized that dyes increase COD and therefore, may contribute to the high COD and low DO values in the Bagmati. However, in this study, dyes were not found to add a significant amount of COD. / by Hillary Monette Green. / M.Eng.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2000. / Includes bibliographical references (p. 151). / The "Decision Aids for Tunneling" (DAT) are a procedure and computer code which can be used to assess uncertainties which are caused by the geologic / geotechnical conditions and from the construction process. In particular the DAT can be used to predict construction costs and time. The computer code determines the overall uncertainty which results from the many individual uncertainties that are present in a tunneling project. These individual uncertainties are input parameters and must be specified by the user. While construction is in progress there is a need for updated predictions. These can be used for improvements in scheduling, resource allocation, financial planning and so on. This work presents an updating procedure and associated code which allows one to refine predictions during construction. Updating not only involves replacing the original prediction by actual data from the excavation but also includes a learning effect. This uses information from the actual excavation to arrive at an improved prediction for the un-excavated part. The Updating Module of the DAT is a tool which helps the user refining input parameters by deriving relevant information from construction data and presenting it together with original input. Graphical presentation of original input, construction information and updated input assists in the interpretation of the information. A mathematical model which is based on Bayes' theorem makes the code also capable of suggesting updated input parameters in some cases. An example project shows that the learning effect has a significant impact on the precision of the prediction and reduces the uncertainty substantially. / by Christoph Haas. / S.M.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009. / Includes bibliographical references (leaves 58-60). / This study was performed to determine the bacterial loading of Kranji Catchment and Reservoir and how this will affect planned recreational use of Kranji Reservoir. Field and laboratory work was conducted in Singapore during the month of January 2009 to characterize the concentration of bacteria at sampling locations in the drainage system of Kranji Catchment and in Kranji Reservoir. Using this data, a first-order attenuation model was constructed and used to evaluate attenuation of bacteria while traveling through the drainage network to the reservoir. GIS tools used this model to predict areas of potential concern in one specific sub-catchment of Kranji Catchment. The USEPA WASP modeling program was used to determine fate and transport of bacteria throughout Kranji Reservoir based on bacteria concentrations flowing into the reservoir. These analyses led to the recommendation that farm run-off near the reservoir was the bacterial source of greatest concern. The relatively high concentrations coupled with short travel time, which diminishes opportunity for attenuation, resulted in high concentrations reaching the reservoir. Residential areas were found to contribute high concentrations of bacteria to the catchment, but due to relatively long travel times from the sources to the main body of the reservoir, have less of an effect on the bacterial concentrations of the main reservoir. Due to the uncharacteristically dry weather Singapore experienced during January 2009, the applicability of the results of this study to wet weather conditions is uncertain. / by Kathleen B. Kerigan and Jessica M. Yeager. / M.Eng.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 64-65). / Building higher skyscrapers increases the concern of wind induced motion. Indeed, in order to ensure serviceability and safety standards, it is the engineers' responsibility to investigate the response of high-rise buildings to wind excitation. Tuned mass dampers are usually used to limit the response of the buildings to wind. However, these devices are generally tuned for a particular bandwidth of frequencies. Therefore, in order to improve the effectiveness of these devices, control schemes must be implemented. For this thesis, the design of a modified friction device (MFD) has been studied. Requiring only a small amount of energy, the MFD is a new kind of semi-active damper that provides stability, accurate control and effectiveness. Using a MATLAB program, it was possible to model a primary structure hit by a certain wind excitation. The modified friction device was designed to counterbalance the effects of wind and decrease displacements and accelerations. It was placed on the top of the building where the displacements are generally the highest. The parameters of the MFD were examined, and many simulations were run in order to optimize the action of the device on the mitigation of wind excitation. The results demonstrate that the MFD effectively mitigates wind induced motion in buildings. Therefore, this thesis corroborates the benefits of implementing modified friction devices in civil structures. / by Saad Mikou. / M.Eng.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2000. / Includes bibliographical references (leaves 142-156). / by Marko Medved. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1996. / Includes bibliographical references (p. 224-227). / by András Farkas. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1994. / Includes bibliographical references (leaves 282-286). / by Theodore Charles Botimer. / Ph.D.