http://hdl.handle.net/1957/22529 2013-05-16T10:40:34Z http://hdl.handle.net/1957/38556 Spatial identification and optimization of upland wetlands in agricultural watersheds Babbar-Sebens, Meghna; Barr, Robert C.; Tedesco, Lenore P.; Anderson, Milo Wetland ecosystems are considered as potential ecological solutions for increasing the capacity of watersheds to store runoff waters upstream, and thereby, decrease risk of downstream flooding. Especially in tile-drained agricultural landscapes, wetlands constructed to intercept these tiles can serve as storage basins for agricultural runoff, leading to both reduction in peak runoff flows and diminished transport of agricultural nutrients. The objective of this study was to develop a watershed-scale methodology for identifying potential sites for wetlands in a tile-drained landscape in the Midwestern USA, and for optimizing the spatial distribution of these wetlands for reductions in peak runoff flows. The benefits of this methodology is demonstrated by using it for selecting appropriate wetland restoration and/or creation sites in Eagle Creek Watershed (ECW), located 10 miles northwest of Indianapolis, IN, USA. Results show that a large number of potential sites could be identified (e.g., 2953 sites in ECW), and with a choice of effective wetland design parameters and with spatial optimization of their areas, locations, and drainage areas, it is possible to achieve significant peak flow reductions with fewer sites and smaller wetlands. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.elsevier.com/. 2013-01-24T00:00:00Z http://hdl.handle.net/1957/38540 Adjacent structure response sensitivity to seismic events using the direct differentiation method White, William S. (William Schaffer) The response of adjacent structural systems to earthquake motions is investigated using the finite element framework OpenSees. Results of sensitivity analyses demonstrate that structural response quantities can increase in either or both of the adjacent structures for specific configurations. The structural models used include steel moment-resisting frames and rigid shear walls. The soil that underlies both buildings is modeled with a "structure-soil- structure spring" that connects the structural models. Due to the variety of building heights in urban environments, all combinations of four-, eight-, and twenty-story buildings are analyzed. Six shallow crustal earthquake motions are selected to model the dynamic responses of structural models. Sensitivity analyses are carried out using the direct differentiation method (DDM) with respect to parameters associated with the structure-foundation-soil systems, including floor mass, story stiffness, and soil stiffness. The DDM allows for computation of the time history of response sensitivity with respect to each parameter, in addition to the deterministic, or mean, time history response computed as part of an ordinary, non-linear, dynamic analysis. The response time histories can then be used to make a first-order approximation of the change in building response with respect to prescribed changes in a given parameter. The results of these analyses demonstrate that the effects of structure-soil-structure interaction are generally negligible for the steel, moment-resisting frame structure pairs investigated. The rigid shear walls demonstrated effects of structure-soil-structure interaction, particularly in the smaller wall mimicking the motion of the larger wall. Further research is needed in this area, particularly in refining the soil model to more fully reflect the response of realistic soil. Graduation date: 2013 2013-04-30T00:00:00Z http://hdl.handle.net/1957/38535 Behavior of open grid steel bridge decks under service and fatigue loads Fetzer, Peter C. Open grid steel bridge decks have been in use for nearly a century. These open grid decks provide an economical and lightweight alternative to traditional reinforced concrete decks. As the transportation infrastructure continues to deteriorate, open grid decks can be used as a cost effective way to rehabilitate structurally deficient bridges. Open grid decks weigh less than conventional reinforced concrete decks and reduce the dead load on a bridge superstructure, thereby increasing the live load capacity. While modern bridge design specifications have evolved to LRFD principles, present design methods for open grid decks are mostly empirical and based on historic practice and performance. Further, fatigue limit states in practice tends to be controlled by cracking in the weak direction, for which no design provisions currently exist. A comprehensive research program was developed to address these issues. The results provide a better understanding of grid deck behavior, and will improve detailing and design provisions. Graduation date: 2013 2013-03-18T00:00:00Z http://hdl.handle.net/1957/38534 Quantification of landslide movement in a forested environment Conner, Jeremy C. Landslides are an insidious natural hazard, which can result in significant damage to public infrastructure. Limited monitoring tools are available, particularly tools suitable for use in forested environments. These tools often only allow a few locations across the slide to be monitored. Terrestrial Laser Scanning (TLS) shows promise as a monitoring technique given the high spatial resolution and accuracy at which measurements can be made. However, current procedures can be time consuming, require advanced skill and judgment by the analyst, and typically require manual methods of feature extraction to quantify landslide movement. To overcome these limitations, this thesis presents and investigates a new methodology to detect and monitor landslide movement in a densely forested area using natural features such as tree trunks. The presented methodology searches through the noisy point cloud dataset to find trees and then fit circles to points sampled on the tree trunk. Next, comparing the movement of the circles between time series terrestrial laser scan surveys provides quantified displacements distributed across the landslide. For quality control purposes a parametric analysis was conducted and revealed that the root mean square error (RMS) of the circle fit and the difference in calculated tree radii between epochs are the dominant parameters in correctly pairing trees between epochs. For the test dataset, the optimal values were a RMS circle-fit of less than 1.5 cm and less than 1.0 cm for the calculated difference in tree radii. Application of the methodology to a case study of Johnson Creek Landslide (JCL) showed that TLS can determine landslide movement comparable to conventional monitoring methods. The displacements observed on markers were within 2 cm from the displacement observed from traditional methods such as total station monitoring. TLS also provides more samples than currently observed for this location, allowing increased detail for landslide modeling and monitoring. Graduation date: 2013 2013-05-01T00:00:00Z