Ordovician through Pennsylvanian strata of the Ouachita and Marathon sedimentary sequences show correlated Nd-Sr isotopic relations, Th/Sc ratios and REE patterns typical of evolved upper crustal sources, indicating that the 2000 km long Ouachita-Marathon fold belt consists primarily of recycled crustal materials. wi thin this sequence, Nd isotopes distinguish three distinct provenance groups: 1) Lower to Middle Ordovician hemipelagites and quartzose turbidites with ε(Nd)(t) = -13 to -16 (T(DM) = 1.8 to 2.1 Ga); 2) Upper Ordovician through Pennsylvanian hemipelagites and quartzolithic turbidites with ε(Nd)(t) = -6 to -10 (TOM = 1.4 to 1.7 Ga); 3) Mississippian tuffs with ε(Nd)(t) = -2 (TOM = 1.1 Ga). These data record a rapid Ordovician (ca. 450 Ma) shift in sedimentary sources within the off-shelf passive-margin sequence of deep-marine cherts and shales. Ouachita Silurian turbidites (ε(Nd) = -7 to -8) are isotopically identical to Middle Ordovician Taconic turbidites of the Sevier basin (Tellico Formation) in eastern Tennessee (ε(Nd) = -7 to -8), suggesting that Appalachian clastic wedges supplied Ouachita deep-sea turbidites beginning in the Late Ordovician. Pennsylvanian non-marine sandstones and shales from the Arkoma, Illinois, and Black Warrior basins have ε(Nd) = -7.5 to -10.0, similar to the thick (>10-12 km) Ouachita Carboniferous turbidite flysch sequence (ε(Nd) -7.5 to -9.6). The remarkable isotopic homogeneity of sediments delivered to the Ouachita-Appalachian region over this period implies extremely effective mixing and dispersal processes on a large (continent-wide) scale, consistent with a collisional belt provenance. A long-lived (ca. 150 Ma) tectonic link between the Appalachians and Ouachitas is thus implied by these data. Mississippian silicic ash-flow tuffs have trace-element and Nd isotopic compositions consistent with a continental-margin arc source. The active volcanic arc which erupted these tuffs apparently extended at least 1000 km from the Ouachita region to south of the Marathon region, but did not supply a significant component of the flysch. The data are consistent with submarine fan models of Ouachita flysch sedimentation demonstrating dominantly longitudinal transport down the axis of a Carboniferous remnant ocean basin from sources to the east. A model is proposed for the evolving Ouachita-Marathon suture between Laurentia and Gondwana, expanding upon Graham et a1. (1975), whereby dominantly Appalachian-derived seafloor detritus was swept up along the flanks of an approaching arc-trench system into sUbduction complexes and recycled incrementally along the length of the collision zone into the Marathon region.

The objective of this research is to develop a theoretical Structural Impairment Detection System (SIDS) for timber railway bridges. Due to fatigue, the timber stringers in timber railway bridges develop shear cracks. These shear cracks lead to higher bridge deflections, higher stresses in the stringers and rail, and shorter fatigue life of the system. A SIDS is proposed which links wheel path accelerations obtained from traversing freight cars to the condition of the bridge. In order to develop the SIDS, two models of timber railway bridges with various levels of structural impairment were developed. The first model was a quasi-static model developed from classical beam theory and implemented in MATLAB. The second model was a dynamic, finite element model created in LS-DYNA. Traversing axle loads were imposed on the models. The results obtained from the model were the wheel paths the axles take as they traverse the bridge. The paths were expressed as vertical displacements as a function of position on the bridge. Wheel path accelerations were obtained by numerically differentiating the vertical displacements. The accelerations were then used to train neural networks to have an input of an acceleration vector and an output of a bridge condition vector. The neural networks were trained on results from both models under three train speeds: 40 mph, 30 mph, and 20 mph. The networks were able to determine the correct bridge condition 90% of the time when the train speed was 40 mph and 70% of the time when the train speed was 30 mph. The networks were not successful in determining bridge condition when the train speed was 20 mph.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 113-116). Also available in electronic version. Access restricted to campus users.

No description available.

No description available.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 266-270).

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 70-74).

No description available.

published_or_final_version / Civil Engineering / Master / Master of Science in Engineering

published_or_final_version / Civil Engineering / Master / Master of Philosophy