Browsing by Subject "Finite element modeling"
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Item Finite element analysis of wood shoring towers used in Urban Search and Rescue(2012-12) Blair, Robert Stevenson; Wheat, Dan L.; Engelhardt, Michael DThis thesis focuses on the finite element modeling and analysis of wood shoring towers used by Urban Search and Rescue (US&R) teams during emergency response situations. These shores are constructed on site to provide temporary stabilization to a damaged structure. A high demand exists for experimental testing of the performance of these shores under non-ideal loading conditions, and for possible design modifications that could improve their overall behavior. To respond to this need, a total of thirteen vertical shores of the type laced post (LP) and plywood laced post (PLP) were constructed and tested at the Ferguson Structural Engineering Laboratory (FSEL) in Austin, Texas. The tests conducted on these shores aimed to investigate their performance under purely vertical load as well as various combinations of vertical and lateral loads. Finite element models for eight of the shores tested at FSEL were built and analyzed in Abaqus to compare the computed results with the actual linear elastic response of the shores. Material properties for the posts in each shore were obtained through further material testing at the conclusion of each shore test. Shore members were assumed to be isotropic. Solid elements were used to model each member, and Cartesian connector elements with a predefined nonlinear stiffness were used to model each nail. In general, the vertical load-displacement response computed from Abaqus exhibited good agreement with the laboratory results for the linear elastic range. The same general modeling scheme was then used to make design changes to the original shores based on observations gained during testing as well as modeling. Each design change was modeled, analyzed, and then compared with the computed results from the original shore design as well as the other design changes. The basis for evaluating the effectiveness of a given shore design involved comparing the bending moment diagrams for each post and the maximum first story nail slips (connector displacements). Recommendations were made for improved shore designs to be verified by experimental testing.Item Finite element modeling of twin steel box-girder bridges for redundancy evaluation(2010-05) Kim, Janghwan; Frank, Karl H.; Williamson, Eric B., 1968-; Tassoulas, John L.; Wood, Sharon L.; Mear, Mark E.; Helwig, ToddBridge redundancy can be described as the capacity that a bridge has to continue carrying loads after suffering the failure of one or more main structural components without undergoing significant deformations. In the current AASHTO LRFD Bridge Design Specification, two-girder bridges are classified as fracture critical, which implies that these bridges are not inherently redundant. Therefore, two-girder bridges require more frequent and detailed inspections than other types of bridges, resulting in greater costs for their operation. Despite the fracture-critical classification of two-girder bridges, several historical events involving the failure of main load-carrying members in two-girder bridges constructed of steel plate girders have demonstrated their ability to have significant reserve load carrying capacity. Relative to the steel plate girder bridges, steel box-girder bridges have higher torsional stiffness and more structural elements that might contribute to load redistribution in the event of a fracture of one or more bridge main members. These observations initiated questions on the inherent redundancy that twin box-girder bridges might possess. Given the high costs associated with the maintenance and the inspection of these bridges, there is interest in accurately characterizing the redundancy of bridge systems. In this study, twin steel box-girder bridges, which have become popular in recent years due to their aesthetics and high torsional resistance, were investigated to characterize and to define redundancy sources that could exist in this type of bridge. For this purpose, detailed finite element bridge models were developed with various modeling techniques to capture critical aspects of response of bridges suffering severe levels of damage. The finite element models included inelastic material behavior and nonlinear geometry, and they also accounted for the complex interaction of the shear studs with the concrete deck under progressing levels of damage. In conjunction with the computational analysis approach, three full-scale bridge fracture tests were carried out during this research project, and data collected from these tests were utilized to validate the results obtained from the finite element models.