This research evaluates the seismic demands for a three-span curved bridge crossing fault-rupture zones. Two approximate procedures which have been proved adequate for ordinary straight bridges crossing fault-rupture zones, i.e., the fault-rupture response spectrum analysis (FR-RSA) procedure and the fault-rupture linear static analysis (FR-LSA) procedure, were considered in this investigation. These two procedures estimate the seismic demands by superposing the peak values of quasi-static and dynamic bridge responses. The peak quasi-static response in both methods is computed by nonlinear static analysis of the bridge under the ground displacement offset associated with fault-rupture. In FR-RSA and FR-LSA, the peak dynamic responses are respectively estimated from combination of the peak modal responses using the complete-quadratic-combination rule and the linear static analysis of the bridge under appropriate equivalent seismic forces. The results from the two approximate procedures were compared to those obtained from the nonlinear response history analysis (RHA) which is more rigorous but may be too onerous for seismic demand evaluation. It is shown that the FR-RSA and FR-LSA procedures which require less modeling and analysis efforts provide reasonable seismic demand estimates for practical applications.

The natural soils and sedimentary rocks are typically formed by deposition and progressive consolidation of marine sediments. Consequently, they are characterized by the presence of closely spaced bedding planes, resulting in anisotropy in their mechanical behaviour. Among anisotropic rocks, the group of sedimentary rocks known as shales is of a particular interest as it is often the host rock in nuclear waste storage and oil industry. The Tournemire shales are anisotropic in terms of deformability and the failure mode, which means that complex constitutive models should be used to describe their mechanical response. In this thesis a pragmatic methodology based on the notion of a microstructure tensor, as suggested by Pietruszczak and Mroz (2001), has been employed for the description of orientation dependent characteristics of Tournemire shale. This has been combined with a plasticity framework that incorporates an anisotropic deviatoric hardening. The formulation requires identification of several parameters including strength descriptors associated with the failure criterion and constants that are involved in describing the anisotropy and strain hardening. All the material functions/parameters have been identified here based on the experimental results reported by Niandou et al. (1997). Using those parameters, the numerical simulations of a number of triaxial tests were conducted and the results compared with the experimental data in order to verify the performance of the model. After the verification stage, the formulation was incorporated in a commercial FE code (Abaqus/standard) using the UMAT interface and was then applied to a numerical analysis of a tunnel excavation within the anisotropic rock mass. The numerical results, including the distribution of the damage and vertical/horizontal displacements, have been compared for different orientations of the bedding planes. / Thesis / Master of Applied Science (MASc)

The Varina-Enon Bridge is a cable-stayed, precast, segmental, post-tensioned box girder bridge located in Richmond, Virginia. Inspectors noticed flexural cracking in July of 2012 that prompted concerns regarding long-term prestress losses in the structure. Prestress losses could impact the future performance, serviceability, and flexural strength of the bridge. Accurately quantifying prestress losses is critical for understanding and maintaining the structure during its remaining service life. Long-term prestress losses are estimated in the Varina-Enon Bridge using two methods. The first utilizes a time-dependent staged-construction analysis in a finite element model of the full structure to obtain predicted prestress losses using the CEB-FIP '90 code expressions for creep and shrinkage. The second method involves collecting data from instrumentation installed in the bridge that is used to back-calculate the effective prestress force. The prestress losses predicted by the finite element model were 44.9 ksi in Span 5, 47.8 ksi in Span 6, and 45.3 ksi in Span 9. The prestress losses estimated from field data were 50.0 ksi in Span 5, 48.0 ksi in Span 6, and 46.7 ksi in Span 9. The field data estimates were consistently greater than the finite element model predictions, but the discrepancies are relatively small. Therefore, the methods used to estimate the effective prestress from field data are validated. In addition, long-term prestress losses in the Varina-Enon Bridge are not significantly greater than expected. / Master of Science / Post-tensioned concrete uses stressed steel strands to apply a precompression force to concrete structures. This popular building technology can be used to create lighter, stiffer structures. Over time, the steel strands experience a reduction in force known as prestress losses. Accurately quantifying prestress losses is critical for understanding and maintaining a structure during its remaining service life. The Varina-Enon Bridge is a cable-stayed, prestressed box girder bridge located in Richmond, Virginia. Inspectors noticed cracking in July of 2012 that prompted concerns regarding long-term prestress losses in the structure. Prestress losses were estimated using two methods. The first method utilized a computer model of the full bridge. The second method used data from sensors installed on the bridge to back calculate prestress losses. It was found that the prestress losses estimated from field data were slightly greater than, but closely aligned with, the computer model results. Therefore, it was concluded that the Varina-Enon Bridge has not experienced significantly more prestress losses than expected.

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