Date of Award
M.S. in Engineering Science
Ahmed Al Ostaz
The 2020 ASCE infrastructure report card has assigned a letter grade of D- for bridges in Mississippi based on poor to fair condition ratings with many approaching the end of their useful service lives. Bridges in northern Mississippi lie up to 100 miles from the New Madrid Fault and fall into the Region 3 Seismic Performance Category defined by AASHTO. The primary objective of this study is to evaluate the performance of commercially available bridge bearings on a common bridge pier type used in northern MS under the combined action of superstructure gravity and lateral seismic loads. The use of bearings as seismic isolation devices to limit the inelastic deformations in bridge substructures is a common practice in high seismic regions (Region 4) but their benefits in moderate ones (Region 3) have not been fully explored in MS. Analytical formulations under lateral load at the bearing levels are first used in the study to characterize modal characteristics and response of the bearing/pier subsystem idealized as a 2DOF oscillator. Effective linear properties of the bearing/pier system defined based on AASHTO provisions are used to determine expected overall behavior. Non-linear pushover analysis is then performed of an existing two-column pier recently designed to satisfy AASHTO criteria. The pier is modeled as a frame using beam and link elements available in a commercial finite element software (SAP2000). The analysis is used to capture the plastic hinge formation sequence, damage limit states in potential hinge locations, and the overall frame response up to the formation of a collapse mechanism. Lastly, non-linear time history analysis is performed using the software to obtain lateral deck/pier displacement histories in the transverse direction. The effectiveness of two common isolation bearings (laminated rubber and disc type) in isolating the pier from the deck motion and reducing the base shear is then demonstrated.
Joshi, Hemant Raj, "EFFECTIVENESS OF SEISMIC BEARINGS ON A TYPICAL ISOLATED TWO-COLUMN RC BRIDGE PIER LOCATED IN NORTH MISSISSIPPI" (2021). Electronic Theses and Dissertations. 2018.