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An Investigation of Partial Isolation of Short Bridge Columns
Dowell, Robert K.Valdes, JulioMehrabadi, Morteza Monte
xii, 71 pages
Seismic design of bridges has been improving as failures due to seismic events are studied in detail. Shear failure of a structural member is a well-known failure type. Preventing shear failure of short bridge columns is the general idea of this thesis. A column is considered "short" if the failure is dominated by shear deformations rather than flexural deformations. Seismic isolation is an option for design of a structure to control the force and displacement demands from static and dynamic loads. In most cases, isolation systems are placed on all columns (i.e., full isolation). In fact, the main codes used for the design of seismic-isolated bridges center on full isolation; there is not a specific code developed for partial isolation of bridges. However, performance may increase significantly if only critical columns, i.e., short bridge columns, are isolated. This study therefore focuses on partial isolation of bridge structures, particularly isolation of the short end columns of a typical, continuous, multi span bridge. A case study of a partial isolated bridge is investigated. Design of the bridge columns and the isolation systems are made, and nonlinear time-history analyses are conducted. The main finding from the analyses is that the design level shear forces of the short columns are reduced by a ratio of about seven (relative to the case where the short columns are not isolated). An increase in the displacement capacity of the system was also found, for the case of partial isolation. This thesis contributes to current bridge design procedures with proved effectiveness of partial isolation of short bridge columns.
Civil, Construction, and Environmental Engineering
Master of Science (M.S.) San Diego State University, 2015
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