Bridges, Tunnels and other Transportation Structures
This presentation evaluates the seismic performance of bridges with hybrid sliding-rocking (HSR) columns and skew-angled seat-type abutments using computational simulation models. HSR columns are segmental columns including end rocking joints and intermediate sliding joints distributed over the column height. The rocking joints and the sliding joints provide these columns with self-centering and significant energy dissipation, respectively. The seismic performance of skewed HSR bridges is compared to that of similar bridges with cast-in-place monolithic columns.
Bridge abutments often need to be skewed (i.e. having angles different than 90 degrees from the longitudinal axis of the superstructure) to accommodate misalignments of the crossing roads/waterways. The superstructure of skewed bridges with seat-type abutments is, however, considerably prone to rotation around the vertical axis during earthquakes, causing significant damage to substructure systems and often leading to abutment unseating. In such cases, conventional concrete columns sustain substantial shear/torsional-induced damage, often leading in bridge partial or complete replacement.
Compared to conventional columns, past shake table tests on HSR bridges together with computational simulations have implied that using HSR columns can reduce both the substructure damages and residual displacements. Specifically, properly designed sliding joints can accommodate a portion of the torsional rotations, which can reduce the respective damages in the HSR columns. Positioning the unbonded post-tensioning strands around the column cross-section also introduces torsional self-centering into the HSR columns, thereby decreasing the deck’s residual displacements caused by its rotation.
In order to evaluate the seismic performance of skewed HSR bridges, their responses under multiple far-field earthquakes, scaled to different hazard levels, are examined in terms of peak and residual displacements; abutment damages (e.g. shear key and bearing pad fracture); abutment unseating; and column damages (e.g. concrete crushing and spalling; shear cracking; rebar yielding and buckling; and post-tensioning tendon yielding and fracture). For this purpose, three bridge archetypes are selected: (1) a two-span bridge with a single-column bent; (2) a two-span bridge with a two-column bent; and (3) a three-span bridge with two single-column bents. To explore the effects of the skew angles, for each bridge archetype, the skew angles of 0, 15, 30, 45, and 60 degrees are considered. Moreover, for each bridge configuration, to allow comparison of their performances, the analyses are performed, first using HSR columns, and, subsequently, considering conventional monolithic columns. All the analyses are conducted using 3D models in the structural analysis software OpenSees, where the HSR columns are simulated using a recently-developed flexibility-based element representing HSR joints, accounting for rocking and sliding, including torsional sliding.
• The presentation is beneficial to both bridge engineering practitioners and academic researchers.
• Considering the large number of structurally deficient bridges in the U.S. and worldwide that need replacement and also the fast growth of the road networks, the presentation’s topic is of regional, national and international interest.
• The audience will be familiarized to a novel Accelerated Bridge Construction system for seismic regions, its advantages over conventional bridge systems when used with skew-angled seat-type abutments, as well as novel bridge simulation techniques.