Self-Centering, Low-Damage Precast Composite Steel-Concrete Columns for Accelerated Bridge Construction in Seismic Regions: Shake-Table Tests and Numerical Modeling

Abstract eng:
An innovative bridge column technology for application in seismic regions has been developed at the University of California, San Diego, in collaboration with the Pacific Earthquake Engineering Research Center. The proposed technology combines a precast composite steel-concrete hollow-core column, with post-tensioning and supplemental energy dissipation. Seismic resilience is enhanced in the form of self-centering capability, facilitation of structural fuse repair, and minimization of damage to the main structural elements. The precast hollow-core column consists of two concentric cylindrical steel shells, with concrete sandwiched in between. The shells act as permanent formwork, the outer one substituting the conventional reinforcing cage by flexure and shear resistance as well as acting as confining reinforcement, and the inner shell preventing concrete from imploding. These features are aimed at improving constructability and reducing on-site construction burdens, thus making the technology suitable for accelerated bridge construction. Large inelastic rotations can be accommodated at the end joints with minimal structural damage: gaps are allowed to open in tension at these locations and to close upon load reversal. Post-tensioned longitudinal bars induce self-centering behavior in combination with gravity forces. Elastomeric pads, placed in series with the post-tensioning bars at their anchorages, protect them from yielding. Specifically designed steel devices across the joints provide energy dissipation by axial hysteresis. High-performance grout and headed reinforcement are used to prevent premature crushing of the mortar joints, required by construction tolerances. This paper summarizes the results obtained from dynamic shake-table tests, as well as from numerical simulations carried out in OpenSees. The superior performance of the proposed technology is also compared to that of conventional reinforcedconcrete columns.

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