SEISMIC ASSESSMENT FOR A PRETENSIONED, ROCKING BRIDGE DESIGNED FOR RAPID CONSTRUCTION

Abstract eng:
A new bridge system has been developed to: 1) reduce on-site construction time by using precast components, 2) eliminate major earthquake damage by utilizing column rocking and confinement of the column ends with a steel tube, and 3) maintain the system functionality after a strong earthquake by minimizing residual drift through the use of pretensioned strands in the columns. A two-span, three-bent complete bridge using the new system has been tested at 25% scale on the shaking tables at the University of Nevada, Reno. The bridge was designed to have the same overall geometry, added mass, and lateral strength of a previously tested, cast-in-place bridge. The residual drifts were almost zero for all tests even after peak drifts more than 12%. At over two times the design load, the concrete damage consisted of a small number of hairline cracks and cosmetic spalling, while many of the reinforcing bars fractured but not the pretensioning strands. The prestressing strands remained elastic up to 3% drift, as intended. The damage to the cast-in-place structure included residual drift, major concrete spalling, spiral fracture, and buckling and fracture of the longitudinal bars.

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