Report No.: CCEER-95-7

Authors: S. Acharya, M. Saiidi, and D. Sanders

Date: November 1995

Sponsoring Agency: Nevada Department of Transportation

Performing Organization:

Department of Civil Engineering/258

University of Nevada, Reno

Reno, NV 89557

Abstract:

This study presents analysis and testing of 0.4-scale as-built and retrofitted reinforced concrete column-footing models under a constant axial load and cyclic lateral displacements simulating earthquakes. Focus was on spread footings and column-footing connections.

The as-built model testing indicated that (1) the footing had insufficient flexural capacity with early strength degradation; (2) cracks on top of the footing appeared early; (3) computed soil-pressure underneath the footing was higher than the allowable pressure.

The retrofit measures included (1) increasing the footing dimensions to improve flexural capacity and soil-pressure under it, and providing a reinforced concrete overlay to minimize cracks; (2) confining the column potential plastic hinge region and enhancing its shear strength using a steel jacket; (3) providing a steel moment-connection between column and footing using a steel base-plate. Test showed that the retrofitted footing performed very well, and the base-plate yielding was associated with stable hysteresis loops and large energy dissipation (Abstract by authors).