Report No.: CCEER-95-5

Authors: I. Darwish, M. Saiidi, and D. Sanders

Date: September 1995

Sponsoring Agency: Nevada Department of Transportation

Performing Organization:

Department of Civil Engineering/258

University of Nevada, Reno

Reno, NV 89557

Abstract:

This study was undertaken to evaluate the seismic damage susceptibility of column-footing connections in some of the existing bridges in Northern Nevada. The focus of the study was on bridges which were built in the late 1960's and have relatively thin, tapered R/C columns which incorporate steel dowels that were inadequately anchored to columns and footings. Two 0.4 scale models of these columns were built and tested under increasing levels of drift. The two models represented the details of "as-built" columns; one for the fixed bases and the other for the one-way hinged bases.

Results of testing indicated that for both columns, considerable strength and stiffness deterioration occurred as a result of bar slippage and eventual pullout from the footing. This also reduced the energy dissipation capacities of the columns making them vulnerable to strong earthquakes. It is concluded that bridge connections represented by those specimens should be strengthened.

Analysis of the specimens included determining the flexural and shear capacities of the columns using different approaches. Also, bond stress and steel stress distribution along development/splice length were calculated. Generally, the good correlation between measured and calculated results suggest that the analytical models can be used to predict the response of the actual bridge columns (Abstract by authors).