Report No.: CCEER-00-3

Title: Shake Table Testing of Flared Bridge Columns With Steel Jacket Retrofit

Authors: B. McElhaney, M. Saiidi and D. Sanders, D

Date: January 2000

Sponsoring Agency: Nevada Department of Transportation (NDOT)

Performing Organization:
Department of Civil Engineering/258
University of Nevada, Reno
Reno, NV 89557


A study incorporating experimental and analytical investigations was performed. The objective of the experimental research was to evaluate the seismic performance of reinforced concrete bridge columns with structural flares and a steel jacket retrofit design for these columns. The objectives of the analytical portion of the study were to: 1) explain the behavior of the column observed during testing, 2) evaluate the validity of the analytical methods by comparing the calculated results to the measured data, and 3) assess the effect of the steel jacket retrofit by comparing experimental data from as-built and retrofitted test specimens.

The prototype column was from a viaduct located on U.S. 395 in Reno, Nevada. It was designed in 1979 in accordance with the 1977 AASHTO Standard Specifications and the 1978 Interim Specifications. Two thirty-percent scale models were constructed and dynamically tested on one of the shake tables at the University of Nevada, Reno. One specimen represented the as-built details and one was outfitted with a steel jacket incorporating an intermediate gap. The two columns were subjected to the Sylmar record of the January 17, 1994 Northridge earthquake. The testing program consisted of multiple motions with gradually increasing intensity of shaking. Testing was performed in the strong direction under nominally constant axial load.

The analysis included: estimating lateral load-deflection relationships, calculating displacement histories and hysteretic responses, and performing a shear analysis using various methods of calculating shear capacity. Also, tie bar strains and other aspects of column behavior observed in the as-built and retrofitted specimens during testing were compared and discussed