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Report No.: CCEER-00-7

Title: A Comparison of Static and Dynamic Performance of Models of Flared Bridge Columns

Authors: C. French and M. Saiidi

Date: October 2000

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

Abstract:

The main objective of this study was to explain the differences between the quasi-static and dynamic test results of two scaled models (HS and FA) of the columns in a bridge supported on reinforced concrete columns with structural flares. Specimen HS was subjected to static loading but FA was subjected to dynamic loading. In both models, concrete crushed under compressive forces due to flexure and wide shear cracks were formed. Column HS failed due to low-cycle fatigue of the longitudinal bars whereas FA failed due to the rupture of column ties.

The effects of three variables were investigated:

  1. The loading history
  2. The material and section properties
  3. The strain rate

To determine the effect of the first parameter the hysteretic energy was used as the main indicator. The effects of the second and third parameters were evaluated based the moment curvature relationships and the shear demand over capacity ratios. The study showed that shake table testing of structural elements could lead to results that are different than those obtained from commonly applied slow cyclic loading. The relatively high strain rate during shake table testing in combination with a loading history that is different from static testing could alter the sequence of failure, thus affecting the seismic response.

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