Report No.: CCEER-94-3
Title: Summary of Pretest Analysis of Cazenovia Creek Bridge
Authors: Bruce M. Douglas, Emmanuel M. Maragakis, and Shiping Feng
Date: April 1994
The National Center for Earthquake Engineering Research
National Science Foundation
New York Department of transportation
Department of Civil Engineering
University of Nevada, Reno
Reno, Nevada 89557
As part of a study to evaluate the basic dynamic characteristics of the southbound bridge of Cazenovia Creek, a detailed parametric study was carried out and is described in this report.
A 3-dimensional analysis model was developed for the modal analysis of the bridge. Also a simple model was constructed for the analysis of the bridge. For the evaluation of the influence of the soil stiffness at the foundation, 8 soil stiffnesses were employed in the modal analyses for both the 3-D and the 2-D models. Finally, for considering the effect of the actual state of the bridge, two further modifications were made in the 3-dimensional model.
The transverse frequencies of the 3-D model and the 2-D model were compared and the difference in frequencies of two models were less than 10 percent for all the comparisons. The influence of the soil stiffness on the dynamic behavior of the bridge should be considered when the soil stiffnesses are less than 10 times the standard value. In the pretest parameter study, the frequencies of both the cracked and uncracked structure were calculated. The properties in the cracked structure had more influence on the fundamental frequency than the other frequencies.
Three loading cases were performed in the parameter study. In the first loading case, two concentrated loads of 150 kips each were horizontally applied to the 1/3 points of the bridge. In the second case, 150 kips were applied to one 1/3 point of the bridge. In the third case, a load of 150 kips was applied to the abutment. The participation factors, displacement and acceleration time histories corresponding to these three loading cases are discussed in the report (Abstract by authors).