DEVELOPMENT OF RATING TOOL FOR PRESTRESSED CONCRETE BRIDGES VULNERABLE TO SHEAR (FHWA-OK-20-01 Revision 1 2280)

Abstract

A study was conducted examining the factors affecting shear capacity and load rating, two potential methods for assessing condition of in-service prestressed concrete bridge girders, and a simple procedure for assessing whether and how a bridge should be rated for shear was developed. First, a detailed literature review was conducted to collect results of experimental shear testing on older prestressed concrete girders and the comparison of those results to capacity calculation methods. This was followed by a parametric study to examine the effect of different design items on load distribution and the difference between AASHTO load distribution equations and grillage models for more than two hundred different bridge configurations. Two methods for assessing condition of in-service girders were examined and further refined. The results of previous shear testing and the grillage model parametric study indicate that there may be conservativism built in when AASHTO load distribution factors are used that leaves open the possibility of increased load ratings for some older bridges. Using a grillage model can increase load ratings, reducing the potential need to load post or take some bridges out of service without sacrificing accuracy and safety. The proposed procedure uses a set of simple criteria to identify bridges potentially vulnerable to shear and modifications to the typical rating procedure to produce an accurate shear rating.