Fatigue assessment of bridge members based on in-service stresses - final report (FHWA-OK-97-06) 2196

Abstract

This report summarizes research activities which are described in detail in interim reports entitled "Field Tests, Analyses, and Laboratory Tests" [Zwerneman et al., 1996], and "Data Acquisition System for Strain Measurements" [Zwerneman et al., 1997]. These two interim reports cover two distinct phases of the research project entitled "Fatigue Assessment of Bridge Members Based on In-Service Stresses." This research was undertaken to (1) evaluate the fatigue life of a specific highway bridge on which poor welds had been applied, and (2) construct a system for measurement of strains on an in-service highway bridge. The second part of the project includes demonstrating a procedure for using the measured strains to estimate remaining fatigue life and establish inspection intervals. Results of the first part of the project have been implemented to reduce the cost of repairs on the evaluated bridge, and results of the second part will be implemented to improve the accuracy of future bridge assessments. The data acquisition system constructed in the second part has been turned over to the Oklahoma Department of Transportation (ODOT) for operation by ODOT personnel. ODOT personnel worked with the researchers to install and operate the system for three load tests on in-service bridges. ODOT personnel also worked with the researchers to evaluate the remaining fatigue life for one of the tested bridges. Using the data acquisition system and the data evaluation procedures developed in this project, ODOT personnel will be better able to manage bridge repair and replacement needs for the future. The data acquisition system and evaluation procedures developed in this research project have the potential to provide benefits far above the cost of development and implementation. Cost savings result from improved fatigue life estimates, more accurate load ratings, and the ability to set intervals for fracture critical inspections on the basis of measured rather than computed stresses.