INVESTIGATING THE REMAINING FATIGUE LIFE OF AN AGING ORTHOTROPIC DECK WITH HEALTH MONITORING AND LABORATORY TESTING

摘要

The A. Murray MacKay Bridge is an aging structure which opened to traffic over 40 years ago. With many of our structures aging, the ability to make confident management decisions supported by reliable engineering has become increasingly important. Evaluating existing structures using the design code approach contains uncertainty which affects management decisions. This paper explores an alternate method that used structural health monitoring (SHM) coupled with laboratory testing to reduce uncertainty in these decisions. The MacKay is the first suspension bridge in North America to have an orthotropic steel plate deck (OSPD), which contains three fatigue prone details of interest. A planning decision is required for when to replace the OSPD, thus the remaining fatigue life of the OSPD is needed. During the summer of 2010, sections of the OSPD near the expansion joints on the MacKay were replaced and 29 specimens from the former deck were obtained for laboratory testing. These specimens were subjected to various stress ranges and number of load cycles to obtain the remaining life S-N curve. Concurrently, key details on the MacKay were instrumented with strain gauges to obtain the in-situ strain range from vehicle loads in the deck for a one year period. This paper will discuss the details of the fatigue testing and monitoring program. Early results and preliminary conclusions for both testing and monitoring will be presented, including the reduction of fatigue life due to corrosion. Ultimately, the evaluation method presented brings more certainty to management decisions regarding infrastructure.