Evaluation of Finger Plate and Flat Plate Connection Design.

摘要

This project investigates the cause(s) of premature deterioration of MoDOT finger plate and flat plate expansion devices under high traffic volumes and then uses that information to design new Load and Resistance Factor Design (LRFD) finger plate and flat plate designs that are intended to last 40 years or more with minimal maintenance. To fully evaluate the expansion devices, a literature review and survey of current expansion devices used by transportation departments across the United States was conducted. The failure of the finger plate expansion devices were found to be contributed primarily to fatigue failure of the weld between the finger plate and the support beam beneath it as well as vertical misalignment due to poor construction. The flat plate expansion device was found to perform inadequately if the bridge span experiences rotation causing a gap between the sliding flat plate and the support angle or if construction of the device is deficient. Experimental testing was conducted on the finger plate device on Eastbound Blanchette Bridge on Highway I-70 in St. Louis and the flat plate device on Route 350 passing over Highway I-435 in Kansas City. The results were also used to validate Finite Element Models (FEMs) of the current expansion device designs. Testing of the finger devices found that dynamic impact in the finger device is generally between 40% and 70% and could be as much as 160% and the effect of misalignment of the fingers can results in 30% additional stresses. Testing of the flat plate device revealed significant stresses build in the sliding plate due to the differential movements of the abutment and bridge span. A robust finger plate device was designed to accommodate bridges which require large expansion lengths on high large volume routes. In addition suggestions for improvements of the existing finger plate device design were made for use on routes with lower traffic volumes. Repair and replacement best practices and details were also developed as part of this project