Structural modification of Bascule bridges for noise mitigation

Noise mitigation and enhancement of skid resistance on Bascule bridge decks, including bridges, pose a considerable challenge. Typically measured noise levels that vary from 60 to 70 dB(A) need to be reduced to eliminate public concern. The objective of this investigation was to find possible modifications to the structure of the open grid decking to reduce the radiated noise from the bridges and at the same time to improve the skid resistance. This study was complementary to the acoustic testing completed in September 1994 at Florida Atlantic University. Deck panels infilled with different types of lightweight infill material for noise mitigation, were tested for fatigue performance and abrasion characteristics. The computer software ANSYS was used to model the grid panel and analyzed for different depths of concrete infill to evaluate the composite action between the infill concrete and the grid panel. A typical case study on counterbalance dynamics of an infilled deck for the Sunrise Boulevard Bridge, included horsepower requirements, trunnion bearing and bending stresses, and flexural strength adequacies of the stringer and floor beams. Skid resistance values for twelve bridges from E-274 and G-analyst measurements were compared for dry and wet conditions, and accident statistics compiled for the period 1988-1992. The cost analysis of identified options was carried out.