Suspension bridge response due to extreme vehicle loads

Abstract

A 269 tonne trailer travelled across the Tamar Suspension Bridge in October 2010, and the authors monitored the response of the structure to the load. The following investigation documents the deflection of towers and the deck during the vehicle's passage, as well as the change in cable tensions. This was achieved by studying monitored data from the bridge collected by accelerometers and strain gauges attached to the stay cables, as well as two robotic total stations that measured the deflection of the mid-span and the sway of the tower saddle. These results were subsequently compared to the response predicted by a finite element (FE) model of the bridge, indicating an accurate match. The FE model was also used to simulate the variation of the dynamic response of the structure, which suggests that the natural frequencies vary depending on the vehicle's location to each mode shape's anti-nodes.