Bridges

Barkers Bridge (S/B) over Run O’Waters Creek on the Hume Hwy, featuring four 12.2 m simply supported spans with precast concrete planks, had encountered significant structural issues. Designed around 1957 and constructed in 1971, the bridge comprises precast, pre-stressed concrete planks with in-filled shear keys, spanning an overall width of 10.54 m and a skew of approximately 45°. Each span consists of seventeen precast pre-stressed concrete planks, transversely tensioned with three Macalloy bars per span, matching the bridge’s skew. These planks rest on elastomeric bearing strips atop reinforced concrete piers and abutments.

The bridge exhibited longitudinal cracking, uplift at slab corners, uneven bearing and partial bearing dislodgement. Defects suggest the bridge planks were moving independently of one another due to defective shear keys. These issues have been noted since the late 1990’s Structural integrity issues arose from ineffective transverse stressing bars, leading to plank displacement and shear key material breakdown. Various rehabilitation options were considered, including external post-tensioning system, core drilling for new Macalloy bars, and adding a new 180 mm thick in-situ concrete deck slab. The latter option was initially adopted but abandoned due to traffic management and Work Health and Safety (WHS) constraints. Subsequent efforts included installing transverse steel beams under the planks, clamped to the kerb and epoxied with soffit, but these failed due to sagging and epoxy debonding. The final solution entailed installing 530 x 250 x 15 mm plates between the planks at the deck’s top, embedded with AC, and mechanically clamping the planks via 26 mm drilled holes. This method successfully rendered the deck composite and addressed the structural issues.

Despite numerous design changes and challenges, the project preserved the bridge’s structural integrity without requiring temporary closures or load limits. The solution provided a durable, safe, and composite deck, ensuring continued serviceability of Barkers Bridge while minimizing traffic disruption.