Deflection controlled prestressed concrete beams

The new SAA concrete structures standard and the new NAASRA bridge design code have been written in parallel and both utilise limit state design philosophy. Because partial prestress is now allowed, new limits can be set for serviceability and this paper discusses an experimental verification of those theoretical new limits for a widely used type of small to medium span bridge. A 12.3 M prestressed precast plank beam has been designed which achieves a span to depth ratio of 32. For a simply supported, deflection controlled beam carrying a large live load this fully utilises the cross section available, and will thoroughly test the present code limits, including fatigue. No topping slab is required for strength, and deflections are intended to be well enough controlled for the beams to directly provide the running surface of the road. Four of these beams have been cast at humes (WA) and this paper reports on the design and results of the experiment to date (a).