INFLUENCES OF THE INCREMENTAL LAUNCHING CONSTRUCTION METHOD ON THE SIZING OF PRESTRESSED CONCRETE BRIDGE DECKS

The construction of a prestressed concrete bridge deck in a fixed form work; placed behind an abutment with incremental launching of the deck as it is gradually built - a process at first sight comparable to a c adenced extrusion - is a very competitive technique for a wide range o f deck spans and sizes, During launching, the movement of the support sections produces transitory stresses that affect the sizing of the de ck and increase the consumption of materials, Although materials are o nly one component of the overall cost of the deck, and the casts assoc iated with the particular building technique used are often much more significant when comparing different alternatives, correct pre-estimat ions of cost cannot fail to take into account this tendency to oversiz e with respect to service requirements. A comparison of the main dimen sions of the cross sections of decks built by incremental launching wi th those built by alternative techniques provides an opportunity to il lustrate the effects on structural sizing, and data interpolation may help in pre-sizing new structures.