Temporary formworks as torsional bracing system for steel-concrete composite bridges during concreting of the deck

Sammanfattning: A critical stage for the construction of steel-concrete composite bridges occurs during casting of the bridge deck, when the wet concrete has still not hardened. The entire construction load is then taken by the non-composite steel sections. Bracing may be needed to make the slender girders rigid enough to resist lateral torsional buckling during this phase. If temporary formwork could be attached and be shown to work as torsional bracing; material could be saved and the construction phase could be safer. Within this thesis some of the commonly used temporary formworks are described and analyzed to see if some of them could work as discrete torsional bracing. Findings from this investigation were that the often used formwork system CUPLOK was easy and suitable to be modified and attached to the girders as discrete torsional bracing. With the modified CUPLOK system attached, three different systems were numerically analyzed using the finite element program Abaqus. One with formwork attached to a laboratory test beam set-up with dimensions according to Mehri and two on real bridges with trapezoidal respective I-girder cross section. Findings from analyzes were that with the modified CUPLOK system attached, the stiffness were increased dramatically on the slender I-girder system and also, but relatively less, on the less slender real bridge I-girder system. No stiffening effect was shown on the specific trapezoidal cross section analyzed herein. Finally the findings are discussed and further research proposed.