Abstract

Composite structures have not been able to compete in Spain with more conventional prestressed concrete bridges in the lower range of medium spans (30 - 90 m.). In this context, twin-girder sections are revealed as a more competent typology because of its sobriety, ease of construction and good structural performance. At present the optimal character of the designs in structural projects is rarely challenged. The present study undertakes an in-depth analysis of the twin-girder section, involving a complete optimisation for the deck. To this end a specific 2D grillage model has been developed, integrating the composite and evolutive character of twin-girder decks, as well as the instability phenomena inherent to thin-walled structures. Several conclusions are drawn after a parametric calculation using this model, regarding the optimum dimensions of all the variables that define the twin-girder section. These conclusions crystallise in a series of formulas that can be used as a design guide.