The ongoing project to build a new road between Aguachica and Cúcuta, in the Andes region of Colombia, includes the design of multiple bridges. Due to the complex topography of the site and the magnitude of the valleys, composite decks consisting of a concrete slab on top of steel I-girders have been proposed.
Six of these bridges were designed by Pedelta. They are continuous span bridges with typical span lengths of about 40 m. In all six cases, due to the existing limiting factors, the metal structure of the deck is conceived to be incrementally launched from one of the abutments. Temporary shoring towers are necessary in some cases to launch the deck. The concrete slab is to be built once the deck is launched.
The bridges were designed according to AASHTO LRFD. Applicable seismic design specifications as well as specifications related to the incremental launching construction method (applicable to the launching of the metal structure of the deck) were also considered. A detailed 3D model of the deck was developed, which included the effect of the concrete slab and the intermediate and support diaphragms as well as the construction phase.
In order to increase the efficiency of the resistant mechanisms of the bridges against seismic loading, seismic isolators were added between the superstructure and substructure of the bridges. The use of such devices increased the fundamental period of the structures in the horizontal directions and thus reduced (considerably) the seismic loads to be considered for the design of their substructures.