With more than 20 years of delay, Cerema designs in France the first composite steel&concrete twin girder road bridge with double composite action in hogging areas.

https://www.cerema.fr/fr/actualites/cerema-concoit-premier-pont-routier-double-action-mixte

(Front Image copiright of Cerema)

It is surprising that in France it has taken so many years to start using a typology widely developed in Spain, with IDEAM being the main driver of this solution.
The double composite action has been developed in Spain since the beginning of the 70s in the typology of composite box girders, and it is from the end of the 90s when the typology of the composite twin girder with double composite action on hogging areas has been developed.
IDEAM has been the maximum exponent in the development of this solution, designing and participating in the execution of several tens of bridges with twin girder or multi-girger composiute cross section with double composite action in hogging áreas from the end of the 90s to the present, with typical spans between 50 and 115 m, among which are:

• Retamar Bridge over Guadarrama river, 1998, 70 m span. https://www.ideam.es/ideam_projects/bridges/puente_de_retamar_sobre_el_rio_guadarrama/
• Viaduct over Jarama river, Madrid, 2003, 75 m span. https://www.ideam.es/ideam_projects/bridges/viaducto_mixto_sobre_el_rio_jarama_en_la_r_3/

• Betxi-Borriol bridge, 2005, 64 m span. https://www.ideam.es/ideam_projects/bridges/puente_de_betxi_borriol/

• 5 Viaductos in Mexico D.F., 2005, with a máximum span of 90 m. https://www.ideam.es/ideam_projects/bridges/viaductos_mixtos_en_mexico_df/

• Bridge over the river Sella, 2005, 80 m span. https://www.ideam.es/ideam_projects/bridges/puente_sobre_el_rio_sella/

• Nalón river Viaduct, 2007, 110 m span. https://www.ideam.es/ideam_projects/bridges/a3aa2project_id14project_category_id11/

• Rajadell Viaduct, 2011, typical spans of 70 m and a main span of 100 m. https://www.ideam.es/ideam_projects/bridges/viaducto_de_rajadell/

• Nueno Viaduct, 2013, 60 m span. https://www.ideam.es/ideam_projects/bridges/a3aa2project_id295project_category_id11/

• Viaduct over river Tajus in Talavera de la Reina, 2015, 114 m span. https://www.ideam.es/ideam_projects/bridges/a3aa2project_id316project_category_id11/
• Viaducto over Mularroya reservoir, 2018, 60 m span. https://www.ideam.es/ideam_projects/bridges/a3aa2project_id362project_category_id11/

• Bridge over river Serpis in Gandía, 2019, 59 m span. https://www.ideam.es/ideam_projects/road-composite-bridges/bridge-over-river-serpis-in-gandia/

• Viaducts of the “Urbana Siervo de La Nación” Highway. Gran Canal. México, 2020, with spans up to 75 m. https://www.ideam.es/ideam_projects/bridges/viaducto-3-autopista-urbana-siervo-de-la-nacion-gran-canal-mexico/

• 5 Launched viaducts in “Atizapán-Atlacomulco” Highway. México, under construction, with typical spans of 60 and 70 m. https://www.ideam.es/ideam_projects/bridges/5-viaductos-en-la-autopista-atizapan-atlacomulco-mexico/

In several cases the cross section in sagging areas was closed with isostatic prefabricated bottom slabs without connection to make the section internally accessible for miantenance, and in others this function was achieved with stiffened steel paltes without connecting to the compostite girders or with a tramex. In other cases in sagging areas the cross section remains open without lower closure, as the French have chosen in their first realization, more than 20 years later.