3D Printed Bridges

Recently, a couple of firms have created short pedestrian bridges built with robots. The company MX3D created a steel bridge that was printed by a robot (with the help from ARUP and Autodesk). The bridge was built off-site and it will be carried to a river in Amsterdam where it will be assembled. The original design was to be printed at the site but it was so complicated they had trouble analyzing (or building) it. They scaled back their ambitions slightly for this somewhat more practical design (photo of steel bridge by Adriaan de Groot).

A similarly organic-shaped bridge was printed using microfibers and cement as ink. However, unlike the steel bridge, the concrete bridge has already been assembled on site in Alcobendas (northeast Madrid). The bridge was designed by the Institute of Advanced Architecture of Catalonia (IAAC) and constructed by Acciona using a machine that was designed and built by D-Shape (photo of concrete bridge by IAAC).

Both bridges turned out to require much more work (and more money) than was originally anticipated. However, such struggles should be expected when developing new technologies. What it means for me and other human bridge engineers is less certain.

Humboldt County Bridges: Highway 101 Bridge across the Eel River at Rio Dell

September 2013 (40.50967, -124.12001) Eel River Bridge

The Eel River Bridge (04 0016R) was built in 1940 with an unfortunate geometry, structure-type, and design for the site. It was originally a three span Pratt through truss bridge, but log jams during floods caused so much damage that the third truss span (and most of the girder spans) had to be replaced in 1964 (see photo below).

The piers were so vulnerable due to earthquakes that lead-rubber isolation bearings were eventually placed between the piers and bearings (in 1986) to reduce the inertia forces from the heavy truss spans.

Also, the remaining through truss spans were constantly in need of repair due to oversize loads damaging the cross-bracing (see photo below).

This bridge is now 78 years old, but it needed constant work to remain in service.