MX3D, a Dutch robotic manufacturing technology startup, is celebrating the completion of its revolutionary 3D printed steel bridge. It will soon be installed over a canal in Amsterdam. Creating the bridge required years of design, engineering, and coding. Printed from over 9,000 pounds of stainless steel, the bridge represents an innovative application of this traditional structural material.
Did you ever wonder why so many steel bridges in the United States are painted green? Does aesthetics, practicality, economics, habit, coincidence, or all of the above dictate the choice?
The history of green-colored bridges can be traced to two renowned bridge engineers, David B. Steinman (1886-1960) and Conde McCullough (1887-1947). These two shared a commitment to designing beautiful and artistic structures that blended in with their natural surroundings.
A child of Jewish immigrants, Steinman grew up in New York City where he developed his love of bridges. Also a writer and a poet, Steinman designed and constructed over 400 bridges in his lifetime, including the Henry Hudson Bridge in New York, the Deer Isle Bridge in Maine, and the Mount Hope Bridge in Rhode Island.
Over time, he earned a national reputation for his bridges. Many consider his Mackinac Bridge, connecting the Upper and Lower Peninsulas of Michigan, to be his most significant work, but for him the St. Johns Bridge, one of his first, would remain his favorite.
The Introduction of ODOT Green
In 1929, Steinman first used green paint for the Mount Hope Bridge and soon after for the St. Johns Bridge in Portland, Oregon. Selected over McCullough to design the St Johns Bridge, Steinman chose green to match the area’s lush greenery, trees, and hilly landscape, even though representatives of a nearby airfield wanted it painted with black and yellow stripes to increase its visibility. Steinman painted all of his later bridges shades of green and claimed credit for the concept of painting bridges with colors.
A quiet intellectual, Conde McCullough designed Oregon’s coastal bridges. Combining beauty with efficiency and economy, he helped build over 600 bridges, including the John McLoughlin Bridge, the Astoria Megler Bridge, the Yaquina Bay Bridge, and the Crooked River High Bridge. His bridges blend with the environment by incorporating designs and materials suited for specifically for each project.
While Steinman used varieties of green, McCullough stuck with one particular shade. This shade, now known as ODOT green (named after the Oregon Department of Transportation), has become the standard, and St. Johns Bridge is now repainted in ODOT green. It was renowned for its resemblance not only to the surrounding vegetation, but to the Statue of Liberty’s distinct green shade.
Green Bridges Gain Traction
McCullough first used it by chance on the John McLoughlin Bridge in 1933. When the bridge won an award as the most beautiful bridge of its class, its color on the submission illustration was green but actually it had been painted black. In order to receive the award, the bridge had to be repainted.
Under the influence of these two creative geniuses, the popularity of green-colored bridges spread throughout Oregon and the United States. Light green is the most common color for bridges in northern New England and has become the national standard among bridge engineers. In 1953, the New Hampshire State Highway Department adopted green for use in all structural applications and the originally specified color for Samuel Morey Bridge between New Hampshire and Vermont was sage green.
Maine and Vermont’s regional bridges are painted light green as well. In 1999, New Hampshire began using a darker shade of green, Dartmouth green, for all of its bridges due to the fading of the color over time.
Using this type of paint on steel structures also has practical benefits in certain regions and weather conditions. ODOT green paint cures best in damp weather, making it particularly suited for the climate of the Northwest.
Beyond practicality, the color green’s association with nature, life, renewal, and healing fits in perfectly with bridges, which foster unity and connection.