World's Longest 3D-Printed Bridge Takes Shape
According to reports, construction is finally underway for what is being dubbed as the world’s longest 3D-printed pedestrian concrete bridge.
The “Bridge Project” is being co-commissioned by the Dutch Directorate-General for Public Works and Water Management (Rijkswaterstaat), Eindhoven University of Technology (TU/e) and designer Michiel van der Kley.
About the Project
Through a collection of project and designer blogs, van der Kley reported that construction on the project was originally slated to begin in May 2019 after the idea was spurred in his studio while the top of the Ministry of Infrastructure and Environment was visiting. According to the post, the former Director General, Jan Hendrik Dronkers, got so enthusiastic about the 3D printing process that he challenged van der Kley to design the structure, in addition to a bicycle tunnel that could be 3D printed.
In tackling the bridge first, van der Kley enlisted Summum Engineering to handle the parametric modeling, in order to elaborate and rationalize the freeform geometry he designed, in addition to Witteveen+Bos. BAM and Weber Beamix were selected for the physical printing, while Dywidag-Systems International was selected for prestressing.
12.03.2020 > Bridge Project by Michiel van der Kley, a concrete 3D printed bridge of 29 meters length. The bridge, which is 3D printed in about 30 parts, will this summer be located in the city of Nijmegen - see more at https://t.co/uQhp9YXUFE pic.twitter.com/9UFlCkslSU— Dutch Design Daily (@DDD_Daily) March 12, 2020
However, the structure also needed a destination location for its completion. Slated to be placed in Nijmegen, The Netherlands, the city was named the Green Capital of Europe in 2018 and wished to have an eye-catching and iconic memento of that year.
To break away from traditional building methods, van der Klay explained that as part of the Bridge Project he was looking for designs that would otherwise be impossible.
“Most concrete constructions are being made with the aid of molds,” the designer wrote on his website. “The molds are not only expensive, but they are also partly responsible for a bigger uniformity.”
However, molds are not used in 3D printing methods and are instead built by stacking materials layer by layer. Additionally, 3D printing allows objects to be constructed piece by piece and then assembled. Both of these elements of 3D printing create vast opportunities to add variety to structures.
In the early stages of modeling the structure, Witteveen+Bos used specifications laid out by researchers from TU/e, which allowed the bridge's geometry to be generated, observed, and assessed for any structural constraints.
From there, three types of outputs were determined: first, exterior surfaces of the segmented bridge as input to the Revit-model and 2D drawings by Witteveen+Bos; second, meshes, including of the internal geometry, as input to their finite element calculations in DIANA; and, third, printing paths for the 3D printers of TU/e, and later BAM and Weber Beamix, based on their printing specifications.
Currently, the pieces are being constructed in Dukenburg, within the city of Nijmegen. Once completed, the bridge will measure 29-meters-long (roughly 95 feet).
Other 3D-Printed Bridges
In August of last year, Guinness World Records named the world’s longest 3D-printed concrete bridge in Shanghai’s Baoshan district. The bridge was built in 2019 by a team from the Tsinghua University School of Architecture.
The 26.3-meter-long, 3.6-meter-wide, concrete bridge was completed Jan. 12, 2019, in the Wisdom Bay Industrial Park. The project was designed and developed by a team under professor Xu Weiguo and was jointly built with the Shanghai Wisdom Bay Investment Management Company.
The bridge’s design structure is modeled after the ancient Anji Bridge in Zhaoxian, China, and adopts a single arch. The distance between abutments in 14.4 meters. According to the university, before the printing process began, a 1:4 scale physical model was built to carry out the structure failure testing, which proved the bridge’s strength can meet the load requirements of holding pedestrians crowding over the whole bridge.
All of the components of the bridge were printed in 450 hours (about 19 days). (The 1,400-year-old Anji Bridge, took more than 10 years to build.) The printing materials of these components are all composite materials composed of polyethylene fiber concrete with various admixtures.
That same year, materials company DSM, engineering firm Royal HaskoningDHV and 3D printer manufacturer CEAD reportedly collaborated to produce a design for a 3D-printed pedestrian bridge made of a composite material.
According to The Architect’s Newspaper, all three Dutch organizations worked together. The 3D printer used can continuously produce glass- or carbon-fiber-reinforced thermoplastics.
The material intended for use in the prototype is composed of a high-performance engineering plastic, with continuous glass fibers added during the 3D printing process.
To produce the bridge, the teams are used CEAD’s CFAM Prime printer, which can make sections up to 13 feet by 6-and-a-half feet by 5 feet. The Architect’s Newspaper went on to specify that while large-scale printers have previously been used to produce formwork molds, which then can be used to make structural components, the 3D printer being used in this project can eventually potentially produce entire bridges.
The designers hoped that the fiber-and-plastic components would be able to better withstand weather. When used in larger structures, plastics can face a brittleness problem, however.
In 2018, the world’s first 3D-printed metal pedestrian bridge was reportedly ready for installation in Amsterdam. At the time, the structure was on display at Dutch Design Week.
The pedestrian-cyclist bridge, designed by Joris Larmaan Lab with structural engineering help from Arup, is 6.3 meters (just over 20 feet) wide, MX3D said, and would be installed over the Oudezijds Achterburgwal, a well-known Amsterdam canal. Steelmaker ArcelorMittal provided metallurgical guidance on the project.
The 12.5-meter-long stainless-steel span took six months to craft, according to MX3D. The firm first announced the bridge project in 2015 and revised its design between 2016 and 2017 after initial testing. The full span was completed in April. The bridge was also made with a steel deck to add additional stability.
Multi-axis industrial robots and specific MX3D software informed and guided four machines in printing the bridge. The design currently weights 4,500 kilograms (roughly 9,920 pounds) and uses 1,100 kilometers of wire. In light of this new kind of construction, a new safety standard was developed, for which the bridge manufacturer worked with Amsterdam officials, while also collaborating with partners from the Alan Turing Institute. The bridge was also equipped with sensors to read bridge traffic and structural integrity.