SINGAPORE: In 2028, the first pedestrian bridge in Singapore to be constructed using 3D-printing will go across the Jurong River, connecting residents from Jurong West to the new Tengah town where more housing developments have been planned.
The use of the new technology is part of the Land Transport Authority (LTA)’s efforts to improve construction productivity amid labour constraints.
Such 3D concrete-printing technology provides manpower savings of up to 50 per cent due to the use of robotic arms, and cuts the time needed to produce a bridge segment from up to one day to four hours.
The bridge, to be located near Block 410 Jurong West Street 42, measures 10m long and 5m wide.
Research and development work for it started in January 2023, costing about $1.4 million for the development of material suitable for 3D printing, engineering design of the bridge, as well as the production and testing of the scale model, said Mr Allan Yeo, deputy director of street design and infrastructure technology at LTA.
LTA organised a media visit on April 2 to DNV Technology Centre (West) laboratory near Joo Koon, where structural load tests were carried out on a smaller model of the bridge – 10m long and 2.5m wide – using 18 tanks, each filled with one metric tonne of water, to assess the structure’s behaviour.
The load of this new bridge will be equal to that of a typical pedestrian bridge, said LTA.
The tests on the smaller model were completed as at March 31, and the collected data will be analysed to validate calculations and to check for structural integrity. Following this, parts of this model may be repurposed by the authority.
LTA added that it will proceed to construct the full-sized bridge if these results are favourable.
Construction of the bridge by 3D concrete-printing is done layer by layer.
Robotic arms squeeze a high-strength concrete mix of cement, sand and water through a nozzle of the printer.
To prevent cracks, uneven surfaces or voids within a printed segment of the bridge, it is essential to ensure the consistent flow of the concrete mix – by controlling the printing speed, pumping from the nozzle, and mixing conditions such as temperature.
The development of the concrete material is crucial to the process – it needs to be relatively fluid during printing, not harden too quickly, and retain its shape after printing.
Material that hardens too quickly could result in cracks in the segments. Material that is too soft would not be able to retain the intended shape and can collapse easily after a few layers are laid out.
The final bridge will consist of 10 concrete segments, which will be threaded tightly together using steel cables along the entire length of the bridge.
This project involved research and testing by LTA, in collaboration with the Singapore Centre for 3D Printing at Nanyang Technological University, engineering consultancy Witteveen+Bos, and 3D concrete printing construction firm CES_Innovfab.
The projected completion of the bridge across Jurong River in 2028 will dovetail with the completion of connecting roads and footpaths that connect with Tengah town, said Yeo.
He added that this particular stretch of Jurong River was identified as structurally suitable and “manageable” to build the new bridge on, as it is narrower in length and has no complex site constraints.
This new bridge is 10m long, shorter than other pedestrian overhead bridges, which are around 20 to 25m long.
On future uses for 3D-printing technology, Yeo said that 3D concrete-printing is still an emerging technology for construction.
He noted that this project serves as a test of the potential feasibility of the technology, and that the authority will continue to explore suitable applications for other projects.
No other sites for similar pedestrian bridges have been identified, said Yeo.
On the total cost of the final 3D printed bridge, he said the authority is unable to provide estimated figures as construction works have not been tendered.
In Singapore, 3D printing has been used to construct the exterior walls of a childcare centre in Woodlands and to create assistive devices such as 3D printed hands for people with disabilities. -The Straits Times/ANN
