On November 6, an engineering research team at the Massachusetts Institute of Technology (MIT) in the United States released research results on a new type of fabric-formwork concrete beam. Using computationally optimized design and sewn cotton fabric formwork, the team successfully produced a 3-meter-long reinforced concrete test beam. Compared with a conventional beam designed for the same load-bearing requirements, the new structure uses only about one-third of the concrete and half of the steel reinforcement. The research results were published in the Journal of Building Engineering, and prototype fabrication and performance testing under service load conditions have been completed.
The research team combined graphic statics with topology optimization techniques to design the beam structure. Graphic statics was used to determine the reinforcement layout paths so that the steel reinforcement bears relatively uniform loads along the length direction; topology optimization was used to determine the necessary distribution regions of concrete material. The final beam consists of a top compression part, inclined connecting struts, and a bottom reinforcement-bearing part, reducing overall material consumption by decreasing the amount of concrete in low-stress regions.
In the formwork fabrication stage, the researchers developed an automated fabric cut-piece generation method that converts the three-dimensional beam model into two-dimensional fabric cutting patterns and incorporates fabric deformation during wet concrete pouring into the calculation. The team fabricated three sets of formwork composed of 36, 56, and 76 fabric pieces, respectively, and compared the shape deviation between the poured beams and the original design through three-dimensional scanning. Test results showed that the formwork composed of 56 fabric pieces achieved a good balance among geometric precision, processing time, and assembly complexity.
The researchers adopted a concrete mix with higher sand content and smaller aggregate particles to accommodate the narrow inclined channels inside the beam. During pouring, concrete compaction was completed through manual layered filling, tapping, and kneading the outer surface of the fabric. The surfaces of all three test beams showed no obvious fabric wrinkles, but there was a certain degree of sagging at the bottom, and some inclined struts deformed inward.
In the structural performance test, the research team gradually loaded 36 buckets of water onto one of the test beams, with the maximum test load reaching about 30% of the design load. Test personnel recorded the deformation of the beam during loading and unloading using precision displacement measurement devices. The measured mid-span deflection differed from the calculation model prediction by about 2%, verifying the design method's ability to predict structural deformation under service loads.
The research team also compared the cost of a single fabric-formwork concrete beam with that of a conventional beam. Under the material and labor cost conditions of the Global South, the estimated costs of the three fabric formwork schemes were about 10% to 20% lower than the conventional scheme; in the Global North, where labor costs are higher, the estimated costs of the fabric formwork schemes were about 16% to 55% higher. The related calculations covered the fabrication of a single beam, and the research team listed irregular exposed beams, roofs and long-span frames, pedestrian structures, and landscape components as potential application targets.
This research is a prototype validation expanded to 3 meters from the team's previous 1.2-meter test beam. The next stage plans to conduct load-to-failure tests on multiple test beams to obtain data on ultimate load-bearing capacity and failure behavior. The research was partially funded by the U.S. National Science Foundation, and the paper was jointly completed by researchers including Mark Hellrich, Josephine Carstensen, and Jackson Jewett.