Council on Tall Buildings and Urban Habitat
 

First Composite Megacolumns Test a Big Success
February 5, 2015
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BEIJING The large research team working on the “Study on the constructability and the engineering properties of composite megacolumns” research project, funded by ArcelorMittal, gathered on February 5th in Beijing to start the test campaign on the first megacolumn samples.

Six specimens representing scaled-down megacolumns, built using an innovative design system with large I-shaped profiles encased in concrete, were assembled in the previous weeks at China Academy of Building Research (CABR)'s laboratories. The innovative aspect of this research is the use of untied hot-rolled Jumbo profiles (flanges thicker than 100mm), instead of plates welded together. The use of hot-rolled profiles is eagerly anticipated by designers and developers, as it will ease construction by reducing the number of on-site operations, and it will also boost construction quality, by avoiding errors and unwanted simplifications in the assembly of profiles originated by welded plates.

According to the research program, which has been peer reviewed by a group of international experts, the column specimens are to be brought to failure by compression only, with eccentricity factors of 0, 10 and 15 percent.

The first specimens were then brought to the Tsinghua University Structural Lab in the Department of Civil Engineering, one of the few that has a press large enough to break the specimens, even though they are only 1:4 scale models of the actual columns.
Researchers in front of the large press at Tsinghua University Column Specimen after failing under 17,300 kN (1,730 metric tons) of force
Researchers held their breath when they realized that the lab press was reaching the maximum capacity (18,000 kN, equal to a load of 1,800 metric tons) and the composite column was still behaving in “elastic mode;” that is, it was not suffering any damage or deformation, beyond that which could be reversed by simply un-loading the specimen. Only at forces close to the max capacity of the press, applied with no eccentricity, did some cracks appear on the edges of the specimen. The column collapsed under a compressive force 10% greater than the limit originally anticipated by the FEM Analysis.

Even if it still too early to prove the design method is correct, and to suggest this as a construction system for actual tall buildings, the researchers were pleased with the behavior of the specimen during the test. The studs performed well by transferring the shear force from the steel profiles to the concrete, thus making the two materials work together in true composite behavior.

One more test with no eccentricity will be performed next, immediately followed by other 1:4 scale tests with 10% and 15% eccentricity.

In April, new tests will be performed with a different strategy, by applying not only an axial force, but a lateral force as well, again with eccentricities between zero and 15%. This will simulate the column behavior under the effect of an earthquake, finally proving the real potential applications of composite megacolumns made of encased hot-rolled steel profiles.
Research group and some external guests in front of Tsinghua University (left to right): Jingye Wang, MKA; Congzhen Xiao, CABR; Rob May, Buro Happold; Donald Davies, MKA; Christoph Odenbreit, University of Luxembourg; Dario Trabucco, CTBUH - IUAV; Olivier Vassart, ArcelorMittal; Nicoleta Popa, ArcelorMittal; Chen Tao, CABR; and Hui Wang, CABR.