DTU destroys building to check computer program

Friday 11 Oct 19

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Jesper Harrild Sørensen
Postdoc
DTU Civil Engineering
+45 45 25 18 41

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Henrik Stang
Vicedirector, Professor, Constituent head of Section
DTU Civil Engineering
+45 45 25 17 35
Loading a two-storey building will clarify whether numerical models in computer programs ensure sufficient strength and load-carrying capacity.

By applying up to 100 tonnes of pressure from test machines, researchers from DTU are destroying a number of two-storey concrete constructions. The experiments are taking place in a new test facility at DTU Civil Engineering, where the researchers are quality-assuring a new generation of computer programs for dimensioning constructions made from prefabricated concrete elements. The numerical calculations in computer programs can cut the consumption of concrete and reinforcing steel as well as the number of man-hours at both the precast concrete element factory and on the building site.

At DTU Civil Engineering, researchers have been working for many years on the theory behind calculating buildings’ load-carrying capacities and toughness. The purpose of the full-scale experiments is to document the quality of these calculations.

“The new generation of digital calculations for calculating the load-carrying capacity of prefabricated concrete constructions assumes that the structure has sufficient toughness and ductility when loaded to breakage point. The model has so far been based on our knowledge about the strength of individual components. However, the full-scale experiments will provide us with new knowledge about how the sub-components interact, and about how the load-carrying capacity of the overall construction depends on the joints between the individual wall elements. The experiments can thus ensure the reliability of computer programs when they are used for dimensioning complex constructions,” says postdoc Jesper Harrild Sørensen, a member of the research team at DTU Civil Engineering which is behind the project.

The experiments are conducted in collaboration with the Danish Precast Concrete Association.

Sustainable construction

The new generation of numerical models for calculating the load-carrying capacity of structures is already being used in the construction industry. Pernille Nyegaard, chief consultant at the Danish Precast Concrete Association, says that the new documentation from the full-scale experiments will contribute significantly to more sustainable concrete construction:

“The new calculation method makes it possible to optimize the structures. By having a precise idea of their load-carrying capacity, we can save on both reinforcement steel and concrete in the structures, because we no longer have to have a large margin of safety in the calculation models,” says Pernille Nyegaard.

Jesper Harrild Sørensen estimates that the calculation model will be an effective tool in building high-rise buildings, where it can potentially reduce the consumption of reinforcement steel by up to 40 per cent, depending on the complexity of the building.

Material testing

The experiments at DTU Civil Engineering are taking place over a six-month period. Once a two-storey experimental structure has been built, it needs at least 28 days to set properly in order for the cast joints to achieve a realistic strength. During the curing period, the structure is optimized for testing by installing measuring equipment. In the course of the experiment, the researchers perform material testing on the reinforcement steel and concrete to determine the strength of the materials. All this information is used to quality-assure the calculation model.

Load to fracture

During the experiment, the researchers use special test facilities at DTU, where the structure is subjected to a horizontal load until it reaches its ultimate load-carrying capacity and is clearly deformed but still staying in one piece. Here, the researchers can follow the breakup and development of cracks, both on the actual structure as well as on a monitor, where a computer shows the changes being registered by the measuring equipment during the test. The experiment lasts for about two hours.

The researchers are building five structures in all, which will all be subjected to break load, and all the data is being used to adjust the final computer model.

The new test facilities are part of a major test centre at DTU—CASMaT—which is funded by the VILLUM FOUNDATION. 

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