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FA 3.3 Structural performance

FA 3.3 Structural performance

Senior Research Scientist

Objective:
To develop and utilize new concrete material combinations and applications

Project manager: Jan Arve Øverli
Disciplinary responsible:    Professor Terje Kanstad
PhD: Linn Grepstad Nes, Håvard Nedrelid, Markus Bernhardt and  Egil Møen
International advisor: Professor Steffen Grünewald, Delft University of Technology, The Netherlands

 

The project includes the following activities:

  • Production and utilization of High performance light weight aggregate (LWA)
  • Ice abrasion
  • Hybrid structures
  • Ductility of LWAC

Main topics

Lightweight aggregate concrete (LWAC)

There is a general scepticism regarding the use of LWAC in heavy loaded structures because of the more brittle postpeak material behaviour and smoother crack surfaces. In our work, the main hypothesis is that the strength and especially the ductility of structural concrete members depend on local multiaxial stress conditions that develop within the compressive zone prior to failure. This was confirmed by multiaxial tests. It led to the hypotheses that fibre reinforcement could be a good solution. This was verified by a series of large beam tests, to study the passive confinement effect of different configurations in the compression zone in a structure. The experiments demonstrated that a reinforced LWAC structure, may satisfy requests for energy dissipation and controlled behaviour, and even a capacity increase, in the postpeak response when steel fibre reinforced. Using LWAC in combination with normal weight concrete is another possibility of structural optimisation with respect to weight. The beams studied are composed by different layers of concrete either cast wetonwet or at different times, and with really promising results. Development of high performance LWA is a parallel activity to further improve the competiveness of LWAC. Different strategies to improve the mechanical properties of expanded clay aggregates have been tested with very good results. New understanding of the strength determining factors as well as the fracture behaviour of LWA was achieved.

Ice abrasion

A purposebuilt test rig was used to simulate the effect of ice sliding against concrete surfaces. The rig allows variation in different parameters such as icepressure, temperature, velocity and material qualities. By exposing new materials for the same test conditions as materials collected from structures with longterm field exposure, we can estimate the expected design lifetime for the new materials. The results have helped to design the exposed ice zone of artic offshore concrete shafts without the expensive steel lining.