Description of work
A thorough analysis of possible reinforcement solutions that fulfil the TailorCrete requirements as regards automation and complex shapes has been carried out and pros and cons have been identified. It has been concluded that traditional reinforcement cannot be excluded. Often, the traditional reinforcement will be combined with other reinforcement types, where steel fibres seem to be the best solution but also glass fibres, polymer fibres and textile reinforcement are considered realistic. Fibre reinforced polymers, carbon fibres and natural fibres are not considered realistic reinforcement solutions.
Automation technology for processing of traditional reinforcement is being developed. Currently, work is ongoing to be able to make comparisons in terms of cost and production time between
- traditional on-site production,
- on-site prefabrication,
- industrial prefabrication of today, and
- prefabrication using robots.
Two examples have been chosen for these comparisons: one reinforcement cage with a complicated geometry, and reinforcement for a double curved wall.
Work on development of a rational method to provide a good reinforcement design for unique concrete structures with complex shapes has been initiated. Two available methods for the design of conventional reinforcement, based on linear finite element analyses using shell elements, were investigated. Both methods, which rely on a sandwich analogy, make it possible to calculate in a rational way the amount of reinforcement needed in unique structures. The two methods were evaluated, and one of them was chosen for further development. The following features were identified not to be covered in any of the two methods discussed: the effect of inclined shear cracking, the choice of optimal reinforcement direction, optimisation for production, and the inclusion of design with steel fibre reinforcement. Continued work within this area will treat these identified lacks.
Development of methods on how to include the positive structural effects of fibre reinforcement has been initiated. The possibility to design steel reinforced concrete beams and slabs with available guidelines such as the FIB Model Code 2010 has been investigated. Furthermore, steel fibre reinforced beams, including ordinary reinforcement, were analysed using nonlinear finite element analyses to develop and verify a more advanced modelling method. Good agreement was shown when experiments were compared with FE analysis; however, the design method presented in FIB Model Code 2010 underestimated the capacity. The underestimation increased with increasing fibre contents.
One essential factor that needs to be fulfilled to be able to include the structural effects of the fibres is to be able to predict how and where the fibres are distributed. A quality monitoring system for verification of fibre amount and type in the fresh concrete is being developed. A prototype of the device was built and evaluated during field tests to prove the measurement principles used. These initial tests showed that a steel fibre detection principle works, and that a volume measurement principle used also works but needs improvement. A Voice Of the Customer (VOC) exercise was done to find out the current way of working with concrete in different steps of the building process and assess the needs for quality monitoring. These inputs will be taken into account in the design of the Fibre reinforcement quality monitoring system.
WP leader: Chalmers