C02 – Integrated Fluid-Actuators

By integrating fluid actuators into structural elements such as beams or slabs, load transfer can be optimized. This can lead to an increase in load-bearing capacity and consequently a reduction in mass.

Adaptive structures are one way to respond to changing loads. Forces generated by actuators are directed into the structure. This creates stresses and deformations within the component that counteract the stresses and deformations caused by external influences. As a result, the material used can be used more efficiently and the overall deformation of the component can be reduced to a minimum.

In the second funding period, the principles of FP1 are extended to biaxially stressed slab structures. These components account for up to 50% of the structural mass in a skeleton structure, for example, and therefore offer even greater potential for resource savings compared to the concrete beams of the first funding period. The additional spatial dimension also raises new issues. Integrated actuators that meet the specific requirements of multi-axial load transfer do not exist in mechanical engineering or related fields. The central question of the second funding period in subproject C02 is therefore

How must fluidic actuators be designed for integration into a slab structure, how must the integration be implemented, and how can stresses, deformations, and vibrations be reduced with this system?

Initially, new methods based on influence matrices were developed for the development of an actuation concept for biaxially stretched slabs. This was accompanied by a close exchange with the actuator design department to enable technically feasible solutions.

^{Summed influences on the vertical translational displacements under a biaxial actuation (a) and a uniaxial actuation rotated by 45° (b) and 135° (c). Picture: (c) Markus Nitzlader}

^{Fields of influence of a uniaxial actuation rotated by 45° (a) and 135° (b) in relation to the vertical translational displacements in the center of the field. Picture: (c) Markus Nitzlader}

The development of the new adaptive system was carried out using numerical simulation models supported by experimental investigations. The investigations ranged from individual components of the actuators to slab segments with integrated actuators and a 2 x 2 m prototype of an adaptive slab. In the latter, the specially developed multi-axial actuators are directly inserted into the cross section of the slab.

^{Foam model to illustrate the actuation concept with simplified actuators and without cover layer. A: biaxial actuator. B: uniaxial actuator. Picture: (c) Matthias Bosch}

^{Prototypes of various actuator pressure chambers. A: Welded steel membrane. B: Bolted steel membrane. C: Bolted elastomer membrane. Picture: (c) Matthias Bosch}

^{Actuator integration within the formwork body of the 2 x 2 m prototype of an adaptive slab without top reinforcement layer. Picture: (c) Markus Nitzlader, Matthias Bosch}

^{Test setup of the 2 x 2 m prototype for a full-surface load (left) and an asymmetrical point load (right). Picture: (c) Markus Nitzlader, Matthias Bosch}

The experimental results show that the adaptive slab can maintain the deformation level of an identical slab without actuators under single load, even under double load. In a case study of a 10 x 10 m slab, it was shown that a reduction in cross-section of up to 43 % can be achieved, which corresponds to a reduction in global warming potential of 35 % compared to a corresponding passive reinforced concrete slab.

Subproject Leader

• Prof. Dr.-Ing. Hansgeorg Binz, Institute for Engineering Design and Industrial Design
• Prof. Dr.-Ing. M.Arch. Lucio Blandini, Institute for Lightweight Structures and Conceptual Design
• Prof. Dr.-Ing. Matthias Kreimeyer, Institute for Engineering Design and Industrial Design