Actuation of concrete slabs under bending with integrated fluidic actuators

Abstract

Previous studies have shown that 33 % to 44 % of the mass embodied in residential and office buildings and up to 50 % in high-rise buildings is attributable to floor slabs. Floor slabs are typically bearing a bending load. Load-transfer through bending is not efficient because the material in the proximity of the neutral plane is practically unloaded thus resulting in a poor material utilization rate. Since bending stiffness is per se significantly lower than axial stiffness, the design of floor slabs is typically governed by deflection limits under out-of-plane loading, which causes significant oversizing. In addition, structures are typically oversized since they are designed to take extreme loading events, which in practice occur only for a small part of the service life. The ongoing climate crisis, the expected world population growth and associated resource scarcity call for new methods and solutions to build material-efficient structures that cause minimum greenhouse gas emissions. Employing adaptation strategies is a promising solution. By integrating structures with components such as sensors, actuators and control units ­ stress and deformation caused by live loads can be reduced actively, which enables significant material savings. Previous work carried out at the University of Stuttgart within the Collaborative Research Center 1244 has demonstrated that it is possible to compensate deflections by integrating fluidic actuators in beam structures subjected to bending. However, it is not obvious how to transfer actuation concepts employed in beams to floor slabs due to multi-axial load-transfer behaviour. In this work, fluidic actuators are strategically integrated into floor slabs to employ multi-axial transfer to counteract the effect of out-of-plane loading. This research also addresses the choice of an optimal layout of the actuators. Numerical simulations of different actuation concepts, such as uniaxial and biaxial actuation have been carried out to derive influence surfaces. The relationship between principal moments and the effect of actuation is quantified numerically. Examples are provided to show how influence surfaces can be employed to select suitable actuation strategies. Results show that displacements can be efficiently compensated through a combination of uniaxial and biaxial actuation.

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