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High demand for living and working space as well as the corresponding infrastructure, caused by a growing population and increasing prosperity worldwide, leads to increased consumption of mineral resources. This is accompanied by high usage of grey energy and a high output of greenhouse gas emissions. Adaptive structures represent a promising approach for mass and resource savings. Through the interaction of actuators, sensors and control units, the structure can adapt to the external loads to reduce stresses and deformations. As a result, the building material required can be reduced. For actuators integrated into slabs, new challenges arise due to the multi-axial load transfer. In particular, the aim is to achieve the largest possible effective range of the applied moment to reduce the number of actuators required. One approach is to optimize the geometry of the force-introducing surfaces inside the structural element. This paper presents a study about the correlations of the geometric parameters using numerical simulations. This enables the pre-dimensioning of the actuator and is thus a first step in its design.

The construction sector is responsible for high grey energy consumption and high greenhouse gas emissions. Adaptive structures can be a suitable solution to counteract this. Actuation of a beam to reduce the mass by counteracting the deflection with integrated fluidic actuators has been proven in previous studies. New challenges are brought about with the actuation of slabs due to the multi-axial load transfer. Many actuator principles are conceivable for this application. A combination of uniaxially acting actuators and complex designs that generate forces in different spatial directions in a targeted manner are possible. This paper presents various principles for the development of actuators integrated into the cross-section of a slab. These are able to manipulate the multi-axial load transfer behaviour directly. For this purpose, the actuator principles are classified according to various aspects. In a second step, numerical investigations are used to prove the effectiveness of the actuator principles.

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.

The building industry accounts for half of the global resource consumption and roughly one third of global CO2 emissions. Global population growth and increasing resource scarcities require engineers and architects to build for more people with less material and emissions. One promising solution are adaptive load-bearing structures. Here, the load-bearing structure is equipped with actuators, sensors, and a control unit which allows the structure to adapt to different load cases, resulting in substantial material savings. While the first prototypes use industry standard actuators to manipulate deformations and stress states, it is essential to develop actuator concepts which fit the specific requirements of civil engineering structures. This paper introduces new concepts for linear actuators, developed within the Collaborative Research Centre (SFB) 1244 Adaptive Skins and Structures for the Built Environment of Tomorrow, which can be used as adaptive concrete columns. The concept of an actuator which actuates a concrete column by external compression through hydraulic pressure is discussed in further detail. This concept allows for controlled axial extension while also increasing the compressive strength of the concrete column.