Maximum load capacity with minimal consumption of materials – this is how supporting structures in construction should be today. Researchers from the University of Stuttgart and Bosch Rexroth have now come a great deal closer to achieving this goal. They have constructed a wooden shell that is much thinner than anything deemed possible up to now. With a four-centimeter thickness, the shell spans a surface of over 100 square meters. The extreme slimness of the shell becomes possible through the use of an adaptive structure.
Structures have always been designed for an exact maximum stress. This type of stress generally only occurs very rarely and only for a short period. A large part of the building materials used today serves these extremely seldom peak loads and is seldom used. The aim of ultra-lightweight structures is to achieve a drastic saving of materials and a better reaction to dynamic loads through an active manipulation of the structure. This manipulation is achieved through hydraulic drives: these drives rest on the points of support of the shell and generate movements that compensate in a specific way for deformations and material stresses caused by wind, snow, and other loads.
The wood shell is supported at four points: three of these points can be moved individually by hydraulic cylinders and freely positioned in space. Sensors record the load status at numerous points on the structure. Targeted movements of the points of support counteract variable loads (for example, through snow or wind) and reduce deformations and material stresses. Compared to conventional, passive structures, this considerably reduces the use of materials for the shell. The load balancing takes place through a Rexroth control system developed for hydraulic drives. The core task of the control system is to implement the complex hydraulic control tasks of the shell structure. In this way, the supporting structure can react to a change in the load status within milliseconds.
Active vibration dampening and the adaptation to changing loads can be applied in many areas of construction; for example, in stadium roofs, high-rise buildings, wide-spanning façade construction, or bridges. The active dampening of dynamic loads enables not only a drastic reduction in weight but furthermore also reduces material fatigue and damage to the structure.
