Pumping vs. Iron: Adaptive Structures for Whole Life Energy Savings

Abstract

The design methodology explained in this paper takes a substantial shift from conventional methods where sizing is based on a single load case i.e. the maximum expected load. The difference from a conventional passive approach is that strategically located elements of the system provide controlled output energy (actuators) in order to manipulate actively the internal flow of forces and stresses. In this way stresses can be homogenized and deflections kept within desired limits. The alternative we are proposing offer a way to actively counteract loads when needed. Two dimensional pin-jointed trusses designed using this methodology show that substantial weight savings can be achieved respect to optimised "passive" structures (designed using Fully Utilised Design method).While the decrease in mass through actuation leads to reduction of embodied energy, it increases the operating energy that the active elements need to provide. Whole life energy analysis, implemented as coupled optimization between embodied and operating energy, reveals that an optimal trade-off exists. Results show that energy savings remain significant even considering the operating energy of the actuators for the entire life-cycle of the structure.