Experimental testing of a small-scale truss beam that adapts to loads through large shape changes

Adaptive structures can modify their shape and internal forces through sensing and actuation in order to maintain optimal performance under changing actions. Substantial whole-life energy can be saved with respect to traditional passive designs through well-conceived adaptive design strategies; the whole-life energy comprises an embodied part in the material and an operational part for structural adaptation. Controlled large shape changes allows a significant stress redistribution so that the design is not governed by rare and extreme loadings. A design process based on optimization of the structural geometry and actuator placement has been formulated. A method that considers geometric nonlinearity is employed for shape and force control. Experimental testing on a small-scale prototype adaptive structure produced by this design process is presented. The structure is a planar truss. Shape adaptation is achieved through controlled length changes of turnbuckles that replace some of the elements. Stress redistribution through shape adaptation is in good accordance with numerical values, with a minimum Pearson correlation coefficient of 0.86. Results show that stress homogenization through controlled large shape changes is feasible.