On the morphology of reconfigurable hybrid structures based on the effective 4-bar mechanism

Abstract

Reconfigurable systems of hinge-connected beams strengthened through struts and continuous cables, utilize their morphology and cable active members through a synergetic process to enhance structural flexibility, stability and energy efficient transformability. The ‘effective 4-bar’ concept may be applied for the transformation of planar n-bar systems, using a sequence of 1–DOF motion steps through selectively locking (n-4) joints of the primary members and actuating the cables, in order to adjust the system’s joints to the desired values during the motion steps involved. The control system includes only two motion actuators located at the structural supports, as well as brakes installed on each individual joint. It performs the reconfiguration sequences through tensioning of one single cable at a time. A numerical investigation presented in the current paper involves four arch systems of 8, 9, 10 and 11-bar linkages with 60/90, 75/75 and 90/60 cm strut lengths on each side of the systems’ circumference. In their initial position, all arch systems have 5.0 m span and 5.35 m height following a quasi-vertical ellipsoid shape. The target configuration of the systems with 4.20 m height corresponds to a quasi- horizontal ellipsoid shape. Different reconfiguration sequences are investigated, in order to achieve the target configuration for each system. The comparative numerical analysis refers to the maximum stresses developed in the members and the required brake torques for each transformation. The analysis provides an insight into the hybrid structural morphology and mechanical characteristics of the members for optimal implementation of the reconfiguration approach.