Active control of axial forces in beam string space frames.

The present work discusses a formulation for active control of axial forces of strings in beam string structures to dynamically and/or statically reduce the responses, and proves both the effectiveness of the control and the applicability of the formulation by analyzing two types of structures; one is an ordinary, one way beam string structure stiffened by stressing in tendons and the other is a three dimensional beam string structure stiffened by cables underneath. The target function to be structurally optimized is expressed by combination of the followings; strain energy stored in a structure to be stiffened or softened by active control, and quadratic functions in terms of displacements, velocities and accelerations. In static case, a strategy is discussed to reduce the strain energy stored in the stiffened portion by prestressing and in dynamic cases a strategy of instantaneous optimization for kinematic energy is investigated.