The stiffness k is assumed as a control parameter. The locations of the connection
points of the spring–damper system are given by the coordinates ξ1 and ξ2. The following parameters, the constant crosssectional
area A, the inertial moment of the cross-sectional area I, mass density ρ, elastic modulus E, shear modulus G, and
shear coefficient κ, are known. The movement of the beams is described by the deflections w1 and w2 perpendicular to the
axis ξ and the rotation angles ψ1 and ψ2.