Determination of Optimal Elastic Springs for Cantilever Beams Supported By Elastic Foundation

In this study, the optimum distribution of the elastic springs in which a built-in cantilever beam is seated, so as to minimize the shear force on the support of the beam, is investigated. The Fourier transform is applied to the vibration equation of the beam written in the time domain and is shown by the structural behaviour transfer function which is made independent from the external influence. For the first and second modes of beam, the optimum locations and amounts of the springs were investigated so that the shear force transfer function amplitude was minimal. Stiffness coefficients of springs are taken as design variables. There are active constraints on the sum of the spring coefficients taken as design variables and passive constraints on each of them as the upper and lower bounds. Optimality criteria are derived using the Lagrange Multipliers method. The gradient information required for solving the optimization problem is analytically derived. Numerical results show that the aimed method is quite effective in finding optimum spring stiffness coefficients.