A mathematical model for analysing the interaction between elements of cable-stayed bridge is proposed. The influence of geometrical, mechanical and physical parameters of cables, pylons and stiffening girder on the behaviour of all structure is observed. Some results and useful recommendations about optimal solution from economical and technical point of view are presented. A way to improve the fatigue conditions of the cable-stayed bridge is installation of active devices, which in the exact moment can decrease deformations and stresses by transferring them from elements with poor load bearing capacity to elements with higher capacity. Properties of such a system can be examined by the proposed approach