An equivalent stiffness approach for modeling non-linearity in the dynamics of pre-tensioned cable-stayed masts

Pre-tensioned cable-stayed masts are slender structures usually employed for telecommunication towers or for meteorological measurements at certain heights above ground level. The structure consists of a vertical beam-column supported along its height by several layers of inclined pre-tensioned cables. A suitable configuration of the pre-tensioning force on the cables system is an important issue since the internal force distribution, significantly affects their structural dynamic behavior. Pre-tensioned stays can exhibit a non-linear behavior due to slackening or snapping. Therefore, a non-linear unilateral model, combined with the taut-cable theory, is required to simulate the incipient slackening conditions in the stays, by using a unilateral restoring-force spring model to simulate the behavior of each cable. In the present paper a based displacement approach is utilized to examine the nonlinear behavior of the system. The proposed approach based on the Equivalent Linearization Method, shows a robust simplified technique capable to linearize the systems characterized by non-linearities due to slackening effects of pre-tensioning in the stays. It is concluded that performance coefficient and the equivalent frequency, may possibly be used as useful indicators for designing pre-tensioned cable-stayed masts where a suitable selection of the initial pre-tensioning force can effectively improve dynamic performance of the system.