Nonlinear dynamic instability behavior of tensegrity grids subjected to impulsive loads

Abstract

Tensegrity systems have the potential of offering a high level of structural efficiency and result in lightweight reconfigurable structures. However, there is few actual application of the tensegrity concept in engineering practice, which can be mainly attributed to the inadequate knowledge concerning the mechanical behavior of these systems. Although, most of the performed instability analyses on tensegrity systems to date concern with progressive collapse under static loads, so far no investigation has been conducted on the dynamic instability of these systems. In this paper, two geometrically rigid configurations assembled from half-cuboctahedron (HC) modules and crystal-cell pyramid (CP) modules under impulsive loads are analyzed, for demonstration purposes, with the intention of comparing critical dynamic loads to critical static loads. Also, other parameters, considered in this work, include the impulsive time duration, self-stress level, struts slenderness ratios, damping ratios, support conditions, and struts strengthening. It is found that in the investigated cases, as the time durations are reduced, being less than quarter of the first natural frequency, the critical load ratios increase and the systems are able to withstand dynamic loads that are substantially in excess of the critical static loads. Decreasing self-stress level by 40% in the studied HC configuration can significantly increase the amount of relative dynamic to static load ratio up to 193%, 177% and 170% under rectangular, triangular and half-wave sine loadings with time duration of 0.05 s, respectively. The increase in critical impulsive load capacity of the studied CP configuration is typically less than 10% for the same reduction of the self-stress level. There is a significant increase in dynamic loads attaining approximately 20% for an increase of 24% in cross-section of critical struts in the studied HC configuration.