Revisiting the fundamental structural dynamic systems: the effect of low gravity

摘要

This paper revisits the fundamental structural dynamic systems with regard to the effect of gravity, and thus self-weight, on their dynamic characteristics and response. Far from being a purely theoretical exercise, as would have been the case in the past, this study is a first step in structural dynamics inspired by-and anticipating-the potential of building under extraterrestrial conditions. More specifically, five basic structural models are considered: (a) the simple pendulum (SP), (b) the rigid inverted pendulum (RIP), (c) the flexural inverted pendulum (FIP), (d) the rigid rocking block (RRB), and (e) the flexural rocking block (FRB). The focus is to identify patterns and regions where low gravity can have a beneficial or detrimental role on the structural response. The paper initially presents the effect of low gravity on the dynamic characteristics of each system and then proceeds with highlighting their self-similar response, along with the differences in response due to low gravity. It is proved that low gravity is detrimental for the SP, while it is beneficial for the RIP and FIP models. Nevertheless, the effect can be both beneficial and detrimental for the RRB and FRB, depending on their parameters as revealed from this investigation. Finally, the main dynamic characteristics of the five cases studied, factorized by the gravitational multiplier (alpha), are quantified and summarized in the form of a representative table.