Dynamic Analysis of a Large Deployable Space Truss Structure Considering Semi-Rigid Joints

Joints are widely used in large deployable structures but show semi-rigidity due to performance degradation and some nonlinear factors affecting the structure's dynamic characteristics. This paper investigates the influence of semi-rigid joints on the characteristics of deployable structures in orbit. A virtual connection element of three DOFs is proposed to model the semi-rigid joints. The governing equations of semi-rigid joints are established and integrated into the dynamic equation of the structures. A series of numerical experiments are carried out to validate the proposed model's accuracy and efficiency, and the deployable truss structures' static and dynamic responses are analyzed. The results show that semi-rigid joints exacerbate the effects of an in-orbit microvibration on the stability of deployable truss structures. Semi-rigid joints lower the dominant frequencies of structures, leading to a 'closely-spaced-frequencies' phenomenon and altering the dynamic responses significantly. The effects of semi-rigid joints on deployable truss structures are long-term and can be used to establish a relationship model between structural performance and service life. Nonlinear effects vary with the external load and depend on the structures' instantaneous status. These results indicate that semi-rigid joints significantly influence the characteristics of deployable structures, which must be considered in the design and analysis of high-precision in-orbit deployable structures.