Dynamic behavior of structures with bolted joints

G, Vamsi Krishna (2016) Dynamic behavior of structures with bolted joints. Masters thesis, Indian Institute of Technology Hyderabad.

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Abstract

Energy dissipation at the interfaces of the mechanical joints is the major source of damping, which decides the dynamic behavior of structures. In majority of structures, micro and macro slip happening at the interfaces is the mechanism for energy dissipation. Modeling of this dissipation using Finite Element (FE) Methods requires very fine meshing at the joint iterfaces (referred as detailed FE method), it places severe restrictions in application of detailed FE methods to real life structures for capturing energy dissipation at joints. Different kinds of reduced order models are being developed to overcome this limitation. One of those models, viz., Masing's contact model is chosen for FE implementation in this work. Masing's traction-seperation contact equations are solved numerically to generate traction-seperation hysteresis curve. Parameters of Masing's equations for a specific bolted configuration are extracted in matching hysteresis curve with that generated for isolated bolted joint configuration using detailed FE method. Masing's contact equations are then discretized and are implemented at the interfaces in commercial FE software using external subroutines. Implementation of Masing's model for different load cases, discretization, and time stepping are checked and limitations are discussed. Subsequently, the modal damping ratio estimation method using mode shape as forced displacement is developed for arbitrary bolted structure. Finally, applicability of Masings model for the damping estimation due to exing of interfaces is studied and the usefulness of reduced order models even in such complex cases are shown.

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