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Rotational stiffness of single-bolt sleeve connections / Timothy C. Moser.

by Moser, Timothy C.

Steel, Structural -- Specifications

Strains and stresses

Strength of materials

Finite element method

Structural analysis (Engineering) -- Mathematical models

Connections (Mathematics)

100 leaves : ill. ; 29 cm.

Thesis advisor: Christopher Raebel

Committee members: Dr. Douglas Stahl, Dr. Hans-Peter Huttelmaier

An introduction to space structures -- Novum Structures' Kugel Knoten system -- Moment capacity of single-bolt sleeve connections -- Rotational stiffness of single-bolt sleeve connections -- Finite element modeling -- Finite element analysis -- Discussion of results and recommendations -- A: Kugel Knoten dimensional and material information -- B: Summary of ANSYS input commands -- C: Element reference guide.

Novum Structures uses a single-bolt sleeve connection to connect hollow tubular members to spherical nodes at the joints of its Kugel Knoten space frame system. A sleeve connection is a shop-assembled connection consisting of four parts: a sleeve, essentially a modified hexagonal nut with an unthreaded hole and a slot or hole in two opposite faces; a bolt with a pin-hole; end-cones that are welded to the ends of the tubular members; and a small locking pin. The sleeve conceals the unthreaded portion of the bolt shaft left exposed by the end-cone, and the pin holds the connection together by preventing the bolt from sliding back inside the tube. Turning the sleeve tightens the bolt.

Novum designs its space frames as space trusses, neglecting the moment capacity and rotational stiffness of the sleeve connections. There are instances, however, where bending moments are applied at the joints of the space frame due to eccentric loading. The least cumbersone and perhaps most economical solution is to take advantage of the strength and stiffness of the sleeve connections. In order to use the inherent strength and stiffness of the sleeve connections, the moment-rotation behavior of the sleeve connections must be understood. An analytical method already exists to calculate the moment capacity of a sleeve connection. No equivalent method exists to compute the stiffness of the connections.

The purpose of this capstone project is to determine the rotational stiffness of three typical sleeve connection sizes, one small, one medium, and one large. A finite element method is employed to model and analyze the connections under zero axial force conditions.

Results of the finite element analyses are presented and compared to actual experimental tests of the same connections. A secant stiffness model is suggested for determining the stiffness of the sleeve connections from the moment-rotation behavior predicted by the finite element analyses. The softest secant model accurately predicts the moment-rotation behavior of the medium and large connection sizes. A stiffer secant model is required to accurately predict the moment rotation behavior of the small connection size.

Additionally, the computed stiffnesses are compared to the American Institute of Steel Construction's stiffness limits for connection classification. The Kugel Knoten connection behaves either as a simple connection or a partially restrained connection depending on the flexural stiffness of the connected member. For practical tube lengths, the medium and large connections qualify as simple connections based on AISC's criteria. The small connection qualifies as a partially restrained connection for practical tube lengths.

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