Arranging the plastic hinges and improving the strength of steel tubes with tapered ends: Analysis and tests

A new form of space structure, polyhedron frames, was developed recently. In polyhedron frame structures, most structural members are under multi-loads of compression, bending and torsion. A new type of tapered member that is obtained by axially connecting a constant-section tube to two tapered and relatively short tubes was proposed to be the structural member of polyhedron frame structures. We named this kind of tapered member a tapered-end tube. This paper has analytically and experimentally proved that tapered-end tubes can restrict the plastic hinge to the interface of the constant-section part and the tapered part, and the location of the plastic hinge can be arranged by correctly choosing the ratio of slope of the tapered ends. Corresponding tests and simulations are done to verify the analytical prediction, and these also reveal that the strength of the tubes is significantly improved by the tapered ends.