Innovative Structural Joint Tolerates High Rotational and Shear Overload

A new beam-to-column (horizontal brace-to-leg) and bracing-to-frame (diagonal brace-to-horizontal brace/leg) connection was developed. It is a comprehensive package in which the solution to all of the shortcomings and deficiencies of all conventional and/or commonly used connections is provided. The major deficiency of basically all the existing beam-to-column connections is their inability to deliver large rotations. In this devised connection, it has been solved by using a totally different geometry—a geometry which does not restrict the joint from deforming freely in a smooth, uniform and non-violent manner. Such mode of deformation, if delivered by a ductile material, should lead to a high energy dissipation capacity. Especially, if the ductility of the constituting material of the connection is not degraded as a result of fabrication operations, or if so, it is restored through practicing a suitable heat treatment process, e.g. annealing, the energy dissipation capacity should improve substantially. Moreover, in order to attract the damage and prevent it from spreading through the beam (bracing) and the column (leg), whose replacement is formidable, the connection should work in a ‘sacrificial’ capacity. This, together with making it ‘replaceable,’ will reduce the cost of aftermath repair substantially, while replacing the damaged beam or column, if possible, is very costly. In addition to its high rotational (bending) capacity, at least 6 times those of conventional joints (depending on the connection design), its ‘shear deformation capacity’ is quite considerable, absolutely incomparable with those of its conventional counterparts, which are virtually ‘nil.’ This connection is a ‘self-contained separate entity’ which comprises two parallel attachment plates between which two circular, or else, tubes are laid and fixed through welding, though alternatively the whole combination can be produced by extrusion. In the ‘original version’ of the connection, the two plates are laid in a parallel relation with the axis of bending, whereas in its ‘alternate version,’ they are laid in an orthogonal relation with the axis of bending. Tests carried out on specimens of the two distinct versions of the connection proved all its claimed characteristics, both in shear and bending. In particular, those carried out more recently, not reported in previous papers (OMAE’02-28264 & OMAE’03-37292), were quite revealing with regard to the ‘shear strength’ and the ‘shear deformation capacity’ of the original version (horizontally-laid-tube, HLT, version) of the connection—far beyond what was expected by the authors.