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A new beam-to-column joint with high rotational as well as shear deformation capacity was devised. This high rotational ‘capacity’ is required to fulfill the great ‘demand’ for rotation arising during earthquakes, severe waves and current loads, etc. Due to its ability to contain damage during an overload, it leaves the connected elements intact. This, together with its replaceability can reduce the cost of post-event repair substantially. Its bending as well as shear performance under “monotonic” loading had already been assessed experimentally (OMAE’02-28864, OMAE’03-37292, OMAE’04-51494 & OMAE’05-67361) and proved well superior to that of conventional joints. In order to study its performance under “cyclic” flexural loading experimentally, new bending tests were conducted on mild steel specimens of the connection. These tests clearly showed the ability of the devised joint to withstand adequate number of cycles in bending and dissipate energy through well-shaped hysteresis loops. This would result in large amount of energy being dissipated in each cycle. Such very ductile response of this connection in bending is expected to be exploited in various circumstances in offshore as well as onshore structures to give rise to a ductile overall behavior of the structure. In particular, it can be utilized for the repair and retrofitting of the aging offshore platforms which need to be treated in a non-destructive manner.

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.

A new universal structural joint was developed. While in bending it has a high rotational capacity, which can be accompanied by large bending stiffness and strength, in shear, it also has a very high shear deformation capacity, which can again be accompanied with large shear stiffness and strength. While the former characteristic makes it a good candidate for being used as a beam-to-column joint, the latter makes it highly applicable in connecting braces of a braced frame to the frame members. The experimental study carried out previously on this joint, concentrated on the performance of its steel specimens under ‘monotonic’ shear loading as well as that of its aluminium specimens under both ‘monotonic’ and ‘cyclic’ shear loading. The current study, however, comprises the experimental investigation into the behaviour of the mild steel specimens of this joint under ‘monotonic’ and ‘cyclic’ shear loading. As expected, the monotonic shear loading of the specimens of this new joint resulted in great amount of shear deformation, in contrary to basically all currently-used structural connections which lack any appreciable shear deformation capacity. Moreover, the specimens tested under cyclic shear loading also performed very well. The hysteresis loops of these specimens were ‘stable’ and ‘well-rounded’, implying large amount of energy dissipation in each cycle. Such very ductile response of the connections in shear is expected to be exploited in various circumstances in offshore as well as onshore structures to result in a ductile overall behavior of the structure.