Fixed strength and stiffness hinges for steel frames

A new type of device able to connect steel beam elements is proposed. Specifically, the device is designed in such a way that the required bending stiffness and limit resistance can be independently imposed. To this goal, the device is realized as a "sandwich" section whose wings possess a particular geometry able to guarantee the required characteristics. Further technological requirement is that the device has to engage plan dimensions equal to those of the elements to which it is connected. The procedure to design the device is presented in the paper with reference to a simple plane steel portal constituted by appropriate profiles in such a way it behaves following an assigned force/displacement diagram. The device is proposed as constraint at the base of the pillars as well as connection node between the beam and the pillars. For each device utilized, even in the same frame, a different limit resistance in terms of bending moment can be fixed. Therefore, the elastic plastic response of the frame to a monotonically increasing load shows a complete independence between elastic and resistance characteristics. The effected application shows the great effectiveness and wide applicability of the proposed device.