Limited Resistance Rigid Perfectly Plastic Hinges for Steel Frames

The paper concerns the proposal of a new special device for steel frames that can be utilized as external constraint as well as internal one connecting the structure beam elements. The device is designed as a rigid perfectly plastic hinge characterized by suitably chosen stiffness and resistance. Its constituting material is steel. The elastic stiffness and the limit resistance, treated as independent of each other, are fixed with the aim of satisfying special features required to the structure. The proposed device is thought as a sandwich section with wing thickness appropriately variable. Its dimensions are designed so that it can exhibit the fixed independent stiffness and limit resistance. More devices can be utilized for a given frame, and each one can be designed in order to exhibit different stiffness and resistances. These features allow the designer to define a structure with optimal requisites both for serviceability conditions and for severe limit states. The device is connected to the end cross section of the relevant beam element, so that any modification in the shape of the beam elements is avoided. The effected applications are related to simple portal steel frames and they show the great effectiveness and wide applicability of the proposed device.