Development of pinching‐free tension‐only CBFs based on the application of metal foam dampers

Metal foam is a relatively new and potentially revolutionary material due to its properties such as the low weight‐to‐stiffness ratio, high damping and energy dissipation capacity. Even if this material is widely used in mechanical, aerospace and automotive industries, it is still not frequently used in civil engineering applications. The large energy dissipation capacity that metal foams possess could be exploited to control the seismic performance of structures, but only few research investigations have been focused on this matter. Within this context, the present paper investigates a possible solution to realize dissipative aluminium foam dampers to be applied in X‐braced steel structures for concentrically braced steel frames (CBFs). The bracing system consists of a steel rod or tube linked to an aluminium foam damper. The damper device is constituted by aluminium foam that provides the structure with dissipation capacity when activated under compression. The permanent deformations of the aluminium foam are absorbed by a wedge device, avoiding a pinching behaviour in the global response. Analytical equations governing the global behaviour of the bracing system are herein presented. An X‐braced steel frame complying with Eurocode 8 provisions is designed and considered as case‐study. The structure is subsequently upgraded by introducing the dissipative device into the bracings. The results of preliminary experimental and numerical tests on the components of the device are herein presented, showing the potentiality of the solution.