Investigation into the behaviour of a ductile multi-tubular force limiting device

A force limiting device ideally possesses rigid-plastic force/shortening characteristics. When such a device is introduced in a compression member, and if the limit load of the device is set somewhat below the buckling load of the member, the member will behave in an elastic-plastic manner. The present paper outlines the non-liner behaviour of a novel multi-tubular, ductile compression member which exhibits an initial axial stiffness, followed by a steady load plateau and subsequent enhanced stiffness and strength, before the final failure. The multi-tubular member acts as an energy absorber and force redistributor. The theoretical cyclic response of the device, obtained using ABAQUS, is presented. For a comparison of the energy absorbing characteristics, two X braced frameworks have been considered, one with conventional tubular bracing, and one with the force limiting devices used for bracing. For relatively large horizontal displacements, the framework incorporating the force limiting devices exhibited greater ductility and energy absorbing characteristics than the conventionally braced framework.