The Development of a New Hysteretic Device: The Crescent Shaped Brace

The Crescent Shaped Braces (CSB) is a new simple steel hysteretic device proposed to be used as an enhanced diagonal brace in framed structures. The CSB allows the practical designer to choose the lateral stiffness independently from the yield strength of the device, due to its peculiar ad-hoc shape. In the present thesis, a complete study referring to the CSB has been presented. Analytical formulas have been developed to describe the behavior of such devices under tensile and compressive loads, in elastic and post-yielding phases. The same device has been studied through extensive numerical simulations to assess the seismic capacity and its response under cyclic loads. As well, the main results of experimental tests conducted on thirteen scaled CSB specimens realized with different cross-sections are presented. The overall experimental response in terms of stiffness, strength, ductility and global instability is compared with the design formulations and with the results of numerical simulations developed with commercial software. It is shown that the overall experimental behavior of CSB is well captured by the design formulas and that commercial software are suitable to simulate the hysteretic response of such device. After the validation of the hysteretic capacities of the Crescent Shaped Braces, a new seismic concept has been proposed within the PBSD and the concept of the enhanced first story. It relies on the total separation between the Vertical Resisting System (VRS) and the Horizontal Resisting System (HRS) in order to attain a certain objective curve of the structure. An applicative example has been studied following this concept and exploiting the advantages of the CSBs as seismic dissipative devices, to be used for the HRS. Some indicative uses of the CSB have been presented, like horizontal link, angle reinforcement for beam-column joints and façade dissipative elements.