Development of H-shaped hysteretic dampers for steel concentrically braced frames

A new type of hysteretic damper, which can easily be mounted at the ends of I-section braces in concentrically braced frames (CBFs), is proposed in this paper. The main goal is to develop a damper which would enable the I-section brace and damper system to perform in a manner similar to a buckling restrained brace (BRB). The proposed cost-effective damper is composed of standard rolled H-sections and plates. Energy is dissipated by the plastic hinges that form in the webs of the H-sections. Experimental and numerical studies were conducted to investigate the behavior of the proposed damper at the component level. In the experimental study, European HEA100 and HEA140 section dampers were subjected to monotonic, stepwise cyclic, low-cycle fatigue loading and to the AISC341 BRB loading protocol. The low-cycle test data was used to calibrate damage laws for each damper. The test results showed that the proposed damper system can offer displacement capacities that are comparable to those expected from BRBs. Numerical analyses employing the finite element method were conducted in order to develop a low-cycle damage law that is based on the equivalent plastic strains. A simple failure criterion was developed to calculate the deformation capacity of a damper subjected to the AISC341 BRB loading protocol. The equivalent plastic strains need to be less than 0.1 when the damper is subjected to the maximum expected deformation. A numerical parametric study was conducted to investigate the behavior of 22 H-section geometries. HEM180, HEM200, W8 × 67, and S6 × 17.2 sections were found to be suitable for applications which require axial load levels larger than 577 kN and deformation capacities larger than 44 mm.