Eurocode-8-conforming seismic design and behaviour factor of high-post-yield stiffness concentrically-braced steel frames

A seismic-resistant steel frame with energy-dissipating, chevron-type braces is proposed. The braces are equipped with replaceable hourglass-shaped pins made of duplex stainless steel. Under design seismic loading, energy is dissipated through inelastic deformations confined in the replaceable pins while the other members remain essentially elastic. As a result, the frame exhibits high post-yield stiffness due to the inherent properties of the stainless-steel pins. A Eurocode-8-based design methodology is adopted for the frame and assessed following the Eurocode-8-compatible INNOSEIS approach. Specifically, the overstrength factor is evaluated through nonlinear pushover analysis while the behaviour factor is assessed through incremental dynamic analysis considering high and medium seismicity site-specific ground motion suites. The determined behaviour factor satisfies the global collapse prevention and life safety objectives while also keeping the maximum residual inter-storey drifts below 1/300 to permit an easy substitution of the damaged pins after the design level earthquake.