Theory of plastic mechanism control: A new approach for the optimization of seismic resistant steel frames

This paper presents an important improvement in seismic design of structures based on the application of the Theory of Plastic Mechanism Control (TPMC). TPMC was originally proposed in the ‘90s requiring an iterative algorithm and upgraded in 2015 leading to the so-called closed form solution. In the recent years, TPMC has shown its value as an effective design procedure which can be applied to any structural typology. Moreover, it has been used as a code competitor design tool in important RFCS founded research projects confirming its effectiveness, simplicity, and suitability to any structural typology. The aim of the TPMC is the design of structures able to exhibit at collapse a global type mechanism. The TPMC was originally based on the extension of the kinematic theorem of plastic collapse to the concept of mechanism equilibrium curve, working in the (Formula presented.) plane (being α the multiplier of the seismic forces and δ the top sway displacement). The novelty of this work is improvement of the design procedure by working in the (Formula presented.) plane, being θ the plastic rotation. This new TPMC approach, namely TPMC(θ), has demonstrated to be as reliable as the former approach, thus leading to structures able to develop a collapse mechanism of global type but with the optimization of the structure using lighter columns. The effectiveness of the new procedure has been confirmed by both pushover and dynamic non-linear analyses.