Eurocode conforming design of BRBF – Part II: Design procedure evaluation

Abstract

Buckling Restrained Braces (BRB) are innovative displacement dependent devices having balanced hysteretic behavior. Frames equipped with such devices are known as Buckling Restrained Braced Frames (BRBF). Application of BRB elements in Europe is seriously limited by the lack of a standardized European design procedure for BRBF.In the first part of this paper the authors propose a Eurocode conforming design procedure for BRBF and provide the seismic design parameters and capacity design rules by enhancing Eurocode 8 specifications on steel Concentrically Braced Frames. This second part introduces 24 BRBF archetypes designed with the proposed procedure. Their performance under seismic excitation is investigated by nonlinear dynamic analysis in an environment developed by the authors through improvement of the methodology in FEMA P-695. Feasibility of the proposed design procedure is evaluated as a function of conditional failure probability of the archetype buildings.The presented assessment required detailed experimental studies on BRB behavior and development of a novel material model that can simulate complex nonlinear hardening under irregular cyclic loading. The material model is implemented in the OpenSees finite element code. A software environment was developed for automatic evaluation of braced frames using OpenSees.The sufficiently low collapse probability of BRBF archetypes confirms the applicability of the proposed design procedure in Europe.