Damage-based optimal design of friction dampers in multistory chevron braced steel frames

Abstract

In this paper, a probability-based design methodology of the friction dampers in multi-story steel frames is proposed. Both the slip force of the device and the stiffness ratio of the system are analyzed as two important parameters, which affect the behavior of the structures equipped with friction devices. The seismic fragility of friction damped braced frames is evaluated and used to identify the optimal ranges of the above-mentioned design parameters so as to minimize the overall damage probability of the structure under the action of strong ground motions. For this purpose, fragility functions of the structural models are derived using nonlinear incremental dynamic analyses. To demonstrate the efficiency of the proposed method, three structural models of steel moment resisting frames with friction damper systems (including chevron braces and damper devices) are considered for the purpose of the seismic performance analysis. The results of the analyses show that the largest damage probability in each structural model corresponds to the case with the higher slip force and the lower stiffness ratio, where the undesirable buckling failure will govern before full activation of friction damper. For the three considered building frames, the optimal range of slip force lies between 40% and 55% of the total weight of structures and the recommended value for stiffness ratio is 2.