PERFORMANCE-BASED PRELIMINARY SEISMIC ANALYSIS APPROACH OF NEW REINFORCED CONCRETE FRAME STRUCTURES

摘要

A formal theoretical basis is developed applying concepts of performance-based engineering for a preliminary seismic analysis of new reinforced concrete structures. Rather than advancement in complex analytical techniques, the presentation of simple concepts relevant to the routine seismic design is here advocated. Within the performance-based seismic engineering framework the procedure is defined in terms of a displacement-based approach. To this end, and according to the performance objective previously selected, the displacement demand assessment takes into account two main aspects. Firstly, the deformation demand derived from the control of both the elastic and the post-elastic torsional twists must not exceed the structural displacement capacity actually provided. Secondly, a partial-sway admissible plastic mechanism is proposed at early stage of the design. The general formulation expressed in the acceleration-displacement spectral format and defined as a function of constant ductility yield point spectra is presented. As a consequence, and following the current state-of-the-art, the system yielding displacement is assumed as the analysis independent variable. Thus, by means of the structure's yield deformation the required strength is suitable computed according to the spectral region governing the design. The strength reduction factor is established in terms of the ductility level derived from the displacement evaluation previously performed. Finally, a general step-bystep algorithm is described, and a numerical example used to illustrate the implementation of the approach is presented.