Seismic resilience assessment of low- and medium-rise existing eccentrically braced steel frames in Mexico City

The goal of this paper is to examine the seismic resilience of existing eccentrically braced frames (EBFs) in Mexico City under intraslab earthquake ground motions. For this purpose, detailed analytical models representative of EBF buildings designed under the 2004 edition of the Mexico City Code seismic criteria were developed as part of this investigation. These analytical models take into account the nonlinear behavior of the shear links including a failure criterion. Results of this investigation revealed that the archetype EBFs exhibit a nonuniform distribution of maximum interstorey drift, IDR max , and link plastic rotation, γ p , along height, which tend to concentrate at the bottom stories. Furthermore, it was found that γ p demands computed from nonlinear dynamic time-history analyses are smaller than that estimated from the current code criterium in Mexico City. Relevant statistical results also include the relationship among IDR max , permanent interstorey drift demand, RIDR max , and γ p . Suitable equations to predict γ p and IDR max demands are proposed based on the empirical trends of the pairs RIDR max - γ p , IDR max - γ p , and IDR max - RIDR max . An estimation of the state of damage of the shear links along-height was performed based on the plastic rotation-based damage states introduced in the literature, which allowed suggesting repair measures to build component-based recovery functions. It is shown that eccentric braced frames are a very resilient structural system to be used in a region of high seismicity such as Mexico City, particularly under strong intraslab earthquakes.