It is also observed that the shear strength balance has an impact in the height-wise distribution of residual drifts, and an important "shake-down" effect is obtained for all cases. From the analysis of the obtained results, it is concluded that when a suitable design criterion is considered, good structural behavior of RC-MRCBFs with steel-X bracing can be obtained. Finally, a brief discussion regarding residual drifts, residual drift ratios, mappings of residual deformations in steel braces and residual rotations in RC beams and columns is presented. Although steel bracings have simpler connections compared to moment resisting frames, they experience lower ductility. Additionally, envelopes of response maxima of dynamic parameters were obtained from the story and global hysteresis curves. Some design parameters currently proposed in MFDC-04 as global ductility capacities, overstrength reduction factors and story drifts corresponding to different limit states were assessed as a function of both the considered shear strength and slenderness ratios for the studied RC-MRCBFs using pushover analyses. In order to observe the principal elements responsible for dissipating the earthquake input energy, yielding mappings for different load-steps were obtained using both nonlinear static and dynamic analyses. Extra vertical steel trusses that are added to braced frames are particularly effective in resisting lateral stresses2. The design of RC-MRCBFs was carried out considering variable contribution of the two main lines of defense of the dual system (RC columns and steel braces). The height of the studied structures ranges from 4 to 20 stories and they were located for design in the lake-bed zone of Mexico City. The nonlinear behavior of low to medium rise ductile RC-MRCBFs using steel X-bracing susceptible to buckling is evaluated in this study. It is also observed that the shear strength balance has an impact in the height-wise distribution of residual drifts, and an important shake-down effect.
#Perfect balance vs braced frame code#
A satisfactory ductile performance of moment-resisting reinforced concrete concentric braced frame structures (RC-MRCBFs) is not warranted by only following the provisions proposed in Mexico's Federal District Code (MFDC-04).
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