Behavior of ductile steel X-braced RC frames in seismic zones

• Published in: Earthquake Engineering and Engineering Vibration Vol. 18; no. 4; pp. 845 - 869
• Main Authors: Godínez-Domínguez, Eber Alberto, Tena-Colunga, Arturo
• Format: Journal Article
• Language: English
• Published: Harbin Institute of Engineering Mechanics, China Earthquake Administration 01.10.2019; Springer Nature B.V
• Subjects: Civil Engineering; Columns (structural); Control; Design; Design parameters; Drift; Ductility; Dynamical Systems; Earth and Environmental Science; Earth Sciences; Earthquakes; Frame structures; Geotechnical Engineering & Applied Earth Sciences; Height; Lake beds; Lakes; Limit states; Nonlinear analysis; Parameters; Ratios; Reinforced concrete; Reinforcement (structures); Reinforcing steels; Seismic activity; Seismic design; Seismic engineering; Seismic response; Seismic zones; Shear strength; Steel; Steel frames; Steel structures; Structural behavior; Vibration; Mexico; residual drifts; RC braced-frames; story drifts; collapse mechanism; seismic design; overstrength; steel-X bracing; nonlinear dynamic analyses
• ISSN: 1671-3664; 1993-503X
• DOI: 10.1007/s11803-019-0539-0

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). The nonlinear behavior of low to medium rise ductile RC-MRCBFs using steel X-bracing susceptible to buckling is evaluated in this study. 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 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). 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. 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. Additionally, envelopes of response maxima of dynamic parameters were obtained from the story and global hysteresis curves. 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. 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. 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. There is a need to improve design parameters currently proposed in MFDC to promote an adequate seismic performance of RC-MRCBFs.