A calibrated simplified model for plane and regular R/C moment resisting frames

Because computational time is still a limitation for building inelastic dynamic analysis, an enhanced version of a simplified model for efficient analysis and design of 2D regular moment resistant reinforced concrete frames is proposed herein. The model is an adaptation of the Modified Fishbone Model (MFB) originally developed for steel Moment Resisting Frames. The MFB replaces all elements of a story with a macro-column,a pair of macro-beams, and a pair of vertical truss elements. Both macro-elements consist of elastic members with inelastic end hinges. A new smooth hysteretic model for the rotational springs of the MFB is proposed herein, considering ductility-based stiffness degradation, ductility- and energy-based strength degradation, and pinching. The responses of the MFB are compared against a force-based fiber model, which considers modified Kent-Park and Menegotto-Pinto models for concrete and steel fibers, respectively. The calibration of the MFB considers a set of pushover analyses and the use of the Particle Swarm Optimization/Nelder-Mead algorithm for the parameter identification phase. A set of plane frames of 1, 5, 10, 15 and 20 stories, with 3, 6 and 9 regular bays is studied with consistent seismic records selected by a Conditional Spectrum from the SIBER-RISK ground motion database. The proposed numerical model presents errors that usually are less than 20% and 40% for the mean and standard deviation, respectively, of the peak responses of story displacement and base shear, and requires between 5 to 30 times less computational time than the counterpart fiber model. The results are acceptable for all tested buildings and the precision is better for larger inelastic behavior.