Response Modification Factor in Intermediate Moment Resisting Frame Building

Abstract

The response modification factor (R) is considered as one of the most important parameters that affect the seismic design of new buildings all around the world. Any improvement in the reliability of modern earthquake-resistant buildings around the world must involve an exhaustive examination of the building response characteristics that have the greatest influence on the values assigned to the factor. The primary goal of this analytical and parametric research is to examine the response modification factor (R) and study the seismic behavior of the buildings in Concrete Moment Resisting Frame System (CMRFS) structures constructed. The research focuses on an Intermediate Moment Resisting Frame System (IMRFS), with 4 and 3 bays in longitudinal and transverse directions for 1,2,3 and 4 stories, each one consists of (18x24) m2 two-way solid slab with 6m center to center span between columns. Nonlinear behavior is applied for beams and columns due to gravity and earthquake loadings. A nonlinear static pushover analysis (fiber hinges) is performed and compared with the available published experimental data. The capacity curve of the structure using the displacement control approach is used to evaluate the response modification factor (R) and is compared with the ASCE code values. A parametric study is carried out to investigate the realistic value of the response modification factor. In this parametric study, the effect of number of stories, size of column section dimensions, member reinforcement and performance point are investigated. Results of this research show that the number of stories and the difference of columns cross sections as well as the maximum lateral displacement that is imposed on the structure during the pushover analysis have a substantial impact on the R-factor value. This research evaluates the pattern and explains the relationship of change in R-factor with an increase in the number of stories and decrease the cross-sectional areas and the redundancy factor and suggesting the real value of (R) for a different number of stories that are exposed to the same conditions and linking it to the values of the Performance Point (PP) and the Performance level of structures against earthquakes.