عنوان مقاله [English]
نویسندگان [English]چکیده [English]
The nonlinear force-displacement curve of RC columns are presented in the current standards for seismic rehabilitation of existing buildings (such as ASCE41) by two displacement-based values of “a” and “b” that correspond to the loss of lateral and axial capacities, respectively. The ASCE41 presents the values of these two parameters as a function of the volumetric ratio of transverse reinforcement. A confinement index is proposed in this paper that accounts for the yield strength and arrangement of the transverse reinforcements as well. This index was used to predict the parameters “a” of 38 tested RC columns and the parameters “b” of 13 other columns. A table is proposed that gives the values of these two parameters based on the values of the proposed confinement index of the columns. It is shown that the proposed confinement index and table predicts more accurate values of the parameters “a” and “b”. Based on the results, maximum difference ratio to experimental values is reduced from 4.7 to 3.6 in comparison with those of update to ASCE41-06 while satisfying its specifications and regulations.