Abstract
This paper presents a spectral shape proxy stems from geometric mean
consisting of spectral ordinates at the structure’s first mode period to
that of much larger period. The proposed model denoted by α_geo is
normalized by spectral ordinate at 2T_1 for reducing dispersion and
scaling level problem. Another arithmetic mean model, α_Ar, is also
developed to be used for comparison purpose of the geometric mean model.
The 26 RC-SMF structures and 78 far-field ground motions are selected to
evaluate the performance of the model as a case study. IDA method is
used to calculate collapse capacities of the selected structures. Series
of linear relationship are developed among the model values and
corresponding structures’ collapse capacities demonstrating strong
coefficient of determinations (R^2). Performances of the presented
models “efficiency” and “sufficiency” aspects are shown to be as
strong as those of recently proposed predictor, SaRatio, while benefits
from simplicity. Utilization of the proposed model are: as an element of
vector valued IM, as a collapse capacity predictor for structures at
far-source sites, collapse margin ratio for collapse safety evaluation
of structures.