Structural Performance Characteristics based Seismic Damage Gradation Schema for Single Storey URBM Buildings in India with a Rigid Diaphragm

Damage gradation is the important aspect in obtaining fragility curves and hence in the estimation of expected damage during hazardous events. This paper presents a new schema for seismic damage gradation, simply referred to as damage gradation, for use in vulnerability analysis of single story unreinforced brick masonry (URBM) buildings with a rigid diaphragm. The new schema for damage gradation is based on structural performance characteristics instead of the fixed limiting values of drift ratios or drift ratio thresholds, for which appropriateness and justifications are provided. The schema is, DG1: earlier of initiation of non-linearity in any of the component piers or attainment of 33% of peak base shear of the building, DG2: attainment of peak base shear of the building, and DG3: fall-off resistance to 60% of peak base shear of the building. The schema is arrived at based on study of capacity curves, along two principal horizontal directions, of a representative set of 35 typical URBM buildings and by establishing, (1) it is inappropriate to adopt the conventional fixed limiting values of drift ratios for damage gradation and, (2) the applicability of drift ratio thresholds is also limited.