Evaluation of the structural performance factors, K for RC buildings according to the Ugandan Seismic code.
Abstract
The main objective of this research was to evaluate the structural performance factor, K (table 4,
US 319:2003) for RC buildings. In the Ugandan code, the K factors account for the ductility of
structures during calculation of seismic load. US 319:2003 suggests a K factor of 2.0 for ductile
moment resisting frames with masonry infills. However, there’s no sound technical basis for this
value.
In this research, the structural performance factor, K for ductile moment resisting frames with
masonry infills was calculated based on nonlinear static analysis (Push over analysis) with the
aid of ETABS v.18 software. 6 RC regular, 18 RC horizontally irregular and 12 RC vertically
irregular RC frame models were analyzed and designed for both gravity and lateral loads. Push
over analysis was thereafter performed at a target displacement 4% of the building height while
considering default and user defined hinge properties assigned to the beams and columns
according to ASCE 41-13 guidelines. Finally, analysis results were exported to Sigma Plot v.14
where the capacity curves for each model was plotted. Thereafter, the structural performance
factors were calculated.
Based on the results, it was observed that the K factor in US 319:2003 gave a good estimate of
the structural performance for short period models (3 stories) and under-estimated the structural
performance for high period models (8 and 12 stories).