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).