Improvements to the Ugandan seismic code in estimation of base shear for concrete buildings

Abstract

This study aimed at improving the Ugandan seismic code’s base shear estimation for reinforced concrete buildings by comparing it with Eurocode8 (EC8) and the American Seismic Code (ASCE/SEI 7-16). Hypothetical symmetrical reinforced concrete moment-resisting framed buildings, ranging from 04 to 20 stories, were analyzed under identical seismic hazard conditions using Equivalent Lateral Force (ELF) and Response Spectrum Methods (RSM) via ETABS software. The results were evaluated using Principal Component Analysis (PCA), sensitivity analysis, hypothesis testing, and Artificial Neural Networks (ANNs) to identify trends and discrepancies across the codes. The study revealed that base shear estimation is strongly influenced by building height and plan dimensions (bay width and number of bays), confirming established structural dynamics principles. RSM analysis consistently produced higher base shear values than ELF across all three codes, with ELF values being up to 82% smaller in some cases. Among the codes, the Ugandan seismic code (US 319:2003) yielded the lowest base shear results, confirming assertions that it underestimates seismic forces compared to international standards. Comparative ratios of RSM base shear between ASCE/SEI 7-16, EC8, and US 319:2003 were 2.15:1, 1.47:1, and 0.95:1, respectively, highlighting significant underestimation by the Ugandan code. An ANN model was developed to predict comparative beta parameters, offering a practical tool for future code improvements. The findings emphasize the need to update the Ugandan seismic code to align with international standards, ensuring safer and more reliable design practices.