Improved Slender Column Design Models for the SBC 304 Saudi Building Code

Received: 15 July 2025 | Revised: 5 August 2025 | Accepted: 15 August 2025 | Online: 8 September 2025

Corresponding author: Rabeea W. Bazuhair

Abstract

The study offers an in-depth examination of the current design provisions for slender reinforced concrete columns in the Saudi Building Code (SBC 304) and the development of advanced predictive models for practical application. Current design procedures in modern building codes, including SBC 304, primarily rely on the moment magnifier method, where linear static moments are magnified using empirical values based on slenderness ratios and end conditions. These procedures, nevertheless, fail to capture geometric and material nonlinearities, leading to inaccurate and sometimes unrealistic design predictions. Based on a detailed analysis of 107 test specimens from three large-scale experimental programs, the study identified notable deficiencies in the existing code provisions when compared with test results. To address these shortcomings, the study proposes improved design formulae for estimating lateral deflection and failure load in slender reinforced concrete columns, incorporating both material and geometric nonlinearities through advanced nonlinear regression techniques. Statistical validation confirms that the proposed equations are more accurate and reliable than current code-based procedures, yielding significantly lower prediction errors and improved consistency. The new lateral displacement formula reduced the average absolute error by 58% (from 12.9 mm to 5.4 mm) and the coefficient of variation by 30% (from 63.1% to 44.1%) compared with existing code procedures. Failure load prediction equations were also significantly improved, with average absolute errors reduced by approximately 89% for predictions based on section capacity and 42% for slender column analysis-based predictions.