Seismic design of residential buildings in Saudi Arabia using SBC301-24 and SBC1101-24: a comparative study with dynamic analysis

Abstract This manuscript presents a side-by-side comparison of seismic design outcomes for a regular, three-story reinforced-concrete moment-frame building in Jeddah (Site Class C) when designed per the Saudi Building Code SBC301‑24 (general structural loads) and the Saudi Residential Building Code SBC1101‑24 (simplified procedure). The authors implement modal response spectrum analysis (SRSS and CQC) per SBC301 and the equivalent static method and apply the SBC1101 simplified procedure subject to its applicability limits. Results show that SBC1101 yields higher lateral story forces, base shear, and overturning moment than SBC301 (SRSS/CQC and ELF), with average increases of 30–45% in base shear relative to modal analysis, and up to ~87% relative to ELF for Seismic Design Category A. Interstory drifts remain far below ASCE 7‑22 allowable limits and P–Δ stability coefficients are well below threshold; hence the studied system exhibits ample drift capacity. The discussion explains the code-level reasons for the differences (e.g., response modification, vertical force distribution rules, and SDS-based scaling) and provides practical guidance for low-rise residential buildings in KSA. The study is contextualized with recent probabilistic seismic hazard assessments for the southwestern region (including Jazan and the Red Sea Rift) and related comparative code studies.