Comparative Seismic Performance of OMF Vs. IMF For Reinforced Concrete Residential Multi-storey Buildings in Tripoli, Libya

Abstract

Abstract— Current construction practices in Tripoli, Libya, still depend on Ordinary Moment Frames (OMF) integrated with ribbed slab systems based on the traditional assumption of low seismicity in the region, however, recent local seismic hazard studies have classified the region Seismic Design Category (SDC) as C or D, which necessitates a critical assessment under the current structural norms. The seismic adequacy of an eight-story reinforced concrete (RC) building was investigated under three different configurations based on American Concrete Institute (ACI 318-19) and American Society of Civil Engineers (ASCE 7-16): conventional OMF with ribbed slabs, Intermediate Moment Frames (IMF) with ribbed slabs, and IMF with solid slabs. The standard OMF-ribbed configuration was analyzed and found to have 23.4% of the beams failing due to critical shear-torsion failures, which is fundamentally not adequate for current demands, while upgrading to an IMF-ribbed system reduced the failure rate to 10.5% (55% improvement) that is still not compliant with the code, and the IMF with a solid slab system achieved 100% structural adequacy with no beam failures, inter-story drift of 0.57%, and column demand-capacity (P-M) ratios within a safe threshold of 0.68. These localized findings suggest that current construction practices may underestimate seismic vulnerability, and consequently, implementing an IMF integrated with a solid slab system provides an enhanced structural configuration to satisfy modern code provisions and warrants consideration in future revisions of local construction regulations.