Assessment of Lateral Load Resistance of Unreinforced Masonry Buildings in Northern Nigeria Using Push-Over Analysis

Unreinforced masonry construction continues to dominate the residential and low-rise commercial building stock in many cities of northern Nigeria, representing a potentially significant vulnerability to lateral loading from wind, seismic ground motion, and accidental impact. This study assesses the lateral load resistance of typical unreinforced masonry building forms in Katsina, Sokoto, and Gusau in the North West geopolitical zone using nonlinear static push-over analysis. Representative building configurations, including single-storey traditional courtyard houses and two-storey semi-detached commercial buildings, were modelled using the equivalent frame method implemented in TreMuri masonry analysis software, with masonry mechanical properties derived from testing of locally produced blocks and mortar joints. Push-over analyses were conducted under increasing lateral load distributions in both principal plan directions, and performance was evaluated against target displacement demands corresponding to design wind and low-level seismic loading for the region. Results indicate that single-storey courtyard buildings achieved target wind performance within their lateral resistance capacity, while two-storey commercial masonry buildings exhibited inter-storey drift ratios at design wind load that approached the damage limitation limit state, with limited ductility reserve beyond first crack. Under low-level seismic loading at 0.05g, push-over analysis showed brittle shear failures in ground-floor piers of the two-storey commercial typology before reaching target displacement. The study identifies in-plane shear failure of ground floor piers as the critical failure mode and recommends grout-filled vertical cores and horizontal bed-joint reinforcement as practical retrofit measures. Keywords: unreinforced masonry, lateral load resistance, push-over analysis, Northern Nigeria, seismic vulnerability.