Structural Analysis of Long-Span Steel Roof Systems for Multi-Purpose Auditoriums in Federal Universities in North-Central Nigeria

The structural design of long-span roof systems for large-capacity university auditoriums in Nigeria presents significant engineering challenges, including efficient load distribution over column-free spans, thermal movement accommodation, and vibration performance under crowd loading. This study analyses structural options for long-span steel roof systems for multi-purpose auditoriums with capacities of 2,000 to 5,000 seats in federal universities in the North Central geopolitical zone, drawing on design case studies at institutions in Nasarawa, Benue, and Niger States. Four structural roof typologies are assessed: Warren truss, Vierendeel truss, space frame, and cable-stayed frame. Structural analyses were conducted using STAAD.Pro under BS EN 1991 load combinations including dead load, imposed crowd load, wind uplift, and thermal expansion over a 45-degree Celsius temperature range. Performance metrics including maximum deflection, member utilisation ratio, steel tonnage, and construction complexity were evaluated for each typology. Results indicate that the cable-stayed frame achieved the most favourable deflection performance under imposed loading with a midspan deflection of span/480, but demanded specialised fabrication and erection expertise not readily available in the North Central contractor market. The space frame provided the best balance of structural efficiency, material economy, and constructability, with member utilisations averaging 0.72 and steel tonnage 18 percent below the equivalent Warren truss. Vibration analysis under synchronised crowd loading confirmed that all four systems achieved fundamental frequencies above 4 Hz, avoiding resonance risk. The study provides a structured selection framework for federal university infrastructure development programmes. Keywords: long-span steel roofs, space frame, auditorium, federal universities, North-Central Nigeria.