Theoretical and Experimental Investigation of Structural Diaphragm Action in Corrugated Metal Deck Roof Systems for Low-Rise Industrial Buildings

Corrugated metal deck roof systems are extensively used in low-rise industrial and warehouse buildings across Nigeria, and their diaphragm action in distributing lateral wind loads to perimeter bracing frames is a structurally significant contribution that is inadequately characterised in Nigerian structural design practice, where roof diaphragm contribution is often conservatively ignored. This study presents a theoretical and experimental investigation of structural diaphragm action in corrugated metal deck roof systems, developing an original mechanical model that accounts for sheet-to-purlin fastener flexibility, end-lap geometry, and in-plane shear stiffness degradation under cyclic loading. Full-scale corrugated deck panel assemblies measuring 4.8 m by 7.2 m were fabricated and tested in a purpose-built in-plane shear loading rig at three fastener configurations representative of practice in industrial building construction across the North West and South West geopolitical zones. Cyclic in-plane shear loading was applied using a horizontal actuator, and panel stiffness, peak shear capacity, and energy dissipation were measured. Parallel finite element models incorporating fastener spring elements were developed and validated against the experimental data. The validated model was applied in parametric studies varying deck profile geometry, sheet gauge, fastener spacing, and purlin span. Results indicate that corrugated deck diaphragms in typical industrial building configurations provide in-plane shear stiffness sufficient to reduce lateral drift in perimeter bracing frames by 25 to 43 percent relative to zero-diaphragm assumptions, with significant implications for bracing member sizing and economy. A design-oriented closed-form expression for diaphragm shear stiffness is derived and benchmarked against ECCS recommendations. Keywords: diaphragm action, corrugated metal deck, lateral load distribution, industrial buildings, shear stiffness.