Structural Behaviour of Hybrid Timber-Steel Diagrid Systems for Tall Buildings in Conakry, Guinea

{ "background": "The development of sustainable, resilient tall buildings in West African coastal cities presents unique challenges due to high wind loads and material availability. Diagrid systems offer efficient lateral load resistance, but their application with hybrid materials in this specific context is underexplored.", "purpose and objectives": "This study investigates the structural performance and feasibility of a hybrid timber-steel diagrid system tailored for the seismic and wind conditions of Conakry. The primary objective is to quantify the system's lateral stiffness, strength, and material efficiency compared to conventional steel-only diagrids.", "methodology": "A parametric finite element model was developed for a 30-storey prototype building. Timber diagonals were modelled for axial action in the primary load path, with steel nodes and perimeter beams. Wind load was the governing action. A non-linear static (pushover) analysis was conducted. Structural efficiency was assessed using a regression model: $\\lambda = \\beta0 + \\beta1(\\frac{At}{A{tot}}) + \\epsilon$, where $\\lambda$ is a drift performance index, $At/A{tot}$ is the timber-to-total area ratio, and $\\epsilon$ is the error term.", "findings": "The hybrid system achieved 85% of the lateral stiffness of a pure steel diagrid while reducing embodied carbon by an estimated 40%. The regression analysis indicated a statistically significant positive relationship between the timber proportion and the drift index ($\\beta_1 = 0.67$, 95% CI [0.52, 0.82]), demonstrating enhanced damping. Stress concentrations at timber-steel connections were identified as critical design points.", "conclusion": "The hybrid timber-steel diagrid is a structurally viable and more sustainable alternative for tall buildings in the target region. Its performance is competitive under wind loads, with significant environmental benefits.", "recommendations": "Further research should focus on connection detailing for long-term durability in humid climates and