Design of rectangular industrial duct plates subjected to out-of-plane pressure considering nonlinear large deformations

Large industrial steel ducts are often rectangular and are built-up of stiffened plates. The plates along with stiffeners act to resist the pressure loads and transfer these loads to the supports. Parallel wide flange steel profiles, usually beams, are used as transverse stiffeners that are spaced perpendicular to the longitudinal axis of duct. The design process involves determining the load carrying capacity and deflection of the plate based on the plate thickness and the spacing between stiffeners. The current analysis and design method for industrial ducts is based on the elastic large deflection plate theory using standard tables. inear finite element parametric study was conducted on dimensionless parameters to investigate the behavior of laterally loaded long plates. Through-thickness yielding of the plate and formation of partial plastic hinges at the ends is allowed. The results are presented in terms of a proposed dimensionless Normalized Load Factor (NLF) representing the applied pressure, the Normalized Deflection Factor (NDF) representing the out-of-plane deflection and the Normalized Maximum Stress Factor (NMSF) representing the maximum stresses induced in the plates. Design equations for deflection and stresses of plates are established with the aid of Bezier curves. A simple design procedure allowing for large deflection and partial yielding of edges is proposed. A limiting value for pressure has been found where it becomes irrelevant to check deflection. Results show that the proposed design procedure is simple and can lead to economic plate thicknesses and spacing of stiffeners in industrial ducts in ambient temperatures.