Relative performances of laminated composite hyperbolic and elliptical paraboloidal shells with cutouts under free vibration

Abstract

Laminated composite materials have gained widespread acceptance in civil engineering due to their outstanding mechanical properties, such as high strength-to-weight and stiffness-to-weight ratios, excellent durability, and resistance to environmental degradation. Among various structural forms, hyperbolic and elliptical paraboloidal shells, which possess a smooth double-curved geometry, offer superior stiffness and aesthetic qualities. These characteristics make them wellsuited for long-span roofing systems and architecturally significant structures. The integration of laminated composites further enhances their efficiency, making them increasingly popular in modern engineering applications. However, practical implementations often require cutouts in shell surfaces for functional necessities such as air-conditioning ducts, skylights, or maintenance access, which may significantly affect their dynamic behaviour. Despite the growing use of hyperbolic and elliptical paraboloidal shells, studies addressing the impact of cutouts on their free vibration characteristics remain limited. Moreover, variations in lamination schemes and support conditions further influence their dynamic response and demand systematic evaluation. The present study aims to fill this research gap by investigating the free vibration behaviour of laminated composite hyperbolic and elliptical paraboloidal shells with cutouts under various boundary conditions and laminate stacking sequences. The influence of cutout geometry, location, and laminate configuration on the fundamental natural frequencies and mode shapes is assessed through detailed finite element modelling. The findings from this research are expected to provide valuable insights for optimizing the design of such advanced shell structures in civil engineering practice.