Higher Mode Vibration of Composite Stiffened Hypar Shell with Cut-Out for Varying Boundary Conditions and Ply Orientation

Volume 8 Issue 2 June - August 2019

Research Paper

Higher Mode Vibration of Composite Stiffened Hypar Shell with Cut-Out for Varying Boundary Conditions and Ply Orientation

Puja Basu Chaudhuri *, Anirban Mitra**, Sarmila Sahoo***

*,***Department of Civil Engineering, Heritage Institute of Technology, Kolkata, India.

**Department of Mechanical Engineering, Jadavpur University, Kolkata, India.

Chaudhuri, P. B., Mitra, A., & Sahoo, S. (2019). Higher Mode Vibration of Composite Stiffened Hypar Shell with Cut-Out for Varying Boundary Conditions and Ply Orientation, i-manager's Journal on Structural Engineering, 8(2), 37-51. https://doi.org/10.26634/jste.8.2.14705

Abstract

Laminated composite shells are used as roofing units in Civil Engineering applications and hypar shells are most popular because of their ease of construction and aesthetic elegance. The aim of the present study is to analyse higher mode free vibration of composite hypar shells. The purpose is to obtain some design guidelines for the practising engineers dealing with such structures. The methodology adopted here is the finite element method based on first order shear deformation theory. Effect of cross curvature is included in the formulation. The isoparametric finite element consists of eight nodes with five degrees of freedom per node is considered. Three noded beam elements with four degrees of freedom per node are used for stiffeners. The generalised Eigen value solution is chosen for the un-damped free vibration analysis. The formulation is validated first by solving standard problems from literature and then new results are obtained for varying boundary conditions, ply orientation and curvature of the shell. The first five modes of natural frequency are presented. In general, it is observed that fundamental frequency increases with the increase in the number of support constraints. There are, however, few departures from this general tendency when two shells of different laminations are compared. Sometimes lamination order may influence the frequency of stiffened composite shell with cut-out more significantly than its boundary conditions. Symmetric lamination exhibits reasonably good performance and may be adopted for all practical purposes.