Deflection, forces and moments of composite stiffened hypar shells with cutout

Abstract

Among the various forms of doubly curved shells, hypar shell is aesthetically appealing and used as roofing units in large column free areas. Cutout is in general provided in roof structures to allow entry of light, venting and to enhance accessibility of parts of the structure, and sometimes to alter the resonant frequency. Though some studies are available for other forms of shells, very few literatures appear to have been published on the effects of cutouts on bending behavior of hypar shell. Finite element method using an eight noded shell element and a three noded beam element both curved and isoparametric is applied to analyze the bending behavior of stiffened hypar shell with cutout. Hypar shell stiffened along the margin of cutouts under the same intensity of loading and different boundary conditions for antisymmetric angle ply lamination is studied for five types of cutouts. The displacements, force and moment resultants are computed at the nodal points of different boundary elements around the openings. The comparative performance of shell characteristics around the opening for different cutouts including longitudinal and transverse of equivalent size reveals that size of the opening is a governing criterion to determine the shell characteristics. Also boundary constraints have large impact on deflection and static stress resultants.