Study of GFRP composite stiffened panels with square opening

Fiber reinforced polymer stiffened panels are the important parts of marine structures. Square openings are necessary for functional purposes in the stiffened panels of marine structures. Finite element software ABAQUS is used to analyse of stiffened panels with and without square opening is carried out using ABAQUS. Reinforcement of square opening is necessary to obtain the original strength and stiffness of stiffened panels under axial loading and combination of axial & pressure loading. The thicknesses of intermediate stiffeners necessary to obtain the original strength and initial stiffness were determined as 8.5, 7.5 and 9 mm under axial loading, constant axial & increasing pressure loading and constant pressure and increasing axial loading respectively. The failure loadings and failure pattern of stiffened panels without opening, with unstrengthened and strengthened square opening are found. Load vs. displacement curves of stiffened panels without opening, with strengthened and unstrengthened square opening under different loading patterns are plotted and shown. The area of strengthened stiffener around opening to the area of stiffeners required to bring back the original load carrying capability of stiffened panels having square opening were determined as 1.34, 1.18 and 1.42 for axial loading, constant axial & increasing pressure loading and constant pressure & increasing axial loading respectively. Hence, the square opening in stiffened panels was observed to have critical behaviour under constant pressure and increasing axial loading.