Following the increasing progress of various industries and the use of plates in the construction of various structures, analysis of plates and plate structures and improving the performance of sections against the loads has become very important. In this direction, the use of fewer materials and having more load-bearing and construction of cost-effective structures has been considered by everyone. Therefore, the use of composite sections and stiffened sections with improved features is an important step in achieving this goal. In the present study, elastic and plastic local buckling of a square box and T-shaped sections stiffened with longitudinal stiffener and the cross sections made of a composite plate called corrugated-core sandwich plate has been investigated. The types of loading on these sections are considered as uniform compressive load and the stresses due to bending. The effect of geometric parameters of sections on the behavior and critical buckling load of the section has been eva‎luated. The analytical method used in this research is the finite strip method based on the classical plate theory. By combining the finite strip method and the classical plate theory, the deformations of the plate are assumed based on its degrees of freedom, and by obtaining the stiffness matrix and stability matrix, the critical stress of the section is calculated by solving an eigenvalue problem. Shape functions used to define the displacement domain are sinusoidal functions in the longitudinal direction and hermitian in the transverse direction. The results obtained from the developed program in MATLAB software are compared with the results of previous studies using the finite strip method, so the results can be considered reliable and accurate. The results of this research show that the use of longitudinal stiffeners in a thinner square box and T-shaped sections is more effective and helps to increase the bearing capacity. In the section consisting of corrugated-core sandwich plates, the use of thin stiffeners does not have a significant effect on the bearing capacity of the section and only reduces its efficiency, but if stronger stiffeners are used local buckling occurs in corrugated-core sandwich plates and by changing the geometric parameters of these plates, the capacity of the whole section can be increased.

مجتبي ازهري، سعيد صرامي

مهدي زندي، نيما نورمحمدي