Local Buckliing Analysis Of Vertically And Rotationally Restrained Composite Plates Under Biaxial Compression

Short-span fiber-reinforced plastic (FRP) thin-walled compositestructures are sections consisting of assemblies of flat panels. They havemany advantages over conventional materials, such as high specificstrength, high specific modulus, low cost, high desighability etc., they arebeing extensively used for civil engineering structural applications,aerospace and so on. However, due to the thin-walled sectional geometryand relatively low stiffness, problems associated with large elasticdeformation and local buckling are common when they are under variouskinds of loads.Local buckling analysis of these short-span FRP compositethin-walled structures are generally accomplished by the discrete plateanalysis, which has the characters of efficient, convenient and making thecomplex stability problem of three-dimensional space structures besimplified to a relatively simple problem of two-dimensional plane plates.In the study, local buckling analysis of a special kind of mathematicalmodel of composite plates, which can treated as the web plate elementsdiscreted from FRP composite thin-walled structures, is presented with thehelp of Rayleigh-Ritz method and the commercial finite element softwareANSYS. The main work of the study consists of four parts:(1) Approximate local buckling analytical solution and explicit designformulas are obtained. Local buckling analysis of a special kind ofmathematical model of orthotropic composite rectangular plates, which aremore universal, representative, and close to engineering practice, subjected to biaxial in-plane compression with the two opposite edges rotationallyrestrained (the vertical restraint stiffness tends to infinity) and the othertwo opposite edges both vertically and rotationally restrained is presentedby the Rayleigh-Ritz method. Approximate local buckling analyticalsolution and several explicit design formulas, which are commonly used inthe stability analysis of thin-walled structures, are obtained.(2) Accuracy validation, error analysis and a proposal of improvingaccuracy are carried out. The accuracy of the approximate local bucklinganalytical solution and explicit design formulas are validated with the helpof the commercial finite element software ANSYS and the solutions whichare available in the literatures. Good agreements are achieved for theRRRR boundary case with a maximum percent difference4.81%, whilethe accuracy is relatively poor for the RRVV boundary case with amaximum percent difference26.37%. In response to this situation, erroranalysis is carried out and a suggestion for improving the accuracy ofRRVV boundary case is proposed.(3) Parametric studies are conducted. In order to evaluate theinfluences of the loading ratio (), the rotationally restrained stiffness(KR), the vertically restrained stiffness (KV) and the aspect ratio (), thecorresponding parametric studies are carried out.(4) Experimental local buckling analysis is conducted. Experimentallocal buckling analysis of orthotropic composite rectangular plates underuniaxial compression with the opposite two edges simply supported andthe other two opposite edges free or simply supported are conducted withthe help of Southwell method and the corresponding error analysis areconducted.The present approximate local buckling solution and explicitformulation can be applied effectively to determine the local bucklingcapacities of composite plates subjected to biaxial in-plane compressionwith the two opposite edges rotationally restrained (the vertical restraintstiffness tends to infinity) and the other two opposite edges both vertically and rotationally restrained and can be further used to predict the localbuckling strength of thin-walled composite structures.