بررسي پايداري الاستيك و غير الاستيك ورق هاي سخت شده با تغيير ضخامت در دو راستا به روش نوار محدود اسپلاين

چكيده انگليسي :

Elastic and Inelastic Stability of Stiffened Plates with Thickness Changing in Two Directions using B3 Spline Finite Strip Method Maryam Mashayekhizadeh m mashayekhizadeh@cv iut ac ir Date of Submission 29 Feb 2012 Department Civil Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mojtaba Azhari mojtaba@cc iut ac irAbstractThe application of plates becoming widespread in various branches of engineering as main structuralelements the strengthening of them in contrast with environmental loads becomes important Amongdifferent environmental loads inplane loads are important which cause buckling in plates So decreasing thehazard of buckling in plates is one of the interests among designers and researchers A way to increase thestrength of plate is to increase the whole thickness of it Using thick plate especially while the plate isconsiderably high needs much more material and the weight becomes enormous One of the ways to decreasethe cost and the weight of plate structure is to increase the thickness locally Increasing the thickness of theplate locally gives an efficient cost structure with enough buckling strength but not as much as thick plate Inorder to supply required strength in such plates it is suggested to add longitudinal stiffeners to them Interestin stiffened plate construction has been propagated during recent years due to it s economic and structuralbenefits Although the stiffening elements cause a negligible increscent in the weight of overall structure their influence on strength and stability is enormous In this case a part of required strength would beprovided by locally increased thickness of the plate and the remained would be provided by added stiffeners This means that using this method neither needs increasing too much the thickness of plate nor usingstiffeners Then achieved structures would be cost efficiently with proportional weight This study isconcerned with buckling analysis of stiffened plate with step variation in thickness in either one or twodirections In addition sometimes the critical stress exceeds proportional limit of the material So the platestructure goes to the plastic range In this case buckling problems become very important since the stiffnessmatrix of the structure is not constant either By using the theory of plasticity and stress strain curve inelasticbuckling problem can be solved which is discussed in this thesis However adding stiffeners to the plate inaddition to locally increasing thickness of the plate complicates the analysis of such plates Therefore due tocomplexity of the closed form solutions for buckling analysis of such plates numerical methods are morerecommended Among the various numerical methods finite strip is an efficient method for predictionbuckling stress of plate structures Comparing with the conventional finite strip method spline finite strip ismore accurate and flexible In this method piecewise cubic polynomials which is called B Spline functionsare used as the longitudinal displacement functions Measuring of abrupt changes in thickness or loading ofplates and various boundary conditions becomes possible by amending the B3 spline functions Differentnumerical examples in the concept of elastic and inelastic buckling are considered to show the accuracy andversatility of the proposed method Keywords Spline Finite Strip Stepped plates Stiffened Stepped plates Locally increased thickness

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بررسي پايداري الاستيك و غير الاستيك ورق هاي سخت شده با تغيير ضخامت در دو راستا به روش نوار محدود اسپلاين

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