in this study, a new efficient semi-analytical method is introduced to give approximate solutions of strongly nonlinear oscillators. the proposed method is based on combination of two different methods, the multi-step homotopy analysis method and spectral method, called the multi-step spectral homotopy analysis method (msham). in this method, firstly, we propose a new spectral homotopy analysis...

in this paper, under appropriate oscillating behaviours of the nonlinear term, we prove some multiplicity results for a class of nonlinear fractional equations. these problems have a variational structure and we find three solutions for them by exploiting an abstract result for smooth functionals defined on a reflexive banach space. to make the nonlinear methods work, some careful analysis of t...

By minimizing the total potential energy function and deploying the virtual work principle, a higher-order stiffness matrix is achieved. This new tangent stiffness matrix is used to solve the frame with geometric nonlinear behavior. Since authors’ formulation takes into account the higher-order terms of the strain vector, the convergence speed of the solution process will increase. In fac...

in this paper we have discussed the main features of a finite clement program which we have developed for nonlinear dynamic analysis of plates and shells with material and geometric nonlinear behaviour. for this purpose, initially, the finite element model which we have used is briefly described. afterwards, the nonlinear viscoplastic material model in one-dimensional and multi-dimensional medi...

a numerical method for solving nonlinear fredholm-volterra integral equations of general type is presented. this method is based on replacement of unknown function by truncated series of well known chebyshev expansion of functions. the quadrature formulas which we use to calculate integral terms have been imated by fast fourier transform (fft). this is a grate advantage of this method which has...

endurance time (et) method is a relatively new performance-based earthquake method for structural evaluation and design. in this method, the structure is subjected to a gradually intensifying accelorogram(s) and its performance is assessed based on the maximum time duration that it can meet the specified performance objectives. using moment-resisting and braced frames which are rehabilitated by...

in this paper,  a heuristic algorithm is proposed in order to solve a nonlinear lexicography goal programming (nlgp) by using an efficient initial point. some numerical experiments showed that the search quality by the proposed heuristic in a multiple objectives problem depends on the initial point features, so in the proposed approach the initial point is retrieved by data envelopment analysis...

Due to their dual behavior under tension and compression, structures with tension-only members show non-linear behavior. To analize such structures, it is necessary to use a nonlinear analysis scheme. Nonlinear analysis methods generally use gradual loading techniques with/without modification of stiffness matrix of the structure. These methods, in addition to being time consuming algorithms, a...

In this paper, the effect of angle between predictor and corrector surfaces on the structural analysis is investigated. Two objective functions are formulated based on this angle and also the load factor. Optimizing these functions, and using the structural equilibrium path’s geometry, lead to two new constraints for the nonlinear solver. Besides, one more formula is achieved, which was p...