Sharif Digital Repository

Aboveground steel tanks are widely utilized in residential and industrial areas, and assurance of their seismic safety is a very important engineering consideration. In this paper, nonlinear response of these tanks using a new dynamic pushover procedure called Endurance Time (ET) method along with conventional nonlinear response history (RHA) is studied. The comparison between the results of RHA and ET method shows reasonable consistency. Based on the level of accuracy observed in this research, it is concluded that ET method can effectively be used in predicting seismic performance of anchored tanks. By considerably reducing the number of required response history analyses for estimating... 

The performance of perturbation method in nonlinear analyses of plates subjected to mechanical, thermal, and thermo-mechanical loadings is investigated. To this end, cylindrical bending of FG plates with clamped and simply-supported edges is considered. The governing equations of Mindlin's first-order shear deformation theory with von Kármán's geometric nonlinearity are solved using one- and two-parameter perturbation methods and the results are compared with the results of an analytical solution. The material properties are assumed to vary continuously through the thickness of the plate according to a power-law distribution of the volume fraction of the constituents. It is shown that the... 

The performance of perturbation method in nonlinear analyses of plates subjected to mechanical, thermal, and thermo-mechanical loadings is investigated. To this end, cylindrical bending of FG plates with clamped and simply-supported edges is considered. The governing equations of Mindlin's first-order shear deformation theory with von Kármán's geometric nonlinearity are solved using one- and two-parameter perturbation methods and the results are compared with the results of an analytical solution. The material properties are assumed to vary continuously through the thickness of the plate according to a power-law distribution of the volume fraction of the constituents. It is shown that the... 

In this study, nonlinear bending of functionally graded (FG) circular sector plates with simply supported radial edges subjected to transverse mechanical loading has been investigated. Based on the first-order shear deformation plate theory with von Karman strain-displacement relations, the nonlinear equilibrium equations of sector plates are obtained. Introducing a stress function and a potential function, the governing equations which are five non-linear coupled equations with total order of ten are reformulated into three uncoupled ones including one linear edge-zone equation and two nonlinear interior equations with total order of ten. The uncoupling makes it possible to present... 

The statistics of isoheight lines in the (2+1) -dimensional Kardar-Parisi-Zhang (KPZ) model is shown to be conformally invariant and equivalent to those of self-avoiding random walks. This leads to a rich variety of exact analytical results for the KPZ dynamics. We present direct evidence that the isoheight lines can be described by the family of conformally invariant curves called Schramm-Loewner evolution (or SLEI) with diffusivity Î=8/3. It is shown that the absence of the nonlinear term in the KPZ equation will change the diffusivity I from 8/3 to 4, indicating that the isoheight lines of the Edwards-Wilkinson surface are also conformally invariant and belong to the universality class of... 

A local anisotropic damage mechanics model based on energy equivalence was used for evaluating the nonlinear static and dynamic response of concrete gravity dams. The cracks within the elements was formulated as coaxial rotating cracks and the effect of hydrodynamic pressure was included using the staggered displacement method. The features of strain rate effects; strain softening and closing/reopening of cracks were included in the model. The mesh objectivity of the nonlinear model was satisfied by the fracture energy conservation technique. The Pine Flat dam was chosen to investigate the performance of the proposed algorithms. It was found that the resulted crack profiles when including... 

The current design procedure known as Force-Based Design (FBD) method, generally, does not lead to uniform distribution of drift, hysteretic energy, and ductility demands (or structural damage) along the height of the moment frames under strong earthquakes and these performance parameters can be much higher and concentrate damage on one or more of the lower structural stories. This paper presents an iterative wave propagation (WP) based technique to calculate the seismic nonlinear response of multistory buildings as an extension of the layered soil media, founded on bedrock and subjected to vertically propagating shear waves, which leads to the introduction of a new Lateral Load Pattern... 

In this article, a particular off-center bracing system is introduced. In this system, the tensile diagonal strut is not straight. When the load is applied, the original geometry changes and thus causes the system to harden. Based on this behavior, a step-by-step analytical method is developed. Using this method, a Geometrically Nonlinear Analysis Program (GNAP) is designed to analyze the elastic force-displacement relation. Extension of this program to dynamic analysis led to a Dynamic Nonlinear Analysis Program (DNAP). The object of this article is to show that such bracing systems will lead to less seismic force on such structures compared to classic concentric bracing systems. On the... 

The present paper introduces a mixed shear-flexural (VM) link element that is capable of modelling shear yielding, flexural yielding, and their interaction under monotonic and cyclic loadings. The inelastic deformations are modelled using the multisurfaces approach with dissimilar yield surfaces and a stiffness matrix with nonzero off-diagonal components in shear-flexural space. A new kinematic hardening and new non-associated flow rules are employed. A special girder, which has an open web in the middle, is introduced and modelled using the developed VM link element. It is shown that the results of analyses using the VM link element are in good agreement with those from a finite element... 

Purpose: This paper aims to study the lateral behavior of cold-formed steel walls with K-shaped bracing by finite element modeling. Design/methodology/approach: The braces which have the same section as those for studs and tracks are connected to the frame by screw connections. By pushover analysis, lateral performance of two frame categories, with different dimensions and bracing arrangements, is examined, and the force-displacement diagram and the ultimate strength of walls are extracted. Probable failure modes during lateral loading including distortional buckling of studs, buckling in braces and failure of connections are simulated in the numerical model, and some strengthening... 

The high degree of intensity values in microring resonators needs a careful treatment of nonlinear phenomena. Nonlinear effects are analyzed in coupling problem of ring-ring directional couplers. It has been observed that the nonlinearity affects the coupling device dramatically, and can be used as controlling techniques in such as coupled resonator optical waveguides. © 2007 Elsevier B.V. All rights reserved  

Packet-level observations are representative of the high sensitivity of TCP/RED computer network behavior with respect to network/RED parameter variations. That is, while we do not have any control on network parameters, mis-choosing of the RED parameters results in complex non-periodic oscillations in the router queue length that may damage the Quality of Service requirements. Characterizing the nature of such behaviors, however, helps the network designers to modify the RED design method in order to achieve better overall performance. In this paper, we first investigate the effect of variations in different RED parameters on the network behavior and then seek for the origin of such complex... 

In the present paper, the nonlinear seismic behavior of a concrete gravity damreservoir- massed foundation system is studied focusing on the foundation material nonlinearity. For this purpose, a finite element program utilizing the elasto-plastic formulation for the foundation medium is provided considering the tensile and shear failure modes. Hoek-Brown and Mohr Coulomb criteria are used as the yield and plastic potential function of the shear failure mode, respectively; and in the tensile failure mode, various levels of the tensile strength are applied to the foundation. Bearing capacity is studied considering the localized plastic elements and forming the sliding path by plastic elements...