Sharif Digital Repository

Fillet welds are widely used in steel construction due to their high strength and economy. In the joints used in construction, eccentricity loads in complex weld stress. The current research involves 72 bending specimens and 16 torsion specimens being modeled to study different design code relationships regarding the plastic properties of welds. In line with an even comprehensive study, the previous experimental programs in this field have been added to the modeling results.Reliability analysis has been applied to examine code relationships more precisely. The analysis involved examination of various uncertainties which showed that applying elastic methods proves more conservative than other... 

Recently, elastic optical networks have attracted high interest to provide more efficiency and scalability in optical core networks. Due to the high transmission rates and the importance of the transmitted data in these networks, a failure may cause vast data losses. Thus, addressing the problem of survivability in these networks is of great importance. According to different time domain behaviors and reliability requirements of incoming traffic, supporting different quality of services is another important concern. On the other hand, using multi-core fibers is a way to scale the network capacity to provide high-speed transmission services but there is a concern that the inter-core crosstalk... 

Access to the data of Tap30, a ride-hailing company in Iran, has allowed us to estimate the demand elasticity of online taxis. As Tap30 divides Tehran into 256 regions for pricing from Jan to June 2018, we assumed that unobservable consumer characteristics near borders are the same for adjacent regions. We used the Regression Discontinuity method to compare ride requests of people who live on two sides of borders and estimated the demand elasticity of Tap30. This research concludes that by 10 percent increase in price, the demand decreases about 3.5 percent on average in 1 hour time period. On the other hand, in 6 hours time period, the demand decreases about 7.5 percent on average by 10... 

Outer membrane proteins play the role of molecular machines in the outer membrane of bacteria to regulate their basic functions. These macromolecules have nano-scale dimensions and they are involved in the classifications of nano-machines and nano-pores. Protein structure is constructed of chain of amino acids. Coarse grained elastic network model of the protein introduces a network of selected point masses, which is located on α-carbon of each amino acid, linked together with harmonic springs that represent the interactions between residues, both the chemical (protein backbone) and physical bonds. Using the harmonic network potential and theory of mechanical vibration, normal modes of... 

The growth of traffic in metro and core networks is not deniable today, in addition to the volume of traffic, their different requirement force operators to dimension IP over optical network for the peak traffics and also cares about requirements of the traffics. this multi-policy enabled network using new extended technology such as Elastic Optical Network and Bandwidth variable transponders is used to design network with minimum cost and resource. There is different quality of service parameter, in this work we focus on end to end latency and survivability. we present ILP formulation for the IP over elastic optical network and introduce these parameters to this formulation, as we know... 

Nanocomposites are fabricated by incorporating nano-scale particles in polymer, metal, or ceramic matrices. Metal matrix nanocomposites are a new kind of materials which have shown superior mechanical features, such as high strength, stiffness, and hardness. However, they are not sensitive to high temperature, in contrast to the polymer matrix nanocomposites. Nanoporous materials, also, have wide range of applications in different fields, such as geology, biology, biomechanics, and electronic. Carbon Nanotubes (CNTs) have shown wonderful properties like high Young’s modulus, high resonance frequency and unique electrical behavior. Wonderful mechanical and electrical properties make CNTs... 

The seepage through foundation of earth dams causes the serious menaces and the reduction in their efficiency. Therefore essential contrivances must be provided against mentioned problem. One of the common and efficient ways to control the seepage through pervious layers under earth dams is plastic concrete cut off wall which is used as a filling material in dam foundation due to the low permeability, plastic behavior and low enough elastic modulus compatible with the adjusted soil. In addition to the mentioned properties, it is important that plastic concrete have an adequate compressive strength to sustain the lateral and vertical loads. Since the change in the ratio W/C (water to cement)... 

In this project, the acoustoelastic simulation of baffled cavities using boundary element method is investigated. At first step, the acoustic field for an enclosed rigid cavity with baffle is formulated and then solved by dual reciprocity boundary element method. In order to derive the governing equation, the acoustic domain is considered without mean flow and the fluid is assumed to be compressible and inviscid. Using the developed model and applying the zoning method, behavior and response of baffled cavities are investigated. In order to study the structure_acoustic interaction, modal reduced order model is used to explain the vibration of structure in combination to acoustic field. The... 

In this study, an elastic-plastic analysis of fiber reinforced metal matrix composite structures loaded by uniaxial uniform tension in the direction perpendicular to the fiber is carried out by assuming elastic-plastic matrix with kinematic hardening. Representative volume element (RVE) is used for this analysis. The element consists of a combined square field composed of a solid circular cylinder fiber and matrix in plane strain condition. Elastic analysis is carried out using Airy stress function and Michell solution. Unknown coefficients of the Airy stress function are determined by satisfying boundary conditions as well as continuity conditions. The governing equation of plastic zone is... 

In this thesis an analytical solution is introduced for finding the elastic fields of stress and strain in a confocal elliptic ring at the state of general plane problem. A confocal elliptic ring is a doubly connected region which its external and internal boundaries are ellipses with the same focal points. We used the method of complex variables, the functions of Kolosov-Muskhelishvili potentials, Laurent series expansion for analytical functions, the method of the analytic continuation of Milne-Thomson, elliptic hyperbolic coordinates, and two dimensional conformal mapping to do this study. the importance of this analysis is because we can simulate some problems of the elasticity by... 

The behavior of a beam under moving mass has been always interested in the dynamic of structures. In this study, the dynamic response of beam and plate with general boundary conditions under moving mass were investigated using the Dynamic Green Function. Since the majority of previous studies did not consider the Coriolis acceleration, therefore, this acceleration was used in the present study. Boundary conditions are modeled by the rotational and translational restraint. By moving close to the spring constants of the rotational and translational restraint to extreme values (zero and/or infinity), the boundary conditions can be attained for the desired combinations of end boundary conditions... 

In this study, an analytical solution is presented for anti-plane scattering of Love waves by a surface-breaking crack normal to the free surface of an ultra-thin layer bonded to a semi-infinte medium within the surface/interface elasticity theory. The Fourier transform techniques are used to formulate the corresponding mixed-boundary value problem as a singular integral equation of the Cauchy type which is solved numerically. Mode III dynamic stress intensity factor at the crack tip, crack face and crack mouth opening displacements, the reflection coefficient at large distances from the crack face, and the stress field on the interface are computed and plotted for different valued of... 

To explain the dependence of sliding friction on or between the layers of wet sand, one first needs to have a rather good understanding of the elastic properties of wet granular material. Experimental work that has been done on the subject so far, has shown that these elastic properties have a peculiar dependence on the water volume fraction of the sand system. But till nowno theoretical model has been presented that could illustrate the physical causes of such findings. More specifically, these handful of theoretical models have not been able to explain the complex relationship between the shear modulus of sand and the water volume percentage. In this thesis at first the nature and... 

The utility of nano-beams in MEMs and NEMs has progressed a lot in recent years. Such systems have found wide spread use in sensors and actuators due to small size, low weight, high accuracy and low energy consumption. By a decrease in size of nano-beams, surface effect increases which makes the classical theories unable to modeling such beams. Therefore new models are required for evaluating the dynamic behavior of nano-beams. In this thesis we have attempted to develop a suitable Coarse-Grain model for analysis of such beams. At first a suitable Coarse-Grain mapping with determined Sutton-Chen potential parameters is introduced for FCC metals. In the next step, EAM is considered as... 

In Former research we determinate elastic response of Brazilian Test of transversely Isotropic material . In Bio-mechanic science surveying mechanical properties and modeling biological organ such as bone , tooth and bio-material such as titanium, zirconium with application in joint replacement is very important . One of method to determine properties of bio-material which mostly has transversely Isotropic behavior is Brazilian Test. Also most rocks has transversely Isotropic behavior, so choosing efficient test is so important. In current issue , load apply in limited area and it is also considered friction in area of jaw loading area .By use of displacement potential function ... 

In the current work, the two- and three-dimensional electro-elastic fields of periodically as well as arbitrarily distributed interacting quantum wires (QWRs) and interacting quantum dots (QDs) of arbitrary shapes within a piezoelectric matrix are studied analytically. The lattice mismatch between the QWR/QD and the barrier is accounted through prescribing an initial misfit strain field within the QWR/QD. The distinction between the electro-mechanical properties of the QWR/QD and those of the barrier is treated by introducing a novel electro-mechanical equivalent inclusion method in Fourier space (FEMEIM). Moreover, the theory can readily treat cases where the QWRs/QDs are multi-phase or... 

DNA molecule is one of the most important macromolecules in cell, which carries genetic information for life. DNA is often in confined geometries, such as, packaging in cell and DNA-protein interactions. While DNA is nearly a stiff polymer, its elastic behaviour plays a crucial role on its functionalities.Therefore, investigating the elastic and mechanical properties of DNA is really important.The elastic behaviour of a long and free DNA can be predicted very accurately by ”worm-like chain“ (WLC) model. In WLC model, DNA is assumed as a elastic rod with harmonic potential of local bending and twist.Many structural properties of DNA have been ignored in this model. But in recent years, by... 

The properties of metamaterials can be tailored through modification of their microstructures geometry. In this regard, a vast range of metamaterials have been designed. Auxetic metamaterials are a novel class of materials exhibiting the interesting characteristic of negative Poisson’s ratio. Theoretically, auxetic metamaterials have improved mechanical properties such as shear modulus and fracture toughness. The design and modeling of auxetic metamaterials is not completed yet. In order to exploit the interesting properties of auxetic metamaterials, their potential applications have been investigated in medical, sports, automobile and defense industries, so far. In the present work, the... 

In this study, static and dynamic buckling of laminated composite beams resting on an elastic foundation under thermal and mechanical load is studied. Beam is resting on an elastic foundation with hardening/softening term. Nonlinear governing equations are obtained based on the energy method and are solved via the multi-term Galerkin method and the Newton-Raphson numerical method. Critical dynamic load is estimated by the Hoff Simitses criterion. The results are validated with the results of available articles in this field. In the following, the effects of different parameters of the problem on the results are examined. Results reveal that for a sufficiently stiff softening elastic... 

Considering the role of fluid storage tanks within or after an earthquake and the irreparable damages of such structures that arise from the flammable or toxic nature of the fluids stored in them, it is very important to ensure stability and durability of the tanks under seismic loading. One of the most important damages to storage tanks within the past earthquakes has been lack of stability of their shells taking place in the form of a local bulge of wall, known as “elephant foot buckling’. This phenomenon is a subsequent of high levels of hoop tension, which is a result of containing liquid pressure, along with axial load of surrounding walls. Recent studies reveal that there is no...